Changes in gene expression during nitrogen starvation in Anabaena variabilis ATCC 29413

Wealand, J L; Myers, Jill A.; Hirschberg, Rona

doi:10.1128/jb.171.3.1309-1313.1989

Cited by 23 publications

(7 citation statements)

References 32 publications

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“…In heterocystous cyanobacteria, heterocyst differentiation after deprivation of fixed nitrogen is accompanied by a transient bleaching response which includes a decrease in the level of mRNA coding for phycocyanin and allophycocyanin (31,57). After heterocysts mature and start fixing nitrogen, normal levels of cpcBA and apcAB mRNAs are reestablished in vegetative cells but not in heterocysts (31).…”

Section: Discussionmentioning

confidence: 99%

Identification and Inactivation of Three Group 2 Sigma Factor Genes in Anabaena sp. Strain PCC 7120

Khudyakov

Golden

2001

J Bacteriol

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Three new Anabaena sp. strain PCC 7120 genes encoding group 2 alternative sigma factors have been cloned and characterized. Insertional inactivation of sigD, sigE, and sigF genes did not affect growth on nitrate under standard laboratory conditions but did transiently impair the abilities of sigD and sigE mutant strains to establish diazotrophic growth. A sigD sigE double mutant, though proficient in growth on nitrate and still able to differentiate into distinct proheterocysts, was unable to grow diazotrophically due to extensive fragmentation of filaments upon nitrogen deprivation. This double mutant could be complemented by wild-type copies of sigD or sigE, indicating some degree of functional redundancy that can partially mask phenotypes of single gene mutants. However, the sigE gene was required for lysogenic development of the temperate cyanophage A-4L. Several other combinations of double mutations, especially sigE sigF, caused a transient defect in establishing diazotrophic growth, manifested as a strong and prolonged bleaching response to nitrogen deprivation. We found no evidence for developmental regulation of the sigma factor genes. luxAB reporter fusions with sigD, sigE, and sigF all showed slightly reduced expression after induction of heterocyst development by nitrogen stepdown. Phylogenetic analysis of cyanobacterial group 2 sigma factor sequences revealed that they fall into several subgroups. Three morphologically and physiologically distant strains, Anabaena sp. strain PCC 7120, Synechococcus sp. strain PCC 7002, and Synechocystis sp. strain PCC 6803 each contain representatives of four subgroups. Unlike unicellular strains, Anabaena sp. strain PCC 7120 has three additional group 2 sigma factors that cluster in subgroup 2.5b, which is perhaps specific for filamentous or heterocystous cyanobacteria.

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Section: Discussionmentioning

confidence: 99%

Identification and Inactivation of Three Group 2 Sigma Factor Genes in Anabaena sp. Strain PCC 7120

Khudyakov

Golden

2001

J Bacteriol

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“…The half-lives of E. coli mRNAs vary from less than 0.5 to more than 20 min, with an average half-life of 2 to 4 min. However, in cyanobacteria the average half-life of total mRNA is approximately 12 to 20 min (23,57), and the few values for specific transcripts so far described fall into this range (2,35). This long half-life of cyanobacterial mRNAs has been related to the long doubling time of cyanobacteria compared to enterobacteria (about 8 h versus about 30 min).…”

Section: Discussionmentioning

confidence: 99%

Transcription of glutamine synthetase genes (glnA and glnN) from the cyanobacterium Synechocystis sp. strain PCC 6803 is differently regulated in response to nitrogen availability

1997

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In the cyanobacterium Synechocystis sp. strain PCC 6803 we have previously reported the presence of two different proteins with glutamine synthetase activity: GSI, encoded by the glnA gene, and GSIII, encoded by the glnN gene. In this work we show that expression of both the glnA and glnN genes is subjected to transcriptional regulation in response to changes in nitrogen availability. Northern blot experiments and transcriptional fusions demonstrated that the glnA gene is highly transcribed in nitrate-or ammonium-grown cells and exhibits two-to fourfold-higher expression in nitrogen-starved cells. In contrast, the glnN gene is highly expressed only under nitrogen deficiency. Half-lives of both mRNAs, calculated after addition of rifampin or ammonium to nitrogen-starved cells, were not significantly different (2.5 or 3.4 min, respectively, for glnA mRNA; 1.9 or 1.4 min, respectively, for glnN mRNA), suggesting that changes in transcript stability are not involved in the regulation of the expression of both genes. Deletions of the glnA and glnN upstream regions were used to delimit the promoter and the regulatory sequences of both genes. Primer extension analysis showed that structure of the glnA gene promoter resembles those of the NtcA-regulated promoters. In addition, mobility shift assays demonstrated that purified, Escherichia coli-expressed Synechocystis NtcA protein binds to the promoter of the glnA gene. Primer extension also revealed the existence of a sequence related to the NtcA binding site upstream from the glnN promoter. However, E. coli-expressed NtcA failed to bind to this site. These findings suggest that an additional modification of NtcA or an additional factor is required for the regulation of glnN gene expression. Glutamine synthetase (GS) catalyzes the ATP-dependent synthesis of glutamine from ammonium and glutamate (49).Glutamine is utilized not only for protein synthesis but also for the synthesis of a number of nitrogen-containing metabolites such as purines, pyrimidines, and amino sugars (38). In addition, in many microorganisms (including cyanobacteria) assimilation of ammonium occurs mainly by the sequential action of GS and glutamate synthase (GS-GOGAT pathway) (40). Because of the importance of glutamine in nitrogen metabolism, it is not surprising that both the catalytic activity and the synthesis of GS are finely regulated in many organisms.Transcriptional regulation of GS-encoding genes has been extensively studied in Escherichia coli and other gram-negative bacteria (reviewed in references 25, 33, and 40). In enteric bacteria, the GS structural gene, glnA, lies within the operon glnA-ntrBC. The ntrB and ntrC gene products, NR II and NR I , respectively, are required for the transcriptional regulation of the operon. These proteins are members of the family of twocomponent bacterial signal transduction systems (50). During nitrogen-limited growth, the DNA binding protein NR I , in its phosphorylated form, acts as a transcriptional activator, promoting high transcription from the 54 ...

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“…Although in diazotrophic species the period of nitrogen starvation is limited to the time required for the nitrogenase complex to be synthesized, cells need to use endogenous reserve materials to survive and may change their pattern of gene expression as do non-feting strains. Indeed, it has been shown that, in Anabaena variabilis ATCC 29413, the transcript abundance of the cpcBA and apcAB genes rapidly diminishes within 1 h of nitrogen starvation [335]. Transcription of these genes is again initiated as soon as combined nitrogen is provided, first by proteolysis of the intracellular reserve materials and later by nitrogen fixation.…”

Section: Responses To Deprivation For Sources Of Combined Nitrogenmentioning

confidence: 99%

Adaptation of cyanobacteria to environmental stimuli: new steps towards molecular mechanisms

Marsac

Houmard

1993

FEMS Microbiology Letters

375

128

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Dating from the Pre‐Cambrian era, cyanobacteria have a long history of adaptation to the Earth's environment. By evolving oxygen via photosynthetic reactions similar to those of plants and green algae, these prokaryotes were essential to the evolution of the present biosphere. They continue to make a large contribution to the equilibrium of the Earth's atmosphere by production oxygen and removing carbon dioxide. To survive in extreme or variable environments, cyanobacteria have developed specific regulatory systems, in addition to more general mechanisms equivalent to those of other prokaryotes or photosynthesis eukaryotes. Specific regulatory systems control the differentiation of specialized nitrogen‐fixing cells and of cell types facilitating the dispersion of species. In the past decade, considerable progress has been made towards understanding the expression of the cyanobacterial genome in response to variations in the intensity and spectral quality of incident light and in response to nutritional conditions, especially carbon, nitrogen and sulphur sources. These studies have provided insights into the relationships between carbon and nitrogen intermediary metabolism, and a start towards understanding of the interconnected pathways which lead from the perception of environmental signals to the regulation of enzyme activities and gene expression. Cyanobacterial regulatory mechanisms share common features with those of other prokaryotes, but are unique since these essentially photo‐autotrophic organisms must maintain a proper cellular C/N balance, in spite of dailty variations in incident light. Thus an appropriate coordination between photosynthesis and other metabolic processes must be achieved through control of the catalytic activity of key enzymes by reducing equivalents and ATP produced by photosynthetic or respiratory electron transport. Recently discovered kinases/phosphatases act by post‐translational modification of specific proteins which probably act as signal transducers or modulators of gene expression in a manner similar to the well‐known two‐component regulatory systems described in other bacteria. In this overview, we present our current knowledge on the molecular aspects of the biology of cyanobacteria, as well as on their mechanisms of resistance to metal ions and their responses to metabolic stress.

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Changes in gene expression during nitrogen starvation in Anabaena variabilis ATCC 29413

Cited by 23 publications

References 32 publications

Identification and Inactivation of Three Group 2 Sigma Factor Genes in Anabaena sp. Strain PCC 7120

Identification and Inactivation of Three Group 2 Sigma Factor Genes in Anabaena sp. Strain PCC 7120

Transcription of glutamine synthetase genes (glnA and glnN) from the cyanobacterium Synechocystis sp. strain PCC 6803 is differently regulated in response to nitrogen availability

Adaptation of cyanobacteria to environmental stimuli: new steps towards molecular mechanisms

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