Functional analyses of candidate effector genes from Hemileia vastatrix based on the type three secretion system of Pseudomonas syringae pv. garcae
T. MAIA (1), G. Marin-Ramirez (1), S. Brommonschenkel (1) (1) Universidade Federal de Viçosa/Departamento de Fitopatologia, Brazil

A number of coffee genes that confer resistance to leaf rust (SH1 to SH9) have been genetically identified, but despite many years of research on this pathossystem, the complementary Avr genes of Hemileia vastatrix have not yet been identified or characterized. To overcome the difficulties of functional studies with this biotrophic pathogen, we have established a functional assay of candidate effectors of H. vastatrix by delivering them via type three secretion system (T3SS) of Pseudomonas syringae pv. garcae (Psgc) into coffee plant cells. We identified H. vastatrix genes encoding secreted proteins and named those without similarity to proteins from other organisms as HvECs (for H. vastatrix Effector Candidates). A calmodulin-dependent adenylate cyclase assay was used to demonstrate the T3SS Psgc-dependent translocation of effector candidate proteins encoded by genes cloned into pEDV vector. Significant levels of cAMP were detected confirming that the reporter protein was translocated effectively into plant cells by T3SS from Psgc. Using this delivery system we assayed HvECs in the cytoplasm of coffee plants carrying individual or combinations of SH genes. We found that HvEC-016 suppresses bacterial virulence towards coffee plants in an SH1 dependent manner. Suppression of disease symptoms in SH1 plants was associated with reduced bacterial multiplication. Our findings indicate that HvEC-016 is a candidate Avr protein recognized directly or indirectly by SH1 protein.

Abstract Number: P11-370
Session Type: Poster