The Maize Sulfite Reductase Is Involved in Cold and Oxidative Stress Responses.

Sulfite reductase (SiR) functions in sulfate assimilation pathway. However, whether it is involved in stress response in crops is largely unknown. Here, the ortholog from () was characterized. The recombinant ZmSiR protein was purified from . It exhibited sulfite-dependent activity and had strong affinity for sulfite. transcripts were markedly up-regulated by cold and methyl viologen (MV) treatments. Overexpression of complemented growth retardation phenotype of mutant. -overexpressing plants were tolerant to severe SO stress and rescued the susceptible phenotype of the knock-down transgenic maize plants with 60% residual transcripts were more susceptible to cold or oxidative stress than wild-type. The severe damage phenotypes of the -compromised maize plants were accompanied by increases of sulfite and HO accumulations, but less amounts of GSH. The qPCR analysis revealed that there was significantly altered expression of several key sulfur metabolism-related genes in -impaired maize lines under cold or MV stress. Particularly, expression was significantly elevated, suggesting that toxic sulfite accumulation in -impaired plants could be attributable to the reduced coupled to increased expression. Together, our results indicate that is involved in cold and oxidative stress tolerance possibly by modulating sulfite reduction, GSH-dependent HO scavenging, and sulfur-metabolism related gene expression. could be exploited for engineering environmental stress-tolerant varieties in molecular breeding of maize.