Modulation of stomatal movements in A.thaliana through a Xanthomonas campestris pv.campestris virulence factor

LAILA TOUM; ADRIAN VOJNOV; GUSTAVO GUDESBLAT

Mar del Plata

Congreso; Reunión Argentina de Fisiología Vegetal; 2012

Sociedad Argentina de Fisiología Vegetal

Stomatal closure induced by microbes associated molecular patterns (PMAMs) is one of the mechanisms of the immediate immune response of plants against pathogens. Evolutionarily, pathogens have developed mechanisms through which they can evade this first line of defense. Our group previously described the existence of a compound secreted by Xanthomonas campestris pv. campestris (Xcc) that can interfere with stomatal closure induced by this bacterium in Arabidopsis thaliana (Plant Physiol. 2009: 1017-1027). This molecule also partially abolish abscisic acid (ABA) induced stomatal closure, and its action is dependent on the presence of MAP kinase 3 (MPK3). In order to elucidate its molecular structure, we performed the purification of the virulence factor from Xcc culture supernatants through a Biogel P2 molecular sieve allowing to determine that their molecular weight is less than 2000 D. The obtained fractions of Biogel P2 are being purified by HPLC to determine its structure. To shed light on the mechanism of action of this molecule we studied the different sensitivity of A. thaliana mutants to this virulence factor. Preliminary results show that in addition to the T-DNA mutant mpk3, neither jar 1-1 nor npr1-3 mutant, involved in the defense against pathogens, respond to it. Moreover, Xcc compound does not affect the H2O2-induced stomatal closure, a second messenger triggered by PMAMs and ABA, suggesting that the target of action of Xcc the virulence factor would be upstream of the generation of reactive oxygen species.