Characterization of three different nitrogen-regulated promoter regions for the expression of glnB and glnA in Azospirillum brasilense

Zamaroczy, Miklos de; Delorme, Frédéric; Elmerich, Claudine

doi:10.1007/bf00262437

Cited by 54 publications

(50 citation statements)

References 65 publications

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“…Taken together, the data indicate that ginBA may form a superoperon with multiple promoters: two upstream of ginB and another upstream of ginA in glnB. In both A. brasilense (10) and R leguminosarum (7), ginA is transcribed from an independent promoter.…”

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confidence: 80%

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The Rhodobacter capsulatus glnB gene is regulated by NtrC at tandem rpoN-independent promoters

Foster‐Hartnett

Kranz

1994

J Bacteriol

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The protein encoded by glnB of Rhodobacter capsulatus is part of a nitrogen-sensing cascade which regulates the expression of nitrogen fixation genes (nij). The expression ofglnB was studied by using lacZ fusions, primer extension analysis, and in vitro DNase I footprinting. Our results suggest that glnB is transcribed from two promoters, one of which requires the R. capsuatus ntrC gene but is rpoN independent. Another promoter upstream of glnB is repressed by NtrC; purified R. capsulatus NtrC binds to sites that overlap this distal promoter region.Most free-living nitrogen-fixing organisms regulate the synthesis of nitrogenase, the enzyme which reduces atmospheric nitrogen to ammonia, in response to environmental oxygen and fixed nitrogen levels. In the photosynthetic bacterium Rhodobacter capsulatus, this signal transduction cascade is mediated by the products of at least five regulatory genes: glnB, ntrB, ntrC, rpoN, nifAl, and nifA2 (for reviews, see references 19 and 20). In the absence of both fixed nitrogen and oxygen, transcription of the genes encoding the nitrogenase polypeptides (nifHDK) and other nifgenes required for the synthesis of nitrogenase is activated by NifAl or NifA2 (25) at promoters recognized by the alternative sigma factor RpoN (CF54, ON, or NtrA). Induction of nifAl and nifA2 occurs when fixed nitrogen is limited and requires ntrC (nifRl) but not rpoN (nifR4) (14,29). R. capsulatus glnB is proposed to be a negative regulator of nif gene transcription, since glnB mutants express nitrogenase constitutively with respect to fixed nitrogen although oxygen repression is still present (22).In R. capsulatus, glnB was proposed to be organized in a ginBA operon. Expression of a glnBA-lacZ fusion was reduced approximately 50% in an ntrC mutant (22), suggesting that the glnB gene could be regulated by the R capsulatus ntrC product.NtrC (NR,) is a member of a family of procaryotic enhancerbinding proteins which characteristically activate RpoN-dependent promoters (reviewed in references 23, 27, and 36). To extend our studies of NtrC activation in R. capsulatus, we have analyzed the glnB promoters in vivo by primer extension analysis and by in vitro DNase I footprinting with purified R capsulatus NtrC (RcNtrC). Our results suggest that the R capsulatus glnB gene is transcribed from tandem promoters, one repressed (glnBpl) and the other activated (glnBp2) genes are cotranscribed, although a second possibility is that the transposon is located in a ginA promoter element within the glnB gene (as discussed below). To confirm that a glnB promoter(s) is regulated by ntrC, we constructed a lacZ fusion (pRKR5) that is dependent solely on glnB promoter function (see the Fig. 1 legend). 13-Galactosidase assays were performed essentially as described previously (22), and the results are shown in Fig. 1. The expression of pRKR5 in the wild-type strain was reduced approximately 40% when cells were induced in media containing ammonia as a nitrogen source. In media lacking ammonia, the expression of pRKR5 in an n...

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confidence: 80%

“…Expression of the glnB-glnA operons in Bradyrhizobium japonicum, Rhizobium leguminosarum biovar viciae, and Azospirillum brasilense has been investigated with respect to levels of fixed nitrogen (7,10,11,24). In both B. japonicum and A. brasilense, two oppositely regulated promoters are located upstream of glnB.…”

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confidence: 99%

The Rhodobacter capsulatus glnB gene is regulated by NtrC at tandem rpoN-independent promoters

Foster‐Hartnett

Kranz

1994

J Bacteriol

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“…d A. thaliana GLB1 is a nuclear gene encoding a chloroplastic protein. (48). The gene is expressed from a 70 -like promoter in nitrogen sufficiency, and transcription is elevated fivefold in nitrogen limitation as a second 54 -dependent promoter is activated.…”

Section: ␣ Proteobacteriamentioning

confidence: 99%

“…The gene is expressed from a 70 -like promoter in nitrogen sufficiency, and transcription is elevated fivefold in nitrogen limitation as a second 54 -dependent promoter is activated. However, expression of glnB is not NtrC dependent (48,49), and it has been proposed that glnB is activated by an NtrC homologue. The glnA promoter does not bear any similarity to the known consensus sites for factors, and glnA transcription is downregulated when molecular nitrogen is the sole nitrogen source (48,49).…”

Section: ␣ Proteobacteriamentioning

confidence: 99%

P_IISignal Transduction Proteins, Pivotal Players in Microbial Nitrogen Control

Arcondéguy

Jack

Merrick

2001

Microbiol Mol Biol Rev

397

456

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SUMMARY The PII family of signal transduction proteins are among the most widely distributed signal proteins in the bacterial world. First identified in 1969 as a component of the glutamine synthetase regulatory apparatus, PII proteins have since been recognized as playing a pivotal role in control of prokaryotic nitrogen metabolism. More recently, members of the family have been found in higher plants, where they also potentially play a role in nitrogen control. The PII proteins can function in the regulation of both gene transcription, by modulating the activity of regulatory proteins, and the catalytic activity of enzymes involved in nitrogen metabolism. There is also emerging evidence that they may regulate the activity of proteins required for transport of nitrogen compounds into the cell. In this review we discuss the history of the PII proteins, their structures and biochemistry, and their distribution and functions in prokaryotes. We survey data emerging from bacterial genome sequences and consider other likely or potential targets for control by PII proteins.

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“…These results indicate that the A. amazonense non-coding regions described above differ from related A. brasilense regions even among nitrogenase structural genes which are highly conserved among diazotrophic bacteria. A set of primers was designed (Table 2) from previously published sequences of nifA and glnB genes from A. brasilense (15,22). A PCR product of approximately 250 bp was detected in A. amazonense DNA ( Figure 2D, lane 1).…”

Section: A Amazonense Nif Genes: Hybridization and Pcrmentioning

confidence: 99%

Partial characterization of nif genes from the bacterium Azospirillum amazonense

Potrich

Passaglia

Schrank

2001

Braz J Med Biol Res

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Azospirillum amazonense revealed genomic organization patterns of the nitrogen fixation genes similar to those of the distantly related species A. brasilense. Our work suggests that A. brasilense nifHDK, nifENX, fixABC operons and nifA and glnB genes may be structurally homologous to the counterpart genes of A. amazonense. This is the first analysis revealing homology between A. brasilense nif genes and the A. amazonense genome. Sequence analysis of PCR amplification products revealed similarities between the amino acid sequences of the highly conserved nifD and glnB genes of A. amazonense and related genes of A. brasilense and other bacteria. However, the A. amazonense non-coding regions (the upstream activator sequence region and the region between the nifH and nifD genes) differed from related regions of A. brasilense even in nitrogenase structural genes which are highly conserved among diazotrophic bacteria. The feasibility of the 16S ribosomal RNA gene-based PCR system for specific detection of A. amazonense was shown. Our results indicate that the PCR primers for 16S rDNA defined in this article are highly specific to A. amazonense and can distinguish this species from A. brasilense.

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Characterization of three different nitrogen-regulated promoter regions for the expression of glnB and glnA in Azospirillum brasilense

Cited by 54 publications

References 65 publications

The Rhodobacter capsulatus glnB gene is regulated by NtrC at tandem rpoN-independent promoters

The Rhodobacter capsulatus glnB gene is regulated by NtrC at tandem rpoN-independent promoters

P_IISignal Transduction Proteins, Pivotal Players in Microbial Nitrogen Control

Partial characterization of nif genes from the bacterium Azospirillum amazonense

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Characterization of three different nitrogen-regulated promoter regions for the expression of glnB and glnA in Azospirillum brasilense

Cited by 54 publications

References 65 publications

The Rhodobacter capsulatus glnB gene is regulated by NtrC at tandem rpoN-independent promoters

The Rhodobacter capsulatus glnB gene is regulated by NtrC at tandem rpoN-independent promoters

PIISignal Transduction Proteins, Pivotal Players in Microbial Nitrogen Control

Partial characterization of nif genes from the bacterium Azospirillum amazonense

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P_IISignal Transduction Proteins, Pivotal Players in Microbial Nitrogen Control