BolCYP79A2 Coordinates SA and JA Signaling Pathways Through BolMYB61/44 to Confer Black Rot Resistance via Modulation of Glucosinolate Biosynthesis in Broccoli

Glucosinolates (GSLs) are important secondary metabolites (SMs) mainly generating in cruciferous plants to response biotic and abiotic stresses. However, the roles and underlying regulatory mechanisms of GSLs in resistance to pathogen-induced disease remains largely unclear. Here, we report BolCYP79A2, a cytochrome P450 gene involved in aromatic GSL biosynthesis, confers strong resistance to Xanthomonas campestris pv. campestris (Xcc)-induced black rot in broccoli. BolCYP79A2 is directionally regulated by two R2R3-MYB transcription factors BolMYB61 and BolMYB44. BolTGA1, a key transcriptional regulator in the salicylic acid (SA) signaling pathway, represses BolMYB61 expression, thereby relieving the BolMYB61-mediated suppression of BolCYP79A2, while BolMYC2, a critical component of the jasmonic acid (JA) signaling pathway, activates BolMYB44 and enhances its positive regulatory effect on BolCYP79A2. Under Xcc infection, BolTGA1 and BolMYC2 were induced along with increased SA and JA accumulation. Furthermore, BolCYP79A2 was confirmed to substantially increase the biosynthesis of gluconasturtiin (GNS), a representative aromatic GSLs. The hydrolysis product of GNS can function as one high bioactive effector to directly kill Xcc pathogen mainly by disrupting the integrity of cell membranes. Summarily, these results elucidate that (BolTGA1-BolMYB61)/(BolMYC2-BolMYB44)-BolCYP79A2 module should coordinate SA and JA signaling pathways to confer resistance to Xcc infection by positively regulating GNS biosynthesis. These findings uncover a novel GSL metabolite-mediated biotic stress resistance pathway, and suggest a potential disease-resistant breeding strategy by precisely regulating SM in crops.