Abstract
Cadmium (Cd) causes Itai-itai disease and rice is a major source of Cd intake. Therefore, reducing Cd accumulation in rice grain is an important issue for human health. We have identified three QTLs responsible for Cd accumulation in rice by using natural variation in rice Cd accumulation. Among them, one QTL gene on the chromosome 7 has been cloned and functionally characterized (Ueno et al., 2010). The protein encoded by this gene OsHMA3 belongs to P-type ATPase and is localized to the tonoplast of all root cells. There were no differences in the expression level and tissue- and cellular localization of this protein between a high and a low Cd-accumulating cultivar. However, the proteins from the low Cd-accumulating cultivar showed transport activity for Cd, whereas that from high Cd-accumulating cultivar did not. When the functional OsHMA3 was over-expressed in rice, the Cd concentration was remarkably reduced in the grain of rice even if grown on Cd-contaminated soil. These results indicate that functional OsHMA3 reduces translocation of Cd from the roots to the shoots by sequestering Cd taken up into the root vacuoles. Ueno et al., PNAS, 107, 16500-16505(2010).
