scholarly journals Two Genes Encoding Protein Kinases of the HstK Family Are Involved in Synthesis of the Minor Heterocyst-Specific Glycolipid in the Cyanobacterium Anabaena sp. Strain PCC 7120

2007 ◽  
Vol 189 (14) ◽  
pp. 5075-5081 ◽  
Author(s):  
Lei Shi ◽  
Jian-Hong Li ◽  
Yong Cheng ◽  
Li Wang ◽  
Wen-Li Chen ◽  
...  
Keyword(s):  
Nitrogenase Activity ◽  
Early Stage ◽  
Kinase Domain ◽  
Filamentous Cyanobacterium ◽  
Regulatory Pathways ◽  
Genes Encoding ◽  
Putative Transcription Factor ◽  
Oxygen Sensitive ◽  
Cyanobacterium Anabaena ◽  
Pcc 7120

ABSTRACT The filamentous cyanobacterium Anabaena sp. strain PCC 7120 can fix N2 under oxic conditions, and the activity of nitrogen fixation occurs exclusively in heterocysts, cells differentiated from vegetative cells in response to a limitation of a combined-nitrogen source in the growth medium. At the late stages of heterocyst differentiation, an envelope layer composed of two glycolipids is formed to limit the entry of oxygen so that the oxygen-sensitive nitrogenase can function. The genome of Anabaena sp. strain PCC 7120 possesses a family of 13 genes (the hstK family), all encoding proteins with a putative Ser/Thr kinase domain at their N termini and a His-kinase domain at their C termini. In this study, we showed that the double mutant D4.3 strain, in which two members of this gene family, pkn44 (all1625) and pkn30 (all3691), were both inactivated, failed to fix N2 in the presence of oxygen (Fox−). In an environment without oxygen, a low level of nitrogenase activity was detectable (Fix+). Heterocyst development in the mutant D4.3 was delayed by 24 h and arrested at a relatively early stage without the formation of the glycolipid layer (Hgl−). Only the minor species of the two heterocyst-specific glycolipids (HGLs) was missing in the mutant. We propose that DevH, a putative transcription factor, coordinates the synthesis of both HGLs, while Pkn44/Pkn30 and the previously characterized PrpJ may represent two distinct regulatory pathways involved in the synthesis of the minor HGL and the major HGL, respectively.

scholarly journals A Pair of Iron-Responsive Genes Encoding Protein Kinases with a Ser/Thr Kinase Domain and a His Kinase Domain Are Regulated by NtcA in the Cyanobacterium Anabaena sp. Strain PCC 7120

2006 ◽  
Vol 188 (13) ◽  
pp. 4822-4829 ◽  
Author(s):  
Yong Cheng ◽  
Jian-Hong Li ◽  
Lei Shi ◽  
Li Wang ◽  
Amel Latifi ◽  
...  
Keyword(s):  
Iron Acquisition ◽  
Iron Chelator ◽  
Kinase Domain ◽  
Iron Limitation ◽  
Filamentous Cyanobacterium ◽  
Wild Type ◽  
Putative Promoter Region ◽  
Iron Deprivation ◽  
Genes Encoding ◽  
Pcc 7120

ABSTRACT The filamentous cyanobacterium Anabaena sp. strain PCC 7120 can fix N2 when combined nitrogen is not available in the growth medium. It has a family of 13 genes encoding proteins with both a Ser/Thr kinase domain and a His kinase domain. The function of these enzymes is unknown. Two of them are encoded by pkn41 (alr0709) and pkn42 (alr0710). These two genes are separated by only 72 bp on the chromosome, and our results indicate that they are cotranscribed. The expression of pkn41 and pkn42 is induced by iron deprivation irrespective of the nature of the nitrogen source. Mutants inactivating either pkn41, pkn42, or both grow similarly to the wild type under normal conditions, but their growth is impaired either in the presence of an iron chelator or under conditions of nitrogen fixation and iron limitation, two situations where the demand for iron is particularly strong. Consistent with these results, these mutants display lower iron content than the wild type and a higher level of expression for nifJ1 and nifJ2, which encode pyruvate:ferredoxin oxidoreductases. Both nifJ1 and nifJ2 are known to be induced by iron limitation. NtcA, a global regulatory factor for different metabolic pathways, binds to the putative promoter region of pkn41, and the induction of pkn41 in response to iron limitation no longer occurs in an ntcA mutant. Our results suggest that ntcA not only regulates the expression of genes involved in nitrogen and carbon metabolism but also coordinates iron acquisition and nitrogen metabolism by activating the expression of pkn41 and pkn42.

scholarly journals PatS and Products of Nitrogen Fixation Control Heterocyst Pattern

2001 ◽  
Vol 183 (8) ◽  
pp. 2605-2613 ◽  
Author(s):  
Ho-Sung Yoon ◽  
James W. Golden
Keyword(s):  
Nitrogen Fixation ◽  
Nitrogenase Activity ◽  
Early Stage ◽  
Critical Role ◽  
Filamentous Cyanobacterium ◽  
Vegetative Cells ◽  
Heterocyst Differentiation ◽  
Partial Restoration ◽  
Fixation Control ◽  
Pcc 7120

ABSTRACT The filamentous cyanobacterium Anabaena sp. strain PCC 7120 forms a developmental pattern of single heterocysts separated by approximately 10 vegetative cells. Heterocysts differentiate from vegetative cells and are specialized for nitrogen fixation. ThepatS gene, which encodes a small peptide that inhibits heterocyst differentiation, is expressed in proheterocysts and plays a critical role in establishing the heterocyst pattern. Here we present further analysis of patS expression and heterocyst pattern formation. A patS-gfp reporter strain revealed clusters of patS-expressing cells during the early stage of heterocyst differentiation. PatS signaling is likely to be involved in the resolution of these clusters. Differentiating cells were inhibited by PatS during the time period 6 to 12 h after heterocyst induction, when groups of differentiating cells were being resolved to a single proheterocyst. Increased transcription ofpatS during development coincided with expression from a new transcription start site. In vegetative cells grown on nitrate, the 5′ end of a transcript for patS was localized 314 bases upstream from the first translation initiation codon. After heterocyst induction, a new transcript with a 5′ end at −39 bases replaced the vegetative cell transcript. A patS mutant grown for several days under nitrogen-fixing conditions showed partial restoration of the normal heterocyst pattern, presumably because of a gradient of nitrogen compounds supplied by the heterocysts. ThepatS mutant formed heterocysts when grown in the presence of nitrate but showed no nitrogenase activity and no obvious heterocyst pattern. We conclude that PatS and products of nitrogen fixation are the main signals determining the heterocyst pattern.

scholarly journals Septum-Localized Protein Required for Filament Integrity and Diazotrophy in the Heterocyst-Forming Cyanobacterium Anabaena sp. Strain PCC 7120

2007 ◽  
Vol 189 (10) ◽  
pp. 3884-3890 ◽  
Author(s):  
Enrique Flores ◽  
Rafael Pernil ◽  
Alicia M. Muro-Pastor ◽  
Vicente Mariscal ◽  
Iris Maldener ◽  
...  
Keyword(s):  
Fluorescent Protein ◽  
Nitrogenase Activity ◽  
Early Stage ◽  
Vegetative Cells ◽  
Reading Frame ◽  
Cyanobacterium Anabaena ◽  
In The Wild ◽  
Z Ring ◽  
Green Fluorescent ◽  
Pcc 7120

ABSTRACT Heterocysts, formed when filamentous cyanobacteria, such as Anabaena sp. strain PCC 7120, are grown in the absence of combined nitrogen, are cells that are specialized in fixing atmospheric nitrogen (N2) under oxic conditions and that transfer fixed nitrogen to the vegetative cells of the filament. Anabaena sp. mutants whose sepJ gene (open reading frame alr2338 of the Anabaena sp. genome) was affected showed filament fragmentation and arrested heterocyst differentiation at an early stage. In a sepJ insertional mutant, a layer similar to a heterocyst polysaccharide layer was formed, but the heterocyst-specific glycolipids were not synthesized. The sepJ mutant did not exhibit nitrogenase activity even when assayed under anoxic conditions. In contrast to proheterocysts produced in the wild type, those produced in the sepJ mutant still divided. SepJ is a multidomain protein whose N-terminal region is predicted to be periplasmic and whose C-terminal domain resembles an export permease. Using a green fluorescent protein translationally fused to the carboxyl terminus of SepJ, we observed that in mature heterocysts and vegetative cells, the protein is localized at the intercellular septa, and when cell division starts, it is localized in a ring whose position is similar to that of a Z ring. SepJ is a novel composite protein needed for filament integrity, proper heterocyst development, and diazotrophic growth.

scholarly journals Manipulation of Pattern of Cell Differentiation in a hetR Mutant of Anabaena sp. PCC 7120 by Overexpressing hetZ Alone or with hetP

Life ◽  
2018 ◽  
Vol 8 (4) ◽  
pp. 60 ◽  
Author(s):  
He Zhang ◽  
Xudong Xu
Keyword(s):  
Cell Differentiation ◽  
Peptide Inhibitor ◽  
Filamentous Cyanobacterium ◽  
Heterocyst Differentiation ◽  
Cyanobacterium Anabaena ◽  
Anabaena Sp ◽  
Pcc 7120

In the filamentous cyanobacterium, Anabaena sp. PCC 7120, single heterocysts differentiate at semi-regular intervals in response to nitrogen stepdown. HetR is a principal regulator of heterocyst differentiation, and hetP and hetZ are two genes that are regulated directly by HetR. In a hetR mutant generated from the IHB (Institute of Hydrobiology) substrain of PCC 7120, heterocyst formation can be restored by moderate expression of hetZ and hetP. The resulting heterocysts are located at terminal positions. We used a tandem promoter, PrbcLPpetE, to express hetZ and hetP strongly in the hetR mutant. Co-expression of hetZ and hetP enabled the hetR mutant to form multiple contiguous heterocysts at both terminal and intercalary positions. Expression of hetZ, alone resulted in terminally located heterocysts, whereas expression of hetP, alone produced enlarged cells in strings. In the absence of HetR, formation of heterocysts was insensitive to the peptide inhibitor, RGSGR.

Early candidacy for differentiation into heterocysts in the filamentous cyanobacterium Anabaena sp. PCC 7120

2009 ◽  
Vol 192 (1) ◽  
pp. 23-31 ◽  
Author(s):  
Masakazu Toyoshima ◽  
Naobumi V. Sasaki ◽  
Makoto Fujiwara ◽  
Shigeki Ehira ◽  
Masayuki Ohmori ◽  
...  
Keyword(s):  
Filamentous Cyanobacterium ◽  
Cyanobacterium Anabaena ◽  
Anabaena Sp ◽  
Pcc 7120

An increase in the level of 2-oxoglutarate promotes heterocyst development in the cyanobacterium Anabaena sp. strain PCC 7120

Microbiology ◽  
2003 ◽  
Vol 149 (11) ◽  
pp. 3257-3263 ◽  
Author(s):  
Jian-Hong Li ◽  
Sophie Laurent ◽  
Viren Konde ◽  
Sylvie Bédu ◽  
Cheng-Cai Zhang
Keyword(s):  
Inorganic Nitrogen ◽  
Cell Types ◽  
Filamentous Cyanobacterium ◽  
Nitrogen Status ◽  
Gene Encoding ◽  
Combined Nitrogen ◽  
Cyanobacterium Anabaena ◽  
Anabaena Sp ◽  
Pcc 7120 ◽  
Heterocyst Development

In the filamentous cyanobacterium Anabaena sp. strain PCC 7120, a starvation of combined nitrogen induces differentiation of heterocysts, cells specialized in nitrogen fixation. How do filaments perceive the limitation of the source of combined nitrogen, and what determines the proportion of heterocysts? In cyanobacteria, 2-oxoglutarate provides a carbon skeleton for the incorporation of inorganic nitrogen. Recently, it has been proposed that the concentration of 2-oxoglutarate reflects the nitrogen status in cyanobacteria. To investigate the effect of 2-oxoglutarate on heterocyst development, a heterologous gene encoding a 2-oxoglutarate permease under the control of a regulated promoter was expressed in Anabaena sp. PCC 7120. The increase of 2-oxoglutarate within cells can trigger heterocyst differentiation in a subpopulation of filaments even in the presence of nitrate. In the absence of a source of combined nitrogen, it can increase heterocyst frequency, advance the timing of commitment to heterocyst development and further increase the proportion of heterocysts in a patS mutant. Here, it is proposed that the intracellular concentration of 2-oxoglutarate is involved in the determination of the proportion of the two cell types according to the carbon/nitrogen status of the filament.

scholarly journals Overproduction of the Flv3B flavodiiron, enhances the photobiological hydrogen production by the nitrogen-fixing cyanobacterium Nostoc PCC 7120

2019 ◽  
Author(s):  
Baptiste Roumezi ◽  
Luisana Avilan ◽  
Véronique Risoul ◽  
Myriam Brugna ◽  
Sophie Rabouille ◽  
...  
Keyword(s):  
Hox Genes ◽  
Nitrogenase Activity ◽  
Clean Energy ◽  
Gene Encoding ◽  
Promising Alternative ◽  
Genes Encoding ◽  
Photosynthetic Microorganisms ◽  
Pcc 7120 ◽  
The Impact ◽  
Overexpressing Strain

Abstract Background: The ability of some photosynthetic microorganisms, particularly cyanobacteria and microalgae, to produce hydrogen (H 2 ) is a promising alternative for renewable, clean-energy production. However, studies of the topic in the last decade have shown that much improvement is needed before sustainable cyanobacterial-based H 2 production becomes economically viable. In this study, we investigated the impact of inducing O 2 -consumption to enhance H 2 photoproduction yields in the heterocyst-forming, N 2 -fixing cyanobacterium Nostoc PCC7120. Results: The flv3B gene, encoding a flavodiiron protein naturally expressed in the heterocyst of Nostoc, was overexpressed. Compared to the wild type, the recombinant strain obtained displayed a significantly higher H 2 production under aerobic growth and phototrophic conditions. Nitrogenase activity assays indicated that flv3B overexpression did not increase the nitrogen fixation rates. On the other hand, quantitative RT-PCR experiments showed that the transcription of the hox genes, encoding the NiFe Hox hydrogenase was greatly elevated in the flv3B overexpressing strain. Conclusion: We conclude that the overproduced Flv3B protein might have enhanced O 2 -consumption, thus creating conditions inducing hox genes and facilitating H 2 production. The present study clearly demonstrates the potential to use metabolic engineered cyanobacteria for photosynthesis driven H 2 production.

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