The SlSRC2-SlMLP1 module regulates broad-spectrum disease resistance by activating steroidal glycoalkaloid...

Global tomato production faces persistent threats from various pathogens, leading to substantial yield and quality losses. Cultivating tomato varieties with broad-spectrum disease resistance (BSR) is therefore a crucial objective for sustainable agriculture. Here, we identified a molecular module centered on the antagonistic regulation between SlSRC2 and SlMLP1, which coordinates BSR against multiple pathogens, including Botrytis cinerea, Phytophthora infestans, and tomato yellow leaf curl virus. SlSRC2 functions as a negative regulator by interacting with and suppressing the nuclear localization of the positive regulator SlMLP1. Both SlMLP1 and SlSRC2 converge on the transcription factor SlERF2a, where they antagonistically modulate its transcriptional activity to regulate the expression of SlGAME12, a key biosynthetic gene for steroidal glycoalkaloids (SGAs). Furthermore, we elucidated that the degradation factors SlPSMC6A and SlSGTA interact with SlMLP1 to mediate the degradation of the SlMLP1-SlERF2a complex and enhance BSR. This degradation relieves SlERF2a-mediated repression of SlGAME12, ultimately promoting SGAs accumulation and thereby boosting plant immunity. Collectively, our findings reveal a novel molecular mechanism by which the SlSRC2-SlMLP1 module regulates BSR in tomato through modulating SGAs biosynthesis, while also providing valuable genetic resources for the breeding of BSR tomato varieties.