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 factorencoding 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 walldegrading 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 GacAGacS 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.

Essential Genes forIn VitroGrowth of the Endophyte Herbaspirillum seropedicae SmR1 as Revealed by Transposon Insertion Site Sequencing

“…Hsero_1027 is homologous to the global regulator gene pecS from the phytopathogen Dickeya dadantii 33937, which is reported to repress the premature expression of virulence genes during the first stage of plant infection, when D. dadantii has to colonize the plant apoplast without provoking symptoms (42). A D.…”

PelN Is a New Pectate Lyase of Dickeya dadantii with Unusual Characteristics

“…The absence of a potential KdgR binding site in the promoter region of pelN suggests that it is controlled by an indirect mechanism. PecS is a negative regulator controlling a large set of genes involved in the symptomatic phase of infection (37,39). GacA is a positive regulator involved in the control of virulence genes during plant infection (40,41).…”

The Role of Secretion Systems and Small Molecules in Soft-Rot Enterobacteriaceae Pathogenicity

“…In Pectobacterium, the T1SS is upregulated by plant extracts and acylhomoserine lactone (AHL), and controlled by GacAS (97,98). In Dickeya, this system is controlled by PecS (59,104) cand GacAS (85). Metalloproteases may play two roles in virulence; they may attack plant cell wall proteins or may degrade enzymes secreted by the pathogen to affect their activity.…”