New genes from Xanthomonas citri subsp. citri involved in bacterial epiphytic survival

MARÍA VICTORIA BARCAROLO; JORGELINA OTTADO; BETIANA S. GARAVAGLIA; NATALIA GOTTIG

Córdoba

Congreso; LII Reunión anual de la Sociedad Argentina de Investigación Bioquímica y biología molecular; 2016

Xanthomonas citri subsp. citri (Xcc) is the causal agent of citrus canker. In this work we analyzed genes from Xcc with unknown function present in several plant pathogens, such as XAC0100 and XAC4007. Expression of these genes in bacteria grown in XVM2, a minimal medium that simulates conditions of the intercellular apoplast of leaves, was analyzed by RT-qPCR and the expression of both genes showed an induction compared to bacteria grown in rich medium. Moreover, RNA was obtained from Xcc recovered from citrus leaves at 0, 3 and 6 days post infection (dpi) and after RT-qPCR, results revealed that both genes were induced at 6 dpi. These results suggest that these genes have a role in plant-pathogen interaction. To characterize the function of XAC0100 and XAC4007 during disease development, we constructed non-polar Xcc mutants in these genes generated by double cross-over events. The resulting ΔXAC0100 and ΔXAC4007 mutant strains were tested for their ability to trigger disease in citrus leaves and hypersensitive response in non-host pepper leaves. No differences were observed in host and non-host interactions. However, ΔXAC0100 and ΔXAC4007 mutants displayed impaired epiphytic survival on citrus leaves, indicating that these genes were required to maintain bacteria on the host plant tissue.