title: Transcriptional regulation of sdiA by cAMP-receptor protein, LeuO, and environmental signals in  Salmonella enterica  serovar Typhimurium.
abstract: The sdiA gene encodes for a LuxR-type transcription factor, which is active when bound to N-acyl homoserine lactones (AHLs). Because  Salmonella enterica  serovar Typhimurium does not produce AHLs, SdiA senses signals produced by other organisms. SdiA is not expressed constitutively, and response is limited to conditions in which elevated expression occurs, but little is known about the regulation of sdiA expression. Here we map the sdiA promoter and define several regulators that directly or indirectly act on the promoter. The major activator of sdiA expression is cAMP-receptor protein (CRP), and we define the CRP operator in the sdiA promoter using promoter and crp mutants. LeuO activates sdiA expression to a lesser extent than does CRP. We demonstrate that LeuO directly binds the sdiA promoter and the Rcs phosphorelay represses sdiA expression. In this study, NhaR, IlvY, and Fur affected sdiA expression indirectly and weakly. Expression in late-stationary phase depended on RpoS. AHL-dependent expression of the SdiA-regulated gene rck correlated to the observed sdiA transcriptional changes in regulator mutants. The data demonstrate that regulation of sdiA involves integration of multiple environmental and metabolic signals.
authors.affiliation: Department of Microbiology and Infectious Diseases, University of Calgary, Calgary, AB, Canada.
authors.forename: Amy L
authors.initials: AL
authors.lastname: Turnbull
authors.forename: Wook
authors.initials: W
authors.lastname: Kim
authors.forename: Michael G
authors.initials: MG
authors.lastname: Surette
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D002373:Cyclic AMP Receptor Protein / Q000235:genetics / Q000378:metabolism*; D004777:Environment; D015964:Gene Expression Regulation, Bacterial; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012486:Salmonella typhimurium / Q000235:genetics* / Q000378:metabolism*; D015534:Trans-Activators / Q000235:genetics* / Q000378:metabolism; D024363:Transcription Initiation Site
chemical_list: D001426:Bacterial Proteins; D002373:Cyclic AMP Receptor Protein; D011993:Recombinant Fusion Proteins; C097686:SdiA protein, bacteria; D015534:Trans-Activators