Faculty Profiles - MA Jian Feng

Papers - MA Jian Feng

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Overexpression of OsHMA3 enhances Cd tolerance and expression of Zn transporter genes in rice

Akimasa Sasaki, Naoki Yamaji, Jian Feng Ma

JOURNAL OF EXPERIMENTAL BOTANY 65 ( 20 ) 6013 - 6021 2014.11

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

As a member of the heavy metal ATPase (HMA) family, OsHMA3 is a tonoplast-localized transporter for Cd in the roots of rice (Oryza sativa). Overexpression of OsHMA3 selectively reduces Cd accumulation in the grain. Further characterization in the present study revealed that overexpression of OsHMA3 also enhances the tolerance to toxic Cd. The growth of both the roots and shoots was similar in the absence of Cd between an OsHMA3-overexpressed line and vector control, but the Cd-inhibited growth was significantly alleviated in the OsHMA3-overexpressed line. The over-expressed line showed higher Cd concentration in the roots, but lower Cd concentration in the shoots compared with the wild-type rice and vector control line, indicating that overexpression of OsHMA3 enhanced vacuolar sequestration of Cd in the roots. The Zn concentration in the roots of the OsHMA3-overexpressed line was constantly higher than that of vector control, but the Zn concentration in the shoots was similar between the overexpressed line and vector control. Five transporter genes belonging to the ZIP family were constitutively up-regulated in the OsHMA3-overexpressed line. These results suggest that shoot Zn level was maintained by up-regulating these genes involved in the Zn uptake/translocation. Taken together, overexpression of OsHMA3 is an efficient way to reduce Cd accumulation in the grain and to enhance Cd tolerance in rice.

DOI： 10.1093/jxb/eru340

The node, a hub for mineral nutrient distribution in graminaceous plants

Naoki Yamaji, Jian Feng Ma

TRENDS IN PLANT SCIENCE 19 ( 9 ) 556 - 563 2014.9

Language：English Publisher：ELSEVIER SCIENCE LONDON

Mineral elements, including both essential and toxic elements, are delivered to different tissues after they are taken up from the roots, but the mechanism (or mechanisms) underlying the distribution remains poorly understood. In graminaceous plants, this distribution occurs in nodes, which have a complex, well-organized vascular system. A transfer of mineral elements between different vascular bundles is required, especially for preferential distribution to developing tissues that have low transpiration but high nutrient requirements. This intervascular transfer is mediated by various transporters localized at different cells in the node. In this opinion article, we propose four modes of distribution for different mineral elements: xylem-switch, phloem-tropic, phloem-kickback, and minimum-shift, based on specific molecular transport processes identified in the nodes mainly of rice (Oryza sativa). We also discuss the prospects for future studies on mineral nutrient distribution in the nodes.

DOI： 10.1016/j.tplants.2014.05.007

Molecular mechanisms of Al tolerance in gramineous plants

Jian Feng Ma, Zhi Chang Chen, Ren Fang Shen

PLANT AND SOIL 381 ( 1-2 ) 1 - 12 2014.8

Language：English Publisher：SPRINGER

Aluminum (Al) toxicity has limited the productivity and expansion of cereal crops on acid soils; however, a number of plant species or cultivars have developed different strategies for detoxifying aluminum both internally and externally.This review focuses on recent progress on molecular mechanisms of Al tolerance in gramineous plants.A common mechanism in all gramineous plants is the secretion of organic acid anions (citrate and malate) from the roots. Genes belonging to ALMT (for Aluminum-activated malate transporter) and MATE (Multidrug and toxic compound extrusion) family involved in the secretion have been identified in several plant species; however, different plant species show different gene expression patterns including Al-induction, spatial and temporal expression, and tissue localization. Furthermore, the mechanisms regulating the gene expression also differ with plant species, which are achieved by increased tandem repeated element, increase of copy number, insertion of transposon, or alteration of cis-acting element. In addition to these common Al exclusion mechanisms, rice as a highly Al-tolerant species has developed a number of other mechanisms for detoxification of Al. A transcription factor for Al tolerance ART1 identified in rice regulates at least 30 genes implicated in internal and external detoxification of Al. These multiple genes may contribute to the high Al tolerance of rice. In the future, regulation mechanisms of Al-tolerance genes need to be further investigated.

DOI： 10.1007/s11104-014-2073-1

Differential expression of Nrat1 is responsible for Al-tolerance QTL on chromosome 2 in rice

Jixing Xia, Naoki Yamaji, Jing Che, Ren Fang Shen, Jian Feng Ma

JOURNAL OF EXPERIMENTAL BOTANY 65 ( 15 ) 4297 - 4304 2014.8

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

Although rice (Oryza sativa) is the most Al-tolerant species among small-grain cereal crops, there is wide genotypic variation in its tolerance to Al toxicity. A number of quantitative trait loci (QTLs) for Al tolerance have been detected, but the responsible genes have not been identified. By using chromosome segment substitution lines, this work found that Nrat1, a gene encoding an Al transporter, is responsible for a QTL previously detected on chromosome 2. Substitution of the chromosome segment containing Nrat1 from Koshihikari (Al-tolerant variety) by that from Kasalath (Al-sensitive variety) decreased Nrat1 expression and Al uptake and tolerance, but increased binding of Al to the cell wall. Nrat1 in Kasalath showed tissue localization similar to Koshihikari in the roots. Although Koshihikari and Kasalath differed in four amino acids in Nrat1 protein, Nrat1 from Kasalath also showed transport activity for Al. Analysis with site-directed mutagenesis revealed that these differences did not affect the Al-transport activity much. Furthermore, there was no correlation between Al tolerance and the open-reading-frame sequence differences in other rice varieties. On the other hand, there was good correlation between Nrat1 expression and Al tolerance; however, sequence comparison of the promoter region up to 2.1 kb did not give a clear difference between the Al-tolerant and -sensitive varieties. Taken together, these results indicate that differential expression of Nrat1 is responsible for the QTL for Al tolerance on chromosome 2, although the mechanism controlling Nrat1 expression remains to be examined.

DOI： 10.1093/jxb/eru201

Physiological and molecular characterization of Si uptake in wild rice species

Namiki Mitani-Ueno, Hisao Ogai, Naoki Yamaji, Jian Feng Ma

PHYSIOLOGIA PLANTARUM 151 ( 3 ) 200 - 207 2014.7

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

Cultivated rice (Oryza sativa) accumulates high concentration of silicon (Si), which is required for its high and sustainable production. High Si accumulation in cultivated rice is achieved by a high expression of both influx (Lsi1) and efflux (Lsi2) Si transporters in roots. Herein, we physiologically investigated Si uptake, isolated and functionally characterized Si transporters in six wild rice species with different genome types. Si uptake by the roots was lower in Oryza rufipogon, Oryza barthii (AA genome), Oryza australiensis (EE genome) and Oryza punctata (BB genome), but similar in Oryza glumaepatula and Oryza meridionalis (AA genome) compared with the cultivated rice (cv. Nipponbare). However, all wild rice species and the cultivated rice showed similar concentration of Si in the shoots when grown in a field. All species with AA genome showed the same amino acid sequence of both Lsi1 and Lsi2 as O. sativa, whereas species with EE and BB genome showed several nucleotide differences in both Lsi1 and Lsi2. However, proteins encoded by these genes also showed transport activity for Si in Xenopus oocyte. The mRNA expression of Lsi1 in all wild rice species was lower than that in the cultivated rice, whereas the expression of Lsi2 was lower in O. rufipogon and O. barthii but similar in other species. Similar cellular localization of Lsi1 and Lsi2 was observed in all wild rice as the cultivated rice. These results indicate that superior Si uptake, the important trait for rice growth, is basically conserved in wild and cultivated rice species.

DOI： 10.1111/ppl.12125

Knockdown of neuropilin-1 suppresses invasion, angiogenesis, and increases the chemosensitivity to doxorubicin in osteosarcoma cells - an in vitro study

B. Yue, J. -F. Ma, G. Yao, M. -D. Yang, H. Cheng, G. -Y. Liu

EUROPEAN REVIEW FOR MEDICAL AND PHARMACOLOGICAL SCIENCES 18 ( 12 ) 1735 - 1741 2014.6

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

OBJECTIVES: Neuropilin-1 (NRP-1) is a novel co-receptor for vascular endothelial growth factor (VEGF). NRP-1 expression in osteosarcoma tissues was significantly higher, and high NRP-1 expression was more frequently occurred in osteosarcoma tissues with advanced clinical stage, positive distant metastasis and poor response to chemotherapy. We tested a hypothesis that the NRP-1 gene plays a role in the invasiveness, angiogenesis and chemoresistance of human OS.MATERIALS AND METHODS: To determine the role of NRP-1 in OS, NRP-1 was stably transfected into the human OS cell line MG-63 to increase the NPR-1 level, and NRP-1 siRNA was stably transfected into the human OS cell line SaOS-2 to knockdown of NRP-1. The effect of NRP-1 on invasion and angiogenesis was assessed by Matrigel invasion assay and in vitro angiogenesis assay. Chemosensitivity to doxorubicin was assessed by MTT assay in the MG-63 and SaOS-2 cells following NRP-1 overexpression or siRNA-induced downregulation of NRP-1.RESULTS: The NRP-1 transfected MG-63 cells showed a markedly higher level of invasion in Matrigel invasion assay. The capillary-like structure formation of endothelial cells was also increased by coculture with the NRP-1 transfected MG-63 cells. On the contrary, the NRP-1 siRNA transfected SaOS-2 cells showed a markedly lower level of invasion in Matrigel invasion assay. The capillary-like structure formation of endothelial cells was also repressed by coculture with the NRP-1 siRNA transfected SaOS-2 cells. NRP-1 overexpression in MG-63 cells increased survival of cells after exposure to doxorubicin. In contrast, downregulation of NRP-1 expression in SaOS-2 cells markedly increased chemosensitivity after exposure to doxorubicin.CONCLUSIONS: We suggest that NRP-1 could be used as a biomarker for OS progression and a novel therapeutic or chemopreventive target for human OS treatment.

Root and shoot transcriptome analysis of two ecotypes of Noccaea caerulescens uncovers the role of NcNramp1 in Cd hyperaccumulation

Matthew J. Milner, Namiki Mitani-Ueno, Naoki Yamaji, Kengo Yokosho, Eric Craft, Zhangjun Fei, Stephen Ebbs, M. Clemencia Zambrano, Jian Feng Ma, Leon V. Kochian

PLANT JOURNAL 78 ( 3 ) 398 - 410 2014.5

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

The Zn/Cd hyperaccumulator, Noccaea caerulescens, has been studied extensively for its ability to accumulate high levels of Zn and Cd in its leaves. Previous studies have indicated that the Zn and Cd hyperaccumulation trait exhibited by this species involves different transport and tolerance mechanisms. It has also been well documented that certain ecotypes of N.caerulescens are much better Cd hyperaccumulators than others. However, there does not seem to be much ecotypic variation for Zn hyperaccumulation in N.caerulescens. In this study we employed a comparative transcriptomics approach to look at root and shoot gene expression in Ganges and Prayon plants in response to Cd stress to identify transporter genes that were more highly expressed in either the roots or shoots of the superior Cd accumulator, Ganges. Comparison of the transcriptomes from the two ecotypes of Noccaea caerulescens identified a number of genes that encoded metal transporters that were more highly expressed in the Ganges ecotype in response to Cd stress. Characterization of one of these transporters, NcNramp1, showed that it is involved in the influx of Cd across the endodermal plasma membrane and thus may play a key role in Cd flux into the stele and root-to-shoot Cd transport. NcNramp1 may be one of the main transporters involved in Cd hyperaccumulation in N.caerulescens and copy number variation appears to be the main reason for high NcNramp1 gene expression underlying the increased Cd accumulation in the Ganges ecotype.

DOI： 10.1111/tpj.12480

Normal root elongation requires arginine produced by argininosuccinate lyase in rice

Jixing Xia, Naoki Yamaji, Jing Che, Ren Fang Shen, Jian Feng Ma

PLANT JOURNAL 78 ( 2 ) 215 - 226 2014.4

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

Plant roots play an important role in the uptake of water and nutrients, structural support and environmental sensing, but the molecular mechanisms involved in root development are poorly understood in rice (Oryza sativa), which is characterized by a dense fibrous root system. Here we report a rice mutant (red1 for root elongation defect 1) with short roots. Morphological and physiological analyses showed that the mutant had a shorter length from the quiescent center (QC) to the starting point of the elongation zone but a similar cell size and number of lateral and crown roots compared with the wild type. Furthermore, the mutant had similar radial structure and nutrient uptake patterns to the wild type. Map-based cloning revealed that the mutant phenotype was caused by a point mutation of a gene encoding an argininosuccinate lyase (ASL), catalyzing the last step of arginine biosynthesis. The OsASL1 gene has two distinct transcripts, OsASL1.1 and OsASL1.2, which result from different transcription start sites, but only OsASL1.1 was able to complement the mutant phenotype. OsASL1.1 was expressed in both the roots and shoots. The protein encoded by OsASL1.1 showed ASL activity in yeast. OsALS1.1 was localized to the plastid. The short root of the mutant was rescued by exogenous addition of arginine, but not by other amino acids. These results indicate that arginine produced by ASL is required for normal root elongation in rice.

DOI： 10.1111/tpj.12476

Rice grain resistance to brown spot and yield are increased by silicon

Leandro J. Dallagnol, Fabricio A. Rodrigues, Mateus V. B. Mielli, Jian F. Ma

TROPICAL PLANT PATHOLOGY 39 ( 1 ) 56 - 63 2014.1

Language：English Publishing type：Research paper (scientific journal) Publisher：SOC BRASILEIRA FITOPATHOLOGIA

Brown spot, caused by Bipolaris oryzae, is one of the most important diseases of rice and can cause a reduction in yield and grain quality. The effect of silicon (Si) on the resistance of rice grains to brown spot was investigated. Plants from cv. Oochikara and its mutant, defective in the Lsi1 transporter (lsi1 mutant), were grown in hydroponic culture either with Si (+ Si; 2 mM) or without Si (-Si). Panicle inoculation with B. oryzae was carried out at the beginning of the milk-grain stage. Panicles were harvested at physiological grain maturity. The supply of Si significantly increased Si concentration in husks compared to -Si plants. Si concentration in husks from cv. Oochikara was up to three times greater than the lsi1 mutant. In the presence of Si, brown spot severity was reduced by 88% in grains from cv. Oochikara and by 53% in grains from lsi1 mutant. Brown spot severity was 77% lower for grains of cv. Oochikara than for the lsi1 mutant, both plant types were grown in the presence of Si. Panicle inoculation reduced significantly the following yield components: number of grains per panicle, the weight of 1000 grains and the percentage of filled grains. Si significantly increased these yield components, especially for inoculated panicles. Considering kernel quality, the panicle inoculation with B. oryzae significantly reduced the yield of husked kernel, yield of whole kernel and kernel diameter, especially for grains from -Si plants. For panicles from + Si plants, the kernel quality was improved under inoculation, compared to -Si plants. Results from this study show that Si improved rice yield and kernel quality in panicles inoculated with B. oryzae. Furthermore the functional Lsi1 gene contributed significantly for increasing the yield of whole kernel and kernel diameter, possibly due to the increasing Si concentration in husks.

DOI： 10.1590/S1982-56762014005000003

An appropriate concentration of arginine is required for normal root growth in rice

Jixing Xia, Naoki Yamaji, Jian Feng Ma

Plant Signaling and Behavior 9 ( APR ) e28717 2014

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

Plant roots play an important role in uptake of water and nutrients, support of above-ground part and environmental sensing, but the molecular mechanisms underlying the root development are poorly understood in rice. We found that a gene (OsASL1) encoding argininosuccinate lyase is involved in normal root development of rice. OsASL1 cleaves argininosuccinate to arginine and fumarate reversibly, the last step in the arginine biosynthetic pathway. Here, we further characterized OsASL1 in terms of expression pattern, subcellular localization, and arginine effect on the root growth. A detailed expression analysis revealed that 2 transcripts of OsASL1, OsASL1.1 and OsASL1.2, showed different expression patterns
OsASL1.1 was expressed in most organs throughout the whole growth period, whereas OsASL1.2 was mainly expressed in the roots. In contrast to plastid-localized OsASL1.1, OsASL1.2 was localized to the cytosol and nucleus. The short-root phenotype of the mutant was not rescued by exogenous addition of the sodium nitroprusside, a nitric oxide donor, but rescued by an appropriate concentration of Arg. Our results indicate that the subcellular localization was determined by the N terminus of OsASL1 and that appropriate concentration of Arg is required for normal root elongation in rice. © 2014 Landes Bioscience.

DOI： 10.4161/psb.28717

A Member of the Heavy Metal P-Type ATPase OsHMA5 Is Involved in Xylem Loading of Copper in Rice

Fenglin Deng, Naoki Yamaji, Jixing Xia, Jian Feng Ma

PLANT PHYSIOLOGY 163 ( 3 ) 1353 - 1362 2013.11

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

Heavy metal-transporting P-type ATPase (HMA) has been implicated in the transport of heavy metals in plants. Here, we report the function and role of an uncharacterized member of HMA, OsHMA5 in rice (Oryza sativa). Knockout of OsHMA5 resulted in a decreased copper (Cu) concentration in the shoots but an increased Cu concentration in the roots at the vegetative stage. At the reproductive stage, the concentration of Cu in the brown rice was significantly lower in the mutants than in the wild-type rice; however, there was no difference in the concentrations of iron, manganese, and zinc between two independent mutants and the wild type. The Cu concentration of xylem sap was lower in the mutants than in the wild-type rice. OsHMA5 was mainly expressed in the roots at the vegetative stage but also in nodes, peduncle, rachis, and husk at the reproductive stage. The expression was up-regulated by excess Cu but not by the deficiency of Cu and other metals, including zinc, iron, and manganese, at the vegetative stage. Analysis of the transgenic rice carrying the OsHMA5 promoter fused with green fluorescent protein revealed that it was localized at the root pericycle cells and xylem region of diffuse vascular bundles in node I, vascular tissues of peduncle, rachis, and husk. Furthermore, immunostaining with an antibody against OsHMA5 revealed that it was localized to the plasma membrane. Expression of OsHMA5 in a Cu transport-defective mutant yeast (Saccharomyces cerevisiae) strain restored the growth. Taken together, OsHMA5 is involved in loading Cu to the xylem of the roots and other organs.

DOI： 10.1104/pp.113.226225

Mn tolerance in rice is mediated by MTP8.1, a member of the cation diffusion facilitator family

Zonghui Chen, Yumi Fujii, Naoki Yamaji, Sakine Masuda, Yuma Takemoto, Takehiro Kamiya, Yusufujiang Yusuyin, Kozo Iwasaki, Shin-ichiro Kato, Masayoshi Maeshima, Jian Feng Ma, Daisei Ueno

JOURNAL OF EXPERIMENTAL BOTANY 64 ( 14 ) 4375 - 4387 2013.11

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

Manganese (Mn) is an essential micronutrient for plants, but is toxic when present in excess. The rice plant (Oryza sativa L.) accumulates high concentrations of Mn in the aerial parts; however, the molecular basis for Mn tolerance is poorly understood. In the present study, genes encoding Mn tolerance were screened for by expressing cDNAs of genes from rice shoots in Saccharomyces cerevisiae. A gene encoding a cation diffusion facilitator (CDF) family member, OsMTP8.1, was isolated, and its expression was found to enhance Mn accumulation and tolerance in S. cerevisiae. In plants, OsMTP8.1 and its transcript were mainly detected in shoots. High or low supply of Mn moderately induced an increase or decrease in the accumulation of OsMTP8.1, respectively. OsMTP8.1 was detected in all cells of leaf blades through immunohistochemistry. OsMTP8.1 fused to green fluorescent protein was localized to the tonoplast. Disruption of OsMTP8.1 resulted in decreased chlorophyll levels, growth inhibition in the presence of high concentrations of Mn, and decreased accumulation of Mn in shoots and roots. However, there was no difference in the accumulation of other metals, including Zn, Cu, Fe, Mg, Ca, and K. These results suggest that OsMTP8.1 is an Mn-specific transporter that sequesters Mn into vacuoles in rice and is required for Mn tolerance in shoots.

DOI： 10.1093/jxb/ert243

LjMATE1: A Citrate Transporter Responsible for Iron Supply to the Nodule Infection Zone of Lotus japonicas (vol 54, pg 585, 2013)

Kojiro Takanashi, Kengo Yokosho, Kazuhiko Saeki, Akifumi Sugiyama, Shusei Sato, Satoshi Tabata, Jian Feng Ma, Kazufumi Yazaki

PLANT AND CELL PHYSIOLOGY 54 ( 10 ) 1749 - 1749 2013.10

A plasma membrane-localized small peptide is involved in rice aluminum tolerance

Jixing Xia, Naoki Yamaji, Jian Feng Ma

PLANT JOURNAL 76 ( 2 ) 345 - 355 2013.10

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

A transcription factor for Al tolerance, ART1, regulates the expression of at least 30 genes in rice. Here we functionally characterized one of the downstream genes, OsCDT3, which encodes a predicted peptide of only 53 amino acid residues rich in cysteine. Knockdown of this gene resulted in decreased tolerance to Al, but did not affect the tolerance to Cd. The aluminum (Al) content in the root residues including cell wall and the plasma membrane of knockdown lines decreased, but the Al concentration in the root cell sap increased compared with those of the wild-type rice. OsCDT3 was mainly expressed in the roots and its expression was specifically induced by Al exposure, not by low pH and other metals. There was a small genotypic variation in OsCDT3 expression level, but no correlation between Al tolerance and the OsCDT3 variation was found among 17 rice cultivars. Analysis of pOsCDT3::GFP transgenic rice showed that OsCDT3 was expressed at all cells in the root tips. Transient expression of OsCDT3 fused with GFP at both N- and C-termini showed that OsCDT3 was anchored to the plasma membrane. Expression of OsCDT3 in yeast conferred tolerance to Al, but not to Cd. Furthermore, OsCDT3 did not show transport activity for Al in yeast, but was able to directly bind Al in vitro. Taken together, our results indicate that OsCDT3 anchoring to the plasma membrane may play a role in stopping entry of Al into the root cells by binding Al, therefore, contributing to high Al tolerance in rice.

DOI： 10.1111/tpj.12296

Adaptation to acidic soil is achieved by increased numbers of cis-acting elements regulating ALMT1 expression in Holcus lanatus

Zhi Chang Chen, Kengo Yokosho, Miho Kashino, Fang-Jie Zhao, Naoki Yamaji, Jian Feng Ma

PLANT JOURNAL 76 ( 1 ) 10 - 23 2013.10

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

Yorkshire fog (Holcus lanatus), which belongs to the Poaceae family and is a close relative of the agronomic crop oat (Avena sativa), is a widely adaptable grass species that is able to grow on highly acidic soils with high levels of Al, but the mechanism underlying the high Al tolerance is unknown. Here, we characterized two accessions of H.lanatus collected from an acid plot (soil pH 3.6, HL-A) and a neutral plot (pH 7.1, HL-N) in terms of Al tolerance, organic acid anion secretion and related gene expression. In response to Al (pH 4.5), the HL-A roots secreted approximately twice as much malate as the HL-N roots, but there was no difference in citrate secretion. Cloning of the gene HlALMT1 responsible for malate secretion showed that the encoded amino acid sequence did not differ between two accessions, but the expression level in the outer cell layers of the HL-A roots was twice as high as in the HL-N roots. This difference was not due to the genomic copy number, but was due to the number of cis-acting elements for an Al-responsive transcription factor (HlART1) in the promoter region of HlALMT1, as demonstrated by both a yeast one-hybrid assay and a transient assay in tobacco protoplasts. Furthermore, introduction of HlALMT1 driven by the HL-A promoter into rice resulted in significantly more Al-induced malate secretion than introduction of HlALMT1 driven by the HL-N promoter. These findings indicate that the adaptation of H.lanatus to acidic soils may be achieved by increasing number of cis-acting elements for ART1 in the promoter region of the HlALMT1 gene, enhancing the expression of HlALMT1 and the secretion of malate.

DOI： 10.1111/tpj.12266

A node-based switch for preferential distribution of manganese in rice

Naoki Yamaji, Akimasa Sasaki, Ji Xing Xia, Kengo Yokosho, Jian Feng Ma

NATURE COMMUNICATIONS 4 2442 2013.9

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

Mineral nutrients, such as manganese, are required for the development of plants and their reproductive organs, but these can be toxic if accumulated at high concentrations. Therefore, plants must have a system for preferentially delivering an adequate amount of minerals to these organs for active growth and development, while preventing mineral overaccumulation in the face of changing environments. Here we show that a member of the Nramp transporter family, OsNramp3, functions as a switch in response to environmental Mn changes. OsNramp3 is constitutively expressed in the node, a junction of vasculatures connecting leaves, stems and panicles. At low Mn concentration, OsNramp3 preferentially transports Mn to young leaves and panicles. However, at high Mn concentration, the OsNramp3 protein is rapidly degraded within a few hours, resulting in the distribution of Mn to old tissues. Our results reveal the OsNramp3-mediated strategy of rice for adapting to a wide change of Mn in the environment.

DOI： 10.1038/ncomms3442

Magnesium transporters and their role in Al tolerance in plants

Zhi Chang Chen, Jian Feng Ma

PLANT AND SOIL 368 ( 1-2 ) 51 - 56 2013.7

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

Magnesium (Mg) is an essential macronutrient for plant growth, which has diverse biological functions. However, little is known about the transport system of this nutrient in plants. In the genome of plants such as rice and Arabidopsis, there are homologues of bacterial Mg transporters (CorA) and some of them have been functionally characterized, but the physiological role of these transporters are poorly understood. On the other hand, Mg is able to alleviate Al toxicity in a number of plant species, but the mechanisms underlying this alleviation are not well understood. Recently, this alleviation has been associated with a Mg transporter in rice. In this paper, we present our opinions on Mg transporters, which are required for uptake, translocation, distribution and storage in plants. Possible mechanisms for Mg-mediated alleviation of Al toxicity are also discussed.

DOI： 10.1007/s11104-012-1433-y

TWIN SISTER OF FT, GIGANTEA, and CONSTANS Have a Positive But Indirect Effect on Blue Light-Induced Stomatal Opening in Arabidopsis

Eigo Ando, Masato Ohnishi, Yin Wang, Tomonao Matsushita, Aiko Watanabe, Yuki Hayashi, Miho Fujii, Jian Feng Ma, Shin-ichiro Inoue, Toshinori Kinoshita

PLANT PHYSIOLOGY 162 ( 3 ) 1529 - 1538 2013.7

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

FLOWERING LOCUS T (FT) is the major regulatory component controlling photoperiodic floral transition. It is expressed in guard cells and affects blue light-induced stomatal opening induced by the blue-light receptor phototropins phot1 and phot2. Roles for other flowering regulators in stomatal opening have yet to be determined. We show in Arabidopsis (Arabidopsis thaliana) that TWIN SISTER OF FT (TSF), CONSTANS (CO), and GIGANTEA (GI) provide a positive effect on stomatal opening. TSF, which is the closest homolog of FT, was transcribed in guard cells, and light-induced stomatal opening was repressed in tsf-1, a T-DNA insertion mutant of TSF. Overexpression of TSF in a phot1 phot2 mutant background gave a constitutive open-stomata phenotype. Then, we examined whether CO and GI, which are upstream regulators of FT and TSF in photoperiodic flowering, are involved in stomatal opening. Similar to TSF, light-induced stomatal opening was suppressed in the GI and CO mutants gi-1 and co-1. A constitutive open-stomata phenotype was observed in GI and CO overexpressors with accompanying changes in the transcription of both FT and TSF. In photoperiodic flowering, photoperiod is sensed by photoreceptors such as the cryptochromes cry1 and cry2. We examined stomatal phenotypes in a cry1 cry2 mutant and in CRY2 overexpressors. Light-induced stomatal opening was suppressed in cry1 cry2, and the transcription of FT and TSF was down-regulated. In contrast, the stomata in CRY2 overexpressors opened even in the dark, and FT and TSF transcription was up-regulated. We conclude that the photoperiodic flowering components TSF, GI, and CO positively affect stomatal opening.

DOI： 10.1104/pp.113.217984

Effect of silicon deficiency on secondary cell wall synthesis in rice leaf

Tsuyoshi Yamamoto, Atsuko Nakamura, Hiroaki Iwai, Tadashi Ishii, Jian Feng Ma, Ryusuke Yokoyama, Kazuhiko Nishitani, Shinobu Satoh, Jun Furukawa

JOURNAL OF PLANT RESEARCH 125 ( 6 ) 771 - 779 2012.11

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

Rice (Oryza sativa L.) is a typical Si-accumulating plant and is able to accumulate Si up to > 10 % of shoot dry weight. The cell wall has been reported to become thicker under Si-deficient condition. To clarify the relationship between Si accumulation and cell wall components, the physical properties of, and macromolecular components and Si content in, the pectic, hemicellulosic, and cellulosic fractions prepared from rice seedlings grown in hydroponics with or without 1.5 mM silicic acid were analyzed. In the absence of Si (the -Si condition), leaf blades drooped, but physical properties were enhanced. Sugar content in the cellulosic fraction and lignin content in the total cell wall increased under -Si condition. After histochemical staining, there was an increase in cellulose deposition in short cells and the cell layer just beneath the epidermis in the -Si condition, but no significant change in the pattern of lignin deposition. Expression of the genes involved in secondary cell wall synthesis, OsCesA4, OsCesA7, OsPAL, OsCCR1 and OsCAD6 was up-regulated under -Si condition, but expression of OsCesA1, involved in primary cell wall synthesis, did not increase. These results suggest that an increase in secondary cell wall components occurs in rice leaves to compensate for Si deficiency.

DOI： 10.1007/s10265-012-0489-3

Functional Characterization of a Silicon Transporter Gene Implicated in Silicon Distribution in Barley

Naoki Yamaji, Yukako Chiba, Namiki Mitani-Ueno, Jian Feng Ma

PLANT PHYSIOLOGY 160 ( 3 ) 1491 - 1497 2012.11

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

Silicon (Si) is a beneficial element for plant growth. In barley (Hordeum vulgare), Si uptake by the roots is mainly mediated by a Si channel, Low Silicon1 (HvLsi1), and an efflux transporter, HvLsi2. However, transporters involved in the distribution of Si in the shoots have not been identified. Here, we report the functional characterization of a homolog of HvLsi1, HvLsi6. HvLsi6 showed permeability for Si and localized to the plasma membrane. At the vegetative growth stage, HvLsi6 was expressed in both the roots and shoots. The expression level was unaffected by Si supply. In the roots, HvLsi6 was localized in epidermis and cortex cells of the tips, while in the leaf blades and sheaths, HvLsi6 was only localized at parenchyma cells of vascular bundles. At the reproductive growth stage, high expression of HvLsi6 was also found in the nodes. HvLsi6 in node I was polarly located at the transfer cells surrounding the enlarged vascular bundles toward the numerous xylem vessels. These results suggest that HvLsi6 is involved in Si uptake in the root tips, xylem unloading of Si in leaf blade and sheath, and intervascular transfer of Si in the nodes. Furthermore, HvLsi2 was found to be localized at the parenchyma cell layer adjacent to the transfer cells with opposite polarity of HvLsi6, suggesting that the coupling of HvLsi6 and HvLsi2 is involved in the intervascular transfer of Si at the nodes. Si translocated via the enlarged vascular bundles is unloaded to the transfer cells by HvLsi6, followed by HvLsi2 to reload Si to the diffuse vascular bundles, which are connected to the upper part of the plant, especially the panicles, the ultimate Si sink.

DOI： 10.1104/pp.112.204578

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