The SlJAZ2/SlJAZ3 Dimer Acts as a Switch of the SlMYC2-SlPR2 Module to Regulate the Cf-19-Mediated Resistance of Tomatoes to Cladosporium fulvum.

Tomato leaf mold caused by Cladosporium fulvum (C. fulvum) is a devastating disease in tomato cultivation and production. The Cf gene confers resistance to C. fulvum. In our previous study, several JAZ family genes were found to be differentially expressed between resistant (Cf-19-mediated) and susceptible materials, especially SlJAZ3, whose expression was significantly upregulated during the Cf-19-mediated resistance response process. To explore the regulatory function of JAZ genes in this disease resistance system, this study focused on SlJAZ3 and found that both SlJAZ3 and its interacting protein SlJAZ2 can positively regulate the resistance response mediated by Cf-19. In addition, SlMYC2, as a positive regulator of the resistance response, can interact with SlJAZ2 (or SlJAZ3) and activate the expression of SlPR2. Notably, SlJAZ3 (or SlJAZ2) competitively binds to SlJAZ2 (or SlJAZ3), reducing its binding to SlMYC2, which helps to restore the transcriptional activation of the downstream defense gene SlPR2. Our findings reveal that the SlJAZ2/SlJAZ3 dimer regulates downstream signal transduction. This study has improved our understanding of Cf-mediated resistance and plant immune mechanisms, laying the foundation for the molecular improvement of tomato disease resistance and endows new significance to the formation of the JAZ-JAZ dimer.