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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.