The host exocyst complex is targeted by a conserved bacterial type III effector protein that promotes virulence

Abstract

For most Gram-negative bacteria, pathogenicity largely depends on the type-III secretion system that delivers virulence effectors into eukaryotic cells. The subcellular targets for the majority of these effectors remain unknown. Here, we show that Xanthomonas campestris, the causal agent of black rot disease, delivers the highly conserved effector XopP that interacts with hosts EXO70 protein. EXO70 is an essential component of the exocyst complex with a role in plant immunity. The XopP/EXO70 interaction is specific and inhibits exocyst-dependent exocytosis without activating a specific plant NLR receptor that guards EXO70. In this way, Xanthomonas efficiently inhibits the hosts PAMP-triggered immunity (PTI) by blocking exocytosis of PR1, callose deposition and the FLS2 immunity-receptor translocation to the plasma membrane, promoting successful infection.