title: PecS is an important player in the regulatory network governing the coordinated expression of virulence genes during the interaction between Dickeya dadantii 3937 and plants.
abstract: Successful infection of a pathogen relies on the coordinated expression of numerous virulence factor-encoding genes. In plant-bacteria interactions, this control is very often achieved through the integration of several regulatory circuits controlling cell-cell communication or sensing environmental conditions. Dickeya dadantii (formerly Erwinia chrysanthemi), the causal agent of soft rot on many crops and ornamentals, provokes maceration of infected plants mainly by producing and secreting a battery of plant cell wall-degrading enzymes. However, several other virulence factors have also been characterized. During Arabidopsis infection, most D. dadantii virulence gene transcripts accumulated in a coordinated manner during infection. This activation requires a functional GacA-GacS two-component regulatory system but the Gac system is not involved in the growth phase dependence of virulence gene expression. Here we show that, contrary to Pectobacterium, the AHL-mediated ExpIR quorum-sensing system does not play a major role in the growth phase-dependent control of D. dadantii virulence genes. On the other hand, the global regulator PecS participates in this coordinated expression since, in a pecS mutant, an early activation of virulence genes is observed both in vitro and in planta. This correlated with the known hypervirulence phenotype of the pecS mutant. Analysis of the relationship between the regulatory circuits governed by the PecS and GacA global regulators indicates that these two regulators act independently. PecS prevents a premature expression of virulence genes in the first stages of colonization whereas GacA, presumably in conjunction with other regulators, is required for the activation of virulence genes at the onset of symptom occurrence.
authors: INRA, UMR217, Interactions Plantes-Pathogènes, F-75005 Paris, France.
authors: Nadia
authors: N
authors: Mhedbi-Hajri
authors: Pierrette
authors: P
authors: Malfatti
authors: Jacques
authors: J
authors: Pédron
authors: Stéphane
authors: S
authors: Gaubert
authors: Sylvie
authors: S
authors: Reverchon
authors: Frédérique
authors: F
authors: Van Gijsegem
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D016974:Dickeya chrysanthemi / Q000235:genetics* / Q000472:pathogenicity; D053263:Gene Regulatory Networks; D005798:Genes, Bacterial; D005809:Genes, Regulator; D009154:Mutation; D010944:Plants / Q000382:microbiology*; D053038:Quorum Sensing; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D014774:Virulence; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; C091100:GacA protein, Bacteria; D012097:Repressor Proteins; D037521:Virulence Factors; C088080:pecS protein, Erwinia chrysanthemi