VOJNOV Adrian Alberto
congresos y reuniones científicas
Stomata modulation by Xanthomonas campestris pv. campestris
Quebec, Canada
Congreso; Molecular Plant Microbe Interaction; 2009
Institución organizadora:
International Society MPMI
Xanthomonas campestris pv. campestris (Xcc) is a bacterial intravascular phytopathogen that is the causal agent of the black rot of crucifers. As with many phytopathogenic bacteria, Xcc produces a range of factors that contribute to the ability of the bacterium to parasitise the host. Among these are extracellular enzymes capable of degrading plant cell components and an extracellular polysaccharide (EPS) called xanthan. These factors may play a number of roles during disease. In Xcc the production of extracellular enzymes and EPS is subject to co-ordinate positive regulation by a cluster of genes, the rpf cluster (for regulation of pathogenicity factors). Mutations in rpf genes lead to a reduced virulence in host plants. Several of the rpf genes, mediate regulation via a small diffusible molecule named DSF (for diffusible signal factor). In this work we attempted to clarify the mechanism of endophytic colonization through stomata of the phytopathogenic bacterium Xcc. We found that movement through stomata of Xcc is dependent on a secreted factor which can prevent both ABA and bacterial induced stomatal closure and whose synthesis is regulated by the rpf/DSF system. To evaluate the physiological relevance for infection of the stomata modulating activity of Xcc, we performed both in vitro and in vivo assays. Unlike wt Xcc, rpfF and rpfC mutants are reduced in migration through plant epidermis, as expected from their compromised ability to modulate stomatal apertures. This result provides evidence that the secreted factor aids movement of bacteria through stomata.In addition, we found that stomatal innate immunity in Arabidopsis requires MPK3, and that the presence of this kinase is also required for the inhibition of ABA induced stomatal closure by Xcc.