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.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Bacterial Proteins / genetics
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Bacterial Proteins / metabolism
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Bradyrhizobium / genetics*
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Bradyrhizobium / metabolism*
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Gene Expression Regulation, Bacterial*
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Hemeproteins / genetics
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Hemeproteins / metabolism
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Histidine Kinase
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Kinetics
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Oxygen / metabolism*
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Plant Roots / microbiology
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Recombinant Fusion Proteins / genetics
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Recombinant Fusion Proteins / metabolism
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Symbiosis / genetics*
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Transcription Factors / genetics
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Transcription Factors / metabolism
Substances
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Bacterial Proteins
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Hemeproteins
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NifA protein, Bacteria
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Recombinant Fusion Proteins
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Transcription Factors
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FixJ protein, Bacteria
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FixL protein, Bacteria
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Histidine Kinase
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Oxygen