Regulation of nitrogen metabolism is altered in a glnB mutant strain of Rhizobium leguminosarum.
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 glnII 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 PII 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.
Amar
M
M
International Institute of Genetics and Biophysics, Naples, Italy.
Patriarca
E J
EJ
Manco
G
G
Bernard
P
P
Riccio
A
A
Lamberti
A
A
Defez
R
R
Iaccarino
M
M
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics; D029968:Escherichia coli Proteins; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D005974:Glutamate-Ammonia Ligase / Q000096:biosynthesis / Q000235:genetics; D005973:Glutamine / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D051922:PII Nitrogen Regulatory Proteins; D010641:Phenotype; D010957:Plasmids; D011401:Promoter Regions, Genetic; D016961:Rhizobium leguminosarum / Q000235:genetics / Q000378:metabolism*; D015534:Trans-Activators; D014157:Transcription Factors; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D051922:PII Nitrogen Regulatory Proteins; D015534:Trans-Activators; D014157:Transcription Factors; C497876:glnG protein, E coli; D005973:Glutamine; C404143:PIID regulatory protein, Bacteria; C081173:glutamine synthetase I; D005974:Glutamate-Ammonia Ligase; D009584:Nitrogen