Regulation of jasmonic acid signalling in tomato cold stress response: Insights into the MYB15-LOXD and...

Cold stress significantly affects the growth and productivity of tomatoes. Despite the known involvement of jasmonate (JA) in cold stress responses, the underlying mechanism remains to be elucidated. Here, we observed that JA peaked 24 h after cold treatment. The expression of the SlLOXD gene, a key player in JA biosynthesis, also peaked at 24 h of cold exposure, and mutation in SlLOXD reduced JA content and cold tolerance. Downstream of JA signalling, the transcription factor SlMYC2 was implicated in enhancing cold resistance by directly binding to the SlCBF1/2 promoters. Furthermore, the SlMYC2-silenced plants and mutants exhibited increased sensitivity to cold damage. Additionally, SlMYB15 directly bound to the SlLOXD and SlMYC2 promoters. Within 6 h of cold stress, SlMYB15 activated SlLOXD expression while repressing SlMYC2 expression. Between 6 and 24 h, the expression level of SlMYB15 decreased, thereby alleviating the repression of SlMYC2 expression. SlMYC2 further enhanced JA signalling through the transcriptional activation of SlLOXD, thus improving cold tolerance in tomato plants. These findings provide valuable insights into the dynamic regulation of the SlLOXD-SlMYC2 -CBF1/2 module by SlMYB15 and its critical role in tomato cold stress responses.