Requires the Type II Secretion System for Pathogenicity and Survival in Grapevine.

is a xylem-limited bacterial pathogen that causes Pierce's disease (PD) of grapevine. In host plants, this bacterium exclusively colonizes the xylem, which is primarily non-living at maturity. Understanding how interfaces with this specialized conductive tissue is at the forefront of investigation for this pathosystem. Unlike many bacterial plant pathogens, lacks a type III secretion system and cognate effectors that aid in host colonization. Instead, utilizes plant cell-wall hydrolytic enzymes and lipases as part of its xylem colonization strategy. Several of these virulence factors are predicted to be secreted via the type II secretion system (T2SS), the main terminal branch of the Sec-dependent general secretory pathway. In this study, we constructed null mutants in and , which encode for the ATPase that drives the T2SS and the major structural pseudopilin of the T2SS, respectively. Both mutants were non-pathogenic and unable to effectively colonize grapevines, demonstrating that the T2SS is required for infection processes. Furthermore, we utilized mass spectrometry to identify type II-dependent proteins in the secretome. In vitro, we identified six type II-dependent proteins in the secretome that included three lipases, a β-1,4-cellobiohydrolase, a protease, and a conserved hypothetical protein. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.