Involvement of GlnK, a PII protein, in control of nitrogen fixation and ammonia assimilation in Pseudomonas stutzeri A1501.
The nitrogen-fixing, root-associated strain Pseudomonas stutzeri A1501 carries a single gene encoding a protein from the PII family, designated glnK. The glnK gene is co-transcribed with two distantly related copies of amtB genes encoding putative ammonium channels. Transcription of glnK was decreased in the presence of ammonia and was partly dependent on NtrC and RpoN under nitrogen-limiting conditions. Inactivation of glnK led to a mutant strain devoid of nitrogenase activity, auxotrophic for glutamine and unable to deadenylylate glutamine synthetase, while inactivation of amtB1 led to a prototrophic and Nif+ mutant strain. RT-PCR analysis showed that nifA transcription was abolished in the glnK mutant, while glnA remained transcribed. Using the yeast two-hybrid system, an interaction between GlnK and the C-terminal domain of NifL was observed, suggesting GlnK-dependent control of NifA activity by NifL. Introduction of a plasmid that expressed nifA from a constitutive promoter restored nitrogen fixation to the glnK mutant, and nitrogenase activity was observed even in the presence of ammonia. GlnK signalling appears to be a key regulatory element in control of ammonia assimilation, of nifA expression and in modulation of NifA activity by NifL.
He
Sheng
S
Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, 100081, Beijing, People's Republic of China. heshengbio@163.com
Chen
Ming
M
Xie
Zhihong
Z
Yan
Yongliang
Y
Li
Hongquan
H
Fan
Ying
Y
Ping
Shuzhen
S
Lin
Min
M
Elmerich
Claudine
C
D000641:Ammonia / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D004269:DNA, Bacterial / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D016680:Genome, Bacterial; D016254:Mutagenesis, Insertional; D009584:Nitrogen / Q000378:metabolism*; D009586:Nitrogen Fixation / Q000235:genetics*; D009591:Nitrogenase / Q000378:metabolism; D051922:PII Nitrogen Regulatory Proteins / Q000235:genetics* / Q000378:metabolism; D010957:Plasmids; D044223:Pseudomonas stutzeri / Q000235:genetics* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic; D020798:Two-Hybrid System Techniques
D001426:Bacterial Proteins; D004269:DNA, Bacterial; C061338:NifA protein, Bacteria; D051922:PII Nitrogen Regulatory Proteins; D014157:Transcription Factors; C084296:nifL protein, Bacteria; D000641:Ammonia; D009591:Nitrogenase; D009584:Nitrogen