CsWRKY15 from tea plant promotes its auto-resistance when intercropped with chestnut.

To explore the role of WRKY transcription factors in resistance, a WRKY15 homologous gene, CsWRKY15, and its promoter were isolated from tea plants when intercropped with chestnut. CsWRKY15 expression was significantly induced by ethephon, polyethylene glycol (PEG), and low temperature. Notably, its expression was strongly induced by exogenous gibberellic acid (GA3). A CsWRKY15 overexpression vector was constructed and transformed into tobacco plants. Overexpressing CsWRKY15 enhanced biotic and abiotic stress tolerance in transgenic tobacco plants by increasing antioxidant enzyme activity, upregulating stress-related genes, and activating GA signaling pathway-related genes. The transgenic tobacco plants also showed improved biotic and abiotic stress resistance through enhanced physiological indicators and strengthened physical barriers. Moreover, the homeodomain-leucine zipper protein HAT5 from tea plants (CsHAT5) bound to the LTR (low temperature responsive element), GARE (GA-responsive element), and MBS (MYB binding site) elements in the CsWRKY15 promoter to activate its expression. These results indicated that CsWRKY15 play a positive regulatory role in both biotic and abiotic stress responses. Overall, enhanced GA biosynthesis and signaling activated CsWRKY15 expression, which in turn upregulated antioxidant enzymes and defense-related genes, promoting auto-resistance in tea plants when intercropped with chestnut and improving tea plants health.