title: Coupling of Flagellar Gene Expression with Assembly in Salmonella enterica.
abstract: There are more than 70 genes in the flagellar and chemosensory regulon of Salmonella enterica. These genes are organized into a transcriptional hierarchy of three promoter classes. At the top of the transcriptional hierarchy is the flhDC operon, also called the flagellar master operon, which is transcribed from the flagellar class 1 promoter region. The protein products of the flhDC operon form a hetero-multimeric complex, FlhD4C2, which directs σ70RNA polymerase to transcribe from class 2 flagellar promoters. Products of flagellar class 2 transcription are required for the structure and assembly of the hook-basal body (HBB) complex. One of the class 2 flagellar genes, fliA, encodes an alternative sigma transcription factor, σ28, which directs transcription from flagellar class 3 promoters. The class 3 promoters direct transcription of gene products needed after HBB completion including the motor force generators, the filament, and the chemosensory genes. Flagellar gene transcription is coupled to assembly at the level of hook-basal body completion. Two key proteins, σ28and FliT, play assembly roles prior to HBB completion and upon HBB completion act as positive and negative regulators, respectively. HBB completion signals a secretion-specificity switch in the flagellar type III secretion system, which results in the secretion of σ28and FliT antigonists allowing these proteins to perform their roles in transcriptional regulation of flagellar genes. Genetic methods have provided the principle driving forces in our understanding of how flagellar gene expression is controlled and coupled to the assembly process.
authors.affiliation: Department of Biology, University of Utah, 257 1400 E. #201, Salt Lake City, UT, 84112, USA.
authors.forename: Fabienne F V
authors.initials: FF
authors.lastname: Chevance
authors.affiliation: Department of Biology, University of Utah, 257 1400 E. #201, Salt Lake City, UT, 84112, USA. Kelly.hughes@utah.edu.
authors.forename: Kelly T
authors.initials: KT
authors.lastname: Hughes
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics*; D012321:DNA-Directed RNA Polymerases / Q000235:genetics; D005407:Flagella / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics*; D005798:Genes, Bacterial / Q000235:genetics; D009876:Operon / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D019779:Salmonella enterica / Q000235:genetics*; D012808:Sigma Factor / Q000235:genetics; D014158:Transcription, Genetic / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D012808:Sigma Factor; D012321:DNA-Directed RNA Polymerases
keywords: Flagellar gene expression; Gene regulation; Genetic manipulations; Real-time PCR; Transposable elements; β-Galactosidase assays; λ-Red