Interaction of wheat methionine sulfoxide reductase TaMSRB5.2 with glutathione S-transferase TaGSTF3-A contributes to seedling osmotic stress resistance

Abstract

Reactive oxygen species (ROS) produced due to drought stress can lead to the oxidation of methionine in plant cells; this can then be reduced by methionine sulfoxide reductases (MSRs). To the best of our knowledge, no information has been reported to date on the function and substrates of wheat cytoplasmic TaMSRB5.2, which is induced by drought mainly both in the leaves and roots. In the present study, its constitutive overexpression in wheat (TaOE) resulted in a notable increase in MSR activity, and enhanced the tolerance of seedlings, particularly to osmotic stress, but also to salt stress. The effects of constitutively active TaMSRB5.2 in wheat included a decrease in ROS accumulation, a heightening of endogenous abscisic acid (ABA) levels, an increase in the sensitivity of stomatal guard cells to exogenous ABA, and an enhancement of intracellular proline content. Wheat glutathione S-transferase F3-A (TaGSTF3-A), a potential interaction substrate of TaMSRB5.2, was identified by screening a wheat cDNA library, and further confirmed by means of yeast two-hybrid, split-luciferase complementation and co-immunoprecipitation assays. Under osmotic stress, TaGSTF3-A expression, overall GST enzyme activity and the ratio of GSH/GSSG in the TaOE lines increased, compared to the wild-type strain. L-buthionine sulfoximine, a GST inhibitor, was found to partially impair the TaMSRB5.2-induced response to osmotic stress. TaMSRB5.2 and TaGSTF3-A were observed to be expressed in the leaves, their proteins localized within the cytoplasm, and both acted in abiotic stress response, according to the present and previous studies. In conclusion, TaMSRB5.2 participates in osmotic response in wheat, partially via TaGSTF3-A.