The SmWRKY12-SmRAP2-7-SmEXPA13 module in Salix matsudana koidz enhances plant tolerance to drought stress

WRKY transcription factors play key roles in plant responses to abiotic stress. In this study, we cloned and characterized the drought-induced WRKY gene SmWRKY12 from Salix matsudana Koidz. Following drought treatment, SmWRKY12 was significantly upregulated in the roots of the drought-tolerant willow variety 9901. Overexpressing SmWRKY12 in willow calli significantly increased drought tolerance. The results of yeast onehybrid and dual-luciferase reporter assays showed that SmWRKY12 can bind to the promoter of the expansin gene SmEXPA13 and activate its expression. The results of yeast two-hybrid and split luciferase complementation assays showed that SmWRKY12 can interact with SmRAP2-7. The results of dual-luciferase and transgenic experiments showed that the combination of SmWRKY12 and SmRAP2-7 significantly increased the transcriptional regulation of SmWRKY12 on SmEXPA13. SmEXPA13 was introduced into willow calli and tobacco plants. Overexpressing SmEXPA13 significantly improved their performance under drought conditions. The results revealed a novel mechanism to tolerate drought stress through the SmWRKY12-SmRAP2-7-SmEXPA13 module in willow. This study also provided a new strategy for the molecular design and breeding of drought-tolerant plants.