Identification of the central quorum sensing regulator of virulence in the enteric phytopathogen, Erwinia carotovora: the VirR repressor

Abstract

SummaryIn the Gram-negative phytopathogen, Erwinia carotovora ssp. atroseptica ( Eca ) virulence depends on the production of a N-(3-oxohexanoyl)-L -homoserine lactone (OHHL) quorum sensing (QS) signal. This work identifies the elusive 'missing link' between QS and virulence in Erwinia. We have identified and characterized a novel regulator of virulence, VirR, in Eca and show that a virR mutation completely restores virulence factor production to an Eca mutant unable to synthesize OHHL. This effect of the virR mutation translates to a restoration of virulence to wild-type levels and thus provides evidence that VirR acts to prevent the production of virulence factors at low cell density. We also show that, in Eca , transcription of virulence genes is controlled by OHHL and that this control is effected through the action of VirR. We also demonstrate that the VirR regulatory pathway is present and functional in both blackleg and soft rotting species of Erwinia .

Mutations in rpsL that confer streptomycin resistance show pleiotropic effects on virulence and the production of a carbapenem antibiotic in Erwinia carotovora

“…The expR gene is located adjacent to carI in the genome; however, the function of ExpR is unclear since an expR mutant appears to have no obvious phenotype in this strain (Rivet, 1998). Exoenzymes are controlled via the LuxR homologue VirR (Burr et al, 2006), while Car production is activated by the third LuxR homologue, CarR (McGowan et al, 1995(McGowan et al, , 2005. In addition to these QS inputs, Car and exoenzyme production are coordinately regulated by the Hor global activator, which is a member of the SlyA family of transcriptional regulators (Thomson et al, 1997;McGowan et al, 2005).…”

A role for the Rcs phosphorelay in regulating expression of plant cell wall degrading enzymes in Pectobacterium carotovorum subsp. carotovorum

“…Survival of infecting Pcc largely depends on production of PCWDE for the transition from latent infection to disease state. A number of global and specific regulatory genes contribute to expression of PCWDE in Pcc (Burr et al, 2006;Chatterjee et al, 1995;Cui et al, 1995Cui et al, , 1999Cui et al, , 2001Cui et al, , 2005Eriksson et al, 1998;Flego et al, 2000;Harris et al, 1998;Hyytiäinen et al, 2003;Liu et al, 1998Liu et al, , 1999Sjöblom et al, 2006). The posttranscriptional Rsm system plays a key role in regulating the expression of PCWDE Cui et al, 1995;Liu et al, 1998).The Rsm system consists of two regulators in Pcc: a small protein, RsmA, and RsmB RNA.…”

Identification of Quorum Quenching Bacteria and Its Biocontrol Potential Against Soft Rot Disease Bacteria, Dickeya dadantii

“…The virulence factor of D. dadantii, Erwinia carotovora subsp. carotovora, Erwinia stewartii, and Pectobac terium atrosepticum is regulated through QS system with 3-oxo-C6HSL as signal recognized by ExpI/ExpR regulator protein (Nasser, Bouillant, Salmond, & Revechon, 1998;Bainton et al, 1992;Chhabra et al, 1993;von Bodman & Farrand, 1995;Burr et al, 2006). Whereas QS system of Ralstonia solanacearum is regulated by C8-HSL and Agrobacterium tumefaciens 3-oxo-C8-HSL (Flavier, Ganova-Raeva, Schell, & Denny, 1997;Piper, von Bodman, & Farrand, 1993).…”

“…enzymes and toxins. Some bacteria such as Ralstonia solanacearum, Pseudomonas aeruginosa, Pectobacterium antrosepticum and several Erwinia species activate their virulence factors expression by QS (Dong, Xu, Li, & Zhang, 2000;Conway & Greenberg, 2001;Burr et al, 2006).…”