Jasmonic Acid Activates Transcription Factor <i>SlMYB13</i> to Enhance Cold Resistance in Tomato

Plant cold stress caused by cold waves often occurs during winter and spring, and seriously affects the growth and yield of tomatoes in horticultural facilities. The cultivation of cold-resistant tomato varieties during winter is therefore of great significance. Methyl jasmonate (MeJA) treatment is known to improve tomato cold tolerance. Using RNA sequencing, the R2R3 MYB transcription factor SlMYB13 (Solyc06g083900) responsive to MeJA and cold stress was identified as a potential regulator in this process. However, its regulatory mechanisms remain unclear. To investigate the role of SlMYB13 in cold resistance of tomatoes, SlMYB13 overexpression and CRISPR-Cas9 knockout seedlings of T₂ generation tomato were treated at 4°C. Tomato plants overexpressing SlMYB13 were more cold-tolerant, whereas SlMYB13-knockout plants exhibited significantly increased sensitivity to cold. Notably, exogenous MeJA application significantly increased cold resistance in the knockout plant. In vitro and vivo analyses revealed that SlMYB13 directly binds to the promoter SlHSP17.7, a small heat shock protein gene involved in cold-stress response. SlMYB13 regulated the expression of SlMYC2, a key regulator of the jasmonic acid signalling pathway at transcription and protein levels, and SlMYC2 also directly binds to the promoter of SlHSP17.7. Collectively, these findings demonstrate that SlMYB13 promotes cold tolerance through SlMYC2-mediated jasmonic acid signalling targeting SlHSP17.7. This study provides valuable insights for the genetic improvement of cold-tolerant tomato cultivars.