記述言語：英語   掲載種別：研究論文（学術雑誌）  

The root-colonizing endophytic fungus Piriformospora indica promotes the root and shoot growth of its host plants. We show that the growth promotion of Arabidopsis thaliana leaves is abolished when the seedlings are grown on media with nitrogen (N) limitation. The fungus neither stimulated the total N content nor did it promote 15NO3- uptake from agar plates to the leaves of the host under N-sufficient or N-limiting conditions. However, when the roots were co-cultivated with 15N-labelled P. indica, more labels were detected in the leaves of N-starved host plants but not in plants supplied with sufficient N. Amino acid and primary metabolite profiles, as well as the expression analyses of N metabolite transporter genes suggest that the fungus alleviates the adaptation of its host from the N limitation condition. P. indica alters the expression of transporter genes, which participate in the relocation of NO3-, NH4+ and N metabolites from the roots to the leaves under N limitation. We propose that P. indica participates in the plant's metabolomic adaptation against N limitation by delivering reduced N metabolites to the host, thus alleviating metabolic N starvation responses and reprogramming the expression of N metabolism-related genes.

DOI： 10.3390/ijms242015372

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記述言語：日本語   出版者・発行元：一般社団法人 日本土壌肥料学会  

DOI： 10.20710/dohikouen.69.0_56_3

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

Cytokinins (CKs), a class of phytohormones with vital roles in growth and development, occur naturally with various side-chain structures, including N6-(Δ2-isopentenyl)adenine-, cis-zeatin- and trans-zeatin (tZ)-types. Recent studies in the model dicot plant Arabidopsis (Arabidopsis thaliana) have demonstrated that tZ-type CKs are biosynthesized via cytochrome P450 monooxygenase (P450) CYP735A and have a specific function in shoot growth promotion. Although the function of some of these CKs has been demonstrated in a few dicotyledonous plant species, the importance of these variations and their biosynthetic mechanism and function in monocots and in plants with distinctive side-chain profiles other than Arabidopsis, such as rice (Oryza sativa), remain elusive. In this study, we characterized CYP735A3 and CYP735A4 to investigate the role of tZ-type CKs in rice. Complementation test of the Arabidopsis CYP735A-deficient mutant and CK profiling of loss-of-function rice mutant cyp735a3 cyp735a4 demonstrated that CYP735A3 and CYP735A4 encode P450s required for tZ-type side-chain modification in rice. CYP735As are expressed in both roots and shoots. The cyp735a3 cyp735a4 mutants exhibited growth retardation concomitant with reduction in CK activity in both roots and shoots, indicating that tZ-type CKs function in growth promotion of both organs. Expression analysis revealed that tZ-type CK biosynthesis is negatively regulated by auxin, abscisic acid, and CK and positively by dual nitrogen nutrient signals, namely glutamine-related and nitrate-specific signals. These results suggest that tZ-type CKs control the growth of both roots and shoots in response to internal and environmental cues in rice.

DOI： 10.1093/plphys/kiad197

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

Plasma membrane (PM) proton-translocating adenosine triphosphatase (H+-ATPase) is a pivotal enzyme for plant growth and development that acts as a primary transporter and is activated by phosphorylation of the penultimate residue, threonine, at the C-terminus. Small Auxin-Up RNA family proteins maintain the phosphorylation level via inhibiting dephosphorylation of the residue by protein phosphatase 2C-D clade. Photosynthetically active radiation activates PM H+-ATPase via phosphorylation in mesophyll cells of Arabidopsis thaliana, and phosphorylation of PM H+-ATPase depends on photosynthesis and photosynthesis-related sugar supplementation, such as sucrose, fructose and glucose. However, the molecular mechanism and physiological role of photosynthesis-dependent PM H+-ATPase activation are still unknown. Analysis using sugar analogs, such as palatinose, turanose and 2-deoxy glucose, revealed that sucrose metabolites and products of glycolysis such as pyruvate induce phosphorylation of PM H+-ATPase. Transcriptome analysis showed that the novel isoform of the Small Auxin-Up RNA genes, SAUR30, is upregulated in a light- and sucrose-dependent manner. Time-course analyses of sucrose supplementation showed that the phosphorylation level of PM H+-ATPase increased within 10 min, but the expression level of SAUR30 increased later than 10 min. The results suggest that two temporal regulations may participate in the regulation of PM H+-ATPase. Interestingly, a 15NO3- uptake assay in leaves showed that light increases 15NO3- uptake and that increment of 15NO3- uptake depends on PM H+-ATPase activity. The results opened the possibility of the physiological role of photosynthesis-dependent PM H+-ATPase activation in the uptake of NO3-. We speculate that PM H+-ATPase may connect photosynthesis and nitrogen metabolism in leaves.

DOI： 10.1093/pcp/pcac157

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：WILEY  

Calcium is an important second messenger in plants. The activation of Ca2+ signalling cascades is critical in the activation of adaptive processes in response to environmental stimuli. Root colonization by the growth promoting endophyte Serendipita indica involves the increase of cytosolic Ca2+ levels in Arabidopsis thaliana. Here, we investigated transcriptional changes in Arabidopsis roots during symbiosis with S. indica. RNA-seq profiling disclosed the induction of Calcineurin B-like 7 (CBL7) during early and later phases of the interaction. Consistently, reverse genetic evidence highlighted the functional relevance of CBL7 and tested the involvement of a CBL7-CBL-interacting protein kinase 13 signalling pathway. The loss-of-function of CBL7 abolished the growth promoting effect and affected root colonization. The transcriptomics analysis of cbl7 revealed the involvement of this Ca2+ sensor in activating plant defense responses. Furthermore, we report on the contribution of CBL7 to potassium transport in Arabidopsis. We analysed K+ contents in wild-type and cbl7 plants and observed a significant increase of K+ in roots of cbl7 plants, while shoot tissues demonstrated K+ depletion. Taken together, our work associates CBL7 with an important role in the mutual interaction between Arabidopsis and S. indica and links CBL7 to K+ transport.

DOI： 10.1111/pce.14420

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：FRONTIERS MEDIA SA  

The Arabidopsis ABC transporter ABCG11 transports lipidic precursors of surface coating polymers at the plasma membrane of epidermal cells. Mutants in ABCG11 exhibit severe developmental defects, suggesting that ABCG11 might also participate in phytohormone-mediated development. Here, we report that ABCG11 is involved in cytokinin-mediated development. The roots of abcg11 mutant seedlings failed to respond to cytokinins and accumulated more cytokinins than wild-type roots. When grown under short-day conditions, abcg11 exhibited longer roots and shorter hypocotyls compared to wild type, similar to abcg14, a knockout mutant in a cytokinin transporter. Treatment with exogenous trans-zeatin, which inhibits primary root elongation in the wild type, enhanced abcg11 primary root elongation. It also increased the expression of cytokinin-responsive Arabidopsis response regulator (ARR) genes, and the signal of the TCS::GFP reporter in abcg11 roots compared to wild-type roots, suggesting that cytokinin signaling was enhanced in abcg11 roots. When we treated only the roots of abcg11 with trans-zeatin, their shoots showed lower ARR induction than the wild type. The abcg14 abcg11 double mutant did not have additional root phenotypes compared to abcg11. Together, these results suggest that ABCG11 is necessary for normal cytokinin-mediated root development, likely because it contributes to cytokinin transport, either directly or indirectly.

DOI： 10.3389/fpls.2022.976267

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SPRINGER JAPAN KK  

Setaria viridis, the wild ancestor of foxtail millet (Setaria italica), is an effective model plant for larger C-4 crops because S. viridis has several desirable traits, such as short generation time, prolific seed production and a small genome size. These advantages are well suited for investigating molecular mechanisms in angiosperms, especially C-4 crop species. Here, we report a procedure for isolating gametes and zygotes from S. viridis flowers. To isolate egg cells, ovaries were harvested from unpollinated mature flowers and cut transversely, which allowed direct access to the embryo sac. Thereafter, an egg cell was released from the cut end of the basal portion of the dissected ovary. To isolate sperm cells, pollen grains released from anthers were immersed in a mannitol solution, resulting in pollen-grain bursting, which released sperm cells. Additionally, S. viridis zygotes were successfully isolated from freshly pollinated flowers. Isolated zygotes cultured in a liquid medium developed into globular-like embryos and cell masses. Thus, isolated S. viridis gametes, zygotes and embryos are attainable for detailed observations and investigations of fertilization and developmental events in angiosperms.

DOI： 10.1007/s10265-022-01393-w

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記述言語：日本語   出版者・発行元：一般社団法人 日本土壌肥料学会  

DOI： 10.20710/dohikouen.67.0_61_2

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

Plants use nitrate, ammonium, and organic nitrogen in the soil as nitrogen sources. Since the elevated CO2 environment predicted for the near future will reduce nitrate utilization by C3 species, ammonium is attracting great interest. However, abundant ammonium nutrition impairs growth, i.e., ammonium toxicity, the primary cause of which remains to be determined. Here, we show that ammonium assimilation by GLUTAMINE SYNTHETASE 2 (GLN2) localized in the plastid rather than ammonium accumulation is a primary cause for toxicity, which challenges the textbook knowledge. With exposure to toxic levels of ammonium, the shoot GLN2 reaction produced an abundance of protons within cells, thereby elevating shoot acidity and stimulating expression of acidic stress-responsive genes. Application of an alkaline ammonia solution to the ammonium medium efficiently alleviated the ammonium toxicity with a concomitant reduction in shoot acidity. Consequently, we conclude that a primary cause of ammonium toxicity is acidic stress.

DOI： 10.1038/s41467-021-25238-7

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：NATL ACAD SCIENCES  

Nitrogen (N) is an essential nutrient that affects multiple plant developmental processes, including flowering. As flowering requires resources to develop sink tissues for reproduction, nutrient availability is tightly linked to this process. Low N levels accelerate floral transition; however, the molecular mechanisms underlying this response are not well understood. Here, we identify the FLOWERING BHLH 4 (FBH4) transcription factor as a key regulator of N-responsive flowering in Arabidopsis Low N-induced early flowering is compromised in fbh quadruple mutants. We found that FBH4 is a highly phosphorylated protein and that FBH4 phosphorylation levels decrease under low N conditions. In addition, decreased phosphorylation promotes FBH4 nuclear localization and transcriptional activation of the direct target CONSTANS (CO) and downstream florigen FLOWERING LOCUS T (FT) genes. Moreover, we demonstrate that the evolutionarily conserved cellular fuel sensor SNF1-RELATED KINASE 1 (SnRK1), whose kinase activity is down-regulated under low N conditions, directly phosphorylates FBH4. SnRK1 negatively regulates CO and FT transcript levels under high N conditions. Together, these results reveal a mechanism by which N levels may fine-tune FBH4 nuclear localization by adjusting the phosphorylation state to modulate flowering time. In addition to its role in flowering regulation, we also showed that FBH4 was involved in low N-induced up-regulation of nutrient recycling and remobilization-related gene expression. Thus, our findings provide insight into N-responsive growth phase transitions and optimization of plant fitness under nutrient-limited conditions.

DOI： 10.1073/pnas.2022942118

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DOI： 10.20710/dojo.92.2_76

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Public Library of Science ({PLoS})  

Author summaryExpression of genes is tightly regulated by transcription factors that physically interact with DNA. Transcription factors recognize specific DNA sequences and selectively regulate the expression of target genes through the specific interactions. We previously found that a group of plant-specific transcription factors, NIGT1 family proteins, recognize two different types of DNA sequences to modulate the expression of a number of genes associated with uptake of nitrogen and phosphorus or related metabolism in Arabidopsis. However, it was unknown how NIGT1 family proteins recognize different types of sequences. In this study, we reveal that dimerization of NIGT1 family proteins is essential to the dual specificity of NIGT1 family proteins and therefore loss of the dimerization ability alters specificity and affinity of NIGT1 family proteins to target DNA sequences. We further suggest that the dimerization of NIGT1 family proteins is an evolutionarily conserved feature to properly respond to changes in nutrient availability. These findings would advance our knowledge on the mode of DNA recognition by transcription factors and have further implications for structural basis on the diverse patterns of the interaction between DNA and transcription factors.Fine-tuning of nutrient uptake and response is indispensable for maintenance of nutrient homeostasis in plants, but the details of underlying mechanisms remain to be elucidated. NITRATE-INDUCIBLE GARP-TYPE TRANSCRIPTIONAL REPRESSOR 1 (NIGT1) family proteins are plant-specific transcriptional repressors that function as an important hub in the nutrient signaling network associated with the acquisition and use of nitrogen and phosphorus. Here, by yeast two-hybrid assays, bimolecular fluorescence complementation assays, and biochemical analysis with recombinant proteins, we show that Arabidopsis NIGT1 family proteins form a dimer via the interaction mediated by a coiled-coil domain (CCD) in their N-terminal regions. Electrophoretic mobility shift assays defined that the NIGT1 dimer binds to two different motifs, 5'-GAATATTC-3' and 5'-GATTC-N-38-GAATC-3', in target gene promoters. Unlike the dimer of wild-type NIGT1 family proteins, a mutant variant that could not dimerize due to amino acid substitutions within the CCD had lower specificity and affinity to DNA, thereby losing the ability to precisely regulate the expression of target genes. Thus, expressing the wild-type and mutant NIGT1 proteins in the nigt1 quadruple mutant differently modified NIGT1-regulated gene expression and responses towards nitrate and phosphate. These results suggest that the CCD-mediated dimerization confers dual mode DNA recognition to NIGT1 family proteins, which is necessary to make proper controls of their target genes and nutrient responses. Intriguingly, two 5'-GATTC-3' sequences are present in face-to-face orientation within the 5'-GATTC-N-38-GAATC-3' sequence or its complementary one, while two 5'-ATTC-3' sequences are present in back-to-back orientation within the 5'-GAATATTC-3' or its complementary one. This finding suggests a unique mode of DNA binding by NIGT1 family proteins and may provide a hint as to why target sequences for some transcription factors cannot be clearly determined.

DOI： 10.1371/journal.pgen.1009197

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier {BV}  

DOI： 10.1016/j.pbi.2020.07.002

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

Wild and weedy relatives of domesticated crops harbor genetic variants that can advance agricultural biotechnology. Here we provide a genome resource for the wild plant green millet (Setaria viridis), a model species for studies of C4 grasses, and use the resource to probe domestication genes in the close crop relative foxtail millet (Setaria italica). We produced a platinum-quality genome assembly of S. viridis and de novo assemblies for 598 wild accessions and exploited these assemblies to identify loci underlying three traits: response to climate, a 'loss of shattering' trait that permits mechanical harvest and leaf angle, a predictor of yield in many grass crops. With CRISPR-Cas9 genome editing, we validated Less Shattering1 (SvLes1) as a gene whose product controls seed shattering. In S. italica, this gene was rendered nonfunctional by a retrotransposon insertion in the domesticated loss-of-shattering allele SiLes1-TE (transposable element). This resource will enhance the utility of S. viridis for dissection of complex traits and biotechnological improvement of panicoid crops.

DOI： 10.1038/s41587-020-0681-2

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記述言語：日本語   出版者・発行元：一般社団法人 日本土壌肥料学会  

DOI： 10.20710/dohikouen.66.0_55_2

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Oxford University Press ({OUP})  

Global climate change is arguably one of the biggest threats of modern times and has already led to a wide range of impacts on the environment, economy, and society. Owing to past emissions and climate system inertia, global climate change is predicted to continue for decades even if anthropogenic greenhouse gas emissions were to stop immediately. In many regions, such as central Europe and the Mediterranean region, the temperature is likely to rise by 2-5 degrees C and annual precipitation is predicted to decrease. Expected heat and drought periods followed by floods, and unpredictable growing seasons, are predicted to have detrimental effects on agricultural production systems, causing immense economic losses and food supply problems. To mitigate the risks of climate change, agricultural innovations counteracting these effects need to be embraced and accelerated. To achieve maximum improvement, the required agricultural innovations should not focus only on crops but rather pursue a holistic approach including the entire ecosystem. Over millions of years, plants have evolved in close association with other organisms, particularly soil microbes that have shaped their evolution and contemporary ecology. Many studies have already highlighted beneficial interactions among plants and the communities of microorganisms with which they coexist. Questions arising from these discoveries are whether it will be possible to decipher a common molecular pattern and the underlying biochemical framework of interspecies communication, and whether such knowledge can be used to improve agricultural performance under environmental stress conditions. In this review, we summarize the current knowledge of plant interactions with fungal endosymbionts found in extreme ecosystems. Special attention will be paid to the interaction of plants with the symbiotic root-colonizing endophytic fungus Serendipita indica, which has been developed as a model system for beneficial plant-fungus interactions.

DOI： 10.1093/jxb/eraa040

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：WILEY  

Nitrogen and phosphorus are two major soil nutrients required for plant growth. Because requirements of both these elements are interdependent, acquisition of one must be balanced with that of the other. However, the mechanism underlying this balanced acquisition remains unclear. Here, we show by in vivo luciferase imaging that the presence of nitrogen sources is a pre-requisite for strong activation of phosphate starvation responses. In addition, we also show that nitrate rather than ammonium is a potent modulator of phosphate starvation-induced gene expression. Furthermore, protoplast-based transient expression assay and chromatin immunoprecipitation assay demonstrate that NIGT1 GARP-type transcriptional repressors, which are encoded by nitrate-inducible genes, directly bind to and repress the promoters of genes encoding SPX proteins. Consistent with the role of SPX proteins in the suppression of the PHR1 transcriptional activator, the master regulator for phosphate starvation responses, nitrate-dependent enhancement of phosphate starvation responses, such as accumulation of anthocyanin and promotion of root hair growth and phosphate uptake, was less evident in the nigt1.1-nigt1.4 quadruple mutant. Consistently, NIGT1 overexpression alleviated the reduction in phosphate uptake under phosphate-replete conditions. We further reveal the intricate feedback regulations involving PHR1, NIGT1, and SPX family proteins in the phosphate starvation signalling network. Importantly, results of mutant protoplast-based assays and in planta analysis using NIGT1 overexpression in the spx1 spx2 double mutant indicated that the NIGT1-SPX-PHR cascade mediates nitrogen status-responsive regulation of phosphate uptake and starvation signalling. These findings uncover the mechanism underlying the balanced acquisition of nitrogen and phosphorus.

DOI： 10.1111/tpj.14637

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：TAYLOR & FRANCIS LTD  

Plants flower under appropriate day-length conditions by integrating temporal information provided by the circadian clock with light and dark information from the environment. A sub-group of plant specific circadian clock-associated PSEUDO-RESPONSE REGULATOR (PRR) genes (PRR7/PRR3 sub-group) controls flowering time both in long-day and short-day plants; however, flowering control by the other two PRR gene sub-groups has been reported only in Arabidopsis thaliana (Arabidopsis), a model long-day plant. Here, we show that an Arabidopsis PRR9/PRR5 sub-group gene can control flowering time (heading date) in rice, a short-day plant. Although PRR5 promotes flowering in Arabidopsis, transgenic rice overexpressing Arabidopsis PRR5 caused late flowering. Such transgenic rice plants produced significantly higher biomass, but not grain yield, due to the late flowering. Concomitantly, expression of Hd3a, a rice florigen gene, was reduced in the transgenic rice.

DOI： 10.1080/09168451.2020.1719822

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：CELL PRESS  

Parasitic plants in the genus Striga, commonly known as witchweeds, cause major crop losses in sub-Saharan Africa and pose a threat to agriculture worldwide. An understanding of Striga parasite biology, which could lead to agricultural solutions, has been hampered by the lack of genome information. Here, we report the draft genome sequence of Striga asiatica with 34,577 predicted protein-coding genes, which reflects gene family contractions and expansions that are consistent with a three-phase model of parasitic plant genome evolution. Striga seeds germinate in response to host-derived strigolactones (SLs) and then develop a specialized penetration structure, the haustorium, to invade the host root. A family of SL receptors has undergone a striking expansion, suggesting a molecular basis for the evolution of broad host range among Striga spp. We found that genes involved in lateral root development in non-parasitic model species are coordinately induced during haustorium development in Striga, suggesting a pathway that was partly co-opted during the evolution of the haustorium. In addition, we found evidence for horizontal transfer of host genes as well as retrotransposons, indicating gene flow to S. asiatica from hosts. Our results provide valuable insights into the evolution of parasitism and a key resource for the future development of Striga control strategies.

DOI： 10.1016/j.cub.2019.07.086

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Springer Science and Business Media {LLC}  

DOI： 10.1038/s41598-019-44185-4

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Springer Science and Business Media {LLC}  

Technology involving the targeted mutagenesis of plants using programmable nucleases has been developing rapidly and has enormous potential in next-generation plant breeding. Notably, the clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated protein-9 nuclease (Cas9) (CRISPR-Cas9) system has paved the way for the development of rapid and cost-effective procedures to create new mutant populations in plants1,2. Although genome-edited plants from multiple species have been produced successfully using a method in which a Cas9-guide RNA (gRNA) expression cassette and selectable marker are integrated into the genomic DNA by Agrobacterium tumefaciens-mediated transformation or particle bombardment3, CRISPR-Cas9 integration increases the chance of off-target modifications4, and foreign DNA sequences cause legislative concerns about genetically modified organisms5. Therefore, DNA-free genome editing has been developed, involving the delivery of preassembled Cas9-gRNA ribonucleoproteins (RNPs) into protoplasts derived from somatic tissues by polyethylene glycol-calcium (PEG-Ca2+)-mediated transfection in tobacco, Arabidopsis, lettuce, rice6, Petunia7, grapevine, apple8 and potato9, or into embryo cells by biolistic bombardment in maize10 and wheat11. However, the isolation and culture of protoplasts is not feasible in most plant species and the frequency of obtaining genome-edited plants through biolistic bombardment is relatively low. Here, we report a genome-editing system via direct delivery of Cas9-gRNA RNPs into plant zygotes. Cas9-gRNA RNPs were transfected into rice zygotes produced by in vitro fertilization of isolated gametes12 and the zygotes were cultured into mature plants in the absence of selection agents, resulting in the regeneration of rice plants with targeted mutations in around 14-64% of plants. This efficient plant-genome-editing system has enormous potential for the improvement of rice as well as other important crop species.

DOI： 10.1038/s41477-019-0386-z

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1080/00380768.2018.1537643

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Springer Science and Business Media {LLC}  

In flowering plants, the switch from floral stem cell maintenance to gynoecium (female structure) formation is a critical developmental transition for reproductive success. In Arabidopsis thaliana, AGAMOUS (AG) terminates floral stem cell activities to trigger this transition. Although CRABS CLAW (CRC) is a direct target of AG, previous research has not identified any common targets. Here, we identify an auxin synthesis gene, YUCCA4 (YUC4) as a common direct target. Ectopic YUC4 expression partially rescues the indeterminate phenotype and cell wall defects that are caused by the crc mutation. The feed-forward YUC4 activation by AG and CRC directs a precise change in chromatin state for the shift from floral stem cell maintenance to gynoecium formation. We also showed that two auxin-related direct CRC targets, YUC4 and TORNADO2, cooperatively contribute to the termination of floral stem cell maintenance. This finding provides new insight into the CRC-mediated auxin homeostasis regulation for proper gynoecium formation.

DOI： 10.1038/s41467-018-07763-0

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掲載種別：研究論文（学術雑誌）  

DOI： 10.1093/pcp/pcy151

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記述言語：英語   出版者・発行元：SPRINGER  

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Wiley-VCH Verlag  

Proper floral patterning, including the number and position of floral organs in most plant species, is tightly controlled by the precise regulation of the persistence and size of floral meristems (FMs). In Arabidopsis, two known feedback pathways, one composed of WUSCHEL (WUS) and CLAVATA3 (CLV3) and the other composed of AGAMOUS (AG) and WUS, spatially and temporally control floral stem cells, respectively. However, mounting evidence suggests that other factors, including phytohormones, are also involved in floral meristem regulation. Here, we show that the boundary gene SUPERMAN (SUP) bridges floral organogenesis and floral meristem determinacy in another pathway that involves auxin signaling. SUP interacts with components of polycomb repressive complex 2 (PRC2) and fine-tunes local auxin signaling by negatively regulating the expression of the auxin biosynthesis genes YUCCA1/4 (YUC1/4). In sup mutants, derepressed local YUC1/4 activity elevates auxin levels at the boundary between whorls 3 and 4, which leads to an increase in the number and the prolonged maintenance of floral stem cells, and consequently an increase in the number of reproductive organs. Our work presents a new floral meristem regulatory mechanism, in which SUP, a boundary gene, coordinates floral organogenesis and floral meristem size through fine-tuning auxin biosynthesis.

DOI： 10.15252/embj.201797499

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：American Society of Plant Biologists ({ASPB})  

Nitrogen (N) is often a limiting nutrient whose availability determines plant growth and productivity. Because its availability is often low and/or not uniform over time and space in nature, plants respond to variations in N availability by altering uptake and recycling mechanisms, but the molecular mechanisms underlying how these responses are regulated are poorly understood. Here, we show that a group of GARP G2-like transcription factors, Arabidopsis thaliana NITRATE-INDUCIBLE, GARP-TYPE TRANSCRIPTIONAL REPRESSOR1/HYPERSENSITIVE TO LOW Pi-ELICITED PRIMARY ROOT SHORTENING1 proteins (NIGT1/HRS1s), are factors that bind to the promoter of the N starvation marker NRT2.4 and repress an array of N starvation-responsive genes under conditions of high N availability. Transient assays and expression analysis demonstrated that NIGT1/HRS1s are transcriptional repressors whose expression is regulated by N availability. We identified target genes of the NIGT1/HRS1s by genome-wide transcriptome analyses and found that they are significantly enriched in N starvation response-related genes, including N acquisition, recycling, remobilization, and signaling genes. Loss of NIGT1/HRS1s resulted in deregulation of N acquisition and accumulation. We propose that NIGT1/HRS1s are major regulators of N starvation responses that play an important role in optimizing N acquisition and utilization under fluctuating N conditions.

DOI： 10.1105/tpc.17.00810

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Springer Nature  

Nitrate is a nutrient signal that triggers complex regulation of transcriptional networks to modulate nutrient-dependent growth and development in plants. This includes time- and nitrate concentration-dependent regulation of nitrate-related gene expression. However, the underlying mechanisms remain poorly understood. Here we identify NIGT1 transcriptional repressors as negative regulators of the Arabidopsis NRT2.1 nitrate transporter gene, and show antagonistic regulation by NLP primary transcription factors for nitrate signalling and the NLP-NIGT1 transcriptional cascade-mediated repression. This antagonistic regulation provides a resolution to the complexity of nitrate-induced transcriptional regulations. Genome-wide analysis reveals that this mechanism is applicable to NRT2.1 and other genes involved in nitrate assimilation, hormone biosynthesis and transcription. Furthermore, the PHR1 master regulator of the phosphorus-starvation response also directly promotes expression of NIGT1 family genes, leading to reductions in nitrate uptake. NIGT1 repressors thus act in two transcriptional cascades, forming a direct link between phosphorus and nitrogen nutritional regulation.

DOI： 10.1038/s41467-018-03832-6

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Palgrave Macmillan Ltd.  

Organ-to-organ signal transmission is essential for higher organisms to ensure coordinated biological reactions during metabolism and morphogenesis. Similar to organs in animals, plant organs communicate by various signalling molecules. Among them, cytokinins, a class of phytohormones, play a key role as root-to-shoot long-distance signals, regulating various growth and developmental processes in shoots 1,2. Previous studies have proposed that trans-zeatin-riboside, a type of cytokinin precursor, is a major long-distance signalling form in xylem vessels and its action depends on metabolic conversion via the LONELY GUY enzyme in proximity to the site of action 3-5. Here we report an additional long-distance signalling form of cytokinin: trans-zeatin, an active form. Grafting between various cytokinin biosynthetic and transportation mutants revealed that root-to-shoot translocation of trans-zeatin, a minor component of xylem cytokinin, controls leaf size but not meristem activity-related traits, whereas that of trans-zeatin riboside is sufficient for regulating both traits. Considering the ratio of trans-zeatin to trans-zeatin-riboside in xylem and their delivery rate change in response to environmental conditions, this dual long-distance cytokinin signalling system allows plants to fine-tune the manner of shoot growth to adapt to fluctuating environments.

DOI： 10.1038/nplants.2017.112

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：NATL ACAD SCIENCES  

Parasitic plants share a common anatomical feature, the haustorium. Haustoria enable both infection and nutrient transfer, which often leads to growth penalties for host plants and yield reduction in crop species. Haustoria also reciprocally transfer substances, such as RNA and proteins, from parasite to host, but the biological relevance for such movement remains unknown. Here, we studied such interspecies transport by using the hemiparasitic plant Phtheirospermum japonicum during infection of Arabidopsis thaliana. Tracer experiments revealed a rapid and efficient transfer of carboxyfluorescein diacetate (CFDA) from host to parasite upon formation of vascular connections. In addition, Phtheirospermum induced hypertrophy in host roots at the site of infection, a form of enhanced secondary growth that is commonly observed during various parasitic plant-host interactions. The plant hormone cytokinin is important for secondary growth, and we observed increases in cytokinin and its response during infection in both host and parasite. Phtheirospermum-induced host hypertrophy required cytokinin signaling genes (AHK3,4) but not cytokinin biosynthesis genes (IPT1,3,5,7) in the host. Furthermore, expression of a cytokinin-degrading enzyme in Phtheirospermum prevented host hypertrophy. Wild-type hosts with hypertrophy were smaller than ahk3,4 mutant hosts resistant to hypertrophy, suggesting hypertrophy improves the efficiency of parasitism. Taken together, these results demonstrate that the interspecies movement of a parasite-derived hormone modified both host root morphology and fitness. Several microbial and animal plant pathogens use cytokinins during infections, highlighting the central role of this growth hormone during the establishment of plant diseases and revealing a common strategy for parasite infections of plants.

DOI： 10.1073/pnas.1619078114

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：NATURE PUBLISHING GROUP  

Organ-to-organ signal transmission is essential for higher organisms to ensure coordinated biological reactions during metabolism and morphogenesis. Similar to organs in animals, plant organs communicate by various signalling molecules. Among them, cytokinins, a class of phytohormones, play a key role as root-to-shoot long-distance signals, regulating various growth and developmental processes in shoots(1,2). Previous studies have proposed that trans-zeatin-riboside, a type of cytokinin precursor, is a major long-distance signalling form in xylem vessels and its action depends on metabolic conversion via the LONELY GUY enzyme in proximity to the site of action(3-5). Here we report an additional long-distance signalling form of cytokinin: trans-zeatin, an active form. Grafting between various cytokinin biosynthetic and transportation mutants revealed that root-to-shoot translocation of trans-zeatin, a minor component of xylem cytokinin, controls leaf size but not meristem activity-related traits, whereas that of trans-zeatin riboside is sufficient for regulating both traits. Considering the ratio of trans-zeatin to trans-zeatin-riboside in xylem and their delivery rate change in response to environmental conditions, this dual long-distance cytokinin signalling system allows plants to fine-tune the manner of shoot growth to adapt to fluctuating environments.

DOI： 10.1038/nplants.2017.112

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELIFE SCIENCES PUBLICATIONS LTD  

A LOV (Light, Oxygen, or Voltage) domain containing blue-light photoreceptor ZEITLUPE (ZTL) directs circadian timing by degrading clock proteins in plants. Functions hinge upon allosteric differences coupled to the ZTL photocycle; however, structural and kinetic information was unavailable. Herein, we tune the ZTL photocycle over two orders of magnitude. These variants reveal that ZTL complexes with targets independent of light, but dictates enhanced protein degradation in the dark. In vivo experiments definitively show photocycle kinetics dictate the rate of clock component degradation, thereby impacting circadian period. Structural studies demonstrate that photocycle dependent activation of ZTL depends on an unusual dark-state conformation of ZTL. Crystal structures of ZTL LOV domain confirm delineation of structural and kinetic mechanisms and identify an evolutionarily selected allosteric hinge differentiating modes of PAS/LOV signal transduction. The combined biochemical, genetic and structural studies provide new mechanisms indicating how PAS/LOV proteins integrate environmental variables in complex networks.

DOI： 10.7554/eLife.21646

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：OXFORD UNIV PRESS  

Plant circadian clocks control the timing of a variety of genetic, metabolic and physiological processes. Recent studies revealed a possible molecular mechanism for circadian clock regulation. Arabidopsis thaliana (Arabidopsis) PSEUDORESPONSE REGULATOR (PRR) genes, including TIMING OF CAB EXPRESSION 1 (TOC1), encode clock-associated transcriptional repressors that act redundantly. Disruption of multiple PRR genes results in drastic phenotypes, including increased biomass and abiotic stress tolerance, whereas PRR single mutants show subtle phenotypic differences due to genetic redundancy. In this study, we demonstrate that constitutive expression of engineered PRR5 (PRR5-VP), which functions as a transcriptional activator, can increase biomass and abiotic stress tolerance, similar to prr multiple mutants. Concomitant analyses of relative growth rate, flowering time and photosynthetic activity suggested that increased biomass of PRR5-VP plants is mostly due to late flowering, rather than to alterations in photosynthetic activity or growth rate. In addition, genome-wide gene expression profiling revealed that genes related to cold stress and water deprivation responses were up-regulated in PRR5-VP plants. PRR5-VP plants were more resistant to cold, drought and salinity stress than the wild type, whereas ft tsf and gi, wellknown late flowering and increased biomass mutants, were not. These findings suggest that attenuation of PRR function by a single transformation of PRR-VP is a valuable method for increasing biomass as well as abiotic stress tolerance in Arabidopsis. Because the PRR gene family is conserved in vascular plants, PRR-VP may regulate biomass and stress responses in many plants, but especially in long-day annual plants.

DOI： 10.1093/pcp/pcw057

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Methods in Molecular Biology  

DOI： 10.1007/978-1-4939-3356-3_13

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記述言語：日本語   出版者・発行元：一般社団法人植物化学調節学会  

<p>Plants maximize fitness by coordinating growth and development of cells as well as organs in response to environmental changes. For the coordination, cell-to-cell and long-distance communication among cells and organs is necessary. Cytokinins, a class of phytohormones that play key roles in various processes of plant growth and development, have been implicated in the communication. It has been shown that cytokinin action is regulated at various steps, including de novo biosynthesis, degradation, transport, perception, and signaling, to play roles in the communication. This review summarizes and provides updates on the regulatory mechanisms of cytokinin action with major emphasis on cytokinin de novo biosynthesis and transport. We also introduce the mechanisms of cytokinin biosynthesis by phytopathogens that exploit cytokinin action for their infection.</p>

DOI： 10.18978/jscrp.51.1_24

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：OXFORD UNIV PRESS  

Nitrogen availability is a major factor determining plant growth and productivity. Plants acquire nitrogen nutrients from the soil through their roots mostly in the form of ammonium and nitrate. Since these nutrients are scarce in natural soils, plants have evolved adaptive responses to cope with the environment. One of the most important responses is the regulation of nitrogen acquisition efficiency. This review provides an update on the molecular determinants of two major drivers of the nitrogen acquisition efficiency: (i) uptake activity (e.g. high-affinity nitrogen transporters) and (ii) root architecture (e.g. low-nitrogen-availability-specific regulators of primary and lateral root growth). Major emphasis is laid on the regulation of these determinants by nitrogen supply at the transcriptional and post-transcriptional levels, which enables plants to optimize nitrogen acquisition efficiency under low nitrogen availability.

DOI： 10.1093/pcp/pcw052

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：WILEY-BLACKWELL  

Nitrogen is a key mineral nutrient playing a crucial role in plant growth and development. Understanding the mechanisms of nitrate uptake from the soil and distribution through the plant in response to nitrogen starvation is an important step on the way to improve nitrogen uptake and utilization efficiency for better growth and productivity of plants, and to prevent negative effects of nitrogen fertilizers on the environment and human health. In this study, we show that Arabidopsis NITRATE TRANSPORTER 2.5 (NRT2.5) is a plasma membrane-localized high-affinity nitrate transporter playing an essential role in adult plants under severe nitrogen starvation. NRT2.5 expression is induced under nitrogen starvation and NRT2.5 becomes the most abundant transcript amongst the seven NRT2 family members in shoots and roots of adult plants after long-term starvation. GUS reporter analyses showed that NRT2.5 is expressed in the epidermis and the cortex of roots at the root hair zone and in minor veins of mature leaves. Reduction of NRT2.5 expression resulted in a decrease in high-affinity nitrate uptake without impacting low-affinity uptake. In the background of the high-affinity nitrate transporter mutant nrt2.4, an nrt2.5 mutation reduced nitrate levels in the phloem of N-starved plants further than in the single nrt2.4 mutants. Growth analyses of multiple mutants between NRT2.1, NRT2.2, NRT2.4, and NRT2.5 revealed that NRT2.5 is required to support growth of nitrogen-starved adult plants by ensuring the efficient uptake of nitrate collectively with NRT2.1, NRT2.2 and NRT2.4 and by taking part in nitrate loading into the phloem during nitrate remobilization.

DOI： 10.1111/tpj.12626

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：OXFORD UNIV PRESS  

Elevated CO2 has been reported to stimulate plant growth under nitrogen-sufficient conditions, but the effects of CO2 on growth in a constantly nitrogen-limited state, which is relevant to most natural habitats of plants, remain unclear. Here, we maintained Arabidopsis seedlings under such conditions by growing a mutant with reduced nitrate uptake activity on a medium containing nitrate as the sole nitrogen source. Under nitrogen-sufficient conditions (i.e. in the presence of ammonium), growth of shoots and roots of both the wild type (WT) and the mutant was increased approximately 2-fold by elevated CO2. Growth stimulation of shoots and roots by elevated CO2 was observed in the WT growing with nitrate as the sole nitrogen source, but in the mutant grown with nitrate, the high-CO2 conditions stimulated only the growth of roots. In the mutant, elevated CO2 caused well-known symptoms of nitrogen-starved plants, including decreased shoot/root ratio, reduced nitrate content and accumulation of anthocyanin, but also had an increased Chl content in the shoot, which was contradictory to the known effect of nitrogen depletion. A high-CO2-responsive change specific to the mutant was not observed in the levels of the major metabolites, although CO2 responses were observed in the WT and the mutant. These results indicated that elevated CO2 causes nitrogen limitation in the seedlings grown with a constantly limited supply of nitrogen, but the Chl content and the root biomass of the plant increase to enhance the activities of both photosynthesis and nitrogen uptake, while maintaining normal metabolism and response to high CO2.

DOI： 10.1093/pcp/pct186

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：NATL ACAD SCIENCES  

Cytokinins are phytohormones that induce cytokinesis and are essential for diverse developmental and physiological processes in plants. Cytokinins of the trans-zeatin type are mainly synthesized in root vasculature and transported to the shoot, where they regulate shoot growth. However, the mechanism of long-distance transport of cytokinin was hitherto unknown. Here, we report that the Arabidopsis ATP-binding cassette (ABC) transporter subfamily G14 (AtABCG14) is mainly expressed in roots and plays a major role in delivering cytokinins to the shoot. Loss of AtABCG14 expression resulted in severe shoot growth retardation, which was rescued by exogenous trans-zeatin application. Cytokinin content was decreased in the shoots of atabcg14 plants and increased in the roots, with consistent changes in the expression of cytokinin-responsive genes. Grafting of atabcg14 scions onto wild-type rootstocks restored shoot growth, whereas wild-type scions grafted onto atabcg14 rootstocks exhibited shoot growth retardation similar to that of atabcg14. Cytokinin concentrations in the xylem are reduced by similar to 90% in the atabcg14 mutant. These results indicate that AtABCG14 is crucial for the translocation of cytokinin to the shoot. Our results provide molecular evidence for the long-distance transport of cytokinin and show that this transport is necessary for normal shoot development.

DOI： 10.1073/pnas.1321519111

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掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.devce1.2013.10.004

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：WILEY-BLACKWELL  

Cytokinins are phytohormones that play key roles in the maintenance of stem cell activity in plants. Although alternative single-step and two-step activation pathways for cytokinin have been proposed, the significance of the single-step pathway which is catalyzed by LONELY GUY (LOG), is not fully understood. We analyzed the metabolic flow of cytokinin activation in Arabidopsis log multiple mutants using stable isotope-labeled tracers and characterized the mutants morphological and developmental phenotypes. In tracer experiments, cytokinin activation was inhibited most pronouncedly by log7, while the other log mutations had cumulative effects. Although sextuple or lower-order mutants did not show drastic phenotypes in vegetative growth, the log1log2log3log4log5log7log8 septuple T-DNA insertion mutant in which the LOG-dependent pathway is impaired, displayed severe retardation of shoot and root growth with defects in the maintenance of the apical meristems. Detailed observation of the mutants showed that LOG7 was required for the maintenance of shoot apical meristem size. LOG7 was also suggested to play a role for normal primary root growth together with LOG3 and LOG4. These results suggest a dominant role of the single-step activation pathway mediated by LOGs for cytokinin production, and overlapping but differentiated functions of the members of the LOG gene family in growth and development.

DOI： 10.1111/j.1365-313X.2011.04795.x

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：BMC  

Background: Over application of phosphate fertilizers in modern agriculture contaminates waterways and disrupts natural ecosystems. Nevertheless, this is a common practice among farmers, especially in developing countries as abundant fertilizers are believed to boost crop yields. The study of plant phosphate metabolism and its underlying genetic pathways is key to discovering methods of efficient fertilizer usage. The work presented here describes a genome-wide resource on the molecular dynamics underpinning the response and recovery in roots and shoots of Arabidopsis thaliana to phosphate-starvation.Results: Genome-wide profiling by micro-and tiling-arrays (accessible from GEO: GSE34004) revealed minimal overlap between root and shoot transcriptomes suggesting two independent phosphate-starvation regulons. Novel gene expression patterns were detected for over 1000 candidates and were classified as either initial, persistent, or latent responders. Comparative analysis to AtGenExpress identified cohorts of genes co-regulated across multiple stimuli. The hormone ABA displayed a dominant role in regulating many phosphate-responsive candidates. Analysis of co-regulation enabled the determination of specific versus generic members of closely related gene families with respect to phosphate-starvation. Thus, among others, we showed that PHR1-regulated members of closely related phosphate-responsive families (PHT1;1, PHT1;7-9, SPX1-3, and PHO1;H1) display greater specificity to phosphate-starvation than their more generic counterparts.Conclusion: Our results uncover much larger, staged responses to phosphate-starvation than previously described. To our knowledge, this work describes the most complete genome-wide data on plant nutrient stress to-date.

DOI： 10.1186/1471-2229-12-62

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER SOC PLANT BIOLOGISTS  

Plants have evolved a variety of mechanisms to adapt to N starvation. NITRATE TRANSPORTER2.4 (NRT2.4) is one of seven NRT2 family genes in Arabidopsis thaliana, and NRT2.4 expression is induced under N starvation. Green fluorescent protein and beta-glucuronidase reporter analyses revealed that NRT2.4 is a plasma membrane transporter expressed in the epidermis of lateral roots and in or close to the shoot phloem. The spatiotemporal expression pattern of NRT2.4 in roots is complementary with that of the major high-affinity nitrate transporter NTR2.1. Functional analysis in Xenopus laevis oocytes and in planta showed that NRT2.4 is a nitrate transporter functioning in the high-affinity range. In N-starved nrt2.4 mutants, nitrate uptake under low external supply and nitrate content in shoot phloem exudates was decreased. In the absence of NRT2.1 and NRT2.2, loss of function of NRT2.4 (triple mutants) has an impact on biomass production under low nitrate supply. Together, our results demonstrate that NRT2.4 is a nitrate transporter that has a role in both roots and shoots under N starvation.

DOI： 10.1105/tpc.111.092221

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：NATL ACAD SCIENCES  

The circadian clock is an endogenous time-keeping mechanism that enables organisms to adapt to external daily cycles. The clock coordinates biological activities with these cycles, mainly through genome-wide gene expression. However, the exact mechanism underlying regulation of circadian gene expression is poorly understood. Here we demonstrated that an Arabidopsis PSEUDO-RESPONSE REGULATOR 5 (PRR5), which acts in the clock genetic circuit, directly regulates expression timing of key transcription factors involved in clock-output pathways. A transient expression assay and ChIP-quantitative PCR assay using mutated PRR5 indicated that PRR5 associates with target DNA through binding at the CCT motif in vivo. ChIP followed by deep sequencing coupled with genome-wide expression profiling revealed the direct-target genes of PRR5. PRR5 direct-targets include genes encoding transcription factors involved in flowering-time regulation, hypocotyl elongation, and cold-stress responses. PRR5-target gene expression followed a circadian rhythm pattern with low, basal expression from noon until midnight, when PRR9, PRR7, and PRR5 were expressed. ChIP-quantitative PCR assays indicated that PRR7 and PRR9 bind to the direct-targets of PRR5. Genome-wide expression profiling using a prr9 prr7 prr5 triple mutant suggests that PRR5, PRR7, and PRR9 repress these targets. Taken together, our results illustrate a genetic network in which PRR5, PRR7, and PRR9 directly regulate expression timing of key transcription factors to coordinate physiological processes with daily cycles.

DOI： 10.1073/pnas.1205156109

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：OXFORD UNIV PRESS  

Nitrogen is the mineral nutrient that often limits plant growth and development. In response to changes in nitrogen supply, plants display elaborate responses at both physiological and morphological levels to adjust their growth and development. Because higher plants consist of multiple organs with different functions and nutritional requirements, they rely on local and long-distance signalling pathways to coordinate the responses at the whole-plant level. Phytohormones have been considered as signalling substances of such pathways. Amongst phytohormones, abscisic acid, auxin, and cytokinins have been closely linked to nitrogen signalling. Recent evidence has provided some insights into how nitrogen and the phytohormone signals are integrated to bring about changes in physiology and morphology. In this review, the evidence is summarized, mostly focusing on examples related to nitrogen acquisition.

DOI： 10.1093/jxb/erq410

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：WILEY-BLACKWELL  

As important components of small RNA (smRNA) pathways, Argonaute (AGO) proteins mediate the interaction of incorporated smRNAs with their targets. Arabidopsis contains 10 AGO proteins with specialized or redundant functions. Among them, AGO1 mainly acts in microRNA (miRNA) and small-interfering RNA (siRNA) pathways for post-transcriptional gene silencing (PTGS), whereas AGO4 regulates transcriptional gene silencing (TGS) via endogenous 24-nucleotide (nt) smRNAs. To fully characterize smRNAs associated with AGO1 and AGO4, we developed a two-step protocol to purify AGO/smRNA complexes from flowers, leaves, roots and seedlings with enhanced purity, and sequenced the smRNAs by Illumina technology. Besides recovering most previously annotated smRNAs, we also identified some additional miRNAs, phased smRNA clusters and small-interfering RNAs derived from the overlapping region of natural antisense transcript pairs (NAT) (nat-siRNAs). We also identified a smRNA distribution feature on miRNA precursors which may help to identify authentic miRNAs. Organ-specific sequencing provided digital expression profiles of all obtained smRNAs, especially miRNAs. The presence and conservation of collateral miRNAs on known miRNA precursors were also investigated. Intriguingly, about 30% of AGO1-associated smRNAs were 24-nt long and unrelated to the 21-nt species. Further analysis showed that DNA-dependent RNA polymerase IV (Pol IV)dependent smRNAs were mainly 24 nt and associated with AGO4, whereas the majority of the potential Pol V-dependent ones were 21-nt smRNAs and bound to AGO1, suggesting the potential involvement of AGO1 in Pol V-related pathways.

DOI： 10.1111/j.1365-313X.2011.04594.x

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記述言語：英語   掲載種別：論文集(書籍)内論文   出版者・発行元：Springer Berlin Heidelberg  

Cytokinins are a class of plant hormones that regulate diverse aspects of plant growth and development. During the past decade, genetic and genomic approaches have succeeded in identifying many genes involved in the de novo synthesis, activation, inactivation, and signaling of cytokinin. Characterization of these genes has not only helped to define basic schemes of cytokinin biosynthesis and signaling, but has also demonstrated that cytokinins play a crucial role in numerous developmental processes. Furthermore, recent studies in rice have highlighted cytokinins as promising targets for crop improvement. This chapter gives an overview of our current understanding of the cytokinin biosynthesis and signaling pathways, and summarizes recent findings on the molecular basis for cytokinin involvement in plant development. © 2010 Springer-Verlag Berlin Heidelberg.

DOI： 10.1007/978-3-642-04670-4_13

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER SOC PLANT BIOLOGISTS  

An interlocking transcriptional-translational feedback loop of clock-associated genes is thought to be the central oscillator of the circadian clock in plants. TIMING OF CAB EXPRESSION1 (also called PSEUDO-RESPONSE REGULATOR1 [PRR1]) and two MYB transcription factors, CIRCADIAN CLOCK ASSOCIATED1 (CCA1) and LATE ELONGATED HYPOCOTYL (LHY), play pivotal roles in the loop. Genetic studies have suggested that PRR9, PRR7, and PRR5 also act within or close to the loop; however, their molecular functions remain unknown. Here, we demonstrate that PRR9, PRR7, and PRR5 act as transcriptional repressors of CCA1 and LHY. PRR9, PRR7, and PRR5 each suppress CCA1 and LHY promoter activities and confer transcriptional repressor activity to a heterologous DNA binding protein in a transient reporter assay. Using a glucocorticoid-induced PRR5-GR (glucorticoid receptor) construct, we found that PRR5 directly downregulates CCA1 and LHY expression. Furthermore, PRR9, PRR7, and PRR5 associate with the CCA1 and LHY promoters in vivo, coincident with the timing of decreased CCA1 and LHY expression. These results suggest that the repressor activities of PRR9, PRR7, and PRR5 on the CCA1 and LHY promoter regions constitute the molecular mechanism that accounts for the role of these proteins in the feedback loop of the circadian clock.

DOI： 10.1105/tpc.109.072892

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER SOC PLANT BIOLOGISTS  

Regulation of protein turnover mediated by ZEITLUPE (ZTL) constitutes an important mechanism of the circadian clock in Arabidopsis thaliana. Here, we report that FLAVIN BINDING, KELCH REPEAT, F-BOX1 (FKF1) and LOV KELCH PROTEIN2 (LKP2) play similar roles to ZTL in the circadian clock when ZTL is absent. In contrast with subtle circadian clock defects in fkf1, the clock in ztl fkf1 has a considerably longer period than in ztl. In ztl fkf1 lkp2, several clock parameters were even more severely affected than in ztl fkf1. Although LATE ELONGATED HYPOCOTYL (LHY) and CIRCADIAN CLOCK ASSOCIATED1 (CCA1) expression levels are lower in ztl than in the wild type, introducing both fkf1 and lkp2 mutations into the ztl mutant dramatically diminished LHY expression without further affecting CCA1 expression. This demonstrates different contributions of ZTL, FKF1, and LKP2 in the regulation of LHY and CCA1 expression. In addition, FKF1 and LKP2 also interacted with TIMING OF CAB EXPRESSION1 (TOC1) and PSEUDO-RESPONSE REGULATOR5 (PRR5), and both proteins were further stabilized in ztl fkf1 and ztl fkf1 lkp2 compared with in ztl. Our results indicate that ZTL, FKF1, and LKP2 together regulate TOC1 and PRR5 degradation and are major contributors to determining the period of circadian oscillation and enhancing robustness.

DOI： 10.1105/tpc.109.072843

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：WILEY-BLACKWELL  

During plant development, distantly-located organs must communicate in order to adapt morphological and physiological features in response to environmental inputs. Among the recognized signaling molecules, a class of phytohormones known as the cytokinins functions as both local and long-distance regulatory signals for the coordination of plant development. This cytokinin-dependent communication system consists of orchestrated regulation of the metabolism, translocation, and signal transduction of this phytohormone class. Here, to gain insight into this elaborate signaling system, we summarize current models of biosynthesis, trans-membrane transport, and long-distance translocation of cytokinins in higher plants.

DOI： 10.1111/j.1744-7909.2010.00898.x

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記述言語：英語   出版者・発行元：OXFORD UNIV PRESS  

DOI： 10.1093/pcp/pcm169

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：WILEY-BLACKWELL PUBLISHING, INC  

We analyzed global gene expression in Arabidopsis in response to various hormones and in related experiments as part of the AtGenExpress project. The experimental agents included seven basic phytohormones (auxin, cytokinin, gibberellin, brassinosteroid, abscisic acid, jasmonate and ethylene) and their inhibitors. In addition, gene expression was investigated in hormone-related mutants and during seed germination and sulfate starvation. Hormone-inducible genes were identified from the hormone response data. The effects of each hormone and the relevance of the gene lists were verified by comparing expression profiles for the hormone treatments and related experiments using Pearson&apos;s correlation coefficient. This approach was also used to analyze the relationships among expression profiles for hormone responses and those included in the AtGenExpress stress-response data set. The expected correlations were observed, indicating that this approach is useful to monitor the hormonal status in the stress-related samples. Global interactions among hormones-inducible genes were analyzed in a pairwise fashion, and several known and novel hormone interactions were detected. Genome-wide transcriptional gene-to-gene correlations, analyzed by hierarchical cluster analysis (HCA), indicated that our data set is useful for identification of clusters of co-expressed genes, and to predict the functions of unknown genes, even if a gene&apos;s function is not directly related to the experiments included in AtGenExpress. Our data are available online from AtGenExpressJapan; the results of genome-wide HCA are available from PRIMe. The data set presented here will be a versatile resource for future hormone studies, and constitutes a reference for genome-wide gene expression in Arabidopsis.

DOI： 10.1111/j.1365-313X.2008.03510.x

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：TAYLOR & FRANCIS LTD  

More than 1,600 genes encoding transcription factors have been identified in the Arabidopsis genome sequence, but their physiological functions are not yet fully understood. In this study, a small subfamily of single-MYB transcription factor genes, designated RSM1, RSM2, RSM3 and RSM4 (RADIALIS-LIKE SANT/MYB 1-4), was characterized. Here, we mainly examined the RSM1 gene, and found that it appears to play a role in close connection with the HLS1 (HOOKLESS 1) gene during early morphogenesis. Etiolated seedlings overexpressing RSM1 showed several phenotypes similar to those of hls1-1, viz., lack of apical hooks with short hypocotyls, and a defect in gravitropism. Furthermore, both RSM1-ox and hls1-1 seedlings were hypersensitive to red light during early photomorphogenesis, displaying shorter hypocotyls than wild-type seedlings. The histochemical profile of the DR5::GUS auxin-reporter in the RMS1-ox seedlings was considerably different from that in the wild-type seedlings. These results are discussed in the context of the possibility that RSM1 is implicated in HLS1-mediated auxin signaling, which is responsible for regulation of the early photomorphogenesis of Arabidopsis thaliana.

DOI： 10.1271/bbb.80348

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記述言語：英語   出版者・発行元：OXFORD UNIV PRESS  

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DOI： 10.14841/jspp.2007.0.683.0

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：TAYLOR & FRANCIS LTD  

In Arabidopsis thaliana, each member of a large family of AS2/LOB (ASYMMETRIC LEAVES 2/LATERAL ORGAN BOUNDARIES) genes encodes a plant specific protein. They are highly homologous to one other. A mutational lesion in the representative AS2 gene results in the development of anomalous asymmetric leaves, implying that these family members commonly play some roles in plant development. In this study, we found that ectopic overexpression of ASL9 (ASYMMETRIC LEAVES 2 LIKE 9) in transgenic plants displayed a markedly anomalous architecture during the development of adult plants. Then we found that among AS2/LOB family members, ASL9 is distinct from the others in that it is exclusively regulated by the plant hormone cytokinin in a manner dependent on His-Asp phosphorelay signal transduction. We further found that when supplied externally in a medium, cytokinin specifically affected the growth properties of ASL9-ox seedlings. Taken together, the results of this study suggest that the cytokinin-induced ASL9 gene is implicated in regulation of the development of Arabidopsis thaliana.

DOI： 10.1271/bbb.60681

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：TAYLOR & FRANCIS LTD  

For higher plants, light is an important external signal, whereas cytokinin acts as an internal hormonal signal, and both are crucial for almost all aspects of development and physiological states. Here we identified and characterized a unique gene, CGA1, encoding a GATA factor, whose expression was rapidly induced by both the light and cytokinin signals in Arabidopsis thaliana.

DOI： 10.1271/bbb.60692

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER SOC PLANT BIOLOGISTS  

Circadian clocks comprise several regulatory feedback loops that control gene transcription. However, recent evidence has shown that posttranslational mechanisms are also required for clock function. In Arabidopsis thaliana, members of the PSEUDO-RESPONSE REGULATOR (PRR) family were proposed to be components of the central oscillator. Using a PRR5-specific antibody, we characterized changes in PRR5 protein levels in relation to its mRNA levels under various circadian conditions. Under long-day conditions, PRR5 mRNA levels are undetectable at dusk but PRR5 protein levels remain maximal. Upon dark transition, however, PRR5 levels decrease rapidly, indicating dark-induced, posttranslational regulation. We demonstrated that the Pseudo-Receiver (PR) domain of PRR5 interacts directly with the F box protein ZEITLUPE (ZTL) in vitro and in vivo. Analyses of mutants and transgenic plants revealed an inverse correlation between PRR5 and ZTL levels, which depends on the PR domain. These results indicate that PRR5 is negatively regulated by ZTL, which likely mediates its ubiquitination and degradation. Phenotypic analyses of prr5 ztl double mutants showed that PRR5 is required for ZTL functions. ZTL contains a Light-Oxygen-Voltage domain, and its activity may be directly regulated by blue light. Consistent with this notion, we found that blue light stabilizes PRR5, although it does not alter ZTL levels. Together, our results show that ZTL targets PRR5 for degradation by 26S proteasomes in the circadian clock and in early photomorphogenesis.

DOI： 10.1105/tpc.107.053033

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：OXFORD UNIV PRESS  

In Arabidopsis thaliana, it is currently believed that the members of a small family of PSEUDO-RESPONSE REGULATOR (PRR) proteins, including TOC1 (TIMING OF CAB EXPRESSION 1), coordinately play roles close to the circadian clock. Among these PRR members, the PRR9 gene is unique in that not only does its transcription oscillate diurnally, but it is also rapidly induced by light in a manner dependent on phytochromes. These events at the level of transcription must be crucial for the clock-associated functions of PRR9. Nonetheless, little is known about the expression of the PRR9 protein product itself in plant cells. Here, we show that PRR9 polypeptides themselves oscillate diurnally, and that they accumulate rapidly in response to light. Our work further suggests that the presence of PRR9 polypeptides is controlled through proteasome-mediated programmed degradation in the dark.

DOI： 10.1093/pcp/pcm122

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掲載種別：研究論文（学術雑誌）  

DOI： 10.1111/j.1365-313X.2006.02737.x

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

In Arabidopsis thaliana, the immediate early response of plants to cytokinin is formulated as the multistep histidine kinase (AHK)→histidine- containing phosphotransmitter (AHP)→response regulator (ARR) phosphorelay signaling circuitry, which is initiated by the cytokinin receptor histidine protein kinases. In the hope of finding components (or genes) that function downstream of the cytokinin-mediated His→Asp phosphorelay signaling circuitry, we carried out genome-wide microarray analyses. To this end, we used a combinatorial microarray strategy by employing not only wild-type plants, but also certain transgenic lines in which the cytokinin-mediated His→Asp phosphorelay signaling circuitry has been genetically manipulated. These transgenic lines employed were ARR21-overexpressing and ARR22-overexpressing plants, each of which exhibits a characteristic phenotype with regard to the cytokinin-mediated His→Asp phosphorelay. The results of extensive microarray analyses with these plants allowed us systematically to identify a certain number of genes that were up-regulated at the level of transcription in response to cytokinin directly or indirectly. Among them, some representatives were examined further in wild-type plants to support the idea that certain genes encoding transcription factors are rapidly and specifically induced at the level of transcription by cytokinin in a manner similar to that of the type-A ARR genes, which are the hallmarks of the His→Asp phosphorelay signaling circuitry. Several interesting transcription factors were thus identified as being cytokinin responsive, including those belonging to the AP2/EREBP family, MYB family, GATA family or bHLH family. Including these, the presented list of cytokinin-up-regulated genes (214) will provide us with valuable bases for understanding the His→Asp phosphorelay in A. thaliana. © 2005 JSPP.

DOI： 10.1093/pcp/pci033

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

According to the current consistent model for the higher plant Arabidopsis thaliana, the scheme for an immediate early response to the plant hormone cytokinin can be formulated as Arabidopsis histidine kinase (AHK) cytokinin receptor-mediated His → Asp phosphorelay signal transduction. Nonetheless, clarification of the comprehensive picture of cytokinin-mediated signal transduction in this higher plant is at a very early stage. As a new approach to this end, we studied whether or not a certain Arabidopsis cell line (named T87) would be versatile for such work on cytokinin signal transduction. We show that T87 cells had the ability to respond to cytokinin, displaying the immediate early induction of type-A Arabidopsis response regulator (ARR) family genes (e.g., ARR6) at the transcriptional level. This event was further confirmed by employing the stable transgenic lines of T87 cells with a set of ARR::LUC reporter transgenes. We also show that T87 cells had the ability to respond to auxin when the expression of a set of AUX/IAA genes (e.g., IAA5) was examined. As postulated for intact plants, in T87 cells too, the induction of IAA5 by auxin was selectively inhibited in the presence of a proteasome inhibitor, while the induction of ARR6 by cytokinin was not significantly affected under the same conditions. Through transient expression assays with T87 protoplasts, it is shown that the intracellular localization profiles of the phosphorelay intermediate Arabidopsis histidine-containing phosphotransfer factor (AHPs
e.g., AHP1 and AHP4) were markedly affected in response to cytokinin, but those of type-A ARRs were not (e.g., ARR15 and ARR16). Taken together, we conclude that, in T87 cells, the AHK-dependent His → Asp phosphorelay circuitry appears to be propagated in response to cytokinin, as in the case of plants, as far as the immediate early responses were concerned. This cultured cell system might therefore provide us with an alternative means to further characterize the mechanisms underlying cytokinin (and also auxin) responses at the molecular level.

DOI： 10.1271/bbb.68.1966

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：OXFORD UNIV PRESS  

Arabidopsis thaliana has a number of response regulators (ARRs) implicated in the histidine (His)--&gt;aspartate (Asp) phosphorelay signal transduction. According to the current consistent model, both the type-A and type-B ARR family members play crucial roles in the cytokinin signaling circuitry. However, this higher plant has a few extra ARRs, on which no attention has been paid so far. Characterization of these extra ARRs might provide us with new insight into the His--&gt;Asp phosphorelay signal transduction in plants. For this reason, in this study we extensively examined the natures of such a representative (named ARR22). Transcripts of ARR22 were expressed predominantly in reproductive organs, and a GFP::ARR22 fusion protein was localized in the cytoplasmic space in onion epidermal cells. The purified ARR22 protein had the ability to undergo phosphorylation in vitro, when incubated with phospho-AHP5, indicating that ARR22 has the fundamental ability to participate into a His-Asp phosphorelay pathway in its own right. In plants, transgenic lines overexpressing ARR22 were characterized (referred to as ARR22-ox), which showed the characteristic dwarf phenotypes with poorly developed root systems. The results of Northern blot hybridization with selected sets of hormone-responsive genes suggested that cytokinin responses are selectively attenuated in ARR22-ox, while other hormone responses (auxin, ABA and ethylene) occur normally. The results of microarray analyses with cytokinin-treated wild-type and ARR22-ox plants further supported the view that cytokinin responses are globally attenuated in ARR22-ox, at least, at the level of gene regulation. Finally, we demonstrated that the dwarf phenotypes of ARR22-ox are very similar to those of the wooden leg (wol) mutant, which has a severe lesion in the AHK4/CRE1 cytokinin-receptor of histidine protein kinase. These results suggested that ARR22 might also be implicated, directly or indirectly, in the cytokinin-responsive His--&gt;Asp phophorelay signal transduction.

DOI： 10.1093/pcp/pch128

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：OXFORD UNIV PRESS  

In Arabidopsis thaliana, a Histidine-to-Aspartate (His--&gt;Asp) phosphorelay is involved in the signal transduction for propagation of certain stimuli, such as plant hormones. Through the phosphorelay, the type-B phospho-accepting response regulator (ARR) family members serve as DNA-binding transcriptional regulators, whose activities are most likely regulated by phosphorylation/dephosphorylation. Based on the fact that this higher plant has 11 type-B ARR family genes, we clarified the expression profiles for all of their transcripts in plants. We constructed and characterized a series of transgenic lines, each carrying a given ARR-promoter::GUS transgene. Transcripts of some type-B ARR family genes were detected more or less ubiquitously in many organs tested, while others were expressed predominantly in reproductive organs. These ARR family members were phylogenetically classified into three sub-families, the largest of which includes the well-characterized ARRI, ARR2, and ARR11 Comparative studies were conducted focusing on ARR20 and ARR21, each of which is a representative member of an uncharacterized minor sub-family. A set of transgenic lines was constructed, in each of which a C-terminal DNA-binding domain lacking the N-terminal phospho-accepting receiver of a given ARR was aberrantly overexpressed. These resulting transgenic lines, including ARR14-C-ox, ARR20-C-ox, and ARR21-C-ox, showed characteristic anomalies during development. These results are discussed with special reference to the His--&gt;Asp phosphorelay signal transduction in A. thaliana.

DOI： 10.1093/pcp/pcg154

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掲載種別：研究論文（学術雑誌）  

The Arabidopsis thaliana AHK4 histidine kinase (also known as CRE1 or WOL) acts as a cytokinin signal transducer, presumably, in concert with downstream components, such as histidine-containing phosphotransfer factors (AHPs) and response regulators (ARRs), through the histidine-to-aspartate (His→Asp) phosphorelay. Among 10 members of the type-A ARR family, the cytokinin-induced expression of ARR15 in roots is selectively impaired in the cre1-1 mutant, which carries a mutation in the AHK4 gene, suggesting a link between this type-A response regulator and the AHK4-mediated cytokinin signal transduction in roots. To address this issue further, we characterized a T-DNA insertion mutant of ARR15, and also constructed transgenic lines (referred to as ARR15-ox) that overexpress the ARR15 gene in a manner independent of cytokinin. While the T-DNA insertion mutant (arr15-1) showed no apparent phenotype, the cytokinin-independent overexpression of ARR15 in ARR15-ox plants resulted in a reduced sensitivity toward exogenously applied cytokinin, not only in elongation of roots in plants, but also in green callus formation (or shoot formation) in explants. Cytokinin-induced expressions of certain type-A ARRs were also down-regulated in ARR15-ox plants. These results support the view that ARR15 acts as a repressor that mediates a negative feedback loop in the cytokinin and AHK4-mediated His→Asp phosphorelay.

DOI： 10.1093/pcp/pcg108

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掲載種別：研究論文（学術雑誌）  

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：OXFORD UNIV PRESS  

In Arabidopsis thaliana, Histidine-to-Aspartate (His--&gt; Asp) phosphorelay is a paradigm of a signaling system that is considered to be involved in response to plant hormones, including ethylene and cytokinin. In the current framework of His--&gt;Asp phosphorelay in this higher plant, the type-B ARR (response regulator) family members appear to act as DNA-binding transcriptional regulators. Although Arabidopsis thaliana has 11 type-B ARR family members, except for ARR1 and ARR2, no biological information is available with regard to others. As the main objective of this study, we characterized another example, ARR1, in terms of not only its in vitro biochemical properties, but also its biological activity in plants. In plants, the ARR11 gene was expressed predominantly in roots. In vitro, ARR11 showed the ability to acquire a phosphoryl group from a histidine-containing phosphotransfer intermediate (AHP), and also it showed the ability to recognize a specific nucleotide sequence, GGATT. These in vitro results supported the view that ARR11 is indeed a DNA-binding transcription factor, the ability of which is most likely modulated by phosphorylation in its receiver domain. In vivo, when a G terminal DNA-binding domain lacking the N-terminal phospho-accepting (or receiver) domain was aberrantly expressed, the resulting transgenic plants showed characteristic anomalies during development of apical parts. The observed anomalies included "unusual proliferation of tissues in cotyledons" and "outgrowth of adventitious shoots near cotyledons". These results with regard to the functions of ARR11 are mainly discussed in comparison with those of the previously characterized type-B response regulators.

DOI： 10.1093/pcp/pcg014

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Japanese Society of Plant Physiologists  

The cytokinin receptor AHK4 histidine kinase, identified in Arabidopsis thaliana, presumably acts in concert with downstream components, such as histidine-containing phosphotransfer (HPt) factors (AHPs) and response regulators (ARRs). In this respect, we characterized a loss-of-function mutant of the AHK4 gene, named cre1-1, which showed a reduced cell number within the vascular tissues in roots. Among the 10 type-A ARR members, the expression of ARR15 and ARR16 in roots was specifically and markedly reduced in cre1-1, suggesting a link between these response regulators and the AHK4-mediated signal transduction in roots. The results for transgenic plants expressing promoter::GUS or promoter::LUC fusion genes showed that both the ARR15 and the ARR16 gene products are accumulated upon cytokinin treatment in roots. The results of GFP-fusion experiments with onion epidermal cells further showed that ARR15 was found in the nucleus, and ARR16 mainly in the cytoplasm. Together, it was suggested that ARR15 and ARR16 are distinctly implicated in the presumed AHK4-mediated signaling pathway in roots.

DOI： 10.1093/pcp/pcf121

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Japanese Society of Plant Physiologists  

His-Asp phosphorelays are evolutionary-conserved powerful biological tactics for intracellular signal transduction. Such a phosphorelay is generally made up of"sensor histidine(His)-kinases", "response regulators", and"histidine-containing(HPt) phosphotransmitters". In the higher plant, Arabidopsis thaliana, results from recent intensive studies suggested that His-Asp phosphorelays may be widely used for propagating environmental stimuli, such as phytohormones(e.g., ethylene and cytokinin). In this study, we first inspected extensively the occurrence of Arabidopsis response regulators in order to compile and characterize them. The results showed that this higher plant has, at least, 14 members of the family of response regulators that can be classified into two distinct subtypes(type-A and type-B), as judged from their structural designs, biochemical properties, and expression profiles. Comparative studies were conducted for each representative(ARR3 and ARR4 for type-A, and ARR10 for type-B). It was suggested that expression of the type-A response regulator is cytokinin-inducible, while that of the type-B response regulator appears to be not. Results from yeast two-hybrid analyses suggested that the type-B response regulator may have an ability to stably interact with a set of HPt phosphotransmitters(AHPs). These and other results will be discussed with special reference to the His-Asp phosphorelay signaling network in Arabidopsis thaliana.

DOI： 10.1093/oxfordjournals.pcp.a029600

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その他リンク： http://dl.ndl.go.jp/info:ndljp/pid/10772734

掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/S0014-5793(98)00611-5

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