Low-affinity cation transporter ( <i>OsLCT1</i> ) regulates cadmium transport into rice grains

<jats:p> Accumulation of cadmium (Cd) in rice ( <jats:italic>Oryza sativa</jats:italic> L.) grains poses a potential health problem, especially in Asia. Most Cd in rice grains accumulates through phloem transport, but the molecular mechanism of this transport has not been revealed. In this study, we identified a rice Cd transporter, OsLCT1, involved in Cd transport to the grains. OsLCT1-GFP was localized at the plasma membrane in plant cells, and OsLCT1 showed Cd efflux activity in yeast. In rice plants, strong <jats:italic>OsLCT1</jats:italic> expression was observed in leaf blades and nodes during the reproductive stage. In the uppermost node, <jats:italic>OsLCT1</jats:italic> transcripts were detected around large vascular bundles and in diffuse vascular bundles. RNAi-mediated knockdown of <jats:italic>OsLCT1</jats:italic> did not affect xylem-mediated Cd transport but reduced phloem-mediated Cd transport. The knockdown plants of <jats:italic>OsLCT1</jats:italic> accumulated approximately half as much Cd in the grains as did the control plants. The content of other metals in rice grains and plant growth were not negatively affected by <jats:italic>OsLCT1</jats:italic> suppression. These results suggest that <jats:italic>OsLCT1</jats:italic> functions at the nodes in Cd transport into grains and that in a standard <jats:italic>japonica</jats:italic> cultivar, the regulation of <jats:italic>OsLCT1</jats:italic> enables the generation of “low-Cd rice” without negative effects on agronomical traits. These findings identify a transporter gene for phloem Cd transport in plants. </jats:p>