INVESTIGADORES
CONFORTE Valeria Paola
congresos y reuniones científicas
Título:
Roles of DSF-regulated virulence factors and biofilm formation in Xanthomonas pathogenicity
Autor/es:
FLORENCIA MALAMUD; VALERIA CONFORTE; LAILA TOUM; LUCIANO RIGANO; PABLO TORRES; PABLO YARYURA; ATILIO CASTAGNARO; MARÍA ROSA MARANO; GUSTAVO GUDESBLAT; ADRIÁN VOJNOV
Lugar:
Angers
Reunión:
Conferencia; 4th Xanthomonas Genomics Conference; 2012
Institución organizadora:
INRA
Resumen:
Xanthomonas campestris pv.
campestris and Xanthomonas citri subsp. citri are the causative agents of black
rot and citrus canker diseases, in cruciferous and citrus plants, respectively.
Cell-cell signalling systems encoded by genes within the rpf cluster are
required for the full virulence of both plant pathogens. Those systems have
been implicated in regulation of production of extracellular enzymes, cyclic
glucan and the exopolysaccharide xanthan and in the regulation of biofilm
formation. Cell-cell communication is mediated by the diffusible signal factor
(DSF), an unsaturated fatty acid. We have made progress in understanding the
roles of xanthan, cyclic glucan and biofilm development in the interaction of
X. Campestris and X. citri with plants and of the mechanistic basis of
regulation of these processes by DSF. New roles for xanthan and cyclic glucan
in disease through suppression of plant immune responses have been uncovered.
We have also revealed the capacity of X. campestris to modulate stomatal
aperture as other bacterial strategy of defence suppression by a DSF-regulated
factor with unknown structure. Xanthan induces susceptibility to X. campestris
in Arabidopsis thaliana and Nicotiana benthamiana by suppressing basal defences
such as callose deposition. Unlike xanthan, which acts only locally, the
effects of cyclic glucan on plant defense suppression and callose deposition
occur in a systemic fashion. Crystal violet staining and confocal laser
scanning microscopy analysis of the bacteria expressing the green fluorescent
protein were used to evaluate attachment and biofilm formation on abiotic and
biotic (leaf) surfaces. The extracellular polysaccharide xanthan (EPS) played a
key role in the biofilm maturation, survival on leaf surfaces and virulence. By
generation of two mutants: X. citri fliC (flagelin gene) and X. citri flgE
(hook gene), both involved in the flagellar structure, we demonstrated that
biofilm formation is a flagellar-dependent process in X. citri being important
in the formation of mushroom-shaped structures and water channels, and in the
dispersion of pioneer cells from the mature biofilm. The absence of flagellin
produced a slight reduction in X. citri pathogenicity and this reduction
was more severe when the complete flagellum structure was absent.