title: Disparate oxygen responsiveness of two regulatory cascades that control expression of symbiotic genes in Bradyrhizobium japonicum.
abstract: Two oxygen-responsive regulatory systems controlling numerous symbiotic genes in Bradyrhizobium japonicum were assayed in free-living cultures for their capacity to activate target genes under different oxygen conditions. NifA- and FixLJ-controlled target genes showed disparate relative expression patterns. Induction of NifA-dependent genes was observed only at oxygen concentrations below 2% in the gas phase, whereas that of FixLJ-controlled targets progressively increased when the oxygen concentration was lowered from 21 to 5, 2, or 0.5%. We propose that this reflects a response to a gradient of increasing oxygen deprivation as bacteria invade their host during root nodule development.
authors.affiliation: Institut für Mikrobiologie, Eidgenössische Technische Hochschule, CH-8092 Zürich, Switzerland.
authors.forename: Michel-Angelo
authors.initials: MA
authors.lastname: Sciotti
authors.forename: Astrid
authors.initials: A
authors.lastname: Chanfon
authors.forename: Hauke
authors.initials: H
authors.lastname: Hennecke
authors.forename: Hans-Martin
authors.initials: HM
authors.lastname: Fischer
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D020369:Bradyrhizobium / Q000235:genetics* / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D006420:Hemeproteins / Q000235:genetics / Q000378:metabolism; D000071677:Histidine Kinase; D007700:Kinetics; D010100:Oxygen / Q000378:metabolism*; D018517:Plant Roots / Q000382:microbiology; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D013559:Symbiosis / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D006420:Hemeproteins; C061338:NifA protein, Bacteria; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; C069289:FixJ protein, Bacteria; C067929:FixL protein, Bacteria; D000071677:Histidine Kinase; D010100:Oxygen