Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

Abstract

Key message

Barley double mutants in two genes involved in starch granule morphology, HvFLO6 and HvISA1, had impaired starch accumulation and higher grain sugar levels than either single mutant.

Abstract

Starch is a biologically and commercially important glucose polymer synthesized by plants as semicrystalline starch granules (SGs). Because SG morphology affects starch properties, mutants with altered SG morphology may be useful in breeding crops with desirable starch properties, including potentially novel properties. In this study, we employed a simple screen for mutants with altered SG morphology in barley (Hordeum vulgare). We isolated mutants that formed compound SGs together with the normal simple SGs in the endosperm and found that they were allelic mutants of the starch biosynthesis genes ISOAMYLASE1 (HvISA1) and FLOURY ENDOSPERM 6 (HvFLO6), encoding starch debranching enzyme and CARBOHYDRATE-BINDING MODULE 48-containing protein, respectively. We generated the hvflo6 hvisa1 double mutant and showed that it had significantly reduced starch biosynthesis and developed shrunken grains. In contrast to starch, soluble α-glucan, phytoglycogen, and sugars accumulated to higher levels in the double mutant than in the single mutants. In addition, the double mutants showed defects in SG morphology in the endosperm and in the pollen. This novel genetic interaction suggests that hvflo6 acts as an enhancer of the sugary phenotype caused by hvisa1 mutation.

DOI： 10.1007/s00122-023-04339-5

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Other Link： https://link.springer.com/article/10.1007/s00122-023-04339-5/fulltext.html

Authorship：Corresponding author   Publishing type：Research paper (scientific journal)  

Sorghum (Sorghum bicolor (L.) Moench) is an important crop originated in Africa that shows susceptibility to herbivores. In this study, we identified two sorghum genotypes with highly contrasting levels of stem damage caused by the caterpillars of Asian stem borer (Ostrinia furnacalis Guenée). Recombinant inbred lines (RILs) from genetic cross between resistant (BTx623) and susceptible (NOG) sorghum were used to perform a quantitative trait locus (QTL) analysis in the field. Two major QTLs responsible for higher NOG infestation by stem borer in three independent field seasons were detected on chromosomes 7 and 9, interestingly in positions that overlapped with two major QTLs for plant height. As plant height and stem borer damage were highly correlated, we propose that sorghum height-associated morphological or physiological traits could be important for stem borer establishment and/or damage in sorghum.

DOI： 10.1080/17429145.2022.2153182

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Authorship：Last author   Language：Japanese   Publisher：Pesticide Science Society of Japan  

DOI： 10.1584/jpestics.w22-17

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

KEY MESSAGE: We show that in rice, the amino acid-conjugates of JA precursor, OPDA, may function as a non-canonical signal for the production of phytoalexins in coordination with the innate chitin signaling. The core oxylipins, jasmonic acid (JA) and JA-Ile, are well-known as potent regulators of plant defense against necrotrophic pathogens and/or herbivores. However, recent studies also suggest that other oxylipins, including 12-oxo-phytodienoic acid (OPDA), may contribute to plant defense. Here, we used a previously characterized metabolic defense marker, p-coumaroylputrescine (CoP), and fungal elicitor, chitooligosaccharide, to specifically test defense role of various oxylipins in rice (Oryza sativa). While fungal elicitor triggered a rapid production of JA, JA-Ile, and their precursor OPDA, rice cells exogenously treated with the compounds revealed that OPDA, rather than JA-Ile, can stimulate the CoP production. Next, reverse genetic approach and oxylipin-deficient rice mutant (hebiba) were used to uncouple oxylipins from other elicitor-triggered signals. It appeared that, without oxylipins, residual elicitor signaling had only a minimal effect but, in synergy with OPDA, exerted a strong stimulatory activity towards CoP production. Furthermore, as CoP levels were compromised in the OPDA-treated Osjar1 mutant cells impaired in the oxylipin-amino acid conjugation, putative OPDA-amino acid conjugates emerged as hypothetical regulators of CoP biosynthesis. Accordingly, we found several OPDA-amino acid conjugates in rice cells treated with exogenous OPDA, and OPDA-Asp was detected, although in small amounts, in the chitooligosaccharide-treated rice. However, as synthetic OPDA-Asp and OPDA-Ile, so far, failed to induce CoP in cells, it suggests that yet another presumed OPDA-amino acid form(s) could be acting as novel regulator(s) of phytoalexins in rice.

DOI： 10.1007/s11103-021-01217-w

PubMed

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

Key message This study describes biological functions of the bHLH transcription factor RERJ1 involved in the jasmonate response and the related defense-associated metabolic pathways in rice, with particular focus on deciphering the regulatory mechanisms underlying stress-induced volatile emission and herbivory resistance. RERJ1 is rapidly and drastically induced by wounding and jasmonate treatment but its biological function remains unknown as yet. Here we provide evidence of the biological function of RERJ1 in plant defense, specifically in response to herbivory and pathogen attack, and offer insights into the RERJ1-mediated regulation of metabolic pathways of specialized defense compounds, such as monoterpene linalool, in possible collaboration with OsMYC2-a well-known master regulator in jasmonate signaling. In rice (Oryza sativa L.), the basic helix-loop-helix (bHLH) family transcription factor RERJ1 is induced under environmental stresses, such as wounding and drought, which are closely linked to jasmonate (JA) accumulation. Here, we investigated the biological function of RERJ1 in response to biotic stresses, such as herbivory and pathogen infection, using an RERJ1-defective mutant. Transcriptome analysis of the rerj1-Tos17 mutant revealed that RERJ1 regulated the expression of a typical family of conserved JA-responsive genes (e.g., terpene synthases, proteinase inhibitors, and jasmonate ZIM domain proteins). Upon exposure to armyworm attack, the rerj1-Tos17 mutant exhibited more severe damage than the wildtype, and significant weight gain of the larvae fed on the mutant was observed. Upon Xanthomonas oryzae infection, the rerj1-Tos17 mutant developed more severe symptoms than the wildtype. Among RERJ1-regulated terpene synthases, linalool synthase expression was markedly disrupted and linalool emission after wounding was significantly decreased in the rerj1-Tos17 mutant. RERJ1 appears to interact with OsMYC2-a master regulator of JA signaling-and many OsJAZ proteins, although no obvious epistatic interaction was detected between them at the transcriptional level. These results indicate that RERJ1 is involved in the transcriptional induction of JA-mediated stress-responsive genes via physical association with OsMYC2 and mediates defense against herbivory and bacterial infection through JA signaling.

DOI： 10.1007/s11103-021-01186-0

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Language：English   Publishing type：Research paper (scientific journal)  

Plants perceive volatiles emitted from herbivore-damaged neighboring plants to urgently adapt or prime their defense responses to prepare for forthcoming herbivores. Mechanistically, these volatiles can induce epigenetic regulation based on histone modifications that alter the transcriptional status of defense genes, but little is known about the underlying mechanisms. To understand the roles of such epigenetic regulation of plant volatile signaling, we explored the response of Arabidopsis (Arabidopsis thaliana) plants to the volatile β-ocimene. Defense traits of Arabidopsis plants toward larvae of Spodoptera litura were induced in response to β-ocimene, through enriched histone acetylation and elevated transcriptional levels of defense gene regulators, including ethylene response factor genes (ERF8 and ERF104) in leaves. The enhanced defense ability of the plants was maintained for 5 d but not over 10 d after exposure to β-ocimene, and this coincided with elevated expression of those ERFs in their leaves. An array of histone acetyltransferases, including HAC1, HAC5, and HAM1, were responsible for the induction and maintenance of the anti-herbivore property. HDA6, a histone deacetylase, played a role in the reverse histone remodeling. Collectively, our findings illuminate the role of epigenetic regulation in plant volatile signaling.

DOI： 10.1093/plphys/kiac077

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Authorship：Corresponding author   Language：English   Publisher：WILEY  

Success of plants largely depends on their ability to defend against herbivores. Since emergence of the first voracious consumers, plants maintained adapting their structures and chemistry to escape from extinction. The constant pressure was further accelerated by adaptation of herbivores to plant defenses, which all together sparked the rise of a chemical empire comprised of thousands of specialized metabolites currently found in plants. Metabolic diversity in the plant kingdom is truly amazing, and although many plant metabolites have already been identified, a large number of potentially useful chemicals remain unexplored in plant bio-resources. Similarly, biosynthetic routes for plant metabolites involve many enzymes, some of which still wait for identification and biochemical characterization. Moreover, regulatory mechanisms that control gene expression and enzyme activities in specialized metabolism of plants are scarcely known. Finally, understanding of how plant defense chemicals exert their toxicity and/or repellency against herbivores remains limited to typical examples, such as proteinase inhibitors, cyanogenic compounds and nicotine. In this review, we attempt summarizing the current status quo in metabolic defense of plants that is predominantly based on the survey of ubiquitous examples of plant interactions with chewing herbivores.

DOI： 10.1111/jipb.13204

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Informa UK Limited  

DOI： 10.1080/17429145.2021.2006334

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY  

A vast array of herbivorous arthropods live with symbiotic microorganisms. However, little is known about the nature and functional mechanism of bacterial effects on plant defense responses towards herbivores. We explored the role of microbes present in extracts of oral secretion (OS) isolated from larvae of Spodoptera litura, a generalist herbivore, in phytohormone signaling-dependent defense responses in Arabidopsis thaliana (Arabidopsis). In response to mechanical damage (MD) with application of bacteria-free OS (OS-) prepared by sterilization or filtration of OS, Arabidopsis leaves exhibited enhanced de novo synthesis of oxylipins, and induction of transcript abundance of the responsible genes, in comparison to those in leaves with MD + nonsterilized OS (OS+), indicating that OS bacteria serve as suppressors of these genes. By contrast, de novo synthesis/signaling of salicylic acid and signaling of abscisic acid were enhanced by OS bacteria. These signaling networks were cross-regulated by each other. Meta-analysis of OS bacteria identified 70 bacterial strains. Among them was Staphylococcus epidermidis, an anaerobic staphylococcus that was shown to contribute to the suppression/manipulation of phytohormone-dependent plant defense signaling. The presence of OS bacteria was consequently beneficial for S. litura larvae hosted by Brassicaceae.

DOI： 10.1111/nph.17444

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI  

In the face of climate change and the predicted increase in the frequency and severity of abiotic stresses (e.g., hot spell, salinity), we sought to investigate the effect of salinity (S), short episodes of high temperature (HS) and combination of salinity and high temperature (SHS), at the reproductive phase, on yield with a special focus on the properties of dead pericarps of Brassica juncea. Three interval exposures to HS resulted in massive seed abortion, and seeds from salt-treated plants germinated poorly. Germination rate and final germination of B. juncea seeds were slightly reduced in the presence of salt and SHS pericarp extracts. All pericarp extracts completely inhibited seed germination of tomato and Arabidopsis, but removal of pericarp extracts almost fully restored seed germination. Heat and salinity profoundly affected the accumulation of phytohormones in dead pericarps. Combined stresses highly reduced IAA and ABA levels compared with salt, and enhanced the accumulation of GA1, but abolished the positive effect of salt on the accumulation of GA4, JA and SA. Interestingly, pericarp extracts displayed priming activity and significantly affected seedling performance in a manner dependent on the species and on the origin of the pericarp. While control pericarps improved and reduced the seedlings' performance of autologous and heterologous species, respectively, pericarps from salt-treated plants were harmless or improved heterologous seedling performance. Thus, the strategy employed by the germinating seed for securing resources is set up, at least partly, by the mother plant in conjunction with the maternal environment whose components are stored in the dead maternal organs enclosing the embryo.

DOI： 10.3390/plants10081627

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

Despite the importance of volatile organic compounds (VOCs) for plants, control mechanisms for their basal and stress-induced biosynthesis and release remain unclear. We sampled and characterized headspace and internal leaf volatile pools in rice (Oryza sativa), after a simulated herbivory treatment, which triggers an endogenous jasmonate burst. Certain volatiles, such as linalool, were strongly upregulated by simulated herbivory stress. In contrast, other volatiles, such as β-caryophyllene, were constitutively emitted and fluctuated according to time of day. Transcripts of the linalool synthase gene transiently increased 1-3 h after exposure of rice to simulated herbivory, whereas transcripts of caryophyllene synthase peaked independently at dawn. Unexpectedly, although emission and accumulation patterns of rice inducible and constitutive VOCs were substantially different, both groups of volatiles were compromised in jasmonate-deficient hebiba mutants, which lack the allene oxide cyclase (AOC) gene. This suggests that rice employs at least two distinct oxylipin-dependent mechanisms downstream of AOC to control production of constitutive and herbivore-induced volatiles. Levels of the JA precursor, 12-oxo-phytodienoic acid (OPDA), were correlated with constitutive volatile levels suggesting that OPDA or its derivatives could be involved in control of volatile emission in rice.

DOI： 10.1111/pce.14126

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Language：English   Publishing type：Research paper (scientific journal)  

Root length is one of the important parameters of root traits directly related to uptake of water and nutrients, however, the molecular mechanisms controlling root length are still not fully understood. Here, we isolated a mutant, dice2 (defective in cell elongation 2) of rice (Oryza sativa) showing short roots. The cell length and meristem size of the roots was decreased in the mutant, but the root function in mineral element uptake normalized by root biomass, root cell width and root anatomy was hardly altered compared with the wild-type rice (WT). Intriguingly, the root growth defect in the mutant could be partially rescued by high temperature. The mutant accumulated more H2O2 and glutamic acid, but less O2  •- in the roots at low temperature than WT, but they became similar at high temperature between two lines. A map-based cloning combined with complementation test revealed that the short-root phenotype was caused by a nucleotide substitution of a gene, which was annotated to encode Lysine Ketoglutarate Reductase Trans-Splicing related 1 (OsLKRT1). OsLKRT1 encodes a cytosol-localized protein and was expressed in both the roots and shoots. Furthermore, OsLKRT1 was expressed in all cells of the root tip and root elongation regions. RNA-seq analysis showed that there was no difference in the expression level of genes involved in root development identified so far. These results indicate that the gene identified in this study is involved in novel pathway required for cell elongation of the roots in rice although its exact role remains to be further investigated.

DOI： 10.1093/jxb/erab240

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：FRONTIERS MEDIA SA  

Jasmonic acid (JA) and its biologically active form jasmonoyl-L-isoleucine (JA-Ile) regulate defense responses to various environmental stresses and developmental processes in plants. JA and JA-Ile are synthesized from a-linolenic acids derived from membrane lipids via 12-oxo-phytodienoic acid (OPDA). In the presence of JA-Ile, the COI1 receptor physically interacts with JAZ repressors, leading to their degradation, resulting in the transcription of JA-responsive genes by MYC transcription factors. Although the biosynthesis of JA-Ile is conserved in vascular plants, it is not recognized by COI1 in bryophytes and is not biologically active. In the liverwort Marchantia polymorpha, dinor-OPDA (dn-OPDA), a homolog of OPDA with two fewer carbons, and its isomer dn-iso-OPDA accumulate after wounding and are recognized by COI1 to activate downstream signaling. The moss Calohypnum plumiforme produces the antimicrobial-specialized metabolites, momilactones. It has been reported that JA and JA-Ile are not detected in C. plumiforme and that OPDA, but not JA, can induce momilactone accumulation and the expression of these biosynthetic genes, suggesting that OPDA or its derivative is a biologically active molecule in C. plumiforme that induces chemical defense. In the present study, we investigated the biological functions of OPDA and its derivatives in C. plumiforme. Searching for the components potentially involving oxylipin signaling from transcriptomic and genomic data revealed that two COI1, three JAZ, and two MYC genes were present. Quantification analyses revealed that OPDA and its isomer iso-OPDA accumulated in larger amounts than dn-OPDA and dn-iso-OPDA after wounding. Moreover, exogenously applied OPDA, dn-OPDA, or dn-iso-OPDA induced the transcription of JAZ genes. These results imply that OPDA, dn-OPDA, and/or their isomers potentially act as biologically active molecules to induce the signaling downstream of COI1-JAZ. Furthermore, co-immunoprecipitation analysis showed the physical interaction between JAZs and MYCs, indicating the functional conservation of JAZs in C. plumiforme with other plants. These results suggest that COI1-JAZ-MYC mediated signaling is conserved and functional in C. plumiforme.

DOI： 10.3389/fpls.2021.688565

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY  

Plants produce a broad variety of defensive metabolites to protect themselves against herbivorous insects. Although polyamines have been implicated in various responses to abiotic and biotic stress, there have been no studies focused on amines in response to insect herbivory. By screening for bioactive amines, we identified isopentylamine as a novel type of herbivory-induced compound in rice leaves, which was derived from the amino acid leucine in stable isotope labelling experiments. Accumulation of isopentylamine increased during herbivory by the brown planthopper (Nilaparvata lugens, BPH) and the rice-feeding armyworm (Mythimna loreyi), as well as in response to treatment with the plant hormone, jasmonic acid. Likewise, isopentylamine accumulation was compromised in rice jasmonate biosynthesis mutants,hebibaandOsjar1. In bio-assays, BPH insects feeding on rice seedlings submerged in 50 mg/L isopentylamine solution had a higher mortality compared with BPH feeding on seedlings submerged in water. Notably, the rice leaves submerged in 50 mg/L solution showed the endogenous concentrations of isopentylamine similar to that induced by BPHs. These results suggest that isopentylamine functions as a new type of plant defence metabolite that is rapidly induced by herbivore attack and deters insect herbivores in rice.

DOI： 10.1111/pce.13902

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

Main conclusionThe dead husk is a vital component of the dispersal unit whose biochemical properties can be modified following exposure to drought. This might affect seed performance and fate, soil properties and consequently plant biodiversity.AbstractWe investigated the effects of extreme drought on the dispersal unit (DU) properties of winter wild oat (Avena sterilis L.) in the Mediterranean ecosystems focusing on a commonly ignored component of the DU, namely the dead floral bracts (husk). DUs were collected from a climate change experimental research station in the Judean Hills, Israel, simulating extreme drought and from two additional sites differing in the rainfall amounts. Our results showed that drought conditions significantly affected A. sterilis reproductive traits displaying reduced DUs and caryopses weights. The husk contributes profoundly to seed performance showing that germination from the intact DUs or the intact florets 1 was higher, faster and more homogenous compared to naked caryopses; no effect of drought on germination properties was observed. The husk stored hundreds of proteins that retain enzymatic activity and multiple metabolites including phytohormones. Changes in rainfall amounts affected the composition and levels of proteins and other metabolites accumulated in the husk, with a notable effect on abscisic acid (ABA). The husk of both control and drought plants released upon hydration substances that selectively inhibited other species seed germination as well as substances that promoted microbial growth. Our data showed that the dead husk represents a functional component of the DU that have been evolved to nurture the embryo and to ensure its success in its unique habitat. Furthermore, drought conditions can modify husk biochemical properties, which in turn might affect seed performance and fate, soil microbiota and soil fertility and consequently plant species diversity.

DOI： 10.1007/s00425-020-03491-2

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Phospholipid signaling plays an important role in plant immune responses against phytopathogenic bacteria in Nicotiana benthamiana. Here, we isolated two phospholipase C2 (PLC2) orthologs in the N. benthamiana genome, designated as PLC2-1 and 2-2. Both NbPLC2-1 and NbPLC2-2 were expressed in most tissues and were induced by infiltration with bacteria and flg22. NbPLC2-1 and NbPLC2-2 (NbPLC2s) double-silenced plants showed a moderately reduced growth phenotype. The induction of the hypersensitive response was not affected, but bacterial growth and the appearance of bacterial wilt were accelerated in NbPLC2s-silenced plants when they were challenged with a virulent strain of Ralstonia solanacearum that was compatible with N. benthamiana. NbPLC2s-silenced plants showed reduced expression levels of NbPR-4, a marker gene for jasmonic acid signaling, and decreased jasmonic acid and jasmonoyl-L-isoleucine contents after inoculation with R. solanacearum. The induction of pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI) marker genes was reduced in NbPLC2s-silenced plants after infiltration with R. solanacearum or Pseudomonas fluorescens. Accordingly, the resistance induced by flg22 was compromised in NbPLC2s-silenced plants. In addition, the expression of flg22-induced PTI marker genes, the oxidative burst, stomatal closure, and callose deposition were all reduced in the silenced plants. Thus, NbPLC2s might have important roles in pre- and post-invasive defenses, namely in the induction of PTI.

DOI： 10.1093/jxb/eraa233

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

We examined the role of ethylene in the production of rice (Oryza sativa) volatile organic compounds (VOCs), which act as indirect defense signals against herbivores in tritrophic interactions. Rice plants were exposed to exogenous ethylene (1 ppm) after simulated herbivory which consisted of mechanical wounds supplemented with the oral secretions (WOS) from the generalist herbivore larvae, Mythimna loreyi. Ethylene treatment highly suppressed VOCs in WOS-treated rice leaves, which was further corroborated by the reduced transcript levels of major VOC biosynthesis genes in ethylene-treated rice. In contrast, the accumulation of jasmonates (JA), known to control the VOCs in higher plants, and transcript levels of primary JA response genes, including OsMYC2, were not largely affected by ethylene application. At the functional level, flooding that is known to promote internode elongation in the young rice via ethylene signaling, consistent with the negative role of ethylene, suppressed the accumulation of VOCs in water-submerged rice leaves. Furthermore, in the maturing stage rice that naturally produced less volatiles, VOCs could be rescued by the application of ethylene perception inhibitor, 1-methylcyclopropene (1-MCP). Our data suggest that ethylene acts as an endogenous suppressor of VOCs in rice that applies to both plant stress responses and development.

DOI： 10.1093/jxb/eraa341

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PUBLIC LIBRARY SCIENCE  

The dead organs enclosing embryos (DOEEs) emerge as central components of the dispersal unit (DU) capable for long-term storage of active proteins and other substances that affect seed performance and fate. We studied the effect of maternal environment (salt and salt+heat) on progeny DU (dry indehiscent fruit) focusing on pericarp properties of Anastatica hierochuntica. Stressed plants displayed increased seed abortion and low level and rate of germination. Hydrated pericarps released antimicrobial factors and allelopathic substances that inhibit germination of heterologous species. Proteome analysis of dead pericarps revealed hundreds of proteins, among them nucleases, chitinases and proteins involved in reactive oxygen species detoxification and cell wall modification. Salt treatment altered the composition and level of proteins stored in the pericarp. We observed changes in protein profile released from seeds of salt-treated plants with a notable increase in a small anti-fungal protein, defensin. The levels of phytohormones including IAA, ABA and salicylic acid were reduced in dead pericarps of stressed plants. The data presented here highlighted the predominant effects of maternal environment on progeny DUs of the desert plant A. hierochuntica, particularly on pericarp properties, which in turn might affect seed performance and fate, soil fertility and consequently plant biodiversity.

DOI： 10.1371/journal.pone.0237045

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY  

Interspecific New Rice for Africa (NERICA) varieties have been recently developed and used in Sub-Saharan Africa but herbivore resistance properties of these plants remain poorly understood. Here we report that, compared to a local Japanese cultivar Nipponbare, NERICA 1, 4 and 10 are significantly more damaged by insect herbivores in the paddy fields. In contrast to high levels of leaf damage from rice skippers and grasshoppers, constitutive and induced volatile organic compounds for indirect plant defense were higher or similar in NERICAs and Nipponbare. Accumulation of direct defense secondary metabolites, momilactones A and B, and p-coumaroylputrescine (CoP) was reduced in NERICAs, while feruloylputrescine accumulated at similar levels in all varieties. Finally, we found that Nipponbare leaves were covered with sharp nonglandular trichomes impregnated with silicon but comparable defense structures were virtually absent in herbivory-prone NERICA plants. As damage to the larval gut membranes by Nipponbare silicified trichomes that pass intact through the insect digestive system, occurs, and larval performance is enhanced by trichome removal from otherwise chemically defended Nipponbare plants, we propose that silicified trichomes work as an important defense mechanism of rice against chewing insect herbivores.

DOI： 10.1111/pce.13775

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We collected Solidago altissima clones to explore their leaf damage resistance, and as a result identified five accessions that exhibited variable defense abilities against the generalist herbivore Spodoptera litura. In order to characterize molecules involved in such natural variation, we focused on ethylene response factors (ERFs) that exhibited distinct transcription patterns in the leaves of the five accessions (e.g., S1 and S2) after wounding: the transcript of SaERF1 and SaERF2 was induced in wounded S1 and S2 leaves, respectively. Although transcription levels of SaERFs in leaves of the five accessions did not correlate with the accessions' phytohormone levels, these transcription levels accorded with the possibility that ethylene and jasmonate signaling play crucial roles in wound-induced transcription of SaERF1 in S1 leaves, and SaERF2 in S2 leaves, respectively. SaERF1 was found to be a positive regulator of the GCC box and DRE element in the upstream regions of promoters of defense genes, whereas SaERF2 served as a negative regulator of genes controlled through the GCC box. Transgenic Arabidopsis plants expressing SaERF1 or SaERF2 showed enhanced and suppressed transcript levels, respectively, of a defensin gene, indicating that ERFs may be partly responsible for herbivore resistance properties of S. altissima accessions.

DOI： 10.1038/s41598-020-62142-4

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Language：English   Publisher：Japanese Society for Plant Biotechnology  

<p>Phosphatidic acid plays an important role in plant immune responses against phytopathogenic bacteria in Nicotiana benthamiana. Here we focused on phosphoinositide dependent protein kinases (PDKs) as a candidate required for phosphatidic acid signaling. Based on Arabidopsis PDK sequences, we identified four putative PDK orthologs in N. benthamiana genome. To address the role of PDKs in plant defense responses, we created all four NbPDKs-silenced plants by virus-induced gene silencing. the NbPDKs-silenced plants showed a moderately reduced growth phenotype. Induction of hypersensitive cell death was compromised in the NbPDKs-silenced plants challenged with Ralstonia solanacearum. The hypersensitive cell death induced by bacterial effectors was also reduced in the NbPDKs-silenced plants. the NbPDKs-silenced plants showed decreased production of salicylic acid, jasmonic acid and jasmonoyl-L-isoleucine, as well as hydrogen peroxide after inoculation with R. solanacearum. These results suggest that NbPDKs might have an important role in the regulation of the hypersensitive cell death via plant hormone signaling and oxidative burst.</p>

DOI： 10.5511/plantbiotechnology.20.0511b

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Plants respond to herbivory by perceiving herbivore danger signal(s) (HDS(s)), including "elicitors", that are present in herbivores' oral secretions (OS) and act to induce defense responses. However, little is known about HDS-specific molecules and intracellular signaling. Here we explored soybean receptor-like kinases (RLKs) as candidates that might mediate HDS-associated RLKs' (HAKs') actions in leaves in response to OS extracted from larvae of a generalist herbivore, Spodoptera litura. Fractionation of OS yielded Frα, which consisted of polysaccharides. The GmHAKs composed of their respective homomultimers scarcely interacted with Frα. Moreover, Arabidopsis HAK1 homomultimers interacted with cytoplasmic signaling molecule PBL27, resulting in herbivory resistance, in an ethylene-dependent manner. Altogether, our findings suggest that HAKs are herbivore-specific RLKs mediating HDS-transmitting, intracellular signaling through interaction with PBL27 and the subsequent ethylene signaling for plant defense responses in host plants.

DOI： 10.1038/s42003-020-0959-4

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

The two-spotted spider mite (Tetranychus urticae) is a plant-sucking arthropod herbivore that feeds on a wide array of cultivated plants. In contrast to the well-characterized classical chewing herbivore salivary elicitors that promote plant defense responses, little is known about sucking herbivores' elicitors. To characterize the sucking herbivore elicitors, we explored putative salivary gland proteins of spider mites by using an Agrobacterium-mediated transient expression system or protein infiltration in damaged bean leaves. Two candidate elicitors (designated as tetranin1 (Tet1) and tetranin2 (Tet2)) triggered early leaf responses (cytosolic calcium influx and membrane depolarization) and increased the transcript abundances of defense genes in the leaves, eventually resulting in reduced survivability of T. urticae on the host leaves as well as induction of indirect plant defenses by attracting predatory mites. Tet1 and/or Tet2 also induced jasmonate, salicylate and abscisic acid biosynthesis. Notably, Tet2-induced signaling cascades were also activated via the generation of reactive oxygen species. The signaling cascades of these two structurally dissimilar elicitors are mostly overlapping but partially distinct and thus they would coordinate the direct and indirect defense responses in host plants under spider mite attack in both shared and distinct manners.

DOI： 10.1111/nph.15813

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Informa UK Limited  

DOI： 10.1080/15592324.2019.1655335

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Language：English   Publishing type：Research paper (scientific journal)  

© 2019 Mitalo, Tokiwa, Kondo, Otsuki, Galis, Suezawa, Kataoka, Doan, Nakano, Ushijima and Kubo. Fruit ripening in response to propylene (an ethylene analog), 1-methylcyclopropene (1-MCP, an ethylene action inhibitor), and low temperature (5°C) treatments was characterized in “Kosui” kiwifruit (Actinidia rufa × A. chinensis). Propylene treatment induced ethylene production, with increased expression levels of 1-aminocyclopropane-1-carboxylic acid (ACC) synthase 1 (AcACS1) and ACC oxidase 2 (AcACO2), and rapid fruit softening together with increased expression levels of polygalacturonase (AcPG) and expansin 1 (AcEXP1) within 5 days (d). Fruit soluble solids concentration (SSC) and contents of sucrose, glucose, and fructose together with the expression levels of β-amylase 1 (Acβ-AMY1), Acβ-AMY2, and invertase (AcINV3-1) increased rapidly after 5 d exposure to propylene. Furthermore, propylene exposure for 5 d was sufficient to induce the production of key aroma volatile compounds, ethyl- and methyl butanoate, accompanied with increased expression levels of alcohol acyl transferase (AcAAT). Application of 1-MCP at the start of the experiment, followed by continuous exposure to propylene, significantly delayed fruit softening, changes in SSC and sugars, and strongly suppressed the production of ethylene, aroma volatiles, and expression of associated genes. During storage, fruit softening, SSC and sugar increase, and increased expression of genes associated with cell wall modification and carbohydrate metabolism were registered without detectable ethylene production; however, these changes occurred faster at 5°C compared to 22°C. Interestingly, ethyl and methyl butanoate as well as AcAAT expression were undetectable in kiwifruit during storage, while they were rescued by post-storage propylene exposure, indicating that the production of aroma volatile compounds is strongly ethylene-dependent. Transcript levels of a NAC-related transcription factor (TF), AcNAC3, increased in response to both propylene and low temperature treatments, while AcNAC5 was exclusively up-regulated by propylene. By contrast, transcript levels of a MADS-box TF, AcMADS2, exclusively increased in response to low temperature. The above findings indicate that kiwifruit ripening is inducible by either ethylene or low temperature signals. However, fruit ripened by low temperature were deficient in ethylene-dependent aroma volatiles, suggesting that ethylene signaling is non-functional during low temperature-modulated ripening in kiwifruit. These data provide further evidence that ethylene-dependent and low temperature-modulated ripening in kiwifruit involve different regulatory mechanisms.

DOI： 10.3389/fpls.2019.00888

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

Feeding of sucking insects, such as the rice brown planthopper (Nilaparvata lugens; BPH), causes only limited mechanical damage on plants that is otherwise essential for injury-triggered defense responses against herbivores. In pursuit of complementary BPH elicitors perceived by plants, we examined the potential effects of BPH honeydew secretions on the BPH monocot host, rice (Oryza sativa). We found that BPH honeydew strongly elicits direct and putative indirect defenses in rice, namely accumulation of phytoalexins in the leaves, and release of volatile organic compounds from the leaves that serve to attract natural enemies of herbivores, respectively. We then examined the elicitor active components in the honeydew and found that bacteria in the secretions are responsible for the activation of plant defense. Corroborating the importance of honeydew-associated microbiota for induced plant resistance, BPHs partially devoid of their microbiota via prolonged antibiotics ingestion induced significantly less defense in rice relative to antibiotic-free insects applied to similar groups of plants. Our data suggest that rice plants may additionally perceive herbivores via their honeydew-associated microbes, allowing them to discriminate between incompatible herbivores-that do not produce honeydew-and those that are compatible and therefore dangerous.

DOI： 10.1093/jxb/erz041

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Other Link： http://orcid.org/0000-0001-9840-8845

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

Plant defense against herbivores is modulated by herbivore-associated molecular patterns (HAMPs) from oral secretions (OS) and/or saliva of insects. Furthermore, feeding wounds initiate plant self-damage responses modulated by danger-associated molecular patterns (DAMPs) such as immune defense-promoting plant elicitor peptides (Peps). While temporal and spatial co-existence of both patterns during herbivory implies a possibility of their close interaction, the molecular mechanisms remain undetermined. Here we report that exogenous application of rice (Oryza sativa) peptides (OsPeps) can elicit multiple defense responses in rice cell cultures. Specific activation of OsPROPEP3 gene transcripts in rice leaves by wounding and OS treatments further suggests a possible involvement of the OsPep3 peptide in rice-herbivore interactions. Correspondingly, we found that simultaneous application of OsPep3 and Mythimna loreyi OS significantly amplifies an array of defense responses in rice cells, including mitogen-activated protein kinase activation, and generation of defense-related hormones and metabolites. The induction of OsPROPEP3/4 by OsPep3 points to a positive auto-feedback loop in OsPep signaling which may contribute to additional enhancement of defense signal(s). Finally, the overexpression of the OsPep receptor OsPEPR1 increases the sensitivity of rice plants not only to the cognate OsPeps but also to OS signals. Our findings collectively suggest that HAMP-DAMP signal integration provides a critical step in the amplification of defense signaling in plants.

DOI： 10.1111/tpj.13883

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER GMBH, URBAN & FISCHER VERLAG  

Pseudomonas syringae pv. tabaci causes wildfire disease by the action of tabtoxinine-beta-lactam (T beta L), a non-specific bacterial toxin. To better understand the molecular mechanisms of wildfire disease and its development, we focused on the phosphoinositide 3-kinase in Nicotiana benthamiana (NbPI3K) and its potential role in the disease outbreak, using L-methionine sulfoximine (MSX) as an easily accessible mimic of the T beta L action. The NbPI3K-silenced plants showed accelerated induction of cell death and necrotic lesion formation by MSX, and the expression of hin1, marker gene for the programmed cell death, was strongly induced in the plants. However, the accumulation of ammonium ions, caused by MSX inhibition of glutamine sythetase activity, was not affected by the NbPI3K-silencing. Interestingly, the expression of PR-1a, a marker gene for salicylic acid (SA) innate immunity signaling, and accumulation of SA were both enhanced in the NbPI3K-silenced plants. Accordingly, the acceleration of MSX-induced cell death by NbPI3K-silencing was reduced in NahG plants, and by double silencing of NbPI3K together with the NbICS1 encoding a SA-biosynthetic enzyme. As silencing of NbPI3K accelerated the T beta L-induced necrotic lesions, and lesions of wildfire disease caused by P. syringae pv. tabaci, these results suggest that the NbPI3K-related pathway might act as a negative regulator of cell death during development of wildfire disease that involves SA-dependent signaling pathway downstream of T beta L action in N. benthamiana.

DOI： 10.1016/j.jplph.2017.07.016

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

Plants synthesize variable mixtures of herbivore-induced plant volatiles (HIPVs) as part of their evolutionary conserved defense. To elucidate the impact of chewing herbivores with different level of adaptation on HIPV profiles in rice, we measured HIPVs released from rice seedlings challenged by either the generalist herbivore Mythimna loreyi (MYL) or the specialist Parnara guttata (PAG). Both herbivores markedly elicited the emission of HIPVs, mainly on the second and third days after attack compared to control plants. In addition, side-by-side HIPV comparisons using MYL and PAG caterpillars revealed that generalist feeding induced comparably more HIPVs relative to specialist, particularly on day two as highlighted by multivariate analysis (PLS-DA) of emitted HIPVs, and further confirmed in mimicked herbivory experiments. Here, mechanically wounded plants treated with water (WW) released more VOCs than untreated controls, and on top of this, oral secretions (OS) from both herbivores showed differential effects on volatile emissions from the wounded plants. Similar to actual herbivory, MYL OS promoted higher amounts of HIPVs relative to PAG OS, thus supporting disparate induction of rice indirect defenses in response to generalist and specialist herbivores, which could be due to the differential composition of their OS. (196 words).

DOI： 10.1007/s10886-017-0882-4

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OXFORD UNIV PRESS  

Insects such as the beet armyworm (Spodoptera exigua) cause extensive damage to maize (Zea mays). Maize plants respond by triggering defense signaling, changes in gene expression, and biosynthesis of specialized metabolites. Leaves of maize inbred line B73, which has an available genome sequence, were infested with S. exigua for 1 to 24 h, followed by comparisons of the transcript and metabolite profiles with those of uninfested controls. The most extensive gene expression responses occurred rapidly, within 4-6 h after caterpillar infestation. However, both gene expression and metabolite profiles were altered within 1 h and continued to change during the entire 24 h experiment. The defensive functions of three caterpillar-induced genes were examined using available Dissociation transposon insertions in maize inbred line W22. Whereas mutations in the benzoxazinoid biosynthesis pathway (Bx1 and Bx2) significantly improved caterpillar growth, the knockout of a 13-lipoxygenase (Lox8) involved in jasmonic acid biosynthesis did not. Interestingly, 9-lipoxygenases, which lead to the production of maize death acids, were more strongly induced by caterpillar feeding than 13-lipoxygenases, suggesting an as yet unknown function in maize defense against herbivory. Together, these results provide a comprehensive view of the dynamic transcriptomic and metabolomic responses of maize leaves to caterpillar feeding.

DOI： 10.1093/jxb/erx274

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OXFORD UNIV PRESS  

The aluminum-activated malate transporter (ALMT) family of proteins transports malate and/or inorganic anions across plant membranes. To demonstrate the possible role of ALMT genes in tomato fruit development, we focused on SlALMT4 and SlALMT5, the two major genes expressed during fruit development. Predicted proteins were classified into clade 2 of the family, many members of which localize to endomembranes. Tissue-specific gene expression was determined using transgenic tomato expressing the beta-glucuronidase reporter gene controlled by their own promoters. Both the genes were expressed in vascular bundles connecting to developing seeds in fruit and in the embryo of mature seeds. Further, SlALMT5 was expressed in embryo in developing seeds in fruit. Subcellular localization of both proteins to the endoplasmic reticulum (ER) was established by transiently expressing the green fluorescent protein fusions in plant protoplasts. SlALMT5 probably localized to other endomembranes as well. Localization of SlALMT5 to the ER was also confirmed by immunoblot analysis. The transport function of both SlALMT proteins was investigated electrophysiologically in Xenopus oocytes. SlALMT5 transported malate and inorganic anions such as nitrate and chloride, but not citrate. SlALMT4 also transported malate, but the results were less consistent perhaps because it did not localize strongly to the plasma membrane. To elucidate the physiological role of SlALMT5 further, we over-expressed SlALMT5 in tomato. Compared with the wild type, overexpressors exhibited higher malate and citrate contents in mature seeds, but not in fruit. We conclude that the malate transport function of SlALMT5 expressed in developing fruit influences the organic acid contents in mature seeds.

DOI： 10.1093/pcp/pcw157

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

Two phenolamides (PAs), p-coumaroylputrescine and feruloylputrescine strongly accumulate in rice (Oryza sativa cv. Nipponbare) leaves subjected to attack of chewing and sucking herbivores. Here we identified and characterized in vitro three novel rice genes that mediated coumaroyl-CoA/feruloyl-CoA conjugation to polyamines, putrescine and agmatine. Interestingly, two genes were highly specific for their polyamine substrates, encoding putrescine N-hydroxycinnamoyltransferase and agmatine N-hydroxycinnamoyltransferase, while the third enzyme could use both polyamines and it was therefore annotated as putrescine/agmatine N-hydroxycinnamoyltransferase. All genes were preferentially expressed in rice roots and developing flowers, and in addition, the putrescine/agmatine N-hydroxycinnamoyltransferase transcripts were strongly induced by wounding in the young rice leaves. Because the wound response of this gene was only partially suppressed in the jasmonoyl-L-isoleucine deficient plants (Osjar1), it suggests that its upregulation (as well as inducible PAs in rice) may be largely independent of jasmonoyl-L-isoleucine signaling pathway. The finding of three closely related genes with a similar and/or overlapping activity in PA biosynthesis provides another striking example of rapid diversification of plant metabolism in response to environmental stresses in nature.

DOI： 10.1111/jipb.12480

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PUBLISHING GROUP  

Induced plant defense responses against insect herbivores are triggered by wounding and/or perception of herbivore elicitors from their oral secretions (OS) and/or saliva. In this study, we analyzed OS isolated from two rice chewing herbivores, Mythimna loreyi and Parnara guttata. Both types of crude OS had substantial elicitor activity in rice cell system that allowed rapid detection of early and late defense responses, i.e. accumulation of reactive oxygen species (ROS) and defense secondary metabolites, respectively. While the OS from M. loreyi contained large amounts of previously reported insect elicitors, fatty acid-amino acid conjugates (FACs), the elicitor-active P. guttata's OS contained no detectable FACs. Subsequently, elicitor activity associated with the high molecular mass fraction in OS of both herbivores was identified, and shown to promote ROS and metabolite accumulations in rice cells. Notably, the application of N-linolenoyl-Gln (FAC) alone had only negligible elicitor activity in rice cells; however, the activity of isolated elicitor fraction was substantially promoted by this FAC. Our results reveal that plants integrate various independent signals associated with their insect attackers to modulate their defense responses and reach maximal fitness in nature.

DOI： 10.1038/srep32537

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPANESE SOC PLANT CELL & MOLECULAR BIOLOGY  

We previously identified SEC14, phospholipid transfer protein superfamily gene, in Nicotiana benthamiana (NbSEC14) that was closely related to phospholipid signaling as well as jasmonic acid-dependent defense responses during plant immune responses against Ralstonia solanacearum. To examine effect of NbSEC14-silencing on basal plant defenses, we used two other bacterial pathogens with different virulent strategies, Pseudomonas syringae pv. tabaci and pv. mellea. NbSEC14-silenced plants showed accelerated growth of P. syringae pv. tabaci and pv. mellea, and formation of necrotic lesions. Induction of JA-related PR-4 gene was compromised in NbSEC14-silenced plants, which was supported by reduced jasmonic acid levels in NbSEC14-silenced plants. These results suggested that NbSEC14 might be regulating plant basal resistance against plant pathogenic Pseudomonads via jasmonic acid-dependent signaling pathway.

DOI： 10.5511/plantbiotechnology.16.0503a

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

Plants defend against attack from herbivores by direct and indirect defence mechanisms mediated by the accumulation of phytoalexins and release of volatile signals, respectively. While the defensive arsenals of some plants, such as tobacco and Arabidopsis are well known, most of rice's (Oryza sativa) defence metabolites and their effectiveness against herbivores remain uncharacterized. Here, we used a non-biassed metabolomics approach to identify many novel herbivory-regulated metabolic signatures in rice. Most were up-regulated by herbivore attack while only a few were suppressed. Two of the most prominent up-regulated signatures were characterized as phenolamides (PAs), p-coumaroylputrescine and feruloylputrescine. PAs accumulated in response to attack by both chewing insects, i. e. feeding of the lawn armyworm (Spodoptera mauritia) and the rice skipper (Parnara guttata) larvae, and the attack of the sucking insect, the brown planthopper (Nilaparvata lugens, BPH). In bioassays, BPH insects feeding on 15% sugar solution containing p-coumaroylputrescine or feruloylputrescine, at concentrations similar to those elicited by heavy BPH attack in rice, had a higher mortality compared to those feeding on sugar diet alone. Our results highlight PAs as a rapidly expanding new group of plant defence metabolites that are elicited by herbivore attack, and deter herbivores in rice and other plants.

DOI： 10.1111/pce.12640

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：BioMed Central Ltd.  

Background: Although leaf herbivory-induced changes in allocation of recently assimilated carbon between the shoot and below-ground tissues have been described in several species, it is still unclear which part of the root system is affected by resource allocation changes and which signalling pathways are involved. We investigated carbon partitioning in root tissues following wounding and simulated leaf herbivory in young Nicotiana attenuata plants. Results: Using 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG), which was incorporated into disaccharides in planta, we found that simulated herbivory reduced carbon partitioning specifically to the root tips in wild type plants. In jasmonate (JA) signalling-deficient COI1 plants, the wound-induced allocation of [18F]FDG to the roots was decreased, while more [18F]FDG was transported to young leaves, demonstrating an important role of the JA pathway in regulating the wound-induced carbon partitioning between shoots and roots. Conclusions: Our data highlight the use of [18F]FDG to study stress-induced carbon allocation responses in plants and indicate an important role of the JA pathway in regulating wound-induced shoot to root signalling.

DOI： 10.1186/s13104-015-0989-z

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER  

Using an in vitro system composed of crushed leaf tissues to simulate the wounding response in rice leaves, we established that synthesis of jasmonic acid (JA) and jasmonic acid-isoleucine (JA-Ile) can only occur in unwounded tissue and, in wounded tissue, that only the chloroplast-located section of the octadecanoid pathway is active, resulting in the accumulation of 12-oxo-phytodienoic acid (OPDA). We further showed that OPDA accumulation in vitro was inhibited by 90% using the general lipase inhibitor, tetrahydrolipstatin, indicating that production of a-linolenic acid was the rate-limiting step in octadecanoid pathway activity in rice following wounding and the enzyme capacity for an active pathway was already present. We confirmed this result by showing that added a-linolenic acid stimulated OPDA synthesis in vitro and stimulated OPDA, JA and JA-Ile synthesis in vivo in unwounded tissue. Thus, the response to wounding can be mimicked by the provision of free a-linolenic acid. Our results draw attention to the key importance of lipase activity in initiation of JA and JA-Ile biosynthesis and our lack of knowledge of the cognate lipase(s), lipase substrate identity and mechanism(s) of activation in wounded and unwounded tissue. (C) 2014 Elsevier Masson SAS. All rights reserved.

DOI： 10.1016/j.plaphy.2014.07.013

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PUBLIC LIBRARY SCIENCE  

Anthocyanin pigments and associated flavonoids have demonstrated antioxidant properties and benefits for human health. Consequently, current plant bioengineers have focused on how to modify flavonoid metabolism in plants. Most of that research, however, does not consider the role of natural biotic stresses (e.g., herbivore attack). To understand the influence of herbivore attack on the metabolic engineering of flavonoids, we examined tobacco plants overexpressing the Arabidopsis PAP1 gene (encoding an MYB transcription factor), which accumulated anthocyanin pigments and other flavonoids/phenylpropanoids. In comparison to wild-type and control plants, transgenic plants exhibited greater resistance to Spodoptera litura. Moreover, herbivory suppressed the PAP1-induced increase of transcripts of flavonoid/phenylpropanoid biosynthetic genes (e.g., F3H) and the subsequent accumulation of these genes' metabolites, despite the unaltered PAP1 mRNA levels after herbivory. The instances of down-regulation were independent of the signaling pathways mediated by defense-related jasmonates but were relevant to the levels of PAP1-induced and herbivory-suppressed transcription factors, An1a and An1b. Although initially F3H transcripts were suppressed by herbivory, after the S. litura feeding was interrupted, F3H transcripts increased. We hypothesize that in transgenic plants responding to herbivory, there is a complex mechanism regulating enriched flavonoid/phenylpropanoid compounds, via biotic stress signals.

DOI： 10.1371/journal.pone.0108849

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATL ACAD SCIENCES  

Plants receive volatile compounds emitted by neighboring plants that are infested by herbivores, and consequently the receiver plants begin to defend against forthcoming herbivory. However, to date, how plants receive volatiles and, consequently, how they fortify their defenses, is largely unknown. In this study, we found that undamaged tomato plants exposed to volatiles emitted by conspecifics infested with common cutworms (exposed plants) became more defensive against the larvae than those exposed to volatiles from uninfested conspecifics (control plants) in a constant airflow system under laboratory conditions. Comprehensive metabolite analyses showed that only the amount of (Z)-3-hexenyl-vicianoside (HexVic) was higher in exposed than control plants. This compound negatively affected the performance of common cutworms when added to an artificial diet. The aglycon of HexVic, (Z)-3-hexenol, was obtained from neighboring infested plants via the air. The amount of jasmonates (JAs) was not higher in exposed plants, and HexVic biosynthesis was independent of JA signaling. The use of (Z)-3-hexenol from neighboring damaged conspecifics for HexVic biosynthesis in exposed plants was also observed in an experimental field, indicating that (Z)-3-hexenol intake occurred even under fluctuating environmental conditions. Specific use of airborne (Z)-3-hexenol to form HexVic in undamaged tomato plants reveals a previously unidentified mechanism of plant defense.

DOI： 10.1073/pnas.1320660111

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PUBLIC LIBRARY SCIENCE  

We previously identified a gene related to the SEC14-gene phospholipid transfer protein superfamily that is induced in Nicotiana benthamiana (NbSEC14) in response to infection with Ralstonia solanacearum. We here report that NbSEC14 plays a role in plant immune responses via phospholipid-turnover. NbSEC14-silencing compromised expression of defense-related PR-4 and accumulation of jasmonic acid (JA) and its derivative JA-Ile. Transient expression of NbSEC14 induced PR-4 gene expression. Activities of diacylglycerol kinase, phospholipase C and D, and the synthesis of diacylglycerol and phosphatidic acid elicited by avirulent R. solanacearum were reduced in NbSEC14-silenced plants. Accumulation of signaling lipids and activation of diacylglycerol kinase and phospholipases were enhanced by transient expression of NbSEC14. These results suggest that the NbSEC14 protein plays a role at the interface between lipid signaling-metabolism and plant innate immune responses.

DOI： 10.1371/journal.pone.0098150

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

The deposition of surface (farinose) flavonoids on aerial parts of some Primula species is a well-documented but poorly understood phenomenon. Here, we show that flavonoid deposition on the leaves and winter buds may contribute strongly to preventing freezing damage in these plants. The ice nucleation temperature of fairy primrose (Primula malacoides) leaves covered with natural flavone was approximately 6 degrees C lower compared to those that had their flavone artificially removed. Additionally, farinose flavonoids on the leaves reduced subsequent electrolyte leakage (EL) from the cells exposed to freezing temperatures. Interestingly, exogenous application of flavone at 4mg/g fresh weight to P. malacoides leaves, which had the original flavone mechanically removed, restored freezing tolerance, and diminished EL from the cells to pretreatment values. Our results suggest that farinose flavonoids may function as mediators of freezing tolerance in P. malacoides, and exogenous application of flavone could be used to reduce freezing damage during sudden but predictable frost events in other plant species.

DOI： 10.1111/jipb.12145

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Landes Bioscience  

The jasmonate signaling pathway is essential for plant development, reproduction, and defense against herbivores and pathogens. When attacked by herbivores, plants elicit defense responses through the rapid accumulation of jasmonates. Although the transduction of the jasmonate burst into downstream responses has been largely resolved in the past decade, how the jasmonate burst is switched off remained unknown. Recently, two mechanisms that involve cytochrome p450-mediated hydroxylation/carboxylation and NaJIH 1-mediated hydrolysis of JA-Ile were identified as major termination mechanisms of JA signaling. Due to a lack of hydrolysis, Nicotiana attenuata plants silenced in the expression of the JIH1 gene accumulated significantly more JA-Ile than did wild type plants and became more resistant to herbivore attack. Although less likely, additional functions of JIH 1, such as contributing to the pool of free Ile and thereby increasing JA-Ile accumulation, remained untested. Here we show that increased isoleucine availability does not explain the observed phenotype in JIH 1-deficient N. attenuata plants © 2014 Landes Bioscience.

DOI： 10.4161/psb.28973

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

Previously, we identified a novel herbivore elicitor-regulated protein in Nicotiana attenuata (nahEr1) that is required to suppress abscisic acid (aBa) catabolism during herbivore attack and activate a full defense response against herbivores. aBa, in addition to its newly defined role in defense activation, mainly controls seed germination and stomatal function of land plants. here we show that N. attenuata seeds silenced in the expression of NaHER1 by rna interference (irhEr1) accumulated less aBa during germination, and germinated faster on aBa-containing media compared with Wt. Curiously, epidermal cells of irhEr1 plants were wrinkled, possibly due to the previously demonstrated increase in transpiration of irhEr1 plants that may affect turgor and cause wrinkling of the cells. We conclude that nahEr1 is a highly pleiotropic regulator of aBa responses in N. attenuata plants. © 2013 Landes Bioscience.

DOI： 10.4161/psb.26365

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

Nicotiana attenuata plants can distinguish the damage caused by herbivore feeding from other types of damage by perceiving herbivore-associated elicitors, such as the fatty acid-amino acid conjugates (FACs) in oral secretions (OS) of Manduca sexta larvae, which are introduced into wounds during feeding. However, the transduction of FAC signals into downstream plant defense responses is still not well established. We identified a novel FAC-regulated protein in N. attenuata (NaHER1
for herbivore elicitor regulated) and show that it is an indispensable part of the OS signal transduction pathway. N. attenuata plants silenced in the expression of NaHER1 by RNA interference (irHER1) were unable to amplify their defenses beyond basal, wound-induced levels in response to OS elicitation. M. sexta larvae performed 2-fold better when reared on irHER1 plants, which released less volatile organic compounds (indirect defense) and had strongly reduced levels of several direct defense metabolites, including trypsin proteinase inhibitors, 17-hydroxygeranyllinallool diterpene glycosides, and caffeoylputrescine, after real and/or simulated herbivore attack. In parallel to impaired jasmonate signaling and metabolism, irHER1 plants were more drought sensitive and showed reduced levels of abscisic acid (ABA) in the leaves, suggesting that silencing of NaHER1 interfered with ABA metabolism. Because treatment of irHER1 plants with ABA results in both the accumulation of significantly more ABA catabolites and the complete restoration of normal wild-type levels of OS-induced defense metabolites, we conclude that NaHER1 acts as a natural suppressor of ABA catabolism after herbivore attack, which, in turn, activates the full defense profile and resistance against herbivores. © 2013 American Society of Plant Biologists. All Rights Reserved.

DOI： 10.1104/pp.113.221150

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

Plants produce jasmonic acid (JA) and its amino acid conjugate, jasmonoyl-L-isoleucine (JA-Ile) as major defense signals in response to wounding and herbivory. In rice (Oryza sativa), JA and JA-Ile rapidly increased after mechanical damage, and this increase was further amplified when the wounds were treated with oral secretions from generalist herbivore larvae, lawn armyworms (Spodoptera mauritia), revealing for the first time active perception mechanisms of herbivore-associated elicitor(s) in rice. In the rice genome, two OsJAR genes can conjugate JA and Ile and form JA-Ile in vitro; however, their function in herbivory-induced accumulation of JA-Ile has not been investigated. By functional characterization of TOS17 retrotransposon-tagged Osjar1 plants and their response to simulated herbivory, we show that OsJAR1 is essential for JA-Ile production in herbivore-attacked, field-grown plants. In addition, OsJAR1 was required for normal seed development in rice under field conditions. Our results suggest that OsJAR1 possesses at least two major functions in rice defense and development that cannot be complemented by the additional OsJAR2 gene function, although this gene previously showed overlapping enzyme activity in vitro.

DOI： 10.1111/jipb.12057

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：BIOMED CENTRAL LTD  

Background: To survive herbivore attack, plants have evolved potent mechanisms of mechanical or chemical defense that are either constitutively present or inducible after herbivore attack. Due to the costs of defense deployment, plants often regulate their biosynthesis using various transcription factors (TFs). MYC2 regulators belong to the bHLH family of transcription factors that are involved in many aspects of plant defense and development. In this study, we identified a novel MYC2 TF from N. attenuata and characterized its regulatory function using a combination of molecular, analytic and ecological methods.
Results: The transcript and targeted metabolite analyses demonstrated that NaMYC2 is mainly involved in the regulation of the biosynthesis of nicotine and phenolamides in N. attenuata. In addition, using broadly-targeted metabolite analysis, we identified a number of other metabolite features that were regulated by NaMYC2, which, after full annotation, are expected to broaden our understanding of plant defense regulation. Unlike previous reports, the biosynthesis of jasmonates and some JA-/NaCOI1-dependent metabolites (e.g. HGL-DTGs) were not strongly regulated by NaMYC2, suggesting the involvement of other independent regulators. No significant differences were observed in the performance of M. sexta on MYC2-silenced plants, consistent with the well-known ability of this specialist insect to tolerate nicotine.
Conclusion: By regulating the biosynthesis of nicotine, NaMYC2 is likely to enhance plant resistance against non-adapted herbivores and contribute to plant fitness; however, multiple JA/NaCOI1-dependent mechanisms (perhaps involving other MYCs) that regulate separate defense responses are likely to exist in N. attenuata. The considerable variation observed amongst different plant families in the responses regulated by jasmonate signaling highlights the sophistication with which plants craft highly specific and fine-tuned responses against the herbivores that attack them.

DOI： 10.1186/1471-2229-13-73

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PUBLIC LIBRARY SCIENCE  

In a transcriptomic screen of Manduca sexta-induced N-acyltransferases in leaves of Nicotiana attenuata, we identified an N-acyltransferase gene sharing a high similarity with the tobacco lignin-biosynthetic hydroxycinnamoyl-CoA: shikimate/quinate hydroxycinnamoyl transferase (HCT) gene whose expression is controlled by MYB8, a transcription factor that regulates the production of phenylpropanoid polyamine conjugates (phenolamides, PAs). To evaluate the involvement of this HCT-like gene in lignin production as well as the resulting crosstalk with PA metabolism during insect herbivory, we transiently silenced (by VIGs) the expression of this gene and performed non-targeted (UHPLC-ESI/TOF-MS) metabolomics analyses. In agreement with a conserved function of N. attenuata HCT-like in lignin biogenesis, HCT-silenced plants developed weak, soft stems with greatly reduced lignin contents. Metabolic profiling demonstrated large shifts (up to 12% deregulation in total extracted ions in insect-attacked leaves) due to a large diversion of activated coumaric acid units into the production of developmentally and herbivory-induced coumaroyl-containing PAs (N', N ''-dicoumaroylspermidine, N', N ''-coumaroylputrescine, etc) and to minor increases in the most abundant free phenolics (chlorogenic and cryptochlorogenic acids), all without altering the production of well characterized herbivory-responsive caffeoyl-and feruloyl-based putrescine and spermidine PAs. These data are consistent with a strong metabolic tension, exacerbated during herbivory, over the allocation of coumaroyl-CoA units among lignin and unusual coumaroyl-containing PAs, and rule out a role for HCT-LIKE in tuning the herbivory-induced accumulation of other PAs. Additionally, these results are consistent with a role for lignification as an induced anti-herbivore defense.

DOI： 10.1371/journal.pone.0062336

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY  

Depending on geographical location, plants are exposed to variable amounts of UVB radiation and herbivore attack. Because the role(s) of UVB in the priming and/or accumulation of plant defence metabolites against herbivores are not well understood, we used field-grown Nicotiana attenuata plants to explore the effects of UVB on herbivore performance. Consistent with previous reports, UVB-exposed plants accumulated higher levels of ultraviolet (UV)-absorbing compounds (rutin, chlorogenic acid, crypto-chlorogenic acid and dicaffeoylspermidine). Furthermore, UVB increased the accumulation of jasmonic acid, jasmonoyl-L-isoleucine and abscisic acid, all phytohormones which regulate plant defence against biotic and abiotic stress. In herbivore bioassays, N. attenuata plants experimentally protected from UVB were more infested by mirids in three consecutive field seasons. Among defence metabolites measured, 17-hydroxygeranyllinalool diterpene glycosides (HGL-DTGs) showed strongly altered accumulation patterns. While constitutive HGL-DTGs levels were higher under UVB, N. attenuata plants exposed to mirid bugs (Tupiocoris notatus) had still more HGL-DTGs under UVB, and mirids preferred to feed on HGL-DTGs-silenced plants when other UVB protecting factors were eliminated by UVB filters. We conclude that UVB exposure not only stimulates UV protective screens but also affects plant defence mechanisms, such as HGL-DTGs accumulation, and modulates ecological interactions of N. attenuata with its herbivores in nature.

DOI： 10.1111/j.1365-3040.2012.02598.x

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：PUBLIC LIBRARY SCIENCE  

Jasmonic acid is an important regulator of plant growth, development and defense. The jasmonate-ZIM domain (JAZ) proteins are key regulators in jasmonate signaling ubiquitously present in flowering plants but their functional annotation remains largely incomplete. Recently, we identified 12 putative JAZ proteins in native tobacco, Nicotiana attenuata, and initiated systematic functional characterization of these proteins by reverse genetic approaches. In this report, Nicotiana attenuata plants silenced in the expression of NaJAZd (irJAZd) by RNA interference were used to characterize NaJAZd function. Although NaJAZd transcripts were strongly and transiently up-regulated in the rosette leaves by simulated herbivory treatment, we did not observe strong defense-related phenotypes, such as altered herbivore performance or the constitutive accumulation of defense-related secondary metabolites in irJAZd plants compared to wild type plants, both in the glasshouse and the native habitat of Nicotiana attenuata in the Great Basin Desert, Utah, USA. Interestingly, irJAZd plants produced fewer seed capsules than did wild type plants as a result of increased flower abscission in later stages of flower development. The early-and mid-developmental stages of irJAZd flowers had reduced levels of jasmonic acid and jasmonoyl-L-isoleucine, while fully open flowers had normal levels, but these were impaired in NaMYB305 transcript accumulations. Previously, NaMYB305-silenced plants were shown to have strong flower abscission phenotypes and contained lower NECTARIN 1 transcript levels, phenotypes which are copied in irJAZd plants. We propose that the NaJAZd protein is required to counteract flower abscission, possibly by regulating jasmonic acid and jasmonoyl-L-isoleucine levels and/or expression of NaMYB305 gene in Nicotiana attenuata flowers. This novel insight into the function of JAZ proteins in flower and seed development highlights the diversity of functions played by jasmonates and JAZ proteins.

DOI： 10.1371/journal.pone.0057868

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

For most plant hormones, biological activity is suppressed by reversible conjugation to sugars, amino acids and other small molecules. In contrast, the conjugation of jasmonic acid (JA) to isoleucine (Ile) is known to enhance the activity of JA. Whereas hydroxylation and carboxylation of JA-Ile permanently inactivates JA-Ile-mediated signaling in plants, the alternative deactivation pathway of JA-Ile by its direct hydrolysis to JA remains unstudied. We show that Nicotiana attenuata jasmonoyl-l-isoleucine hydrolase 1 (JIH1), a close homologue of previously characterized indoleacetic acid alanine resistant 3 (IAR3) gene in Arabidopsis, hydrolyzes both JA-Ile and IAA-Ala in vitro. When the herbivory-inducible NaJIH1 gene was silenced by RNA interference, JA-Ile levels increased dramatically after simulated herbivory in irJIH1, compared with wild-type (WT) plants. When specialist (Manduca sexta) or generalist (Spodoptera littoralis) herbivores fed on irJIH1 plants they gained significantly less mass compared with those feeding on wild-type (WT) plants. The poor larval performance was strongly correlated with the higher accumulation of several JA-Ile-dependent direct defense metabolites in irJIH1 plants. In the field, irJIH1 plants attracted substantially more Geocoris predators to the experimentally attached M. sexta eggs on their leaves, compared with empty vector plants, which correlated with higher herbivory-elicited emissions of volatiles known to function as indirect defenses. We conclude that NaJIH1 encodes a new homeostatic step in JA metabolism that, together with JA and JA-Ile-hydroxylation and carboxylation of JA-Ile, rapidly attenuates the JA-Ile burst, allowing plants to tailor the expression of direct and indirect defenses against herbivore attack in nature.

DOI： 10.1111/j.1365-313X.2012.05117.x

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER SOC PLANT BIOLOGISTS  

The role of the alternative respiratory pathway in the protection of plants against biotic stress was examined in transgenic tobacco (Nicotiana attenuata) plants (irAOX) silenced in the expression of ALTERNATIVE OXIDASE (AOX) gene. Wild-type and irAOX plants were independently challenged with (1) chewing herbivores (Manduca sexta), (2) piercing-sucking insects (Empoasca spp.), and (3) bacterial pathogens (Pseudomonas syringae pv tomato DC3000), showing that all these treatments can strongly elicit accumulation of AOX gene transcripts in wild-type plants. When N. attenuata chemical defenses and resistance were examined, irAOX plants showed wild-type levels of defense-related phytohormones, secondary metabolites, and resistance to M. sexta. In contrast, piercing-sucking leafhoppers (Empoasca spp.) caused more leaf damage and induced significantly higher salicylic acid levels in irAOX compared with wild-type plants in the field and/or glasshouse. Subsequently, irAOX plants accumulated lower levels of defense metabolites, 17-hydroxygeranyllinalool diterpene glycosides, caffeoylputrescine, and nicotine compared with wild-type plants under prolonged attack of Empoasca spp. in the glasshouse. Finally, an accelerated cell death phenotype was observed in irAOX plants infected with P. syringae, which correlated with higher levels of salicylic acid and hydrogen peroxide levels in pathogen-infected irAOX compared with wild-type leaves. Overall, the AOX-associated changes in phytohormone and/or redox levels appear to support the resistance of N. attenuata plants against cell piercing-sucking insects and modulate the progression of cell death in pathogen-infected tissues but are not effective against rapidly feeding specialist herbivore M. sexta.

DOI： 10.1104/pp.112.200865

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER SOC PLANT BIOLOGISTS  

The organized lignocellulosic assemblies of cell walls provide the structural integrity required for the large statures of terrestrial plants. Silencing two CINNAMYL ALCOHOL DEHYDROGENASE (CAD) genes in Nicotiana attenuata produced plants (ir-CAD) with thin, red-pigmented stems, low CAD and sinapyl alcohol dehydrogenase activity, low lignin contents, and rubbery, structurally unstable stems when grown in the glasshouse (GH). However, when planted into their native desert habitat, ir-CAD plants produced robust stems that survived wind storms as well as the wild-type plants. Despite efficient silencing of NaCAD transcripts and enzymatic activity, field-grown ir-CAD plants had delayed and restricted spread of red stem pigmentation, a color change reflecting blocked lignification by CAD silencing, and attained wild-type-comparable total lignin contents. The rubbery GH phenotype was largely restored when field-grown ir-CAD plants were protected from wind, herbivore attack, and ultraviolet B exposure and grown in restricted rooting volumes; conversely, it was lost when ir-CAD plants were experimentally exposed to wind, ultraviolet B, and grown in large pots in growth chambers. Transcript and liquid chromatography-electrospray ionization-time-of-flight analysis revealed that these environmental stresses enhanced the accumulation of various phenylpropanoids in stems of field-grown plants; gas chromatography-mass spectrometry and nuclear magnetic resonance analysis revealed that the lignin of field-grown ir-CAD plants had GH-grown comparable levels of sinapaldehyde and syringaldehyde cross-linked into their lignins. Additionally, field-grown ir-CAD plants had short, thick stems with normal xylem element traits, which collectively enabled field-grown ir-CAD plants to compensate for the structural deficiencies associated with CAD silencing. Environmental stresses play an essential role in regulating lignin biosynthesis in lignin-deficient plants.

DOI： 10.1104/pp.112.196717

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER SOC PLANT BIOLOGISTS  

The JASMONATE ZIM DOMAIN (JAZ) proteins function as negative regulators of jasmonic acid signaling in plants. We cloned 12 JAZ genes from native tobacco (Nicotiana attenuata), including nine novel JAZs in tobacco, and examined their expression in plants that had leaves elicited by wounding or simulated herbivory. Most JAZ genes showed strong expression in the elicited leaves, but NaJAZg was mainly expressed in roots. Another novel herbivory-elicited gene, NaJAZh, was analyzed in detail. RNA interference suppression of this gene in inverted-repeat (ir)JAZh plants deregulated a specific branch of jasmonic acid-dependent direct and indirect defenses: irJAZh plants showed greater trypsin protease inhibitor activity, 17-hydroxygeranyllinalool diterpene glycosides accumulation, and emission of volatile organic compounds from leaves. Silencing of NaJAZh also revealed a novel cross talk in JAZ-regulated secondary metabolism, as irJAZh plants had significantly reduced nicotine levels. In addition, irJAZh spontaneously developed leaf necrosis during the transition to flowering. Because the lesions closely correlated with the elevated expression of programmed cell death genes and the accumulations of salicylic acid and hydrogen peroxide in the leaves, we propose a novel role of the NaJAZh protein as a repressor of necrosis and/or programmed cell death during plant development.

DOI： 10.1104/pp.112.193771

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER SOC PLANT BIOLOGISTS  

A large number of plants accumulate N-acylated polyamines (phenolamides [PAs]) in response to biotic and/or abiotic stress conditions. In the native tobacco (Nicotiana attenuata), the accumulation of two major PAs, caffeoylputrescine and dicaffeoylspermidine (DCS), after herbivore attack is known to be controlled by a key transcription factor, MYB8. Using a broadly targeted metabolomics approach, we show that a much larger spectrum of PAs composed of hydroxycinnamic acids and two polyamines, putrescine and spermidine, is regulated by this transcription factor. We cloned several novel MYB8-regulated genes, annotated as putative acyltransferases, and analyzed their function. One of the novel acyltransferases (AT1) is shown to encode a hydroxycinnamoyl-coenzyme A: putrescine acyltransferase responsible for caffeoylputrescine biosynthesis in tobacco. Another gene (acyltransferase DH29), specific for spermidine conjugation, mediates the initial acylation step in DCS formation. Although this enzyme was not able to perform the second acylation toward DCS biosynthesis, another acyltransferase gene, CV86, proposed to act on monoacylated spermidines, was isolated and partially characterized. The activation of MYB8 in response to herbivore attack and associated signals required the activity of LIPOXYGENASE3, a gene involved in jasmonic acid (JA) biosynthesis in N. attenuata. These new results allow us to reconstruct a complete branch in JA signaling that defends N. attenuata plants against herbivores: JA via MYB8's transcriptional control of AT1 and DH29 genes controls the entire branch of PA biosynthesis, which allows N. attenuata to mount a chemically diverse (and likely efficient) defense shield against herbivores.

DOI： 10.1104/pp.111.187229

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER SOC PLANT BIOLOGISTS  

R2R3-MYB transcription factors (TFs) are involved in diverse aspects of plant biology. Recently an R2R3-MYB was identified in Petunia x hybrida line P720 to have a role in the transcriptional regulation of floral volatile production. We propose a more foundational role for the R2R3-MYB TF EMISSION OF BENZENOIDS II (EOBII). The homolog of EOBII was isolated and characterized from P. x hybrida 'Mitchell Diploid' (MD) and Nicotiana attenuata. For both MD and N. attenuata, EOBII transcript accumulates to high levels in floral tissue with maximum accumulation at flower opening. When EOBII transcript levels are severely reduced using a stable RNAi (ir) approach in MD and N. attenuata, ir-EOBII flowers fail to enter anthesis and prematurely senesce. Transcript accumulation analysis demonstrated core phenylpropanoid pathway transcripts and cell wall modifier transcript levels are altered in ir-EOBII flowers. These flowers can be partially complemented by feeding with a sucrose, t-cinnamic acid, and gibberellic acid solution; presumably restoring cellular aspects sufficient for flower opening. Additionally, if ethylene sensitivity is blocked in either MD or N. attenuata, ir-EOBII flowers enter anthesis. These experiments demonstrate one R2R3-MYB TF can control a highly dynamic process fundamental to sexual reproduction in angiosperms: the opening of flowers.

DOI： 10.1104/pp.111.176248

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

Inducible plant defenses against herbivores are controlled by a transient burst of jasmonic acid (JA) and its conversion to the active hormone (3R,7S)-jasmonoyl-L-isoleucine (JA-Ile). JA-Ile shows high affinity for binding to the COI1 protein complex with JAZ repressor protein(s), a multi component JA-Ile receptor, promoting hormone-dependent ubiquitination and degradation of JAZ transcriptional repressors. Degradation of JAZ proteins in Arabidopsis leads to the release of a bHLH transcription factor, MYC2, which functions as a master regulator of JA-dependent defense responses. Because the activity of the MYC2 coincides with the presence of active jasmonate in cells, it is unlikely that MYC2, alone, regulates prolonged transcriptional responses of genes encoding enzymes required for the accumulation of defense metabolites. In this review, we focus on MYC2 and a specific group of MYC2-regulated 'secondary' transcription factors as critical components of the JA signal transduction pathway that controls inducible chemical defense responses in plants.

DOI： 10.1080/17429145.2010.544779

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Other Link： http://orcid.org/0000-0001-9840-8845

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER SOC PLANT BIOLOGISTS  

Jasmonic acid (JA) and ethylene (ET) are known to play important roles in mediating plant defense against herbivores, but how they affect development in herbivore-attacked plants is unknown. We used JA-deficient (silenced in LIPOXYGENASE3 [asLOX3]) and ET-insensitive (expressing a mutated dominant negative form of ETHYLENE RESPONSE1 [mETR1]) Nicotiana attenuata plants, and their genetic cross (mETR1asLOX3), to examine growth and development of these plants under simulated herbivory conditions. At the whole plant level, both hormones suppressed leaf expansion after the plants had been wounded and the wounds had been immediately treated with Manduca sexta oral secretions (OS). In addition, ectopic cell expansion was observed around both water-and OS-treated wounds in mETR1asLOX3 leaves but not in mETR1, asLOX3, or wild-type leaves. Pretreating asLOX3 leaves with the ET receptor antagonist 1-methylcyclopropane resulted in local cell expansion that closely mimicked the mETR1asLOX3 phenotype. We found higher auxin (indole-3-acetic acid) levels in the elicited leaves of mETR1asLOX3 plants, a trait that is putatively associated with enhanced cell expansion and leaf growth in this genotype. Transcript profiling of OS-elicited mETR1asLOX3 leaves revealed a preferential accumulation of transcripts known to function in cell wall remodeling, suggesting that both JA and ET act as negative regulators of these genes. We propose that in N. attenuata, JA-ET cross talk restrains local cell expansion and growth after herbivore attack, allowing more resources to be allocated to induced defenses against herbivores.

DOI： 10.1104/pp.110.156232

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER SOC PLANT BIOLOGISTS  

Although phenylpropanoid-polyamine conjugates (PPCs) occur ubiquitously in plants, their biological roles remain largely unexplored. The two major PPCs of Nicotiana attenuata plants, caffeoylputrescine (CP) and dicaffeoylspermidine, increase dramatically in local and systemic tissues after herbivore attack and simulations thereof. We identified NaMYB8, a homolog of NtMYBJS1, which in BY-2 cells regulates PPC biosynthesis, and silenced its expression by RNA interference in N. attenuata (ir-MYB8), to understand the ecological role(s) of PPCs. The regulatory role of NaMYB8 in PPC biosynthesis was validated by a microarray analysis, which revealed that transcripts of several key biosynthetic genes in shikimate and polyamine metabolism accumulated in a NaMYB8-dependent manner. Wild-type N. attenuata plants typically contain high levels of PPCs in their reproductive tissues; however, NaMYB8-silenced plants that completely lacked CP and dicaffeoylspermidine showed no changes in reproductive parameters of the plants. In contrast, a defensive role for PPCs was clear; both specialist (Manduca sexta) and generalist (Spodoptera littoralis) caterpillars feeding on systemically preinduced young stem leaves performed significantly better on ir-MYB8 plants lacking PPCs compared with wild-type plants expressing high levels of PPCs. Moreover, the growth of M. sexta caterpillars was significantly reduced when neonates were fed ir-MYB8 leaves sprayed with synthetic CP, corroborating the role of PPCs as direct plant defense. The spatiotemporal accumulation and function of PPCs in N. attenuata are consistent with the predictions of the optimal defense theory: plants preferentially protect their most fitness-enhancing and vulnerable parts, young tissues and reproductive organs, to maximize their fitness.

DOI： 10.1104/pp.109.151738

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：INFORMA HEALTHCARE  

Fluorescence imaging in plants is unusually challenging because of the large amounts of photosynthetic pigments contained in green plant tissues. For example, chlorophyll can obstruct the penetration of light and has high levels of autofluorescence at wavelengths that are often used for fluorescence imaging. Until now, mostly confocal laser scanning microscopy or the use of non-green parts of the plants, typically roots, have been used to overcome these limitations. We constructed tobacco (Nicotiana attenuata) plants expressing GFP-sporamin fusion polypeptide in their vascular tissues. As expected, it was not possible to visualize GFP fluorescence in tobacco leaves or stems using a stereomicroscope and filters specific for GFP detection; however, G FP fluorescence was readily detectable when virus-induced gene silencing (VIGS) was used to transiently silence the phytoene desaturase (PDS) gene in order to bleach chlorophyll-containing tissues. This method is an inexpensive alternative to confocal laser scanning microscopy for the detection of GFP fusion proteins or promoter-GFP reporter fusions in plant leaves.

DOI： 10.2144/000113345

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Authorship：Corresponding author  

DOI： 10.4161/psb.5.10.13124

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Language：English   Publisher：WILEY-BLACKWELL PUBLISHING, INC  

Plants must respond to biotic and abiotic challenges to optimize their Darwinian fitness in nature. Many of these challenges occur repeatedly during a plant&apos;s lifetime, and their sequence and timing can profoundly influence the fitness outcome of a plant&apos;s response. The ability to perceive, store and recall previous stressful events is likely useful for efficient, rapid and cost-effective responses, but we know very little about the mechanisms involved. Using jasmonate-elicited anti-herbivore defence responses as an example, we consider how &apos;memories&apos; of previous attacks could be created in (1) the biosynthetic processes involved in the generation of the oxylipin bursts elicited by herbivore attacks; (2) the perception of oxylipins and their transduction into cellular events by transcription factors and transcriptional activators; and (3) the role of small RNAs in the formation of long-term stress imprints in plants.

DOI： 10.1111/j.1365-3040.2008.01862.x

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Other Link： http://orcid.org/0000-0001-9840-8845

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER SOC PLANT BIOLOGISTS  

Many G2/M phase-specific genes in plants contain mitosis-specific activator (MSA) elements, which act as G2/M phase-specific enhancers and bind with R1R2R3-Myb transcription factors. Here, we examined the genome-wide effects of NtmybA2 overexpression, one of the R1R2R3-Myb transcription factors in tobacco (Nicotiana tabacum). We used a custom-made 16-K cDNA microarray for comparative transcriptome analysis of transgenic tobacco BY-2 cell lines that overexpress NtmybA2 or its truncated hyperactive form. The microarray was also used to determine the transcript profile during the cell cycle in synchronized cultures of BY-2 cells. Combined microarray data from transgenic lines and synchronized cells revealed that overexpression of the truncated hyperactive form of NtmybA2, but not its full-length form, preferentially up-regulated many G2/M phase-specific genes in BY-2 cells. We determined promoter sequences of several such up-regulated genes and showed that all contain MSA-like motifs in the proximal regions of their promoters. One of the up-regulated genes, NtE2C, encoding for cyclin-specific ubiquitin carrier proteins, contained a single functional MSA-like motif, which specifically controlled the expression of a reporter gene in the G2/M phase in BY-2 cells. Furthermore, a genomic footprint experiment showed that the MSA element in the NtE2C promoter interacted with nuclear proteins in vivo. Therefore, we propose that the transcription of many G2/M phase-specific genes in tobacco is positively regulated by NtmybA2, in most cases through direct binding to the MSA elements.

DOI： 10.1104/pp.109.135582

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Background: Rapid herbivore-induced jasmonic acid (JA) accumulation is known to mediate many induced defense responses in vascular plants, but little is known about how JA bursts are metabolized and modified in response to repeated elicitations, are propagated throughout elicited leaves, or how they directly influence herbivores.
Methodology/Principal Findings: We found the JA burst in a native population of Nicotiana attenuata to be highly robust despite environmental variation and we examined the JA bursts produced by repeated elicitations with Manduca sexta oral secretions (OS) at whole- and within-leaf spatial scales. Surprisingly, a 2(nd) OS-elicitation suppressed an expected JA burst at both spatial scales, but subsequent elicitations caused more rapid JA accumulation in elicited tissue. The baseline of induced JA/JA-Ile increased with number of elicitations in discrete intervals. Large veins constrained the spatial spread of JA bursts, leading to heterogeneity within elicited leaves. 1(st)-instar M. sexta larvae were repelled by elicitations and changed feeding sites. JA conjugated with isoleucine (JA-Ile) translates elicitations into defense production (e. g., TPIs), but conjugation efficiency varied among sectors and depended on NaWRKY3/6 transcription factors. Elicited TPI activity correlated strongly with the heterogeneity of JA/JA-Ile accumulations after a single elicitation, but not repeated elicitations.
Conclusions/Significance: Ecologically informed scaling of leaf elicitation reveals the contribution of repeated herbivory events to the formation of plant memory of herbivory and the causes and importance of heterogeneity in induced defense responses. Leaf vasculature, in addition to transmitting long-distance damage cues, creates heterogeneity in JA bursts within attacked leaves that may be difficult for an attacking herbivore to predict. Such unpredictability is a central tenet of the Moving Target Model of defense, which posits that variability in itself is defensive.

DOI： 10.1371/journal.pone.0004697

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A plant-specific family of WRKY transcription factors regulates plant responses to pathogens and abiotic stresses. Here, we identify two insect-responsive WRKY genes in the native tobacco Nicotiana attenuata: WRKY3, whose transcripts accumulate in response to wounding, and WRKY6, whose wound responses are significantly amplified when fatty acid amino acid conjugates (FACs) in larval oral secretions are introduced into wounds during feeding. WRKY3 is required for WRKY6 elicitation, yet neither is elicited by treatment with the phytohormone wound signal jasmonic acid. Silencing either WRKY3 or WRKY6, or both, by stable transformation makes plants highly vulnerable to herbivores under glasshouse conditions and in their native habitat in the Great Basin Desert, Utah, as shown in three field seasons. This susceptibility is associated with impaired jasmonate (JA) accumulation and impairment of the direct (trypsin proteinase inhibitors) and indirect (volatiles) defenses that JA signaling mediates. The response to wounding and herbivore-specific signals (FACs) demonstrates that these WRKYs help plants to differentiate mechanical wounding from herbivore attack, mediating a plant's herbivore-specific defenses. Differences in responses to single and multiple elicitations indicate an important role of WRKY3 and WRKY6 in potentiating and/or sustaining active JA levels during continuous insect attack.

DOI： 10.1105/tpc.108.058594

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OXFORD UNIV PRESS  

We previously demonstrated that a -1,3-, 1,6-oligoglucan (AaGlucan) from the fungus Alternaria alternata 102 shows strong elicitor activity in tobacco BY-2 cells. We have used cDNA microarray analysis to monitor global changes in gene expression in tobacco cells treated with this A. alternata fraction or with laminarin. In total, we identified 265 genes that were induced 1 h after treatment with an AaGlucan-enriched fraction or laminarin. Among them, we characterized in detail a novel tobacco R2R3 MYB-type transcription factor homolog (NtMYBGR1) and two DC1 domain-containing genes (NtDC1A and NtDC1B). Microarray data, together with overexpression and metabolic analyses, indicated that NtMYBGR1, but not the NtDC1 proteins, primarily targets the phenylpropanoid synthesis-related genes PAL and 4CL. These results suggest that NtMYBGR1 specifically regulates defense responses in BY-2 cells by enhancing phenylpropanoid metabolism in response to AaGlucan and laminarin elicitors.

DOI： 10.1093/pcp/pcm115

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ACADEMIC PRESS INC ELSEVIER SCIENCE  

Tobacco BY-2 class IV chitinases (TBC-1, TBC-3) were rapidly and transiently induced by the beta-1,3-, 1,6-glucan elicitor from Alternaria alternata 102 (AaGlucan). The full-length cDNA and 5'-flanking region of a gene encoding class IV chitinases were isolated on the basis of the amino acid sequence of TBC-1. Sequence analysis indicated that NtChitIV encoded TBC-1, TBC-3, or both. Since purified TBC-1 and TBC-3 from BY-2 cells lack a chitin binding domain in the N-terminal region, these enzymes suggested to be derived from NtChitIV by post-translational proteolytic processing. The transcripts of NtChitIV accumulated rapidly within I h after treatment with AaGlucan. Accumulation was maximal 3 h after treatment. Reporter gene assays were used to analyze the promoter regions involved in the transcriptional control of NtChitIV, and these assays revealed that the 1.89-kb NtChitIV promoter was activated by AaGlucan but not by salicylic acid (SA) or methyl jasmonate (MeJA). The AaGlucan-induced transcriptional activation via 1.89-kb NtChitIV promoter was attenuated by pretreatment with SA or MeJA. These results suggest that NtChitIV expression is particularly induced by AaGlucan and that the AaGlucan-dependent signaling pathway is different from the SA- and MeJA-dependent signaling pathways. (c) 2006 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.bbrc.2006.12.009

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© 2007 Springer. All rights reserved. Tobacco has played historically important role in the discovery and functional analysis of salicylic acid (SA) as a plant hormone. Using this model, it was demonstrated for the first time that tobacco mosaic virus (TMV) infection results in the accumulation of SA in infected tissues that is to activate local and systemic expression of pathogenesis-related proteins in the cells. Furthermore, SA has been shown to function as a major factor in the development of systemic acquired resistance (SAR) in plants. To promote the importance of tobacco as a model plant, we generated and sequenced cDNA libraries from tobacco BY-2 cells, depositing about 20,000 EST sequence information in the public databases. Selected cDNA clones were then used to prepare the first large-scale 16K microarray of tobacco. In this chapter, we describe our results of a large scale gene expression analysis, using the tobacco BY-2 cells, treated with a 40 μM salicylic acid. In total, 376 genes (corresponding to individual ESTs) were at least 2-fold upregulated by SA, relative to their expression levels in control cells. Amid, a large number of genes overlapped with known defense-related genes in plants, whilst the others represented novel targets of SA in plants. The kinetic analysis of the SA-responsive genes, together with functional analysis of these genes in the plant defense, is presented in this chapter.

DOI： 10.1007/1-4020-5184-0_13

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：BLACKWELL PUBLISHING  

Target metabolic and large-scale transcriptomic analyses of tobacco (Nicotiana tabacum L.) Bright Yellow-2 (BY-2) cells were employed to identify novel gene(s) involved in methyl jasmonate (MJ)-dependent function in plants. At the metabolic level, we describe the specific accumulation of several phenylpropanoid-polyamine conjugates in MJ-treated BY-2 cells. Furthermore, global gene expression analysis of MJ-treated cells using a 16K cDNA microarray containing expressed sequence tags (ESTs) from BY-2 cells revealed 828 genes that were upregulated by MJ treatment within 48 h. Using time-course expression data we identified a novel MJ-inducible R2R3 MYB-type transcription factor (NtMYBJS1) that was co-expressed in a close temporal pattern with the core phenylpropanoid genes phenylalanine ammonia-lyase (PAL) and 4-coumarate:CoA ligase (4CL). Overexpression of NtMYBJS1 in tobacco BY-2 cells caused accumulation of specific phenylpropanoid conjugates in the cells. Subsequent microarray analysis of NtMYBJS1 transgenic lines revealed that a limited number of genes, including PAL and 4CL, were specifically induced in the presence of the NtMYBJS1 transgene. These results, together with results of both antisense expression analysis and of gel mobility shift assays, strongly indicate that the NtMYBJS1 protein functions in tobacco MJ signal transduction, inducing phenylpropanoid biosynthetic genes and the accumulation of phenylpropanoid-polyamine conjugates during stress.

DOI： 10.1111/j.1365-313X.2006.02719.x

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DOI： 10.1007/3-540-32674-X_19

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

The plant-tumorigenic 6b (AK-6b) gene of Agrobacterium tumefaciens strain AKE10 induces morphological alterations to tobacco plants, Nicotiana tabacum. To investigate the molecular mechanisms underlying these processes, we generated transgenic tobacco harboring the AK-6b gene under the control of a dexamethazone-inducible promoter. Upon induction, transgenic tobacco seedlings exhibited distinct classes of aberrant morphologies, most notably adventitious outgrowths and stunted epicotyls. Histological analysis revealed massive proliferation and altered venation in the newly established outgrowths. Prominent vascular development suggested that auxin metabolism or signaling had been altered. Indeed, basipetal auxin transport in the hypocotyls of the transgenic seedlings was reduced by 50-80%, whereas intracellular auxin contents were only slightly reduced. Analysis of cell extracts by HPLC revealed a large accumulation of phenolic compounds, including the flavonoid kaempferol-3-rutinoside, in transgenic plants compared with wild-type seedlings. As some naturally occurring flavonoids have been shown to affect auxin transport, we suggest that the AK-6b gene expression impairs auxin transport via modulation of phenylpropanoid metabolism, and ultimately results in the observed morphological alterations.

DOI： 10.1007/s00425-005-0080-4

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Language：English   Publisher：OXFORD UNIV PRESS  

DOI： 10.1111/j.1365-313X.2006.02719.x

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

In order to determine whether the disease symptoms caused by virulent strains of Rhodococcus fascians are due to increased cytokinin activity in infected tissues, germinating peas (Pisum sativum cv Novella) were inoculated with either a virulent strain or a nonvirulent strain of Rhodococcus fascians. The nonvirulent strain lacked both the ipt gene and the putative cytokinin oxidase/dehydrogenase homologue, fas5. Control peas were not inoculated. Twelve cytokinins were isolated from pea shoots 3, 6 and 9 days post-inoculation. Within 6 days of inoculation the levels of cytokinin free bases, ribosides, O-glucosides and nucleotides were decreased in shoots inoculated with the virulent strain, and were increased in shoots inoculated with the nonvirulent strain relative to the uninoculated control. The results are discussed with respect to the classic Skoog and Miller (1965) model of organogenesis and to the possible involvement of the plant cytokinin oxidase/dehydrogenase during infection by virulent strains of R. fascians.

DOI： 10.1007/s10725-005-7752-8

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

Expression patterns of three Arabidopsis thaliana cytokinin oxidase/dehydrogenase promoter::GUS reporter fusions were investigated in tobacco plants. While cytokinin oxidase/dehydrogenase promoter 2 showed no expression in tobacco, the cytokinin oxidase/dehydrogenase promoters 3 and 4 were active in various tissues throughout development of the tobacco. Recently, the 1452 bp promoter region of AtCKX3 was reported as almost inactive in Arabidopsis. In contrast, the 1627 bp DNA fragment preceding the AtCKX3 coding region drove expression of the reporter GUS gene in various tobacco tissues. The promoter was mainly expressed in tobacco leaves and roots during early stages of development but also later in young flower buds as well as in pollen grains. The construct was particularly active before (hypocotyl region) and during (vascular system) lateral root initiation, supporting the idea of an inhibitory role of active cytokinins in the process of root initiation. The cytokinin oxidase/dehydrogenase promoter 4::GUS fusion in tobacco was shown to share some common (but weaker) expression patterns with promoter 3, namely in the leaves and pollen, but also conferred specific expression in tobacco root cap cells and trichomes. In addition, the response of cytokinin oxidase/dehydrogenase promoter::GUS reporter fusions to infection with the leafy gall-forming bacteria Rhodococcus fascians was examined. While an avirulent strain of R. fascians did not induce expression of any of the cytokinin oxidase/dehydrogenase promoters, the cytokinin oxidase/dehydrogenase promoter 3::GUS fusion was specifically induced at the site of infection when plants were challenged with a virulent strain of R. fascians, providing a possible explanation for the lack of significantly elevated cytokinin concentrations in tissues infected with virulent strains of R. fascians.

DOI： 10.1007/s10725-005-2547-5

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Other Link： http://orcid.org/0000-0001-9840-8845

Language：English   Publishing type：Research paper (scientific journal)   Publisher：OXFORD UNIV PRESS  

To understand how plant cell changes gene expression during cell division and after termination of cell division, we analyzed the change of gene expression during the growth of tobacco BY-2 cell lines using a cDNA microarray, which contained about 9,200 expression sequence tag fragments and corresponded to about 7,000 genes. We found that log phase cells predominantly expressed DNA/chromosome duplication gene homologs. In addition, many genes for basic transcription and translation machineries, as well as proteasomal genes, were up-regulated at the log phase. About half of the kinesin homolog genes, but not myosin homolog genes, were predominantly expressed at the dividing phase as well; In contrast, stationary phase cells expressed genes for many receptor kinases, signal transduction machineries and transcription factors. Several hundreds of genes showed differential expression after incubation of stationary phase cells with medium containing either salicylic acid or abscisic acid. These findings suggested that BY-2 cells at the stationary phase express genes for perceiving extracellular signals.

DOI： 10.1093/pcp/pch155

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：URBAN & FISCHER VERLAG  

Two-week-old Phaseolus vulgaris plants, wick-fed with 1 mmol/L salicylic acid (SA) or 50 nmol/L dihydrozeatin (DHZ), showed partial inhibition of the accumulation of white clover mosaic virus (WCIMV) in infected primary leaves. This inhibition was measured as a decrease in the accumulation of both viral mRNA and viral coat protein, especially at the early stages of infection. Salicylic acid treatment resulted in moderately increased expression of phenylalanine ammonia lyase (PAL), NPR I, PR1 and HSP70 genes that participate in resistance to pathogens in plants. In contrast, DHZ treatments did not induce significant changes in expression of these genes. The expression of the P. vulgaris alternative oxidase (AOX) gene homolog, an enzyme implicated in plant resistance to viruses, showed low constitutive expression during the first 11 days post-infection and was not affected by either SA or DHZ. It appears that, while SA induced the NPR1-PR1 pathogen defense pathway genes, both SA and DHZ may use a different pathway to induce resistance to WCIMV infection in P vulgaris plants.

DOI： 10.1078/0176-1617-01255

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

The 6b gene (AK-6b) of Agrobacterium tumefaciens AKE10 can substitute for the requirement of tobacco tissues for auxin and cytokinin to maintain callus growth in the culture medium. To identify compounds that might be involved in this process we analyzed phenolic metabolites in transgenic tobacco tissues expressing the AK-6b gene. On medium containing both cytokinin and auxin (SH medium), transgenic calli accumulated higher levels of chlorogenic acid, caffeoyl putrescine, rutin and kaempferol-3-rutinoside, than did wild-type tissues. In contrast, the levels of scopolin and its aglycone, scopoletin were lower in transgenic tissues. On hormone-free medium, these phenolic compounds showed neither significant levels nor an apparent relationship with AK-6b transcript levels, except for the negatively correlated levels of scopoletin and AK-6b transcripts. Apparently, the AK-6b gene acts, in SH medium, to redirect the synthesis of scopolin in tobacco tissues towards the preferential synthesis of caffeic acid derivatives and flavonoids. (C) 2003 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.phytochem.2003.10.015

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OXFORD UNIV PRESS  

We previously reported that the Agrobacterium tumefaciens C58-6b gene confers resistance to growth-inhibitory levels of exogenously applied N-6-benzyladenine (BA, cytokinin) in transgenic tobacco (Nicotiana tabacum) seedlings. Here, we found that intracellular levels of indoleacetic acid (IAA, auxin) increased in transgenics but declined in wildtype seedlings upon BA treatment. Since exogenously supplied I-naphthalene acetic acid (NAA), a stable synthetic auxin, counteracted the growth inhibition of wild-type seedlings by BA, we suggest that BA-induced growth inhibition in wild-type seedlings occurs, at least in part, as a result of intracellular IAA deficiency. Further HPLC analysis of cell extracts from BA-treated seedlings revealed that a fluorescent compound, later identified as the phenylpropanoid, scopolin, and the major phenolic compound, chlorogenic acid, accumulated earlier in transgenics than in wild-type seedlings. Gene transcripts encoding phenylalanine ammonia-lyase, cinnamate 4-hydroxylase, and 4-coumarate:CoA ligase, which are responsible for the early steps of phenylpropanoid biosynthesis, accumulated earlier and to higher levels in transgenics than in wild-type seedlings as determined by Northern hybridization analysis, thus accounting for the early accumulation of scopolin and chlorogenic acid in transgenics. As some phenolic compounds, including chlorogenic acid and scopoletin (aglycon of scopolin) are suggested to inhibit IAA catabolism, we further propose that C58-6b gene expression protects IAA from degradation by inducing the early phenylpropanoid pathway.

DOI： 10.1093/pcp/pcf112

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Language：Japanese   Publisher：The Japanese Society for Chemical Regulation of Plants  

DOI： 10.18978/jscrp.36.1_24

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER VERLAG  

DOI： 10.1007/s004250050748

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：KLUWER ACADEMIC PUBL  

Three random translational P-glucuronidase (gus) gene fusions were previously obtained in Arabidopsis thaliana, using Agrobacterium-mediated transfer of a gus coding sequence without promoter and ATG initiation site. These were analysed by IPCR amplification of the sequence upstream of gus and nucleotide sequence analysis. In one instance, the gus sequence was fused, in inverse orientation, to the nos promoter sequence of a truncated tandem T-DNA copy and translated from a spurious ATG in this sequence. In the second transgenic line, the gus gene was fused to A. thaliana DNA, 27 bp downstream an ATG. In this Line, a large deletion occurred at the target site of the T-DNA. In the third line, gus is fused in frame to a plant DNA sequence after the eighth codon of an open reading frame encoding a protein of 619 amino acids. This protein has significant homology with animal and plant (receptor) serine/threonine protein kinases. The twelve subdomains essential for kinase activity are conserved. The presence of a potential signal peptide and a membrane-spanning domain suggests that it may be a receptor kinase. These data confirm that plant genes can be tagged as functional translational gene fusions.

DOI： 10.1023/A:1005902730810

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：INST EXPERIMENTAL BOTANY, ACAD SCI CZECH REPUBLIC  

Five cultivars of Oenothera biennis have been tested for callogenesis and organogenesis on different media. The cultivar CV3 has been transformed by Agrobacterium tumefaciens strain which introduces into the plant genome kanamycin resistance gene and the T-DNA ipt gene which causes increased levels of cytokinins. Transformed tissues showed elevated levels of cytokinins and grew as teratomas forming clumps of short, branched shoots with small modified leaves. Roots appeared rarely in later subcultivations of some teratomous clones.

DOI： 10.1007/BF02879628

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Authorship：Corresponding author  

DOI： 10.1007/BF00210916

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Language：Czech   Publishing type：Research paper (scientific journal)   Publisher：INST SCI TECH INFORM AGR  

The incorporation of bacterial genes into the potato genome induces the formation of phenotypically different transformants that show expressive growth and metabolic changes. The transformants cv. Zvikov 1361 are noted for their excessive root formation which is stimuled by the presence of the plasmid Ri. It is necessary to limit the rhizogenesis in order to induce transformant tuberization. 2,3,5-triiodobenzoic acid and cumarin in the concentration 2 and 4 mg.1-1 TIBA or 25 and 50 mg.1-1 cumarin limit the root growth and induce axillary microtubers.
Another type has been derived by the transformation of the cv. Oreb with plasmid LDA 1334. This type also brings gene 4 into potatoes and induces higher synthesis of cytokinins. The transformants were noted for the formation of multiple shoots which were not able to produce roots and tubers on media modified by auxin substances. Only transformant grafting on a tomato has caused elongation and stem rooting in the soil and also the formation of tubers in flower-pots. The tubers were smaller and had a prolonged shape and contained few starch grains. During the analysis of amino acids it was remarkable to observe two to three times lower proline content. The shortage of proline in transformants could result in the lower resistance of transformants under less positive conditions.
In the next vegetation period we verified the influence of exogenously applied proline on transgenic cv. Oreb in leaves that were growing in an experimental field and in a hotbed. As a result of the bioassays on coleoptile oat segments, it is evident that proline in leaves lowers the content of auxin substances in most cases and evokes inhibitions. The changes suggest the possible presence of abscisic acid which could contribute to the regulation of leaf stomata.

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Language：English   Publisher：INST EXPERIMENTAL BOTANY, ACAD SCI CZECH REPUBLIC  

The dependence of luciferase activity in the homogenate of leaves of transgenic tobacco plants with chimeric firefly luciferase gene on ATP concentration and temperature was studied. The optimum ATP concentration was between 0.625 mM. and 2.5 mM. The activity rapidly decreased if the homogenate was kept in 25-degrees-C and is completely lost during 30 min.

DOI： 10.1007/BF02921140

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Language：English   Publishing type：Research paper, summary (international conference)   Publisher：OXFORD UNIV PRESS  

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Language：English   Publishing type：Research paper, summary (international conference)   Publisher：OXFORD UNIV PRESS  

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Language：English   Publishing type：Research paper, summary (international conference)   Publisher：SPRINGER HEIDELBERG  

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Language：English   Publisher：Japanese Society of Plant Physiologists  

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Other Link： https://projects.repo.nii.ac.jp/?action=repository_uri&item_id=185232

Event date： 2022.8.8 - 2022.8.12

Language：English   Presentation type：Poster presentation  

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Language：English   Presentation type：Oral presentation (keynote)  

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