SmMYC2 positively regulates the resistance to Botrytis cinerea in Salvia miltiorrhiza.

This study unravels the function of SmMYC2 regulating resistance to B. cinerea in S. miltiorrhiza. Salvia miltiorrhiza is a traditional medicinal herb and commonly used to treat cardiovascular and cerebrovascular diseases. Gray mold caused by Botrytis cinerea poses a significant threat to production of many medicinal plants. The key transcription factor SmMYC2 has been found to contribute to promoting the biosynthesis of tanshinones or phenolic acids, and also mediated salt resistance in S. miltiorrhiza. However, limited information underlying its role of resistance to B. cinerea is available. In this study, simultaneous improvement of tanshinone and phenolic acid biosynthesis was observed in transgenic S. miltiorrhiza plants overexpressing SmMYC2 (OE-SmMYC2). Besides, expression pattern analysis revealed that SmMYC2 transcript increased significantly after B. cinerea infection. OE-SmMYC2 plants significantly improved their resistance to B. cinerea, and enhanced the expression level of the defense marker genes, such as SmPR1, SmPR10, SmSam a1, and SmPR-STH2. Besides, three antioxidant enzymes including catalase, peroxidase and superoxide dismutase were increased in OE-SmMYC2 lines, and SmMYC2 reduced the H2O2 accumulation. Overall, our results revealed that SmMYC2 played positive regulatory roles in resistance to B. cinerea in S. miltiorrhiza.