The OsZIP2 transporter is involved in root-to-shoot translocation and
intervascular transfer of cadmium in rice
Abstract
Cadmium (Cd) is a toxic metal that poses serious threats to human
health. Rice is a major source of dietary Cd but how rice plants
transport Cd to the grain is not fully understood. Here, we characterize
the function of the ZIP (ZRT, IRT-like protein) family protein, OsZIP2,
in the root-to-shoot translocation of Cd and intervascular transfer of
Cd in nodes. OsZIP2 is localized at the plasma membrane and exhibited Cd
2+ transport activity when heterologously expressed in
yeast. OsZIP2 is strongly expressed in xylem parenchyma cells in
roots and in enlarged vascular bundles in nodes. Knockout of
OsZIP2 significantly enhanced root-to-shoot translocation of Cd
and alleviated the inhibition of root elongation by excess Cd stress;
whereas overexpression of OsZIP2 decreased Cd translocation to
shoots and resulted in Cd sensitivity. Knockout of OsZIP2
increased Cd allocation to the flag leaf but decreased Cd allocation to
the panicle and grain. We further reveal that the variation of
OsZIP2 expression level contributes to grain Cd concentration
among rice germplasms. Our results demonstrate that OsZIP2 functions in
root-to-shoot translocation of Cd in roots and intervascular transfer of
Cd in nodes, which can be used for breeding low Cd rice varieties.