Transport of effector proteins from bacterial pathogens into host cells is crucial for pathogen virulence. In gram-negative bacteria, transport occurs through the specialized type III secretion system. In the February issue, Xiaofeng Zhou and colleagues demonstrate that the protein VrpA—an essential virulence factor for Xanthomonas spp.—is required for efficient protein secretion via the type III secretion system and that it localizes to the bacterial periplasmic space. These findings expand the mechanical understanding of this important secretory process in Xanthomonas spp.