SlMYC2 Mediates the JA Pathway by Responding to Chlorocholine Chloride in the Regulation of Resistance to TYLCD

Tomato yellow leaf curl disease (TYLCD) significantly affects tomato yield. The jasmonic acid (JA) pathway is crucial in the defence response of plants; however, its role in plant resistance to TYLCD remains undefined. In production, CCC (chlorocholine chloride) is often used to cultivate strong seedlings to enhance seedling vitality and improve stress resistance. However, the mechanism through which CCC enhances disease resistance in tomatoes remains unclear. In this study, tomato seedlings were exogenously sprayed with 300 mg/L CCC before and after inoculation with tomato yellow leaf curl virus (TYLCV). The results indicated that no significant tomato yellow virus disease phenotype was observed in tomato seedlings after spraying with CCC and subsequent inoculation with the virus. Spraying CCC on seedlings inoculated with the virus and exhibiting typical phenotypes can significantly alleviate the yellowing and curling symptoms of new leaves and improve photosynthesis-related indicators in tomato plants. The detection of virus copy numbers within the plants revealed that the virus copy numbers in plants treated with CCC were significantly lower than those in the control group. Transcriptomic analysis revealed that, after spraying CCC, the key enzyme genesAOS2andAOCin the JA synthesis pathway in tomatoes were significantly upregulated, whereas the expressions ofJAZ2andMYC2genes, which negatively regulate JA synthesis, were significantly downregulated. In the stable state, JAZ proteins interact withMYC2and inhibit its transcriptional activity ofMYC2. Tomatoes overexpressingMYC2andJAZ2exhibit a significant decrease in TYLCD resistance. These results indicated that exogenous spraying CCC affected the expression of genes such asMYC2andJAZ2, and then regulated JA pathway, increased the endogenous JA content in plants, and enhanced the disease resistance of tomato plants to TYLCD. This study provides a scientific reference for effectively preventing and controlling TYLCD in tomato production and reducing the influence of TYLCD on tomato yield and quality.