Boron deficiency increases expressions of asparagine synthetase, glutamate dehydrogenase and glutamine synthetase genes in tobacco roots irrespective of the nitrogen source

We analyzed the upstream region of the GDH2 gene, which encodes the NAD-linked glutamate dehydrogenase in Saccharomyces cerevisiae, for elements important for the regulation of the gene by the nitrogen source. The levels of this enzyme are high in cells grown with glutamate as the sole source of nitrogen and low in cells grown with glutamine or ammonium. We found that this regulation occurs at the level of transcription and that a total of six sites are required to cause a CYC1-lacZ fusion to the GDH2 gene to be regulated in the same manner as the NAD-linked glutamate dehydrogenase. Two sites behaved as upstream activation sites (UASs). The remaining four sites were found to block the effects of the two UASs in such a way that the GDH2-CYC1-lacZ fusion was not expressed unless the cells containing it were grown under conditions favorable for the activity of both UASs. This complex regulatory system appears to account for the fact that GDH2 expression is exquisitely sensitive to glutamine, whereas the expression of GLN1, coding for glutamine synthetase, is not nearly as sensitive.

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Nitrogen Metabolism of an Anoxygenic Filamentous Phototrophic Bacterium Oscillocholris trichoides Strain DG-6

Microbiology ◽

10.1134/s0026261721040068 ◽

2021 ◽

Vol 90 (4) ◽

pp. 428-434

Author(s):

R. N. Ivanovsky ◽

N. V. Lebedeva ◽

O. I. Keppen ◽

T. P. Tourova

Keyword(s):

Glutamine Synthetase ◽

Nitrogen Source ◽

Glutamate Dehydrogenase ◽

Molecular Nitrogen ◽

Single Gene ◽

Nitrogen Sources ◽

Entire Family ◽

Ammonium N ◽

Expression Product ◽

Typical Strain

Abstract— The possible nitrogen sources for Osc. trichoides DG6, a typical strain of the Oscillochloridaceae family, are ammonium, N2, glutamate, asparagine, glycine, and glutamine. The assimilation of molecular nitrogen occurs with the participation of nitrogenase, the structural gene of which, nifH, is located in the gene cluster which also includes the genes of the nifD and nifK nitrogenase subunits and the auxiliary nifB gene. Considering that nifHBDK clusters have been also annotated in the genomes of other members of the Oscillochloridaceae family, including uncultured and candidate taxa, it can be assumed that the ability to fix nitrogen is a property immanent for this entire family. The pathways for assimilating ammonium in the cells grown using different nitrogen sources may differ. Osc. trichoides DG6 growing in a medium containing ammonium assimilated it with the participation of glutamate dehydrogenase, which is determined by a single gene. The expression product of this gene has dual functionality and can be used to implement the reaction with both NAD and NADP. With the growth of Osc. trichoides DG6 on a medium with glutamate as the only nitrogen source all the enzymes necessary for the implementation of the GS‑GOGAT pathway were found in the cells. However, for the glutamine synthetase reaction, ammonium, which was absent in the growth medium, was required. The source of ammonium may be glutamate metabolized through glutamate dehydrogenase.

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Role of the complex upstream region of the GDH2 gene in nitrogen regulation of the NAD-linked glutamate dehydrogenase in Saccharomyces cerevisiae

Molecular and Cellular Biology ◽

10.1128/mcb.11.12.6229-6247.1991 ◽

1991 ◽

Vol 11 (12) ◽

pp. 6229-6247

Author(s):

S M Miller ◽

B Magasanik

Keyword(s):

Saccharomyces Cerevisiae ◽

Glutamine Synthetase ◽

Nitrogen Source ◽

Glutamate Dehydrogenase ◽

Regulatory System ◽

Sole Source ◽

Lacz Fusion ◽

Upstream Region ◽

In Cells

We analyzed the upstream region of the GDH2 gene, which encodes the NAD-linked glutamate dehydrogenase in Saccharomyces cerevisiae, for elements important for the regulation of the gene by the nitrogen source. The levels of this enzyme are high in cells grown with glutamate as the sole source of nitrogen and low in cells grown with glutamine or ammonium. We found that this regulation occurs at the level of transcription and that a total of six sites are required to cause a CYC1-lacZ fusion to the GDH2 gene to be regulated in the same manner as the NAD-linked glutamate dehydrogenase. Two sites behaved as upstream activation sites (UASs). The remaining four sites were found to block the effects of the two UASs in such a way that the GDH2-CYC1-lacZ fusion was not expressed unless the cells containing it were grown under conditions favorable for the activity of both UASs. This complex regulatory system appears to account for the fact that GDH2 expression is exquisitely sensitive to glutamine, whereas the expression of GLN1, coding for glutamine synthetase, is not nearly as sensitive.

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Regulation of glutamine-repressible gene products by the GLN3 function in Saccharomyces cerevisiae

Molecular and Cellular Biology ◽

10.1128/mcb.4.12.2758-2766.1984 ◽

1984 ◽

Vol 4 (12) ◽

pp. 2758-2766

Author(s):

A P Mitchell ◽

B Magasanik

Keyword(s):

Saccharomyces Cerevisiae ◽

Glutamine Synthetase ◽

Glutamate Dehydrogenase ◽

Opposite Effect ◽

Nuclear Gene ◽

Yeast Saccharomyces Cerevisiae ◽

Two Dimensional Gel Electrophoresis ◽

Regulatory Circuit ◽

Glutamate Dehydrogenase Activity ◽

Glutamine Limitation

Mutants of the yeast Saccharomyces cerevisiae have been isolated which fail to derepress glutamine synthetase upon glutamine limitation. The mutations define a single nuclear gene, GLN3, which is located on chromosome 5 near HOM3 and HIS1 and is unlinked to the structural gene for glutamine synthetase, GLN1. The three gln3 mutations are recessive, and one is amber suppressible, indicating that the GLN3 product is a positive regulator of glutamine synthetase expression. Four polypeptides, in addition to the glutamine synthetase subunit are synthesized at elevated rates when GLN3+ cultures are shifted from glutamine to glutamate media as determined by pulse-labeling and one- and two-dimensional gel electrophoresis. The response of all four proteins is blocked by gln3 mutations. In addition, the elevated NAD-dependent glutamate dehydrogenase activity normally found in glutamate-grown cells is not found in gln3 mutants. Glutamine limitation of gln1 structural mutants has the opposite effect, causing elevated levels of NAD-dependent glutamate dehydrogenase even in the presence of ammonia. We suggest that there is a regulatory circuit that responds to glutamine availability through the GLN3 product.

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