Cloning and characterisation of the Azospirillum brasilense glnD gene and analysis of a glnD mutant.
Nitrogen regulation in bacteria involves the capacity to sense the availability of fixed nitrogen and to translate a signal indicating nitrogen deficiency or nitrogen excess into a cellular response. One of the key enzymes in this complex regulation process, the uridylyltransferase/uridylyl-removing (UTase) enzyme, encoded by the glnD gene, was characterised in the diazotroph Azospirillum brasilense, which promotes plant growth. The glnD gene product is responsible for the uridylylation of both P(II)-like nitrogen regulatory proteins, P(II) and P(Z), depending on the nitrogen status of the cell. The nitrogen-regulated activity of the main ammonium-assimilating enzyme, glutamine synthetase, is not altered in a glnD-Tn 5-B30 insertion mutant. UTase influences processes that are regulated by the NtrB-NtrC two-component histidine protein kinase system, such as ammonium uptake and nitrate assimilation. Moreover, the glnD gene product is indispensable for the activation of nitrogen fixation. Transcription of glnD is up-regulated under nitrogen-fixing conditions. This regulation is only partially dependent on the global nitrogen regulation (Ntr) system.
Van Dommelen
A
A
Centre of Microbial and Plant Genetics, K.U. Leuven, Kasteelpark Arenberg 20, B-3001 Heverlee, Belgium.
Keijers
V
V
Somers
E
E
Vanderleyden
J
J
D015806:Azospirillum brasilense / Q000201:enzymology* / Q000235:genetics*; D001483:Base Sequence; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000235:genetics; D015870:Gene Expression; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D009154:Mutation; D009586:Nitrogen Fixation / Q000235:genetics; D009713:Nucleotidyltransferases / Q000235:genetics*; D051922:PII Nitrogen Regulatory Proteins; D010641:Phenotype; D010944:Plants / Q000382:microbiology
D004269:DNA, Bacterial; D051922:PII Nitrogen Regulatory Proteins; D009713:Nucleotidyltransferases; C022515:regulatory protein uridylyltransferase