ZmWRKY104 positively regulates salt tolerance by modulating ZmSOD4 expression in maize

Salinity impairs plant growth, limiting agricultural development. It is desirable to identify genes responding to salt stress and their mechanism of action. We identified a function of the Zea mays WRKY transcription factor, ZmWRKY104, in salt stress response. ZmWRKY104 was localized in the nucleus and showed transcriptional activation activity. Phenotypic and physiological analysis showed that overexpression of ZmWRKY104 in maize increased the tolerance of maize to salt stress and alleviated salt-induced increases in O2− accumulation, malondialdehyde (MDA) content, and percent of electrolyte leakage. Further investigation showed that ZmWRKY104 increased SOD activity by regulating ZmSOD4 expression. Yeast one-hybrid, electrophoretic mobility shift test, and chromatin immunoprecipitation–quantitative PCR assay showed that ZmWRKY104 bound directly to the promoter of ZmSOD4 by recognizing the W-box motif in vivo and in vitro. Phenotypic, physiological, and biochemical analysis showed that ZmSOD4 increased salt tolerance by alleviating salt-induced increases in O2− accumulation, MDA content, and percent of electrolyte leakage under salt stress. Taken together, our results indicate that ZmWRKY104 positively regulates ZmSOD4 expression to modulate salt-induced O2− accumulation, MDA content, and percent of electrolyte leakage, thus affecting salt stress response in maize.