Study of the Xanthomonas citri subsp. citri type three protein secretion system in citrus canker

CECILIA VRANYCH; AINELÉN PIAZZA; GERMÁN SGRO; JORGELINA OTTADO; NATALIA GOTTIG

Córdoba

Congreso; XI Congreso Argentino de Microbiología General; 2015

Citrus canker, caused by Xanthomonas citri subsp. citri (Xcc), is one of the most severe diseases affecting citrus production worldwide. Plant-pathogenic bacteria colonize their hosts through the secretion of virulence effector proteins which depends on the type III protein secretion system (TTSS), present in many other pathogenic bacteria. This system (named Hrp pilus) mediates the translocation of effector proteins across the bacterial membrane through the plant cell wall and the plasma membranes, and elicits the hypersensitive response (HR). Xcc mutants in TTSS are unable to colonize vegetable tissues. HrpE protein is a principal component of the Xcc Hrp pilus. Although the role and mechanisms of HrpE in the assembling, secretion and translocation of proteins in Xcc is well described, little is known about other functions of HrpE in plant-pathogen interactions. At the moment, there is no evidence about possible plant proteins that may interact with HrpE. In order to identify citrus proteins that could interact with HrpE, we performed yeast two hibrid assays. We detected interactors belonging to the following categories: enzymes participating in phytohormone production, membrane proteins and proteins involved in stress, degradation mechanisms, redox reaction, cell rearrangement and apoptosis. In order to analyze the physiological importance of these protein-protein interactions that we found in vitro, Arabidopsis thaliana mutant plants in the different genes that encode the identified proteins were used to evaluate the response to HrpE proteins. These results could help us determine if these identified proteins are involved in the recognition of bacterial HrpE protein. This approach would allow us to select plant proteins and then evaluate them in Citrus. To conclude, this study is useful to enable the characterization of new plant proteins involved in citrus canker and will contribute to the understanding of infection processes and plant-pathogen interactions.