Molecular analysis of the role of the bacteriophytochrome protein in the virulence of the plant pathogen Xanthomonas campestris pv.campestris

FLORENCIA MALAMUD; HERNÁN BONOMI; LAILA TOUM; FERNANDO A GOLDBAUM; ADRIAN VOJNOV

Angers

Conferencia; 4th Xanthomonas genomics conference; 2012

Federation of European microbiologist societies

Light is an important source of energy information for a wide range of organisms. In plants and other photosynthetic organisms, photoreceptor proteins called phytochromes regulate functions related to growth and development. Surprisingly photoreceptors called bacteriophytochromes, homologues of the phytochromes, are also found in non-photosynthetic bacteria, including pathogens, although their role is poorly understood.Xanthomonas campestris pv. campestris (Xcc), the causal agent of black rot of crucifers is a phytopathogen of worldwide economic relevance. The Xcc genome encodes one putative bacteriophytochrome (phy). Recent results from our laboratory suggest that light modulates biofilm formation. Furthermore we have established that mutation of phy leads to altered level of xanthan polysaccharide, a virulence factor which is also directly involvedin biofilm formation. Moreover the absence of the Phy protein in Xcc results in an increase of the production of secreted proteins, such as amylases and peptidases. Our results also show that Xcc phy is more virulent than the wild-type strain. Part of the phy mutant strain virulence may be attributed to its capacity to keep the plant stomata open. We have also studied callose synthesis during the infection and we have observed that it issignificantly reduced in the phy strain compared to wild-type strain. Taken together, the results we are presenting in this work clearly indicate a direct link between virulence mechanisms and the Phy bacteriophytochrome in Xcc. It is likely that Phy senses light, probably Red and Far-Red ratio, modulating the Xcc infection cycle.