DEGs affected by erucamide and predicted interaction between erucamide and indicated HrcC

Numerous Gram-negative bacterial pathogens employ the type III secretion system (T3SS), a multi-protein injectisome, to deliver virulence proteins into host cells and cause diseases. We uncover erucamide as a previously unknown phytoalexin of both dicots and monocots that block the T3SS function of multiple bacterial pathogens. Genetically impairing erucamide accumulation or exogenous application in Arabidopsis highlighted erucamide’s role in anti-bacterial immunity. Erucamide binds HrcC, a key T3SS component, to block injectisome assembly. Analyses of erucamide analogues and HrcC mutants indicated that the erucamide-HrcC binding is required for inhibiting T3SS in vitro and anti-bacterial resistance in plants, suggesting an essential role of erucamide-HrcC binding in disease resistance. This work reveals a plant chemical defense that targets major virulence machinery in bacterial pathogens.