The C-type ATP-binding cassette transporter OsABCC7 is involved in the root-to-shoot translocation of arsenic in rice

Zhong Tanga, Y. Chenb, A.J. Millerb and F.J. Zhaoa

a State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Resources and Environmental Sciences, Nanjing Agricultural University, China

b Department of Metabolic Biology, John Innes Centre, UK

Tangzhong@njau.edu.cn

Rice is a major dietary source of inorganic arsenic, a non-threshold carcinogen. Reducing arsenic accumulation in rice grain is of critical importance for food safety. In our work, 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 Pro-GUS showed 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)-glutathione complex but not for As(III). Knockout of OsABCC7 in rice significantly decreased As(III) 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).

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