title: Role of the LysR-type transcriptional regulator PecT and DNA supercoiling in the thermoregulation of pel genes, the major virulence factors in Dickeya dadantii.
abstract: Bacteria are colonizers of various environments and host organisms, and they are often subjected to drastic temperature variations. Dickeya dadantii is a pathogen infecting a wide range of plant species. Soft rot, the visible symptom, is mainly due to the production of pectate lyases (Pels) that destroy plant cell walls. The production of Pels is controlled by a complex regulation system that responds to various stimuli, such as the presence of pectin, growth phase and temperature. Despite numerous regulatory studies, the thermoregulation mechanism of Pel production remains unexplained. Here, we show that PecT, a previously identified repressor, modulates pel gene expression in a temperature-dependent manner, and we demonstrate that PecT binding on pel promoters increases concomitantly with temperature. High temperatures relax the DNA in D. dadantii, and remarkably, artificial relaxation of DNA at low temperatures increases PecT binding to DNA. Deletion of pecT augmented the capacity of D. dadantii to initiate soft-rot symptoms at high temperatures. These results reveal that DNA topology and PecT act in concert to fine-tune D. dadantii virulence in response to temperature. This novel combination between DNA topology and a conventional transcriptional regulator extends our understanding of the thermoregulation mechanisms involved in bacterial virulence.
authors.affiliation: Université Lyon 1, F-69622, Villeurbanne, France; INSA de Lyon, F-69621, Villeurbanne, France; CNRS UMR5240 Microbiologie, Adaptation et Pathogénie, F69622, Villeurbanne, France.
authors.forename: Elodie
authors.initials: E
authors.lastname: Hérault
authors.forename: Sylvie
authors.initials: S
authors.lastname: Reverchon
authors.forename: William
authors.initials: W
authors.lastname: Nasser
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D004269:DNA, Bacterial / Q000737:chemistry; D004278:DNA, Superhelical / Q000378:metabolism*; D004755:Enterobacteriaceae / Q000201:enzymology / Q000235:genetics* / Q000472:pathogenicity*; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D011133:Polysaccharide-Lyases / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D013696:Temperature; D037521:Virulence Factors / Q000235:genetics* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004278:DNA, Superhelical; D012097:Repressor Proteins; D037521:Virulence Factors; D011133:Polysaccharide-Lyases; C023911:pectate lyase