A positive transcription factor in osmotic stress tolerance, ZAT10, is regulated by MAP kinases in Arabidopsis

Abstract

Osmotic stress is induced by several environmental stresses such as drought, cold and salinity. Osmotic stress may finally leads to oxidative damage, ionic imbalance and growth inhibition in plants. Gene expression analyses indicated that ZAT10 transcription factor, a novel substrate of Arabidopsis MPKs, could be induced by environmental stresses that result in osmotic stress. As previously reported, ZAT10 overexpressing transgenic plants showed enhanced tolerance to osmotic stress. However, in contrast to previous report, a zat10 knockout mutant showed an osmotic stress sensitive phenotype. To determine the biological function of EAR domain and phosphorylation sites of ZAT10, we constructed two transgenic plants expressing two ZAT10 mutant proteins having EAR domain mutations (ZAT10(EAR)) and phosphorylation site mutations (ZAT10(AA)). The phenotype of zat10 was complemented by the expression of ZAT10(EAR) mutant, however not by the expression of ZAT10(AA) mutant, indicating that the phosphorylation sites in ZAT10 by MPKs are involved in stress tolerance but the EAR domain is not. In this report, we suggest that ZAT10 function as a positive regulator in osmotic stress tolerance and the phosphorylation of ZAT10 is required for its function in Arabidopsis.