Function Of Rice OsABCC9 Gene In Cadmium Tolerance And Accumulation

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.Previous high-throughput analysis revealed that the C-type ABC transporter OsABCC9 is up-regulated by Cd treatment,However,the molecular mechanisms underlying Cd detoxification and accumulation are not fully understood in plants.In this study,the involvement of OsABCC9 in Cd tolerance and accumulation in rice was investigated.The experimental results are summarized as follows:1.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.2.Heterologous expression of OsABCC9 in yeast enhanced Cd tolerance along with an increase of intracellular Cd content.Therefore,the Cd tolerance conferred by OsABCC9 is most likely due to vacuolar sequestration of Cd rather than Cd extrusion.3.To investigate the role of OsABCC9 in Cd tolerance in planta,we created osabcc9 knockout mutants using the CRISPR/Cas9 approach.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.Taken together,these results indicated that OsABCC9 mediates Cd tolerance and accumulation through sequestration of Cd into the root vacuoles in rice.Further study of ABC transporters will provide new genetic resources for rice to resist cadmium,and enable the development of low-Cd crops,thus reducing dietary intake of Cd by humans.