研究者詳細 - 馬　建鋒

論文 - 馬　建鋒

分割表示 344 件中 201 - 220 件目／全件表示 >>

Transport of silicon from roots to panicles in plants

Jian Feng Ma, Naoki Yamaji, Namiki Mitani-Ueno

PROCEEDINGS OF THE JAPAN ACADEMY SERIES B-PHYSICAL AND BIOLOGICAL SCIENCES 87 ( 7 ) 377 - 385 2011年7月

記述言語：英語出版者・発行元：JAPAN ACAD

Silicon (Si) is the most abundant minerals in soil and exerts beneficial effects on plant growth by alleviating various stresses. The transport of Si from soil to the panicles is mediated by different transporters. Lsi1, belonging to a NIP group of the aquaporin family, is responsible for the uptake of Si from soil into the root cells in both dicots and monocots although its expression patterns and cellular localization differ with plant species. The subsequent transport of Si out of the root cells towards the stele is medicated by an active efflux transporter, Lsi2. Lsi1. and Lsi2 are polarly localized at the distal and proximal sides, respectively, of both exodermis and endodermis in rice root. Silicon in the xylem sap is presented in the form of monosilicic acid and is unloaded by Lsi6, a homolog of Lsi1 in rice. Lsi6 is also involved in the inter-vascular transfer of Si at the node, which is necessary for preferential Si distribution to the panicles.

DOI： 10.2183/pjab.87.377

Identification of a Cis-Acting Element of ART1, a C2H2-Type Zinc-Finger Transcription Factor for Aluminum Tolerance in Rice

Tomokazu Tsutsui, Naoki Yamaji, Jian Feng Ma

PLANT PHYSIOLOGY 156 ( 2 ) 925 - 931 2011年6月

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

Rice (Oryza sativa) is one of the most aluminum (Al)-tolerant species among small-grain cereals. Recent identification of a transcription factor AL RESISTANCE TRANSCRIPTION FACTOR1 (ART1) revealed that this high Al tolerance in rice is achieved by multiple genes involved in detoxification of Al at different cellular levels. ART1 is a C2H2-type zinc-finger transcription factor and regulates the expression of 31 genes in the downstream. In this study, we attempted to identify a cis-acting element of ART1. We used the promoter region of SENSITIVE TO AL RHIZOTOXICITY1, an Al tolerance gene in the downstream of ART1. With the help of gel-shift assay, we were able to identify the cis-acting element as GGN(T/g/a/C)V(C/A/g)S(C/G). This element was found in the promoter region of 29 genes among 31 ART1-regulated genes. To confirm this cis-acting element in vivo, we transiently introduced this element one or five times tandemly repeated sequence with 35S minimal promoter and green fluorescent protein reporter together with or without ART1 gene in the tobacco (Nicotiana tabacum) mesophyll protoplasts. The results showed that the expression of green fluorescent protein reporter responded to ART1 expression. Furthermore, the expression increased with repetition of the cis-acting element. Our results indicate that the five nucleotides identified are the target DNA-binding sequence of ART1.

DOI： 10.1104/pp.111.175802

Elevated expression of TcHMA3 plays a key role in the extreme Cd tolerance in a Cd-hyperaccumulating ecotype of Thlaspi caerulescens

Daisei Ueno, Matthew J. Milner, Naoki Yamaji, Kengo Yokosho, Emi Koyama, M. Clemencia Zambrano, Molly Kaskie, Stephen Ebbs, Leon V. Kochian, Jian Feng Ma

PLANT JOURNAL 66 ( 5 ) 852 - 862 2011年6月

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

P>Cadmium (Cd) is a highly toxic heavy metal for plants, but several unique Cd-hyperaccumulating plant species are able to accumulate this metal to extraordinary concentrations in the aboveground tissues without showing any toxic symptoms. However, the molecular mechanisms underlying this hypertolerance to Cd are poorly understood. Here we have isolated and functionally characterized an allelic gene, TcHMA3 (heavy metal ATPase 3) from two ecotypes (Ganges and Prayon) of Thlaspi caerulescens contrasting in Cd accumulation and tolerance. The TcHMA3 alleles from the higher (Ganges) and lower Cd-accumulating ecotype (Prayon) share 97.8% identity, and encode a P-1B-type ATPase. There were no differences in the expression pattern, cell-specificity of protein localization and transport substrate-specificity of TcHMA3 between the two ecotypes. Both alleles were characterized by constitutive expression in the shoot and root, a tonoplast localization of the protein in all leaf cells and specific transport activity for Cd. The only difference between the two ecotypes was the expression level of TcHMA3: Ganges showed a sevenfold higher expression than Prayon, partly caused by a higher copy number. Furthermore, the expression level and localization of TcHMA3 were different from AtHMA3 expression in Arabidopsis. Overexpression of TcHMA3 in Arabidopsis significantly enhanced tolerance to Cd and slightly increased tolerance to Zn, but did not change Co or Pb tolerance. These results indicate that TcHMA3 is a tonoplast-localized transporter highly specific for Cd, which is responsible for sequestration of Cd into the leaf vacuoles, and that a higher expression of this gene is required for Cd hypertolerance in the Cd-hyperaccumulating ecotype of T. caerulescens.

DOI： 10.1111/j.1365-313X.2011.04548.x

High-Resolution Secondary Ion Mass Spectrometry Reveals the Contrasting Subcellular Distribution of Arsenic and Silicon in Rice Roots

Katie L. Moore, Markus Schroeder, Zhongchang Wu, Barry G. H. Martin, Chris R. Hawes, Steve P. McGrath, Malcolm J. Hawkesford, Jian Feng Ma, Fang-Jie Zhao, Chris R. M. Grovenor

PLANT PHYSIOLOGY 156 ( 2 ) 913 - 924 2011年6月

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

Rice (Oryza sativa) takes up arsenite mainly through the silicic acid transport pathway. Understanding the uptake and sequestration of arsenic (As) into the rice plant is important for developing strategies to reduce As concentration in rice grain. In this study, the cellular and subcellular distributions of As and silicon (Si) in rice roots were investigated using high-pressure freezing, high-resolution secondary ion mass spectrometry, and transmission electron microscopy. Rice plants, both the lsi2 mutant lacking the Si/arsenite efflux transporter Lsi2 and its wild-type cultivar, with or without an iron plaque, were treated with arsenate or arsenite. The formation of iron plaque on the root surface resulted in strong accumulation of As and phosphorous on the epidermis. The lsi2 mutant showed stronger As accumulation in the endodermal vacuoles, where the Lsi2 transporter is located in the plasma membranes, than the wild-type line. As also accumulated in the vacuoles of some xylem parenchyma cells and in some pericycle cells, particularly in the wild-type mature root zone. Vacuolar accumulation of As is associated with sulfur, suggesting that As may be stored as arsenite-phytochelatin complexes. Si was localized in the cell walls of the endodermal cells with little apparent effect of the Lsi2 mutation on its distribution. This study reveals the vacuolar sequestration of As in rice roots and contrasting patterns of As and Si subcellular localization, despite both being transported across the plasma membranes by the same transporters.

DOI： 10.1104/pp.111.173088

Isolation and Characterization of a Barley Yellow Stripe-Like Gene, HvYSL5

Luqing Zheng, Miho Fujii, Naoki Yamaji, Akimasa Sasaki, Miki Yamane, Isamu Sakurai, Kazuhiro Sato, Jian Feng Ma

PLANT AND CELL PHYSIOLOGY 52 ( 5 ) 765 - 774 2011年5月

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

Yellow stripe-like (YSL) family transporters, belonging to a novel subfamily of oligopeptide transporter (OPT), has been proposed to be involved in metal uptake and long-distance transport, but only a few of them have been functionally characterized so far. In the present study, we isolated an uncharacterized member of the YSL family, HvYSL5, in barley based on expressed sequence tag (EST) information. HvYSL5 shared 50% identity with HvYS1, a transporter for the ferric-mugineic acid complex, at the amino acid level. Promoter analysis showed that the HvYSL5 upstream sequence contains both iron deficiency response element 1 and 2 (IDE1 and 2). HvYSL5 was expressed in the roots and the expression was greatly induced by Fe deficiency, but not by deficiency of other metals including Zn, Cu and Mn. Spatial investigation showed that much higher expression of HvYSL5 was found in the mature zones of the roots, but not in the root tips. Furthermore, the expression showed a diurnal rhythm, being the highest in the morning, but with no expression in the afternoon. HvYSL5 was localized in all root cells, and subcellular localization analysis showed that HvYSL5 is likely to be localized in the vesicles. Knockdown of HvYSL5 did not result in any detectable phenotype changes. Although the exact role of HvYSL5 remains to be examined, our results suggest that it is involved in the transient storage of Fe or phytosiderophores.

DOI： 10.1093/pcp/pcr009

Isolation and functional characterization of an influx silicon transporter in two pumpkin cultivars contrasting in silicon accumulation

Namiki Mitani, Naoki Yamaji, Yukiko Ago, Kozo Iwasaki, Jian Feng Ma

PLANT JOURNAL 66 ( 2 ) 231 - 240 2011年4月

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

P>A high accumulation of silicon (Si) is required for overcoming abiotic and biotic stresses, but the molecular mechanisms of Si uptake, especially in dicotyledonous species, is poorly understood. Herein, we report the identification of an influx transporter of Si in two Cucurbita moschata (pumpkin) cultivars greatly differing in Si accumulation, which are used for the rootstocks of bloom and bloomless Cucumis sativus (cucumber), respectively. Heterogeneous expression in both Xenopus oocytes and rice mutant defective in Si uptake showed that the influx transporter from the bloom pumpkin rootstock can transport Si, whereas that from the bloomless rootstock cannot. Analysis with site-directed mutagenesis showed that, among the two amino acid residues differing between the two types of rootstocks, only changing a proline to a leucine at position 242 results in the loss of Si transport activity. Furthermore, all pumpkin cultivars for bloomless rootstocks tested have this mutation. The transporter is localized in all cells of the roots, and investigation of the subcellular localization with different approaches consistently showed that the influx Si transporter from the bloom pumpkin rootstock was localized at the plasma membrane, whereas the one from the bloomless rootstock was localized at the endoplasmic reticulum. Taken together, our results indicate that the difference in Si uptake between two pumpkin cultivars is probably the result of allelic variation in one amino acid residue of the Si influx transporter, which affects the subcellular localization and subsequent transport of Si from the external solution to the root cells.

DOI： 10.1111/j.1365-313X.2011.04483.x

Physiological, genetic, and molecular characterization of a high-Cd-accumulating rice cultivar, Jarjan

Daisei Ueno, Emi Koyama, Naoki Yamaji, Jian Feng Ma

JOURNAL OF EXPERIMENTAL BOTANY 62 ( 7 ) 2265 - 2272 2011年4月

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

Cadmium (Cd) in rice is a major source of Cd intake for people on a staple rice diet. The mechanisms underlying Cd accumulation in rice plant are still poorly understood. Here, we characterized the physiology and genetics of Cd transport in a high-Cd-accumulating cultivar (Jarjan) of rice (Oryza sativa). Jarjan showed 5- to 34-fold higher Cd accumulation in the shoots and grains than the cultivar Nipponbare, when it was grown in either a non-Cd-contaminated or a Cd-contaminated soil. A short-term uptake experiment showed no significant difference in Cd uptake by the roots between the two cultivars. However, Jarjan translocated 49% of the total Cd taken up to the shoots, whereas Nipponbare retained most of the Cd in the roots. In both concentration- and time-dependent experiments, Jarjan showed a superior capacity for root-to-shoot translocation of Cd. These results indicate that the high-Cd-accumulation phenotype in Jarjan results from efficient translocation of Cd from roots to shoots. Genetic analysis using an F(2) population derived from Jarjan and Nipponbare revealed that plants showing high- and low-Cd-accumulation phenotypes segregated in a 1:3 ratio, indicating that high accumulation in Jarjan is controlled by a single recessive gene. Furthermore, we isolated OsHMA3, a gene encoding a tonoplast-localized Cd transporter from Jarjan. The OsHMA3 protein was localized in all roots cells, but the sequence has a mutation leading to loss of function. Therefore, failure to sequester Cd into the root vacuoles by OsHMA3 is probably responsible for high Cd accumulation in Jarjan.

DOI： 10.1093/jxb/erq383

Further characterization of an aluminum influx transporter in rice

Jixing Xia, Naoki Yamaji, Jian Feng Ma

Plant Signaling and Behavior 6 ( 1 ) 160 - 163 2011年1月

記述言語：英語掲載種別：研究論文（学術雑誌）

Nrat1 is a plasma membrane-localized aluminum transporter recently identified in rice, which is a member of Nramp family. Here, we further characterized this transporter in terms of transport substrate specificity. Heterologous assay in yeast showed that Al transport activity by Nrat1 was unaffected by the presence of high concentration of Ca, but significantly inhibited by trivalent ions including Yb and Ga, analogs of Al. Knockout of Nrat1 did not affect the uptake of Cd and Mn in rice. On the other hand, over expression of Nrat1 led to enhanced Al uptake by rice roots compared with wild-type rice, but did not affect Cd uptake. These results provide further evidence that unlike other Nramp members, Nrat1 is an influx transporter for trivalent Al ion. © 2011 Landes Bioscience.

DOI： 10.4161/psb.6.1.14319

Further characterization of a rice Si efflux transporter, Lsi2.

Yamaji, N, Ma, J. F

Soil Science and Plant Nutrition 57 259 - 264 2011年

Silicon efflux transporters isolated from two pumpkin cultivars contrasting in Si uptake

Namiki Mitani-Ueno, Naoki Yamaji, Jian Feng Ma

Plant Signaling and Behavior 6 ( 7 ) 73 - 76 2011年

記述言語：英語掲載種別：研究論文（学術雑誌）

The accumulation of silicon (Si) differs greatly with plant species and cultivars due to different ability of the roots to take up Si. In Si accumulating plants such as rice, barley and maize, Si uptake is mediated by the influx (Lsi1) and efflux (Lsi2) transporters. Here we report isolation and functional analysis of two Si efflux transporters (CmLsi2-1 and CmLsi2-2) from two pumpkin (Cucurbita moschata Duch.) cultivars contrasting in Si uptake. These cultivars are used for rootstocks of bloom and bloomless cucumber, respectively. Different from mutations in the Si influx transporter CmLsi1, there was no difference in the sequence of either CmLsi2 between two cultivars. Both CmLsi2-1 and CmLsi2-2 showed an efflux transport activity for Si and they were expressed in both the roots and shoots. These results confirm our previous finding that mutation in CmLsi1, but not in CmLsi2-1 and CmLsi2-2 are responsible for bloomless phenotype resulting from low Si uptake. © 2011 Landes Bioscience.

DOI： 10.4161/psb.6.7.15462

Plasma membrane-localized transporter for aluminum in rice

Jixing Xia, Naoki Yamaji, Tomonari Kasai, Jian Feng Ma

PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 107 ( 43 ) 18381 - 18385 2010年10月

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

Aluminum (Al) is the most abundant metal in the Earth's crust, but its trivalent ionic form is highly toxic to all organisms at low concentrations. How Al enters cells has not been elucidated in any organisms. Herein, we report a transporter, Nrat1 (Nramp aluminum transporter 1), specific for trivalent Al ion in rice. Nrat1 belongs to the Nramp (natural resistance-associated macrophage protein) family, but shares a low similarity with other Nramp members. When expressed in yeast, Nrat1 transports trivalent Al ion, but not other divalent ions, such as manganese, iron, and cadmium, or the Al-citrate complex. Nrat1 is localized at the plasma membranes of all cells of root tips except epidermal cells. Knockout of Nrat1 resulted in decreased Al uptake, increased Al binding to cell wall, and enhanced Al sensitivity, but did not affect the tolerance to other metals. Expression of Nrat1 is up-regulated by Al in the roots and regulated by a C2H2 zinc finger transcription factor (ART1). We therefore concluded that Nrat1 is a plasma membrane-localized transporter for trivalent Al, which is required for a prior step of final Al detoxification through sequestration of Al into vacuoles.

DOI： 10.1073/pnas.1004949107

Gene limiting cadmium accumulation in rice

Daisei Ueno, Naoki Yamaji, Izumi Kono, Chao Feng Huang, Tsuyu Ando, Masahiro Yano, Jian Feng Ma

PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 107 ( 38 ) 16500 - 16505 2010年9月

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

Intake of toxic cadmium (Cd) from rice caused Itai-itai disease in the past and it is still a threat for human health. Therefore, control of the accumulation of Cd from soil is an important food-safety issue, but the molecular mechanism for the control is unknown. Herein, we report a gene (OsHMA3) responsible for low Cd accumulation in rice that was isolated from a mapping population derived from a cross between a high and low Cd-accumulating cultivar. The gene encodes a transporter belonging to the P(1B)-type ATPase family, but shares low similarity with other members. Heterologous expression in yeast showed that the transporter from the low-Cd cultivar is functional, but the transporter from the high-Cd cultivar had lost its function, probably because of the single amino acid mutation. The transporter is mainly expressed in the tonoplast of root cells at a similar level in both the low and high Cd-accumulating cultivars. Overexpression of the functional gene from the low Cd-accumulating cultivar selectively decreased accumulation of Cd, but not other micronutrients in the grain. Our results indicated that OsHMA3 from the low Cd-accumulating cultivar limits translocation of Cd from the roots to the above-ground tissues by selectively sequestrating Cd into the root vacuoles.

DOI： 10.1073/pnas.1005396107

Involvement of Silicon Influx Transporter OsNIP2;1 in Selenite Uptake in Rice

Xue Qiang Zhao, Namiki Mitani, Naoki Yamaji, Ren Fang Shen, Jian Feng Ma

PLANT PHYSIOLOGY 153 ( 4 ) 1871 - 1877 2010年8月

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

Rice (Oryza sativa) as a staple food, provides a major source of dietary selenium (Se) for humans, which essentially requires Se, however, the molecular mechanism for Se uptake is still poorly understood. Herein, we show evidence that the uptake of selenite, a main bioavailable form of Se in paddy soils, is mediated by a silicon (Si) influx transporter Lsi1 (OsNIP2;1) in rice. Defect of OsNIP2;1 resulted in a significant decrease in the Se concentration of the shoots and xylem sap when selenite was given. However, there was no difference in the Se concentration between the wild-type rice and mutant of OsNIP2;1 when selenate was supplied. A short-term uptake experiment showed that selenite uptake greatly increased with decreasing pH in the external solution. Si as silicic acid did not inhibit the Se uptake from selenite in both rice and yeast (Saccharomyces cerevisiae) at low pHs. Expression of OsNIP2;1 in yeast enhanced the selenite uptake at pH 3.5 and 5.5 but not at pH 7.5. On the other hand, defect of Si efflux transporter Lsi2 did not affect the uptake of Se either from selenite or selenate. Taken together, our results indicate that Si influx transporter OsNIP2;1 is permeable to selenite.

DOI： 10.1104/pp.110.157867

Knockout of a Bacterial-Type ATP-Binding Cassette Transporter Gene, AtSTAR1, Results in Increased Aluminum Sensitivity in Arabidopsis

Chao-Feng Huang, Naoki Yamaji, Jian Feng Ma

PLANT PHYSIOLOGY 153 ( 4 ) 1669 - 1677 2010年8月

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

ATP-binding cassette (ABC) transporters represent a large family in plants, but the functions of most of these transporters are unknown. Here we report a gene, AtSTAR1, only encoding an ATP-binding domain of a bacterial-type ABC transporter in Arabidopsis (Arabidopsis thaliana). AtSTAR1 is an ortholog of rice (Oryza sativa) OsSTAR1, which has been implicated in aluminum (Al) tolerance. Knockout of AtSTAR1 resulted in increased sensitivity to Al and earlier flowering. Unlike OsSTAR1, AtSTAR1 was expressed in both the roots and shoots and its expression was not induced by Al or other stresses. Investigation of tissue-specific localization of AtSTAR1 through beta-glucuronidase fusion revealed that AtSTAR1 was predominantly expressed at outer cell layers of root tips and developing leaves, whose localization is also different from those of OsSTAR1. However, introduction of OsSTAR1 into atstar1 mutant rescued the sensitivity of atstar1 to Al, indicating that AtSTAR1 has a similar function as OsSTAR1. Furthermore, we found that AtSTAR1 may interact with ALS3, a transmembrane-binding domain in Arabidopsis to form a complex because introduction of OsSTAR1, a functional substitute of AtSTAR1, into als3 mutant resulted in the loss of OsSTAR1 protein. All these findings indicate that AtSTAR1 is involved in the basic detoxification of Al in Arabidopsis.

DOI： 10.1104/pp.110.155028

Silicon enhances growth independent of silica deposition in a low-silica rice mutant, lsi1

Mami Isa, Shuqin Bai, Takushi Yokoyama, Jian Feng Ma, Yushi Ishibashi, Takashi Yuasa, Mari Iwaya-Inoue

PLANT AND SOIL 331 ( 1-2 ) 361 - 375 2010年6月

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

To examine whether silica bodies are essential for silicon-enhanced growth of rice seedlings, we investigated the response of rice, Oryza sativa L., to silicon treatment. Silicic acid treatment markedly enhanced the SPAD (soil plant analytical development) values of leaf blades and the growth and development of leaves and lateral roots in cvs. Hinohikari and Oochikara, and a low-silicon mutant, lsi1. Combination of ethanol-benzene displacement and staining with crystal violet lactone enabled more detailed histochemical analysis to visualize silica bodies in the epidermis under bright-field microscopy. Supply of silicon induced the development of motor cells and silica bodies in epidermal cells in Hinohikari and Oochikara but not or marginal in lsi1. X-ray analytical microscopy detected silicon specifically in the leaf sheath, the outermost part of the stem, and the leaf blade midrib, suggesting that silicon is distributed to tissues involved in maintaining rigidity of the plant to prevent lodging, rather than being passively deposited in growing tissues. Silicon supplied at high dose accumulated in all rice seedlings and enhanced growth and SPAD values with or without silica body formation. Silicon accumulated in the cell wall may play an important physiological role different from that played by the silica deposited in the motor cell and silica bodies.

DOI： 10.1007/s11104-009-0258-9

Understanding how plants cope with acid soils

Jian Feng Ma, Peter R. Ryan

FUNCTIONAL PLANT BIOLOGY 37 ( 4 ) III - VI 2010年

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

Supplying food and fuel to meet the demands of a growing population is a challenge facing every society. Crop yields will need to increase significantly over the next 40 years to support an extra two billion people by 2050. Acid soils limit plant production around the world but especially in the tropical and sub-tropical latitudes where a large proportion of the population increases are expected to occur. Aluminium toxicity and phosphorus deficiency are two of the major stresses affecting plant growth on acid soils. How plants combat these stresses was a theme at the '7th International Symposium on Plant-Soil Interactions at Low pH', held in Guangzhou in 2009, and the focus of this issue of FPB. We provide an overview of recent progress in the area and introduce a selection of invited papers for this research front on acid soils.

DOI： 10.1071/FPv37n4_FO

A specific transporter for iron(III)-phytosiderophore in barley roots (vol 46, pg 563, 2006) 査読

Murata Y, Ma J. F, Yamaji N, Ueno D, Nomoto K, Iwashita T

Plant Journal 61 ( 1 ) 188 - 188 2010年

Silicon Transporters in Higher Plants

Jian Feng Ma

MIPS AND THEIR ROLE IN THE EXCHANGE OF METALLOIDS 679 99 - 110 2010年

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-VERLAG BERLIN

Silicon (Si) is the second most abundant element in the Earth's crust and exerts beneficial effects on plant growth and production by alleviating both biotic and abiotic stresses including diseases, pests, lodging, drought and nutrient imbalance. Silicon is taken up by the roots in the form of silicic acid, a noncharged molecule. Recently both influx (Lsi1) and efflux (Lsi2) transporters for silicic acid have been identified in gramineous plants including rice, barley and maize. Lsi1 and its homologs are influx Si transporters, which belong to a Nod26-like major intrinsic protein (NIP) subfamily in the aquaporin protein family. They are responsible for the transport of Si from the external solution to the root cells. On the other hand, Lsi2 and its homologs are efflux Si transporters, belonging to putative anion transporters and are responsible for the transport of Si out of the cells toward the xylem. All influx transporters show polar localization at the distal side. Among efflux transporters, Lsi2 in rice shows polar localization at the proximal side, but that in barley and maize does not show polar localization. The cell-specificity of localization of Si transporters and expression patterns are different between species. Rice Si transporters are also permeable to arsenite.

DOI： 10.1007/978-1-4419-6315-4_8

Isolation and characterisation of two MATE genes in rye

Kengo Yokosho, Naoki Yamaji, Jian Feng Ma

FUNCTIONAL PLANT BIOLOGY 37 ( 4 ) 296 - 303 2010年

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

Multidrug and toxic compound extrusion (MATE) proteins are widely present in bacteria, fungi, plants and mammals. Recent studies have showed that a group of plant MATE genes encodes citrate transporter, which are involved in the detoxification of aluminium or translocation of iron from the roots to the shoots. In this study, we isolated two homologous genes (ScFRDL1 and ScFRDL2) from this family in rye (Secale cereale L.). ScFRDL1 shared 94.2% identity with HvAACT1, an Al-activated citrate transporter in barley (Hordeum vulgare L.) and ScFRDL2 shared 80.6% identity with OsFRDL2, a putative Al-responsive protein in rice (Oryza sativa L.). Both genes were mainly expressed in the roots, however, they showed different expression patterns. Expression of ScFRDL1 was unaffected by Al treatment, but up-regulated by Fe-deficiency treatment. In contrast, expression of ScFRDL2 was greatly induced by Al but not by Fe deficiency. The Al-induced up-regulation of ScFRDL2 was found in both the root tips and basal roots. Furthermore, the expression pattern of ScFRDL2 was consistent with citrate secretion pattern. Immunostaining showed that ScFRDL1 was localised at all cells in the root tips and central cylinder and endodermis in the basal root. Taken together, our results suggest that ScFRDL1 was involved in efflux of citrate into the xylem for Fe translocation from the roots to the shoots, while ScFRDL2 was involved in Al-activated citrate secretion in rye.

DOI： 10.1071/FP09265

The role of the rice aquaporin Lsi1 in arsenite efflux from roots

Fang-Jie Zhao, Yukiko Ago, Namiki Mitani, Ren-Ying Li, Yu-Hong Su, Naoki Yamaji, Steve P. McGrath, Jian Feng Ma

NEW PHYTOLOGIST 186 ( 2 ) 392 - 399 2010年

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

When supplied with arsenate (As(V)), plant roots extrude a substantial amount of arsenite (As(III)) to the external medium through as yet unidentified pathways. The rice (Oryza sativa) silicon transporter Lsi1 (OsNIP2;1, an aquaporin channel) is the major entry route of arsenite into rice roots. Whether Lsi1 also mediates arsenite efflux was investigated.Expression of Lsi1 in Xenopus laevis oocytes enhanced arsenite efflux, indicating that Lsi1 facilitates arsenite transport bidirectionally.Arsenite was the predominant arsenic species in arsenate-exposed rice plants. During 24-h exposure to 5 mu M arsenate, rice roots extruded arsenite to the external medium rapidly, accounting for 60-90% of the arsenate uptake. A rice mutant defective in Lsi1 (lsi1) extruded significantly less arsenite than the wild-type rice and, as a result, accumulated more arsenite in the roots. By contrast, Lsi2 mutation had little effect on arsenite efflux to the external medium.We conclude that Lsi1 plays a role in arsenite efflux in rice roots exposed to arsenate. However, this pathway accounts for only 15-20% of the total efflux, suggesting the existence of other efflux transporters.

DOI： 10.1111/j.1469-8137.2010.03192.x

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