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 Anabaena sp. Strain PCC 7120 Gene devH Is Required for Synthesis of the Heterocyst Glycolipid Layer

2005 ◽  
Vol 187 (7) ◽  
pp. 2326-2331 ◽  
Author(s):  
Martha E. Ramírez ◽  
Pratibha B. Hebbar ◽  
Ruanbao Zhou ◽  
C. Peter Wolk ◽  
Stephanie E. Curtis
Keyword(s):  
Nitrogen Fixation ◽  
Nitrogenase Activity ◽  
Regulatory Protein ◽  
Protein A ◽  
Filamentous Cyanobacterium ◽  
Fixed Nitrogen ◽  
Ultrastructural Studies ◽  
Anabaena Sp ◽  
Pcc 7120 ◽  
Mutant Forms

ABSTRACT In response to deprivation for fixed nitrogen, the filamentous cyanobacterium Anabaena sp. strain PCC 7120 provides a microoxic intracellular environment for nitrogen fixation through the differentiation of semiregularly spaced vegetative cells into specialized cells called heterocysts. The devH gene is induced during heterocyst development and encodes a product with characteristics of a trans-acting regulatory protein. A devH mutant forms morphologically distinguishable heterocysts but is Fox−, incapable of nitrogen fixation in the presence of oxygen. We demonstrate that rearrangements of nitrogen fixation genes take place normally in the devH mutant and that it is Fix+, i.e., has nitrogenase activity under anoxic conditions. The Fox− phenotype was shown by ultrastructural studies to be associated with the absence of the glycolipid layer of the heterocyst envelope. The expression of glycolipid biosynthetic genes in the mutant is greatly reduced, and heterocyst glycolipids are undetectable.

scholarly journals Anabaena sp. strain PCC 7120 conR contains a LytR-CpsA-Psr domain, is developmentally regulated, and is essential for diazotrophic growth and heterocyst morphogenesis

Microbiology ◽  
2011 ◽  
Vol 157 (3) ◽  
pp. 617-626 ◽  
Author(s):  
Rodrigo A. Mella-Herrera ◽  
M. Ramona Neunuebel ◽  
James W. Golden
Keyword(s):  
Nitrogenase Activity ◽  
Growth Defect ◽  
Filamentous Cyanobacterium ◽  
Developmentally Regulated ◽  
Vegetative Cells ◽  
Septum Formation ◽  
Insertional Inactivation ◽  
Step Down ◽  
Pcc 7120 ◽  
Diazotrophic Growth

The conR (all0187) gene of the filamentous cyanobacterium Anabaena (Nostoc) sp. strain PCC 7120 is predicted to be part of a family of proteins that contain the LytR-CpsA-Psr domain associated with septum formation and cell wall maintenance. The conR gene was originally misannotated as a transcription regulator. Northern RNA blot analysis showed that conR expression was upregulated 8 h after nitrogen step-down. Fluorescence microscopy of a P conR –gfp reporter strain revealed increased GFP fluorescence in proheterocysts and heterocysts beginning 9 h after nitrogen step-down. Insertional inactivation of conR caused a septum-formation defect of vegetative cells grown in nitrate-containing medium. In nitrate-free medium, mutant filaments formed abnormally long heterocysts and were defective for diazotrophic growth. Septum formation between heterocysts and adjacent vegetative cells was abnormal, often with one or both poles of the heterocysts appearing partially open. In a conR mutant, expression of nifH was delayed after nitrogen step-down and nitrogenase activity was approximately 70 % of wild-type activity, indicating that heterocysts of the conR mutant strain are partially functional. We hypothesize that the diazotrophic growth defect is caused by an inability of the heterocysts to transport fixed nitrogen to the neighbouring vegetative cells.

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 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 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.

scholarly journals Inactivation of a Heterocyst-Specific Invertase Indicates a Principal Role of Sucrose Catabolism in Heterocysts of Anabaena sp.

2010 ◽  
Vol 192 (20) ◽  
pp. 5526-5533 ◽  
Author(s):  
Rocío López-Igual ◽  
Enrique Flores ◽  
Antonia Herrero
Keyword(s):  
Fluorescent Protein ◽  
Northern Analysis ◽  
Filamentous Cyanobacterium ◽  
Nitrogen Deprivation ◽  
Vegetative Cells ◽  
Anabaena Sp ◽  
Green Fluorescent ◽  
Pcc 7120 ◽  
Diazotrophic Growth

ABSTRACT Anabaena sp. strain PCC 7120 is a filamentous cyanobacterium that carries out N2 fixation in specialized cells called heterocysts, which exchange nutrients and regulators with the filament's vegetative cells that perform the photosynthetic fixation of CO2. The Anabaena genome carries two genes coding for alkaline/neutral invertases, invA and invB. As shown by Northern analysis, both genes were expressed monocistronically and induced under nitrogen deprivation, although induction was stronger for invB than for invA. Whereas expression of an InvA-N-GFP fusion (green fluorescent protein [GFP] fused to the N terminus of the InvA protein [InvA-N]) was homogeneous along the cyanobacterial filament, consistent with the lack of dependence on HetR, expression of an InvB-N-GFP fusion upon combined nitrogen deprivation took place mainly in differentiating and mature heterocysts. In an hetR genetic background, the InvB-N-GFP fusion was strongly expressed all along the filament. An insertional mutant of invA could grow diazotrophically but was impaired in nifHDK induction and exhibited an increased frequency of heterocysts, suggesting a regulatory role of the invertase-mediated carbon flux in vegetative cells. In contrast, an invB mutant was strongly impaired in diazotrophic growth, showing a crucial role of sucrose catabolism mediated by the InvB invertase in the heterocysts.

scholarly journals Novel DNA-Binding Proteins in the Cyanobacterium Anabaena sp. Strain PCC 7120

2002 ◽  
Vol 184 (14) ◽  
pp. 3931-3940 ◽  
Author(s):  
Olga A. Koksharova ◽  
C. Peter Wolk
Keyword(s):  
Dna Binding ◽  
Insertional Mutagenesis ◽  
Binding Proteins ◽  
Dna Binding Proteins ◽  
Vegetative Cells ◽  
Heterocyst Differentiation ◽  
The Third ◽  
Cyanobacterium Anabaena ◽  
Anabaena Sp ◽  
Pcc 7120

ABSTRACT As an approach towards elucidation of the biochemical regulation of the progression of heterocyst differentiation in Anabaena sp. strain PCC 7120, we have identified proteins that bind to a 150-bp sequence upstream from hepC, a gene that plays a role in the synthesis of heterocyst envelope polysaccharide. Such proteins were purified in four steps from extracts of vegetative cells of Anabaena sp. Two of these proteins (Abp1 and Abp2) are encoded by neighboring genes in the Anabaena sp. chromosome. The genes that encode the third (Abp3) and fourth (Abp4) proteins are situated at two other loci in that chromosome. Insertional mutagenesis of abp2 and abp3 blocked expression of hepC and hepA and prevented heterocyst maturation and aerobic fixation of N2.

scholarly journals cyAbrB transcriptional regulators as safety devices to inhibit heterocyst differentiation in Anabaena

2019 ◽  
Author(s):  
Akiyoshi Higo ◽  
Eri Nishiyama ◽  
Kota Nakamura ◽  
Yukako Hihara ◽  
Shigeki Ehira
Keyword(s):  
Cell Differentiation ◽  
Nitrogen Sources ◽  
Oxygenic Photosynthesis ◽  
Promoter Regions ◽  
Independent Manner ◽  
Vegetative Cells ◽  
Heterocyst Differentiation ◽  
Safety Devices ◽  
Unique Cell ◽  
Pcc 7120

AbstractCyanobacteria are monophyletic organisms that perform oxygenic photosynthesis. While they exhibit great diversity, they have a common set of genes. However, the essentiality of them for viability has hampered the elucidation of their functions. One example of the genes is cyabrB1 encoding a transcriptional regulator. In the present study, we investigated the function of cyabrB1 in heterocyst-forming cyanobacterium Anabaena sp. PCC 7120 through CRISPR interference, a method we recently utilized for the photosynthetic production of a useful chemical in the strain. Conditional knockdown of cyabrB1 in the presence of nitrate resulted in formation of heterocysts. Two genes, hetP and hepA, which are required for heterocyst formation, were up-regulated by cyabrB1 knockdown in the presence of combined nitrogen sources. The genes are known to be induced by HetR, a master regulator of heterocyst formation. hetR was not induced by cyabrB1 knockdown. hetP and hepA were repressed by direct binding of cyAbrB1 to their promoter regions in a HetR-independent manner. In addition, the over-expression of cyabrB1 abolished heterocyst formation upon nitrogen depletion. Also, knockout of cyabrB2, a paralogue gene of cyabrB1, in addition to cyabrB1 knockdown, enhanced heterocyst formation in the presence of nitrate, suggesting functional redundancy of cyAbrB proteins. We propose that a balance between amounts of HetR and cyAbrB1 is a key factor influencing heterocyst differentiation during nitrogen step-down. cyAbrB proteins are essential safety devices inhibiting heterocyst differentiation.ImportanceSpore formation in Bacillus subtilis and Streptomyces represents non-terminal differentiation and has been extensively studied as models of prokaryotic cell differentiation. In the two organisms, many cells differentiate simultaneously, and the differentiation is governed by a network in which one regulator stands at the top. Differentiation of heterocysts in Anabaena sp. PCC 7120 has also been extensively studied. The differentiation is unique because it is terminal and only 5-10% vegetative cells differentiate into heterocysts. In the present study, we identified cyAbrB1 as a repressor of two genes that are essential for heterocyst formation, hetP and hepA, independent of HetR, which is a master activator for heterocyst differentiation. The finding is reasonable for unique cell differentiation of Anabaena because cyAbrB1 could suppress heterocyst differentiation tightly in vegetative cells, while only cells in which HetR is over-expressed could differentiate into heterocysts.

scholarly journals c-di-GMP Homeostasis Is Critical for Heterocyst Development in Anabaena sp. PCC 7120

2021 ◽  
Vol 12 ◽  
Author(s):  
Min Huang ◽  
Ju-Yuan Zhang ◽  
Xiaoli Zeng ◽  
Cheng-Cai Zhang
Keyword(s):  
Nitrogen Starvation ◽  
Filamentous Cyanobacterium ◽  
Nitrogen Deprivation ◽  
Heterocyst Differentiation ◽  
Combined Nitrogen ◽  
Heterocyst Frequency ◽  
Genes Encoding ◽  
Anabaena Sp ◽  
Opposing Effects ◽  
Pcc 7120

c-di-GMP is a ubiquitous bacterial signal regulating various physiological process. Anabaena PCC 7120 (Anabaena) is a filamentous cyanobacterium able to form regularly-spaced heterocysts for nitrogen fixation, in response to combined-nitrogen deprivation in 24h. Anabaena possesses 16 genes encoding proteins for c-di-GMP metabolism, and their functions are poorly characterized, except all2874 (cdgS) whose deletion causes a decrease in heterocyst frequency 48h after nitrogen starvation. We demonstrated here that c-di-GMP levels increased significantly in Anabaena after combined-nitrogen starvation. By inactivating each of the 16 genes, we found that the deletion of all1175 (cdgSH) led to an increase of heterocyst frequency 24h after nitrogen stepdown. A double mutant ΔcdgSHΔcdgS had an additive effect over the single mutants in regulating heterocyst frequency, indicating that the two genes acted at different time points for heterocyst spacing. Biochemical and genetic data further showed that the functions of CdgSH and CdgS in the setup or maintenance of heterocyst frequency depended on their opposing effects on the intracellular levels of c-di-GMP. Finally, we demonstrated that heterocyst differentiation was completely inhibited when c-di-GMP levels became too high or too low. Together, these results indicate that the homeostasis of c-di-GMP level is important for heterocyst differentiation in Anabaena.

scholarly journals Functional Overlap ofhetPandhetZin Regulation of Heterocyst Differentiation inAnabaenasp. Strain PCC 7120

2018 ◽  
Vol 200 (9) ◽  
pp. e00707-17 ◽  
Author(s):  
He Zhang ◽  
Shuai Wang ◽  
Yali Wang ◽  
Xudong Xu
Keyword(s):  
Nitrogenase Activity ◽  
Terrestrial Ecosystems ◽  
Heterocyst Differentiation ◽  
Content Type ◽  
Reverse Transcription Quantitative Pcr ◽  
Dependent Cell ◽  
Major Factors ◽  
Pcc 7120 ◽  
Relationship Of

ABSTRACTHetR plays a key role in regulation of heterocyst differentiation and patterning inAnabaena. It directly regulates genes involved in heterocyst differentiation (such ashetPandhetZ), genes involved in pattern formation (patA), and many others. In this study, we investigated the functional relationship ofhetPandhetZand their role in HetR-dependent cell differentiation. Coexpression ofhetPandhetZfrom the promoter ofntcA, which encodes the global nitrogen regulator, enabled ahetRmutant to form heterocysts with low aerobic nitrogenase activity. Overexpression ofhetZrestored heterocyst differentiation in ahetPmutant and vice versa. Overexpression ofhetRrestored heterocyst formation in either ahetPor ahetZmutant but not in ahetZ hetPdouble mutant. The functional overlap ofhetPandhetZwas further confirmed by reverse transcription-quantitative PCR (RT-qPCR) and transcriptomic analyses of their effects on gene expression. In addition, yeast two-hybrid and pulldown assays showed the interaction of HetZ with HetR. HetP and HetZ are proposed as the two major factors that control heterocyst formation in response to upregulation ofhetR.IMPORTANCEHeterocyst-forming cyanobacteria contribute significantly to N2fixation in marine, freshwater, and terrestrial ecosystems. Formation of heterocysts enables this group of cyanobacteria to fix N2efficiently under aerobic conditions. HetR, HetP, and HetZ are among the most important factors involved in heterocyst differentiation. We present evidence for the functional overlap ofhetPandhetZand for the key role of the HetR-HetP/HetZ circuit in regulation of heterocyst differentiation. The regulatory mechanism based on HetR, HetP, and HetZ is probably conserved in all heterocyst-forming cyanobacteria.

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