Contribution of cell surface carbohydrates to the Xylella fastidiosa-grapevine interaction
J. RAPICAVOLI (1), B. Blanco-Ulate (2), R. Figueroa-Balderas (2), A. Morales-Cruz (2), D. Cantu (2), M. Roper (1) (1) University of California, U.S.A.; (2) University of California, U.S.A.

Plants detect invading organisms through recognition of conserved pathogen-associated molecular patterns (PAMP). Recognition leads to activation of PAMP-triggered immunity (PTI). Successful plant pathogens must subvert or overcome PTI to establish and cause disease. Suppression of PTI by secreted effector proteins is a well-known strategy employed by bacterial plant pathogens. However, some bacterial pathogens can evade host recognition by actively altering the composition and/or structure of carbohydrates on the cell surface. Xylella fastidiosa is a xylem-limited bacterium that causes destructive diseases in economically important crops, notably Pierce’s disease of grapevine. X. fastidiosa lacks the quintessential Type III secretion system and its suite of effectors that could dampen PTI responses. Thus, the mechanisms utilized by this pathogen to combat PTI have remained obscure. We demonstrate that X. fastidiosa utilizes cell surface carbohydrates to shield PAMPs from the grapevine innate immune system, thus altering recognition and subsequent deployment of defense responses. Interestingly, mutation of the prominent O antigen surface carbohydrate resulted in swift recognition of X. fastidiosa by the grapevine host. We identified distinct transcriptional and phenotypic responses activated by O antigen mutant strains during the early stages of infection in grapevine. These results provide novel insight into the molecular mechanisms underlying this host-pathogen interaction.

Abstract Number: P7-202
Session Type: Poster