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Journal of Bacteriology, December 2007, p. 8928-8943, Vol. 189, No. 24
0021-9193/07/$08.00+0     doi:10.1128/JB.01088-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

New Target Genes Controlled by the Bradyrhizobium japonicum Two-Component Regulatory System RegSR{triangledown} ,{dagger}

Andrea Lindemann,1 Annina Moser,1,{ddagger} Gabriella Pessi,1 Felix Hauser,1 Markus Friberg,2 Hauke Hennecke,1 and Hans-Martin Fischer1*

Institute of Microbiology, ETH, Zürich, Switzerland,1 Institute of Computational Science, ETH, Zürich, Switzerland2

Received 10 July 2007/ Accepted 25 September 2007

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.

* Corresponding author. Mailing address: Institute of Microbiology, Eidgenössische Technische Hochschule, Wolfgang-Pauli-Strasse 10, CH-8093 Zürich, Switzerland. Phone: 41 44 632 44 19. Fax: 41 44 633 14 58. E-mail: fischerh{at}micro.biol.ethz.ch

{triangledown} Published ahead of print on 19 October 2007.

{dagger} Supplemental material for this article may be found at http://jb.asm.org/.

{ddagger} Present address: Biozentrum, University of Basel, Klingelbergstrasse 50/70, CH-4056 Basel, Switzerland.

Journal of Bacteriology, December 2007, p. 8928-8943, Vol. 189, No. 24
0021-9193/07/$08.00+0     doi:10.1128/JB.01088-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

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  • Mesa, S., Hauser, F., Friberg, M., Malaguti, E., Fischer, H.-M., Hennecke, H. (2008). Comprehensive Assessment of the Regulons Controlled by the FixLJ-FixK2-FixK1 Cascade in Bradyrhizobium japonicum. J. Bacteriol. 190: 6568-6579 [Abstract] [Full Text]  


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