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Poster: Molecular & Cellular Plant-Microbe Interactions: MPMI


The bifunctional catalase/peroxidase KatG is required for pathogenicity of Xanthomonas albilineans on sugarcane
M. JAIN (1), L. Fleites (2), S. Zhang (2), D. Gabriel (2) (1) Department of Plant Pathology, University of Florida, U.S.A.; (2) Department of Plant Pathology, University of Florida, U.S.A.

Survival and multiplication of phytopathogenic bacteria, and disease progression are essentially contingent upon the pathogen's ability to detoxify reactive oxygen species (primarily H2O2) generated either endogenously through aerobic respiration or by the oxidative burst of plant cells during plant-pathogen interactions. Xanthomonas albilineans (Xal) is a gram-negative, xylem-invading pathogen that causes sugarcane leaf scald disease. Two putative catalase genes XALc_0265 (srpA) and XALc_2991 (katE), and a bifunctional catalase/peroxidase XALc_0959 (katG) have been annotated in silico in the genome of Xal FL07-1. Xal katG was replaced by an enhanced Green Florescent Protein marker gene (gfp) via splice overlap PCR.Challenge inoculations of decapitated sugarcane plants by Xal ÄkatG::gfp exhibited a significant reduction in pathogenic symptoms on the newly emerged leaf blades. In addition bacterial viability in planta was significantly reduced compared to the wild type Xal FL07-1. Full-length katG cloned in the broad host range vector pUFR047 complemented the ÄkatG::gfp mutant strain for both pathogenicity and endophytic survival of the bacterium. Given that Xal katG is predicted to have a non-classical secretion potential, its role is also being investigated in dampening the apoplastic, non-specific low amplitude systemic wave of H2O2 elicited by the host cell that is essential for establishment of innate plant immunity.