CHARACTERISATION OF A DSF-HYPER PRODUCING MUTANTS OF XANTHOMONAS AXONOPODIS PV. CITRI (XAC)

TORRES PABLO; FILIPPONE PAULA; SICILIANO FLORENCIA; MARANO MARÍA ROSA; SENDÍN LORENA; CASTAGNARO ATILIO; DANKERT M; VOJNOV ADRIAN

Iguazú Misiones

Congreso; XL Reunión Anual de la Sociedad Argentina de Investigaciones en Bioquímica y Biología Molecular (SAIB); 2004

SOCIEDAD ARGENTINA DE INVESTIGACIÓN BIOQUÍMICA Y BIOLOGÍA MOLECULAR

Xac causes bacterial chancrous a serious disease of citrus. In the related bacterium Xanthomonas campestris pv. campestris (Xcc), the rpfF gene is involved in production of a diffusible extracellular factor (DSF) that positively regulates synthesis of virulenceassociated functions like extracellular polysaccharide (EPS) and extracellular enzymes. In addition, in L medium, strains of Xcc carrying mutations in genes within the rpf cluster grew as matrixenclosed aggregates. DSF perception and signal transduction have been suggested to involve the two-component system comprising RpfC and RpfG. Mutation of rpfC, which encodes the sensor component, leads to over-production of DSF and reduced production in virulence factors. The addition of DSF can phenotypically restore rpfF but not rpfC mutants to wild type. We demonstrated here that a deletion and kanamicin resistance cassette insertion in the rpfC homolog of Xac, as in Xcc, leads to overproduction of DSF. rpfC Xac mutant has shown a decreased of cyclic ß-1,2 glucan and the extracellular enzyme endoglucanase productions. Supplementation of L medium with DSF (from the rpfC Xac mutant) before bacterial inoculation allowed for normal dispersed growth of rpfF Xcc mutant but not in rpfC of both Xac and Xcc. The results suggest that rpfC may be involved in controlling virulence factors of Xac mediated by DSF