JA-CmMYC2 and SA-CmWRKY40 signaling networks relieve the inhibition of CmTLP15/22 on the cold tolerance of melon seedlings.

Cold stress is a major environmental factor that restricts plant growth and development. Previous studies report that thaumatin-like proteins (TLPs) contribute to plant cold responses, but the underlying molecular mechanism remains unclear. Using melon, a warm-adapted vegetable crop, we performed transcriptome analysis and identified CmTLP15/22 as key cold-responsive genes. Silencing CmTLP15/22 increased CmCBF1/2/4 expression and antioxidant capacity and improved cold tolerance in melon seedlings. Protein-DNA interaction assays identified CmMYC2 and CmWRKY40 as transcription factors that bind the CmTLP15/22 promoter and repress its expression. CmMYC2 can also bind the CmWRKY40 promoter and activate its expression. Cold stress and jasmonic acid (JA)/salicylic acid (SA) treatments increased CmMYC2 and CmWRKY40 expression, whereas JA and SA inhibited CmTLP15/22 expression. Silencing CmMYC2 or CmWRKY40 reduced CmCBF1/2/4 expression and weakened antioxidant activity, which decreased melon cold tolerance. In summary, this study reveals that JA-CmMYC2 and SA-CmWRKY40 signaling pathways act together to repress CmTLP15/22, thereby enhancing melon cold tolerance.