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  • 1
    Electronic Resource
    Electronic Resource
    The ntrBC genes of Rhizobium leguminosarum are part of a complex operon subject to negative regulation (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 9 (1993), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: We report here that ntrB and ntrC genes of Rhizobium leguminosarum biovar phaseoli are cotranscribed with an open reading frame (called 0RF1) of unknown Unction. The promoter region of the 0RF1-ntrB-ntrC operon was mapped immediately upstream of ORF1 and two in vivo transcription initiation sites were identified, both preceded by −35/−10 promoter consensus sequences. Some major aspects differentiate ft leguminosarum from the enteric nitrogen regulatory system: the ntrBC genes are cotranscribed with 0RF1 which is homologous to an ORF located upstream of ntrBC of R. capsulatus and to the 0RF1 located upstream of the fis gene of Escherichia coir, ntrBC are not transcribed from a −24/−12 promoter and are only autogenously repressed. Moreover, the intracellular concentration of the NtrC protein increases when the bacterium is grown on ammonium salts, white under the same conditions the promoter of one of its target genes, glnII, is 12 times less active.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1993.tb01717.x
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  • 2
    Electronic Resource
    Electronic Resource
    Regulation of nitrogen metabolism is altered in a glnB mutant strain of Rhizobium leguminosarum (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 11 (1994), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: We isolated a Rhizobium leguminosarum mutant strain altered in the glnB gene. This event, which has never been described in the Rhizobiaceae, is rare in comparison to mutants isolated in the contiguous gene, glnA. The glnB mutation removes the glnBA promoter but in vivo does not prevent glnA expression from its own promoter, which is not nitrogen regulated. The glnB mutant strain does not grow on nitrate as a sole nitrogen source and it is Nod+, Fix+. Two –24/–12 promoters, for the glnll and glnBA genes, are constitutively expressed in the glnB mutant, while two –35/–10-like promoters for glnA and ntrBC are unaffected. We propose that the glnB gene product, the P11 protein, plays a negative role in the ability of NtrC to activate transcription from its target promoters and a positive role in the mechanism of nitrate utilization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1994.tb00346.x
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  • 3
    Electronic Resource
    Electronic Resource
    Inhibition of glutamine synthetase II expression by the product of the gstI gene (2000)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 37 (2000), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: We report the identification of a previously unrecognized gene that is involved in the regulation of the Rhizobium leguminosarum glnII (glutamine synthetase II) gene. This gene, which is situated immediately upstream of glnII, was identified by means of a deletion/complementation analysis performed in the heterologous background of Klebsiella pneumoniae. It has been designated gstI (glutamine synthetase translational Inhibitor) because, when a complete version of gstI is present, it is possible to detect glnII-specific mRNA, but neither GSII activity nor GSII protein. The gstI gene encodes a small (63 amino acids) protein, which acts in cis or in trans with respect to glnII and is transcribed divergently with respect to glnII from a promoter that was found to be strongly repressed by the nitrogen transcriptional regulator NtrC. A mutated version of GstI lacking the last 14 amino acids completely lost its capacity to repress glnII expression. Our results indicate that gstI mediates the translation inhibition of glnII mRNA and, based on in silico analyses, a mechanism for GstI action is proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2000.02018.x
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  • 4
    Electronic Resource
    Electronic Resource
    Activation of the Rhizobium leguminosarum glnII gene by NtrC is dependent on upstream DNA sequences (1992)
    Springer
    Molecular genetics and genomics 234 (1992), S. 337-345 
    Details
    ISSN: 1617-4623
    Keywords: Nitrogen assimilation ; Gene regulation ; Promoter ; Deletion analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The cloning and sequence determination is reported of the DNA region of Rhizobium leguminosarum coding for glutamine synthetase II (GSII). An open reading frame (ORF) encoding 326 amino acids was defined as the glnII gene on the basis of its similarity to other glnII genes and the ability of a DNA fragment carrying this ORF to complement the glutamine auxotrophy of a Klebsiella pneumoniae glnA mutant. We find that the glnII gene in R. leguminosarum is transcribed as a monocistronic unit from a single promoter, which shows structural features characteristic of rpoN(ntrA)-dependent promoters. In K. pneumoniae, such promoters require the ntrC and rpoN(ntrA) gene products for transcription. The intracellular level of glnII mRNA changes when R. leguminosarum is grown on different nitrogen sources, as expected for regulation by the nitrogen regulatory system. Promoter deletion analysis has shown that an extensive upstream DNA sequence (316 bp) is essential for in vivo activation of the glnII promoter in different biovars of R. leguminosarum. This DNA region requires a wild-type ntrC gene for activity and includes two conserved putative NtrC-binding site sequences. The results conclusively show that transcription from the R. leguminosarum glnII promoter is fully dependent on positive control by NtrC protein and on an upstream activator sequence (UAS).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00538692
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