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The plant pathogen Pseudomonas fuscovaginae contains two conserved quorum sensing systems involved in virulence and negatively regulated by RsaL and the novel regulator RsaM

Mattiuzzo, Maura, Bertani, Iris, Ferluga, Sara, Cabrio, Laura, Bigirimana, Joseph, Guarnaccia, Corrado, Pongor, Sandor, Maraite, Henri, Venturi, Vittorio
Environmental microbiology 2011 v.13 no.1 pp. 145-162
Burkholderia vietnamiensis, Pseudomonas aeruginosa, Pseudomonas fuscovaginae, genes, plant pathogens, proteins, quorum sensing, virulence
Pseudomonas fuscovaginae is a Gram-negative fluorescent pseudomonad pathogenic towards several plant species. Despite its importance as a plant pathogen, no molecular studies of virulence have thus far been reported. In this study we show that P. fuscovaginae possesses two conserved N-acyl homoserine lactone (AHL) quorum sensing (QS) systems which we designated PfsI/R and PfvI/R. The PfsI/R system is homologous to the BviI/R system of Burkholderia vietnamiensis and produces and responds to C10-HSL and C12-HSL whereas PfvI/R is homologous to the LasI/R system of Pseudomonas aeruginosa and produces several long-chain 3-oxo-HSLs and responds to 3-oxo-C10-HSL and 3-oxo-C12-HSL and at high AHL concentrations can also respond to structurally different long-chain AHLs. Both systems were found to be negatively regulated by a repressor protein which was encoded by a gene located intergenically between the AHL synthase and LuxR-family response regulator. The pfsI/R system was regulated by a novel repressor designated RsaM while the pfvI/R system was regulated by both the RsaL repressor and by RsaM. The two systems are not transcriptionally hierarchically organized but share a common AHL response and both are required for plant virulence. Pseudomonas fuscovaginae has therefore a unique complex regulatory network composed of at least two different repressors which directly regulate the AHL QS systems and pathogenicity.