記述言語：英語   掲載種別：研究論文（学術雑誌）  

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

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

Phosphoenolpyruvate carboxylase (PEPC, EC 4.1.1.31) is believed to play a significant role in supporting nitrogen fixation via anaplerotic CO2 fixation for recycling carbon in nodules. Using the antisense technique, we decreased the expression levels of the nodule-enhanced PEPC gene (Ljpepc1) in a determinate legume plant (Lotus japonicus) in order to look at the influence of the symbiotic phenotype and biochemical parameters. Three independent transgenic L. japonicus plants (designated as Asppc1, Asppc2 and Asppc3) were prepared using a Ljpepc1 DNA fragment which is under the control of the cauliflower mosaic virus 35S promoter. Extensive suppression of the Ljpepc1 transcript in nodules of Asppc plants (T3 homologous plants) was confirmed by RNA gel blot, Western blot and enzyme activity assays. In nodules of Asppc plants, PEPC activity was reduced to about 10% of that of non-transformants and the plants showed typical nitrogen-deficient symptoms without a supply of nitrogen nutrient, and returned to normal growth when nitrate was supplied at 2.5 mM. The acetylene reduction activity per fresh weight of nodules of these Asppc plants decreased by 29% at 35 dai (days after infection). Various enzyme activities and metabolite levels were surveyed using Asppc plants at 35 dai. Significant reduction of sucrose synthase and asparagine aminotransferase activities was observed in Asppc nodules. In addition, sucrose, succinate, asparagine, aspartate and glutamate contents also decreased in Asppc nodules. The data are discussed in terms of a role for PEPC in the carbon/nitrogen metabolic flux in nodules.

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出版者・発行元：Wiley  

<jats:title>Summary</jats:title><jats:p>Salt tolerance quantitative trait loci analysis of rice has revealed that the <jats:italic><jats:styled-content style="fixed-case">SKC</jats:styled-content>1</jats:italic> locus, which is involved in a higher K<jats:sup>+</jats:sup>/Na<jats:sup>+</jats:sup> ratio in shoots, corresponds to the <jats:italic>Os<jats:styled-content style="fixed-case">HKT</jats:styled-content>1;5</jats:italic> gene encoding a Na<jats:sup>+</jats:sup>‐selective transporter. However, physiological roles of Os<jats:styled-content style="fixed-case">HKT</jats:styled-content>1;5 in rice exposed to salt stress remain elusive, and no <jats:italic>Os<jats:styled-content style="fixed-case">HKT</jats:styled-content>1;5</jats:italic> gene disruption mutants have been characterized to date. In this study, we dissected two independent T‐<jats:styled-content style="fixed-case">DNA</jats:styled-content> insertional <jats:italic>Os<jats:styled-content style="fixed-case">HKT</jats:styled-content>1;5</jats:italic> mutants. Measurements of ion contents in tissues and <jats:sup>22</jats:sup>Na<jats:sup>+</jats:sup> tracer imaging experiments showed that loss‐of‐function of Os<jats:styled-content style="fixed-case">HKT</jats:styled-content>1;5 in salt‐stressed rice roots triggers massive Na<jats:sup>+</jats:sup> accumulation in shoots. Salt stress‐induced increases in the <jats:italic>Os<jats:styled-content style="fixed-case">HKT</jats:styled-content>1;5</jats:italic> transcript were observed in roots and basal stems, including basal nodes. Immuno‐staining using an anti‐Os<jats:styled-content style="fixed-case">HKT</jats:styled-content>1;5 peptide antibody indicated that Os<jats:styled-content style="fixed-case">HKT</jats:styled-content>1;5 is localized in cells adjacent to the xylem in roots. Additionally, direct introduction of <jats:sup>22</jats:sup>Na<jats:sup>+</jats:sup> tracer to leaf sheaths also demonstrated the involvement of Os<jats:styled-content style="fixed-case">HKT</jats:styled-content>1;5 in xylem Na<jats:sup>+</jats:sup> unloading in leaf sheaths. Furthermore, Os<jats:styled-content style="fixed-case">HKT</jats:styled-content>1;5 was indicated to be present in the plasma membrane and found to localize also in the phloem of diffuse vascular bundles in basal nodes. Together with the characteristic <jats:sup>22</jats:sup>Na<jats:sup>+</jats:sup> allocation in the blade of the developing immature leaf in the mutants, these results suggest a novel function of Os<jats:styled-content style="fixed-case">HKT</jats:styled-content>1;5 in mediating Na<jats:sup>+</jats:sup> exclusion in the phloem to prevent Na<jats:sup>+</jats:sup> transfer to young leaf blades. Our findings further demonstrate that the function of Os<jats:styled-content style="fixed-case">HKT</jats:styled-content>1;5 is crucial over growth stages of rice, including the protection of the next generation seeds as well as of vital leaf blades under salt stress.</jats:p>

DOI： 10.1111/tpj.13595

DOI： 10.1101/2022.04.29.489905_references_DOI_VviP7H9CeyfXb6ND15ry7LrlJfO

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その他リンク： https://onlinelibrary.wiley.com/doi/full-xml/10.1111/tpj.13595

出版者・発行元：Oxford University Press (OUP)  

High aluminum (Al) tolerance of rice (Oryza sativa) is controlled by multiple tolerance genes, but the regulatory mechanisms underlying the differential expression of these genes are poorly understood. Here, we investigated the factors regulating the expression of OsFRDL4, a gene encoding a citrate efflux transporter involved in Al-induced citrate secretion from the roots. Analysis with chromosome segment substitution lines derived from cv Nipponbare (high OsFRDL4 expression) and cv Kasalath (low OsFRDL4 expression) revealed that the differential expression of OsFRDL4 is responsible for the quantitative trait locus for Al tolerance detected previously on chromosome 1. Comparison of the OsFRDL4 gene structure in cv Nipponbare and cv Kasalath showed that there was no difference in the position of the transcriptional start site, but a 1.2-kb insertion showing high similarity to the solo long terminal repeat of the retrotransposon was found in the promoter region of OsFRDL4 in cv Nipponbare. This insertion showed higher promoter activity and contained nine cis-acting elements for ALUMINUM RESISTANCE TRANSCRIPTION FACTOR1 (ART1). However, this insertion did not alter the spatial expression or cellular localization of OsFRDL4. Furthermore, this insertion was found in most japonica varieties but was largely absent from indica varieties or wild rice species. These results indicate that the 1.2-kb insertion in the OsFRDL4 promoter region in japonica subspecies is responsible for their higher expression level of OsFRDL4 due to the increased number of cis-acting elements of ART1. Our results also suggest that this insertion event happened at the initial stage of domestication of japonica subspecies.

DOI： 10.1104/pp.16.01214

DOI： 10.1093/pcp/pcy171_references_DOI_D1EdT3QAOdetu9zVjVX26M3u5Rd

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その他リンク： https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-16H06296/

出版者・発行元：Springer Science and Business Media LLC  

To reduce cadmium (Cd) intake, remediation of Cd-contaminated soil and breeding crops with low Cd accumulation are important. This study aims to isolate rice mutants with altered accumulation of Cd. We used rice seeds mutated by N-methyl-N-nitrosourea for screening. The mutant was physiologically, genetically, and molecularly characterized. Cd accumulation was compared among five rice varieties cultivated in a Cd-contaminated soil. From 1000 lines screened, we isolated a line (TCM213) with high Cd accumulation. There was no difference in the root Cd uptake, but a higher root-to-shoot translocation of Cd was found in TCM213 compared with a common rice cultivar, T-65. The expression and sequence of OsNramp5 and OsHMA2 did not differ between TCM213 and T-65. However, several SNPs and deletion were found in the sequence of OsHMA3, although its expression and tissue localization were similar to those of T-65. Genetic analysis of an F2 population derived from T-65 and TCM213 showed that the variation of OsHMA3 explained 72 % of variation in total Cd accumulation. TCM213 accumulated the largest Cd amount in the shoots among five Cd-accumulating varieties. High Cd accumulation in TCM213 results from loss of function of OsHMA3, and its high Cd accumulation has potential for efficient phytoremediation of Cd-contaminated soil.

DOI： 10.1007/s11104-016-3014-y

DOI： 10.1111/nph.19070_references_DOI_X4qnl1wmZpNzWMGYzzRuImrYB6V

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その他リンク： http://link.springer.com/article/10.1007/s11104-016-3014-y/fulltext.html

記述言語：英語  

DOI： 10.1038/ncomms12138

DOI： 10.1093/pcp/pcy124_references_DOI_WN4YIVJiFp2VIFOjFja9z11CVvc

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その他リンク： https://www.nature.com/articles/ncomms12138.pdf

出版者・発行元：Oxford University Press (OUP)  

Rice (Oryza sativa) is characterized by having fibrous root systems; however, the molecular mechanisms underlying the root development are not fully understood. Here, we isolated a rice mutant with short roots and found that the mutant had a decreased cell size of the roots and shoots compared with wild-type rice. Map-based cloning combined with whole-genome sequencing revealed that a single nucleotide mutation occurred in a gene, which encodes a putative cation-chloride cotransporter (OsCCC1). Introduction of OsCCC1 cDNA into the mutant rescued the mutant growth, indicating that growth defects of both the roots and shoots are caused by loss of function of OsCCC1. Physiological analysis showed that the mutant had a lower concentration of Cl(-) and K(+) and lower osmolality in the root cell sap than the wild type at all KCl supply conditions tested; however, the mutant only showed a lower Na(+) concentration at high external Na(+) Expression of OsCCC1 in yeast increased accumulation of K(+), Na(+), and Cl(-) The expression of OsCCC1 was found in both the roots and shoots, although higher expression was found in the root tips. Furthermore, the expression in the roots did not respond to different Na(+), K(+), and Cl(-) supply. OsCCC1 was expressed in all cells of the roots, leaf, and basal node. Immunoblot analysis revealed that OsCCC1 was mainly localized to the plasma membrane. These results suggest that OsCCC1 is involved in the cell elongation by regulating ion (Cl(-), K(+), and Na(+)) homeostasis to maintain cellular osmotic potential.

DOI： 10.1104/pp.16.00017

DOI： 10.1016/j.jplph.2021.153409_references_DOI_UVHy4rCvcC2E2alBraOBN98cBRg

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その他リンク： https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-13F03388/

出版者・発行元：Oxford University Press (OUP)  

The multidrug and toxic compound extrusion (MATE) transporters represent a large transporter family in plants, but the role of most genes in this family has not been examined. We functionally characterized a MATE family member, OsFRDL2, in rice (Oryza sativa). OsFRDL2 showed an efflux transport activity for citrate when it was expressed in both Xenopus oocytes and cultured tobacco cells. OsFRDL2 was mainly expressed in the roots and its expression was not induced by iron (Fe) deficiency, but it was rapidly up-regulated by aluminum (Al). Furthermore, the expression of OsFRDL2 was regulated by ART1, a C2H2-type zinc-finger transcription factor for Al tolerance. OsFRDL2 protein was localized at unidentified vesicles in the cytosol, but not co-localized with either mitochondria or peroxisomes when expressed in both onion epidermal cells and cultured tobacco cells. Knockout of OsFRDL2 decreased Al-induced secretion of citrate from the roots, but did not affect the internal citrate concentration. The Al-induced inhibition of root elongation was similar between the OsFRDL2 knockout line and its wild-type rice. Knockout of OsFRDL2 did not affect the translocation of Fe from the roots to the shoots. A double mutant between osfrdl2 and osfrdl4 or osfrdl1 did not further decrease the Al-induced citrate secretion and Fe translocation compared with the single mutant. Collectively, our results indicate that although OsFRDL2 is involved in the Al-induced secretion of citrate, its contribution to high Al tolerance is relatively small in rice.

DOI： 10.1093/pcp/pcw026

DOI： 10.1111/nph.15252_references_DOI_ZWbPieIcUk9aWWLtjMFoAi3a7Hf

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出版者・発行元：Proceedings of the National Academy of Sciences  

<jats:title>Significance</jats:title>
<jats:p>
Contamination of water and foods with arsenic (As) poses a threat to millions of people worldwide. Because the rice grain is the major source of As intake, reducing the transfer of As from soil to the grain is a pressing public health issue. We found that a member of the
<jats:italic>Oryza sativa</jats:italic>
C-type ATP-binding cassette transporter (OsABCC) family, OsABCC1, detoxifies As and reduces the amount of As in the rice grain. OsABCC1 in the upper nodes of rice plants restricts the distribution of As to the grain by sequestering it in the vacuoles of the phloem companion cells of diffuse vascular bundles directly connected to the grain. Our work suggests a strategy for limiting As accumulation in rice grains and thereby reducing human As exposure.
</jats:p>

DOI： 10.1073/pnas.1414968111

DOI： 10.5167/uzh-106488

PubMed

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その他リンク： https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-24248014/

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