Rice cadmium transporter responsible for grain cadmium accumulation

Uraguchi, Shimpei*; Kamiya, Takehiro*; Sakamoto, Takuya*; Kasai, Koji*; Sato, Yutaka*; Nagamura, Yoshiaki*; Ishikawa, Satoru*; Suzui, Nobuo; Fujimaki, Shu; Fujiwara, Toru*

Cadmium (Cd) is one of the toxic environmental contaminants known to harm human health. Cd in rice grains is the major source of Cd intake in Japanese people. Precedent studies showed the importance of nodes in xylem to phloem Cd transfer and that of phloem Cd transport in grain Cd accumulation. Identification of Cd transporting molecules in rice will enable to reduce Cd accumulation in grains. However, no Cd transporter responsible for phloem Cd transport has been revealed so far. In the present study, we identified a novel rice transporter OsLCT1. This transporter had a efflux activity of Cd and some other cations. Subcelluler localization analysis suggested that OsLCT1 was localized to plasma membrane. Expression profile analysis demonstrated that OsLCT1 was strongly expressed in leaf blades and nodes at the reproductive stages. We generated the RNAi-mediated OsLCT1 knockdown rice plants and these plants accumulated approximately a half of Cd in the grains compared to control plants. The growth of knock-down plants was comparable to that of control plants. The present study first identified the transporter expressed at nodes responsible for rice grain Cd accumulation.