H-NS-dependent activation of pectate lyases synthesis in the phytopathogenic bacterium Erwinia chrysanthemi is mediated by the PecT repressor.
Production of the main virulence determinant pectate lyases (Pels) of the phytopathogenic bacterium Erwinia chrysanthemi is modulated by a complex regulatory network involving the repressor proteins KdgR, PecS and PecT and the activator systems Pir, ExpI-ExpR and CRP. Of these regulators, CRP and PecT are particularly important since the absence of CRP or a slight overproduction of PecT leads to a drastic reduction in synthesis of Pel species. Recently, it has been shown that production of Pel species is strongly reduced in an E. chrysanthemi hns mutant, suggesting an activator function of the nucleoid-associated protein H-NS in the expression of the pel genes. Here, we report that the reduced synthesis of Pel species in the hns mutant results from a negative control, exerted by H-NS, on the transcription of the regulatory gene pecT. This H-NS/PecT cascade regulation is one of the first elucidations of a positive effect of H-NS on target gene expression. Moreover, we found that H-NS also represses the expression of expI, expR and pel genes. H-NS control is the result of H-NS binding to extended regions within the pecT, expI, expR and pel genes. Investigation of the simultaneous binding of CRP, RNA polymerase (RNAP) and H-NS on the pelD gene revealed that these three proteins form a nucleoprotein com-plex. Together, these data indicate that, by exerting a negative control at multiple levels, H-NS plays a crucial role in the E. chrysanthemi pel regulatory network.
Nasser
William
W
Unité de Microbiologie et Génétique, UMR-CNRS 5122, INSA, Batiment Louis Pasteur, 11 Avenue Jean Capelle, F-69621 Villeurbanne Cedex, France. nasser@insa.insa-lyon.fr
Reverchon
Sylvie
S
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins; D002373:Cyclic AMP Receptor Protein / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D016974:Dickeya chrysanthemi / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity*; D015964:Gene Expression Regulation, Bacterial; D009698:Nucleoproteins / Q000235:genetics / Q000378:metabolism; D011133:Polysaccharide-Lyases / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors; D014774:Virulence / Q000235:genetics
D001426:Bacterial Proteins; D002352:Carrier Proteins; D002373:Cyclic AMP Receptor Protein; D004268:DNA-Binding Proteins; C115748:ExpR protein, Erwinia; C031908:H-NS protein, bacteria; D009698:Nucleoproteins; C098627:PecT protein, Erwinia chrysanthemi; D012097:Repressor Proteins; D015534:Trans-Activators; D014157:Transcription Factors; C081685:expI protein, Erwinia; D012321:DNA-Directed RNA Polymerases; C097529:PelE protein, Erwinia chrysanthemi; D011133:Polysaccharide-Lyases; C023911:pectate lyase