XANTHOMONAS CAMPESTRIS SUPPRESSES STOMATAL DEFENSE

GUDESBLAT GE; TORRES PABLO; VOJNOV ADRIAN

Villa Carlos Paz

Congreso; Sociedad Argentina de Microbiología General; 2008

Pathogen-induced stomatal closure is part of the plant innate immune response. In order to penetrate leaves through stomata, pathogens must avoid the stomatal response of the host. In this work we describe a factor secreted by the bacterial phytopathogen Xanthomonas campestris pv campestris (Xcc) that is capable of interfering with stomatal closure induced by bacteria or by abscisic acid (ABA). We found that living Xcc, as well as ethyl acetate extracts from Xcc culture supernatants, are capable of reverting stomatal closure induced by bacteria, lypopolisaccharide (lps) or ABA. Xcc ethyl acetate extracts also complemented the infectivity of Pseudomonas syringae pv tomato (Pst) mutants deficient in the production of the coronatine (cor) toxin, which is required to overcome stomatal defense. By contrast, the rpfF and rpfC mutant strains of Xcc, that are unable to respectively synthesize or perceive a diffusible molecule involved in bacterial cell to cell signaling, were incapable of reverting stomatal closure, indicating that suppression of stomatal response by Xcc requires an intact rpf/DSF system. In addition, we found that guard cell-specific MAP kinase 3 (MPK3) Arabidopsis antisense mutants were unresponsive to bacteria or lps in promotion of stomatal closure, and also more sensitive to Pst cor deficient mutants, showing that MPK3 is required for stomatal immune response.