State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, China.
Department of Metabolic Biology, John Innes Centre, Norwich Research Park, Norwich, UK.
Plant Cell Physiol. 2019 Jul 1;60(7):1525-1535. doi: 10.1093/pcp/pcz054.
Rice is a major dietary source of inorganic arsenic (As), a nonthreshold carcinogen. Reducing As accumulation in rice grain is of critical importance for food safety. In the present study, we investigated the role of a member of the rice C-type ATP-binding cassette (ABC) transporter (OsABCC) family, OsABCC7, in arsenite [As(III)] accumulation in rice. Quantitative real-time RT-PCR showed that OsABCC7 was expressed intensively in the roots and the expression was strongly suppressed by As(III) exposure. Transgenic rice plants expressing OsABCC7 Promoter-GUS (β-glucuronidase) suggest that the gene was predominantly expressed in the xylem parenchyma cells in the stele region of the primary and lateral roots. Transient expression of OsABCC7: GFP fusion protein in Nicotiana benthamiana leaf cells showed that the protein was localized at the plasma membrane. When expressed in Xenopus laevis oocytes, OsABCC7 showed an efflux activity for As(III)-phytochelatin and As(III)-glutathione complexes, but not for As(III). Knockout of OsABCC7 in rice significantly decreased As concentration in the xylem sap and As concentration in the shoots, but had little effect on root As concentration. Taken together, our results indicate that OsABCC7 is involved in the root-to-shoot translocation of As(III).
水稻是无机砷（As）的主要膳食来源，而砷是一种无阈值的致癌物质。减少稻米中砷的积累对食品安全至关重要。本研究调查了水稻 C 型 ABC 转运蛋白（OsABCC）家族成员 OsABCC7 在亚砷酸盐（As（III））积累中的作用。定量实时 RT-PCR 显示，OsABCC7 在根中强烈表达，并且表达受 As（III）暴露强烈抑制。表达 OsABCC7 Promoter-GUS（β-葡萄糖醛酸酶）的转基因水稻植株表明，该基因主要在主根和侧根的木质部薄壁细胞中表达。OsABCC7: GFP 融合蛋白在烟草叶细胞中的瞬时表达表明该蛋白定位于质膜上。当在非洲爪蟾卵母细胞中表达时，OsABCC7 对 As（III）-植物螯合肽和 As（III）-谷胱甘肽复合物表现出外排活性，但对 As（III）没有活性。水稻中 OsABCC7 的敲除显著降低了木质部汁液和地上部分的 As 浓度，但对根中的 As 浓度影响很小。综上所述，我们的结果表明 OsABCC7 参与了 As（III）从根部到地上部分的转运。
