title: The role of SwrA, DegU and P(D3) in fla/che expression in B. subtilis.
abstract: In B. subtilis swarming and robust swimming motility require the positive trigger of SwrA on fla/che operon expression. Despite having an essential and specific activity, how SwrA executes this task has remained elusive thus far. We demonstrate here that SwrA acts at the main σ(A)-dependent fla/che promoter PA(fla/che) through DegU. Electrophoretic mobility shift assays (EMSA) reveal that SwrA forms a complex with the phosphorylated form of DegU (DegU~P) at PA(fla/che) while it is unable to do so with either unphosphorylated DegU or the DegU32(Hy) mutant protein. Motility assays show that a highly phosphorylated DegU is not detrimental for flagellar motility provided that SwrA is present; however, DegU~P represses PA(fla/che) in the absence of SwrA. Overall, our data support a model in which DegU~P is a dual regulator, acting either as a repressor when alone or as a positive regulator of PA(fla/che) when combined with SwrA. Finally, we demonstrate that the σ(D)-dependent PD3(fla/che) promoter plays an important role in motility, representing a contingent feedback loop necessary to maintain basal motility when swrA is switched to the non-functional swrA(-) status.
authors.affiliation: Department of Biology and Biotechnology, Università degli Studi di, Pavia, Pavia, Italy.
authors.forename: Serena
authors.initials: S
authors.lastname: Mordini
authors.affiliation: Department of Biology and Biotechnology, Università degli Studi di, Pavia, Pavia, Italy.
authors.forename: Cecilia
authors.initials: C
authors.lastname: Osera
authors.affiliation: Department of Electrical, Computer and Biomedical Engineering, Università degli Studi di, Pavia, Pavia, Italy.
authors.forename: Simone
authors.initials: S
authors.lastname: Marini
authors.affiliation: Department of Biology and Biotechnology, Università degli Studi di, Pavia, Pavia, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Scavone
authors.affiliation: Department of Electrical, Computer and Biomedical Engineering, Università degli Studi di, Pavia, Pavia, Italy.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Bellazzi
authors.affiliation: Department of Biology and Biotechnology, Università degli Studi di, Pavia, Pavia, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Galizzi
authors.affiliation: Department of Biology and Biotechnology, Università degli Studi di, Pavia, Pavia, Italy.
authors.forename: Cinzia
authors.initials: C
authors.lastname: Calvio
mesh_terms: D001412:Bacillus subtilis / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D005407:Flagella / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D010766:Phosphorylation / Q000502:physiology; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; C066497:DegU protein, Bacteria; D012808:Sigma Factor