title: Regulation of the co-evolved HrpR and HrpS AAA+ proteins required for Pseudomonas syringae pathogenicity.
abstract: The bacterial AAA+ enhancer-binding proteins (EBPs) HrpR and HrpS (HrpRS) of Pseudomonas syringae (Ps) activate σ(54)-dependent transcription at the hrpL promoter; triggering type-three secretion system-mediated pathogenicity. In contrast with singly acting EBPs, the evolution of the strictly co-operative HrpRS pair raises questions of potential benefits and mechanistic differences this transcription control system offers. Here, we show distinct properties of HrpR and HrpS variants, indicating functional specialization of these non-redundant, tandemly arranged paralogues. Activities of HrpR, HrpS and their control proteins HrpV and HrpG from Ps pv. tomato DC3000 in vitro establish that HrpRS forms a transcriptionally active hetero-hexamer, that there is a direct negative regulatory role for HrpV through specific binding to HrpS and that HrpG suppresses HrpV. The distinct HrpR and HrpS functionalities suggest how partial paralogue degeneration has potentially led to a novel control mechanism for EBPs and indicate subunit-specific roles for EBPs in σ(54)-RNA polymerase activation.
authors.affiliation: Division of Biology, Faculty of Natural Sciences, Sir Alexander Fleming Building, Imperial College London, London SW7 2AZ, UK.
authors.forename: Milija
authors.initials: M
authors.lastname: Jovanovic
authors.forename: Ellen H
authors.initials: EH
authors.lastname: James
authors.forename: Patricia C
authors.initials: PC
authors.lastname: Burrows
authors.forename: Fabiane G M
authors.initials: FG
authors.lastname: Rego
authors.forename: Martin
authors.initials: M
authors.lastname: Buck
authors.forename: Jörg
authors.initials: J
authors.lastname: Schumacher
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D015153:Blotting, Western; D002850:Chromatography, Gel; D004268:DNA-Binding Proteins / Q000378:metabolism*; D024202:Electrophoretic Mobility Shift Assay; D019143:Evolution, Molecular; D005786:Gene Expression Regulation / Q000235:genetics* / Q000502:physiology; D046912:Multiprotein Complexes / Q000378:metabolism*; D010957:Plasmids / Q000235:genetics; D044224:Pseudomonas syringae / Q000737:chemistry* / Q000472:pathogenicity*; D051877:RNA Polymerase Sigma 54 / Q000378:metabolism; D012808:Sigma Factor / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D014161:Transduction, Genetic; D001616:beta-Galactosidase
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C085855:HrpL protein, Pseudomonas syringae; C085856:HrpR protein, Pseudomonas syringae; D046912:Multiprotein Complexes; D012808:Sigma Factor; D014157:Transcription Factors; C060789:hrpS protein, Pseudomonas syringae; D051877:RNA Polymerase Sigma 54; D001616:beta-Galactosidase