title: New target genes controlled by the Bradyrhizobium japonicum two-component regulatory system RegSR.
abstract: RegSR-like proteins, members of the family of two-component regulatory systems, are present in a large number of proteobacteria in which they globally control gene expression mostly in a redox-responsive manner. The controlled target genes feature an enormous functional diversity. In Bradyrhizobium japonicum, the facultative root nodule symbiont of soybean, RegSR activate the transcription of the nitrogen fixation regulatory gene nifA, thus forming a RegSR-NifA cascade which is part of a complex regulatory network for gene regulation in response to changing oxygen concentrations. Whole-genome transcription profiling was performed here in order to assess the full regulatory scope of RegSR. The comparative analysis of wild-type and delta regR cells grown under oxic and microoxic conditions revealed that expression of almost 250 genes is dependent on RegR, a result that underscores the important contribution of RegR to oxygen- or redox-regulated gene expression in B. japonicum. Furthermore, transcription profiling of delta regR bacteroids compared with wild-type bacteroids revealed expression changes for about 1,200 genes in young and mature bacteroids. Incidentally, many of these were found to be induced in symbiosis when wild-type bacteroids were compared with free-living, culture-grown wild-type cells, and they appeared to encode diverse functions possibly related to symbiosis and nitrogen fixation. We demonstrated direct RegR-mediated control at promoter regions of several selected target genes by means of DNA binding experiments and in vitro transcription assays, which revealed six novel direct RegR target promoters.
authors.affiliation: Institute of Microbiology, Eidgenössische Technische Hochschule, Wolfgang-Pauli-Strasse 10, CH-8093 Zürich, Switzerland.
authors.forename: Andrea
authors.initials: A
authors.lastname: Lindemann
authors.forename: Annina
authors.initials: A
authors.lastname: Moser
authors.forename: Gabriella
authors.initials: G
authors.lastname: Pessi
authors.forename: Felix
authors.initials: F
authors.lastname: Hauser
authors.forename: Markus
authors.initials: M
authors.lastname: Friberg
authors.forename: Hauke
authors.initials: H
authors.lastname: Hennecke
authors.forename: Hans-Martin
authors.initials: HM
authors.lastname: Fischer
mesh_terms: D020369:Bradyrhizobium / Q000235:genetics* / Q000378:metabolism*; D004269:DNA, Bacterial / Q000235:genetics / Q000378:metabolism; D017353:Gene Deletion; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D009586:Nitrogen Fixation; D020411:Oligonucleotide Array Sequence Analysis; D010100:Oxygen / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012333:RNA, Messenger / Q000096:biosynthesis; D015398:Signal Transduction; D013559:Symbiosis; D014158:Transcription, Genetic
chemical_list: D004269:DNA, Bacterial; D012333:RNA, Messenger; D010100:Oxygen