Suppression of / Changes Zn and Cd Root-to-Shoot Translocation in a Zn/Cd Status-Dependent Manner.

In tobacco, the efficiency of Zn translocation to shoots depends on Zn/Cd status. Previous studies pointed to the specific contribution of root parts in the regulation of this process, as well as the role of / (from the ZIP family; Zrt Irt-like Proteins). Here, to verify this hypothesis, / RNAi lines were generated. Then, in plants exposed to combinations of Zn and Cd concentrations in the medium, the consequences of / suppression for the translocation of both metals were determined. Furthermore, the apical, middle, and basal root parts were examined for accumulation of both metals, for Zn localization (using Zinpyr-1), and for modifications of the expression pattern of genes. Our results confirmed the role of / in the control of Zn/Cd-status-dependent transfer of both metals to shoots. Furthermore, they indicated that the middle and basal root parts contributed to the regulation of this process by acting as a reservoir for excess Zn and Cd. Expression studies identified several candidate genes that interact with / in the root in regulating Zn and Cd translocation to the shoot, primarily in the basal root part and in the middle one.