Excessive cadmium (Cd) accumulation in grains of
(Oryza sativa) is a serious health risk. Transporters in the nodes of rice
distribute mineral elements, including toxic ones, to different plants
tissues. However, the mechanism of Cd accumulation in grains is quite
unknown. A group of researchers led by Xiaohua Hao from Hunan Normal
University in China identified a node-expressed transporter gene, OsCCX2,
which could be involved in controlling Cd accumulation.
Knockout of the OsCCX2 gene caused a great reduction of Cd content in the
rice grains. Further analysis showed that disruption of this gene led to a
reduced root-to-shoot translocation of Cd. Moreover, Cd distribution was
also disturbed in internodes and leaves.
OsCCX2 was found to be localized to plasma membrane, and is mainly expressed
in xylem region of vascular tissues at the nodes. OsCCX2 might function as
an efflux transporter, responsible for Cd loading into xylem vessels.
The findings of the study revealed a novel Cd transporter involved in grain