Identification and characterization of genes involved in the type VI secretion system in Xanthomonas axonopodis pv. manihotis
N. MONTENEGRO (1), A. Alvarez (1), S. Restrepo (1), A. J. Bernal (1)
(1) Universidad de Los Andes, Bogotá, COLOMBIA
Phytopathology 100:S86

The type VI protein secretion system (T6SS) in gram-negative bacteria has been shown to participate in several cellular processes, including pathogenesis. During pathogenesis of Pseudomonas aeruginosa and Vibrio cholerae, this system secretes effector proteins that interact with target proteins in the host cell, thus contributing to the infection process. The system has been studied in animal pathogens and some substrates have been identified with roles in a diverse set of processes. However, there is a paucity of data for the importance of this system in plant pathogenic bacteria-host interactions. In this study, we have identified the presence of the T6SS in Xanthomonas axonopodis pv. manihotis (Xam), the causal agent of bacterial blight in cassava (Manihot esculenta). Bioinformatics analysis of nine structural genes (e.g. clpB, vgrG, ompA, hcp and fha) and six candidate genes, confirmed the existence of a full T6SS in Xam. We subsequently used site-directed mutagenesis of some of the structural genes involved in the T6SS. These mutants were inoculated in susceptible plants and the results suggest an importance of this secretion system in the pathogenicity of Xam. This study shows the importance of the novel T6SS in the virulence of Xanthomonas and it is considerably relevant for the understanding of plant- pathogen interactions.