The tonoplast-localized transporter OsABCC9 is involved in cadmium tolerance and accumulation in rice

Cadmium (Cd) is a highly toxic element to living organisms, and its accumulation in the edible portions of crops poses a potential threat for human health. The molecular mechanisms underlying Cd detoxification and accumulation are not fully understood in plants. In this study, the involvement of a C-type ABC transporter, OsABCC9, in Cd tolerance and accumulation in rice was investigated. The expression of OsABCC9 was rapidly induced by Cd treatment in a concentration-dependent manner in the root. The transporter, localized on the tonoplast, was mainly expressed in the root stele under Cd stress. OsABCC9 knockout mutants were more sensitive to Cd and accumulated more Cd in both the root and shoot compared to the wild-type. Moreover, the Cd concentrations in the xylem sap and grain were also significantly increased in the knockout lines, suggesting that more Cd was distributed from root to shoot and grain in the mutants. Heterologous expression of OsABCC9 in yeast enhanced Cd tolerance along with an increase of intracellular Cd content. Taken together, these results indicated that OsABCC9 mediates Cd tolerance and accumulation through sequestration of Cd into the root vacuoles in rice.