Glutathione plays a role in the cross-homeostasis between Fe and Zn

In our previous study, we found that additional iron (Fe) could increase Zn tolerance in Arabidopsis (Shanmugam et al., 2011). To understand the mechanism involved, we initiated a genetic screen. We isolated zinc tolerance induced by iron 1, designated zir1, with a defect in Fe-mediated Zn tolerance. Using map-based cloning and genetic complementation, we identify that ZIR1 encoded an enzyme involved in glutathione biosynthesis. The point mutation in ZIR1 causes the reduction of γ-ECS activity resulting in only 15% of the wild-type glutathione level in the ZIR1 mutant. This reduction of glutathione associate the Fe restoration under excess Zn. Therefore, glutathione is required for the cross-homeostasis between Zn and Fe.