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 overexpressed could differentiate into heterocysts. The goal of this research was to understand regulation of heterocyst differentiation in anabaena sp. In fact, several genes related to peptidoglycan metabolism are transcribed from hetrdependent, heterocyst speci. Rearrangement of nif genes during cyanobacterial heterocyst differentiation by r. Growth, heterocyst differentiation and nitrogenase activity. The genome of the circular chromosome of the pcc 7120 strain of anabaena has. In the present study, we investigated the functions of sigma factors. Characterization of a gene controlling heterocyst differentiation in the cyanobacterium anabaena 7120 william j.
Heterocysts are microaerobic, nfixing cells that form in a patterned array within oproducing filamentous cyanobacteria. Ntg has been observed to inhibit the heterocyst differentiation by affecting the enzyme level. The deposition of the envelope is the first visible sign of differentiation and can be observed by staining with alcian blue b. The results of the prediction were enriched in genes encoding outer membrane proteins and enzymes related to peptidoglycan. A gene cluster that regulates both heterocyst differentiation. Carr department of biochemistry, university of liverpool, p. Expression of hetr is upregulated by nitrogen deprivation, and its upregulation depends on ntca. The impact of calcium signals in virtually all cells has led to the study of their role in prokaryotic organisms as stress response modulators. Anabaena 7120 mutant 216 fails to differentiate heterocyst.
The time required for differentiation of a vegetative cell into a heterocyst is approximately the same as the division time of the vegetative. Structure of transcription factor hetr required for. Heterocyst differentiation and pattern formation in. Heterocyst differentiation in the cyanobacterium anabaena cylindrica is initiated by the removal of fixed nitrogen from the medium. Heterocyst differentiation and nitrogen fixation in the. Pcc 7120 at 3, 8 or 24 h after nitrogen stepdown, reevaluated in and the transition to heterocyst differentiation or hormogonia formation in nostoc punctiforme seven timepoints from 0. Fura influences heterocyst differentiation in anabaena sp. Heterocyst pattern formation controlled by a diffusible. Upon the depletion of combined nitrogen, 5 to 10% of vegetative cells that perform oxygenic photosynthesis differentiate into heterocysts. Control of phycobiliprotein proteolysis and heterocyst. Mutation of the murc and murb genes impairs heterocyst differentiation in anabaena sp. Robert tabita2 department of microbiology, the university of texas at austin, austin, texas 78712, and fport aransas marine laboratory, the university of texas at.
The hetn gene, when present on a multicopy plasmid, is able to suppress heterocyst differentiation. While heterocyst development has been shown to require proper peptidoglycan remodeling, the role of peptidoglycan synthesis has remained unclear. Growth, heterocyst differentiation and nitrogenase. Transcriptional regulation of heterocyst differentiation in.
Growth, heterocyst differentiation and nitrogenase activity in the cyanobacteria anabaena variahilis and anabaena cylindrica in response to molybdenum and vanadium by e. The transcript levels of sigc, sige, and sigg increased during heterocyst differentiation, while sigj. Expression of the anabaena hetr gene from a copper. Identification and characterization of a gene controlling heterocyst differentiation in the cyanobacterium anabaena 7120. Nitrogen starvation induces the differentiation of n2fixing heterocysts in the filamentous cyanobacterium anabaena sp. Anabaena is a filamentous cyanobacterium that forms specialized cells for nitrogen fixation, called heterocysts, which differentiate from vegetative. In contrast, in calothrix brevissima, ammonium inhibited heterocyst differentiation and loss of polarity followed as a consequence. Pats influences the heterocyst patterning by inhibiting heterocyst differentiation when a group of differentiating cells come together to form a pro heterocyst immature heterocyst. Rearrangement of nif genes during cyanobacterial heterocyst. Hetn, a putative ketoacyl reductase, is required for heterocyst pattern maintenance in the filamentous cyanobacterium anabaena sp. Pcc 7120, fura is a global transcriptional regulator whose expression is strongly induced by ntca in proheterocysts and remains stably expressed in mature heterocysts. Buikema and robert haselkorn department of molecular genetics and cell biology, university of chicago, chicago, illinois 60637 usa anabaena 7120 mutant 216 fails to differentiate heterocysts. Pcc 7120, heterocysts are regularly intercalated among vegetative cells, and are usually sep arated by 1020 vegetative.
Overexpression of a 54basepair gene, pats, blocked heterocyst differentiation in anabaena sp. There are several instances of cellular differentiation in prokaryotes, including the formation of spores in bacillus, the fruiting bodies of myxococcus, and the stalked cells of caulobacter. Increased expression of the hetr gene is seen in developing and mature heterocysts in response to fixed nitrogen limitation. A bioinformatic prediction to identify possible interactions of yfr1 with mrnas was carried out by using the sequences of yfr1 from several heterocyst forming strains, including nostoc sp.
During heterocyst differentiation, expression of approximately 500 genes is upregulated with spatiotemporal regulation. We mapped four likely transcriptional start sites for hetr and identified a specific transcript that is positively autoregulated. Pdf fura influences heterocyst differentiation in anabaena. Heterocyst differentiation in anabaena ambigua sciencedirect. Characterization of hetn, a protein involved in heterocyst. Regulation of co2 on heterocyst differentiation and nitrate. Structural features of heterocysts can be predicted from consideration of their physiology. A novel genome rearrangement involved in heterocyst differentiation of the cyanobacterium anabaena sp. They found that cell division was asymmetrical and heterocysts developed only from the smaller daughter cell of a division arising. The vegetative cells of particular filamentous cyanobacteria can differentiate into three different cell types. The heterocystspecific nsir1 small rna is an early marker of.
Its specialized nitrogenfixing cells, called heterocysts, are semiregularly distributed along filaments. Pcc 7120 produces specialized, terminally differentiated cells called heterocysts that are the sites of nitrogen fixation. Heterocyst differentiation and tryptophan metabolism in the. The recent sequencing of the genome of anabaena sp. Oshiro,a min joo kim,a benjamin philmus,b loralyn m. Heterocyst differentiation and nitrogen fixation in anabaena. Request pdf transcriptional regulation of heterocyst differentiation in anabaena sp. Incubation of cultures for periods of up to 12 h immediately prior to or following removal of fixed nitrogen, at a light intensity 500 mi einsteins cm2 s1. Rearrangement of nitrogen fixation genes during heterocyst. Matveyev department of botany, stockholm university, s106 91 stockholm, sweden. Heterocyst differentiation in anabaena cylindrica filaments grown with air was reversed by the addition of 4 mm ammonium chloride up to 8 to 10 h after induction. Hetr plays a key role in regulation of heterocyst differentiation and patterning in anabaena. Pata patterns the heterocysts along the filaments, and it is also important for cell division.
Changes in the expression of sigma factor genes on the chromosome of anabaena pcc 7120 during heterocyst differentiation were determined by qrtpcr figure 1a. Investigation of gene regulation during heterocyst differentiation with a replicative plasmid containing gfp reporter gene. In anabaena, heterocyst differentiation is accompanied by rearrangement of some nitrogen fixation genes. However, apparently no such effect was encountered in the rivularian alga gloeotrichia ghosei singh and tiwari, 1970. The process leads to the differentiation of another heterocyst near the center of the newly created chain, to conserve the regular spacing and frequency. When cultured in the presence of a combined nitrogen source, usually in the form of nitrate or ammonium, all cells along the filament perform photosynthesis.
Heterocysts are specialized cells for nitrogen fixation, and its differentiation is triggered by limitation of combined nitrogen in the medium. Heterocyst differentiation and cell division in the. A calcium signal is involved in heterocyst differentiation. Frah is required for reorganization of intracellular. Heterocyst differentiation in the filamentous cyanobacterium anabaena pcc 7120 requires a functional hetr gene. Cyanobacteria use two mechanisms to separate these activities. Heterocyst and akinete differentiation in cyanobacteria.
Regulation by hetc of genes required for heterocyst. Characterization of a gene controlling heterocyst differentiation in. A calcium signal is involved in heterocyst differentiation in the cyanobacterium anabaena sp. Effect on heterocyst differentiation of nitrogen fixation in vegetative. Compared to ntca, the global nitrogen regulator, hetr is more specifically required for heterocyst differentiation, and overexpression of hetr leads to production of multiple contiguous heterocysts.
It directly regulates genes involved in heterocyst differentiation such as hetp and hetz, genes involved in pattern formation pata, and many others. Little is known about the biochemical properties of hetn. Regulation of co2 on heterocyst differentiation and. After that time certain cells were irreversibly committed to differentiation, and addition of fixed nitrogen did not repress heterocyst differentiation 1. Oshiro, a min joo kim, a benjamin philmus, b loralyn m. Heterocysts inhibit the differentiation of adjacent vegetative cells, and as the vegetative interval lengthens new heterocysts form mid way between existing ones wilcox et al. Functional overlap of hetp and hetz in regulation of. A sitespecific recombination between an 11 basepair direct repeat sequence flanking the. Thus, the heterocyst spacing pattern is maintained during. Heterocyst differentiation and pattern formation in cyanobacteria.
Formation and maintenance of nitrogenfixing cell patterns. In the process of differentiation from a vegetative cell to a heterocyst, cell division is stopped, an. This provides a model for the study of gene differentiation in the formation of heterocysts and akinetes. Mulligan department of molecular genetics and cell biology, the university of chicago, illinois 60637, u. We cloned the promoter regions of hetr, hetc, hepb, hepk, devb, hgld, hgle alr5351 see reference 30, hetn, pats, pata, patb, xisa, nifb, coxbii, and rbcl into the shuttle vector phb912, respectively, introduced the resulting plasmids into anabaena sp. Peter wolk3,4 and xudong xu1 1the state key laboratory of freshwater ecology and biotechnology, institute of hydrobiology, chinese. Mutation of the murc and murb genes impairs heterocyst. Heterocyst development takes about 24 h to complete, when approximately 10% of. Jul 23, 2010 the genome of anabaena variabilis atcc 294 has also been completed.
By giving uv exposure to the alga it has been found out that 12 h. Many filamentous cyanobacteria grow as multicellular organisms that show a developmental pattern of single nitrogenfixing heterocysts separated by approximately 10 vegetative cells. Wolkhetc, a gene coding for a protein similar to bacterial abc protein exporters, is involved in early regulation of heterocyst differentiation in anabaena sp. Box 147, liverpool l69 3bx, england summary heterocyst differentiatio in th cyanobacteriuen m anabaena cylindrica is initiate bd. In the present study, we investigated the functions of sigma factors of rna polymerase in. Yfr1 is a strictly conserved small rna in cyanobacteria.
Growth, heterocyst differentiation and nitrogenase activity in the cyanobacteria anabaena variabilis and anabaena cylindrica in response to molybdenum and vanadium author. Unlike most other strains of anabaena, anabaena sp. Increased expression of the hetr gene is seen in developing and mature heterocysts. Two lines of evidence suggest that ntca is the main 2. Heterocysts are terminally differentiated cells of some filamentous cyanobacteria that fix nitrogen for the entire filament under oxic growth conditions. Pcc 7120, a filamentous cyanobacterium, being capable of heterocyst differentiation and aerobic n 2. Effect on heterocyst differentiation of nitrogen fixation. One rearrangement involves the nitrogenfixation genes nifh, nifd. Filament fragmentation and the regression of developing heterocysts 20.
Genebygene microarrays have been used to analyze the response to nitrogen stress in anabaena sp. In anabaena 7120, heterocysts are spaced approximately 1020 cells apart, depending on growth conditions. Cell selection during differentiation and pattern formation 20 a. Anabaena provides a model for the study of gene differentiation in the formation of heterocysts. May 01, 2018 based on the studies in anabaena 7120, ntca and hetr have been shown to be the two key regulators in control of heterocyst differentiation 8, 9. These specialized cells occur singly at regular intervals within filaments of vegetative cells. In the present study, overexpression of fura partially suppressed heterocyst differentiation by impairing morphogenesis at an early stage. Cell differentiation and pigment composition in anabaena cylindrica. Formation and maintenance of nitrogen fixing cell patterns in. Anabaena 7120 mutant 216 fails to differentiate heterocysts. Heterocyst differentiation in the cyanobacterium anabaena sp. In the filamentous, heterocyst forming cyanobacteria, two different cell types, the co2fixing vegetative cells and the n2fixing heterocysts, exchange nutrients and regulators for diazotrophic growth.
N2fixing heterocysts, sporelike akinetes, and motile hormogonia. Og sensor involved in the initiation of heterocyst differentiation. Regulation of genes involved in heterocyst differentiation in. Since h 2 is produced only in the heterocysts, understanding heterocyst differentiation is crucial to the improvement of photobiological h 2 production. Anabaena is a filamentous cyanobacterium that produces specialized cells, called. Heterocyst differentiation is integrated into a series of physiological responses that take place. A gene cluster that regulates both heterocyst differentiation and pattern formation in anabaena sp. Heterocyst spacing 18 a patterns of heterocyst differentiation 18 b genes involved in heterocyst spacing 18 c disruption of heterocyst pattern 18. The heterocystspecific nsir1 small rna is an early marker. We show here that the sequence of this fragment contains a single open reading frame hetr, encoding a 299aminoacid protein. Pcc7120, from here on anabaena 7120, differentiate heterocysts, a specialized cell type devoted to n 2. Pcc 7120 article pdf available in febs letters 58716 july 20 with 117 reads how we measure reads. A pats null mutant showed an increased frequency of. Transconjugants of anabaena pcc 7120 containing the cloned alr9018 gene fixed 50% more n2 than pcc 7120, suggesting that multiple copies of alr9018 enhance heterocyst development.
The genome of anabaena undergoes at least two specific developmentally regulated dna rearrangements during heterocyst differentiation. The maintenance and assembly of the outer membrane rely on proteins of the omp85 family. Regulation of genes involved in heterocyst differentiation. The transcript levels of sigc, sige, and sigg increased during heterocyst differentiation, while sigj was downregulated. The integrity of the cell wall and its remodeling during. This is the first report showing that the epsilon plasmid of anabaena pcc 7120 contains genes involved in heterocyst differentiation. In this study, we investigated the functional relationship of hetp and hetz and their role in hetrdependent cell differentiation. Expression of the anabaena hetr gene from a copperregulated.