Global contamination of soils with toxic cadmium (Cd) is a serious health threat. Here we found that a tandem duplication of a gene encoding a manganese/Cd transporter, OsNramp5, was responsible for low-Cd accumulation in Pokkali, an old rice cultivar. This duplication doubled the expression of OsNramp5 gene but did not alter its spatial expression pattern and cellular localization. Higher expression of OsNramp5 increased uptake of Cd and Mn into the root cells but decreased Cd release to the xylem. Introgression of this allele into Koshihikari, an elite rice cultivar, through backcrossing significantly reduced Cd accumulation in the grain when cultivated in soil heavily contaminated with Cd but did not affect both grain yield and eating quality. This study not only reveals the molecular mechanism underlying low-Cd accumulation but also provides a useful target for breeding rice cultivars with low-Cd accumulation.

有毒镉 (Cd) 对土壤的全球污染是一种严重的健康威胁。在这里，我们发现编码锰/镉转运蛋白的基因OsNramp5的串联重复是造成 Pokkali（一种古老的水稻品种）低镉积累的原因。这种重复使OsNramp5基因的表达加倍，但没有改变其空间表达模式和细胞定位。OsNramp5的高表达增加根细胞对 Cd 和 Mn 的吸收，但减少释放到木质部的 Cd。当在受 Cd 严重污染的土壤中耕种时，通过回交将该等位基因渗入到优良水稻品种 Koshihikari 中，可显着减少谷物中的 Cd 积累，但不会影响谷物产量和食用品质。该研究不仅揭示了低镉积累的分子机制，而且为培育低镉积累的水稻品种提供了有用的靶标。