Others The phytosiderophore efflux transporter TOM2 is involved in metal transport in rice

Nozoye, Tomoko  ,  Nagasaka, Seiji  ,  Kobayashi, Takanori  ,  Sato, Yuki  ,  Uozumi, Nobuyuki  ,  Nakanishi, Hiromi  ,  Nishizawa, Naoko K.

2015-10-02 , The American Society for Biochemistry and Molecular Biology , Department of Global Agricultural Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo , Research Institute for Bioresources and Biotechnology, Ishikawa Prefectural University , Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University
ISSN:1083-351X(online)
NCID:AA1202441X
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UTokyo Research掲載「植物の生育に必要な金属輸送に関与するタンパク質の発見」 URI: http://www.u-tokyo.ac.jp/ja/utokyo-research/research-news/identification-of-a-crucial-metal-transporter-for-plant-growth.html
UTokyo Research "Identification of a crucial metal transporter for plant growth" URI: http://www.u-tokyo.ac.jp/en/utokyo-research/research-news/identification-of-a-crucial-metal-transporter-for-plant-growth.html
Iron (Fe) is an essential metal element for all living organisms. Graminaceous plants produce and secrete mugineic acid family phytosiderophores from their roots to acquire Fe in the soil. Phytosiderophores chelate and solubilize insoluble Fe hydroxide in the soil. Subsequently, plants take up Fe-phytosiderophore complexes through specific transporters on the root cell membrane. Phytosiderophores are also thought to be important for the internal transport of various transition metals including Fe. In the present study, we analyzed TOM2 and TOM3, rice homologs of transporter of mugineic acid family phytosiderophores 1 (TOM1), a crucial efflux transporter directly involved in phytosiderophore secretion into the soil. Transgenic rice analysis using promoter-β-glucuronidase (GUS) revealed that TOM2 was expressed in tissues involved in metal translocation, while TOM3 was expressed only in restricted parts of the plant. Strong TOM2 expression was observed in developing tissues during seed maturation and germination, while TOM3 expression was weak during seed maturation. Transgenic rice in which TOM2 expression was repressed by RNA interference showed growth defects compared to non-transformants and TOM3-repressed rice. Xenopus laevis oocytes expressing TOM2 released 14C-labeled deoxymugineic acid (DMA), the initial phytosiderophore compound in the biosynthetic pathway in rice. In onion epidermal and rice root cells, the TOM2-GFP fusion protein localized to the cell membrane, indicating that the TOM2 protein is a transporter for phytosiderophore efflux to the cell exterior. Our results indicate that TOM2 is involved in the internal transport of DMA, which is required for normal plant growth.
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