Abstract
Intake of Cd from rice is a serious concern for human health, however the mechanisms controlling Cd accumulation in rice are poorly understood. Herein, we report a transporter (CASTLE1) specifically responsible for low Cd accumulation in rice shoots. We detected a QTL on chromosome 7, by using a mapping population derived from a cross between a high- (Anjana Dhan) and low-cadmium (Nipponbare) accumulating cultivar, and finally were able to isolate the candidate gene (CASTLE1), belonging to P-type ATPase. Allelic CASTLE1 genes were mainly expressed in the root at a similar level in both accessions. Immunostaining showed the localization at tonoplast and vesicles of all root cells. Knockdown of CASTLE1 in Nipponbare resulted in increased Cd accumulation in the shoots, whereas over-expression of this gene resulted in decreased Cd accumulation. Yeast expression analysis showed that CASTLE1 from Nipponbare showed transport activity for Cd, whereas that from Anjana Dhan did not. These results indicate that functional CASTLE1 in Nipponbare plays a role in sequestrating Cd into the vacuoles and vesicles in the roots, thereby reducing Cd translocation to the upper parts.
