Are you looking for read ebook online? Search for your book and save it on your Kindle device, PC, phones or tablets. Download Molecular Genetic Approaches Towards The Understanding Of Heterocyst Differentiation And Pattern Formation In The Cyanobacterium Anabaena Sp PDF full book. Access full book title Molecular Genetic Approaches Towards The Understanding Of Heterocyst Differentiation And Pattern Formation In The Cyanobacterium Anabaena Sp.
| Author | : Yuping Cai |
| Publisher | : |
| Total Pages | : 372 |
| Release | : 1991 |
| Genre | : Anabaena |
| ISBN | : |
| Author | : Pritty B. Borthakur |
| Publisher | : |
| Total Pages | : 194 |
| Release | : 2008 |
| Genre | : Anabaena |
| ISBN | : |
The goal of this research was to understand regulation of heterocyst differentiation in Anabaena sp. strain PCC 7120 by characterizing regulatory genes for heterocyst formation and their mutants. Anabaena is a filamentous cyanobacterium that forms specialized cells for nitrogen fixation, called heterocysts, which differentiate from vegetative cells at intervals of 10--12 cells. Two genes, patS and hetN, are known to suppress the differentiation of vegetative cells into heterocysts for establishing a de novo pattern and maintaining a pattern of heterocysts along the filament. A mutant, UHM100, was created to study the function of both genes by deleting patS and making expression of hetN conditional. This study has established that PatS and HetN are members of two separate heterocyst suppression pathways. In absence of nitrogen, inactivation of both patS and hetN increases heterocyst differentiation to nearly 100%, giving rise to a phenotype called 'multiple contiguous heterocysts' (Mch). UHM100 has an Mch phenotype even in the presence of combined nitrogen, which usually suppresses heterocyst differentiation. In absence of both patS and hetN, the expression of hetR, a master regulator of heterocyst differentiation, was observed in ~55% cells and was asynchronous. The distribution of heterocysts next to a vegetative cell in UHM 100 was found to be nonrandom. These results suggest that besides PatS and HetN, there are other factors that influence pattern formation in Anabaena PCC 7120. A heterocyst-deficient (Hef) spontaneous mutant, NSM6, was isolated from UHM 100. A novel gene, alr9018, from the Anabaena Epsilon plasmid complemented NSM6 and restored the Mch phenotype of this mutant. 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. This is the first report showing that the Epsilon plasmid of Anabaena PCC 7120 contains genes involved in heterocyst differentiation. Expression of alr9018 was observed in both vegetative cells and heterocysts. Similar to alr9018, hetR could also restore the Mch phenotype in NSM6, suggesting functional similarity between a1r9018 and hetR. The Alr9018 protein contains an NTPase domain, which is a characteristic of proteins involved in signal transduction.
| Author | : Rodrigo Andres Mella Herrera |
| Publisher | : |
| Total Pages | : |
| Release | : 2010 |
| Genre | : |
| ISBN | : |
Many multicellular cyanobacteria produce specialized nitrogen-fixing heterocysts. During diazotrophic growth of the model organism Anabaena (Nostoc) sp. strain PCC 7120, a regulated developmental pattern of single heterocysts separated by about 10 to 20 photosynthetic vegetative cells is maintained along filaments. Heterocyst structure and metabolic activity function to accommodate the oxygen-sensitive process of nitrogen fixation. This dissertation focuses on my research on heterocyst development, including morphogenesis, transport of molecules between cells in a filament, differential gene expression, and pattern formation. We using microarray experiments we found that conR (all0187) gene is necessary for normal septum-formation of vegetative cells, diazotrophic grow, and heterocyst morphogenesis. In our studies we characterized the expression of sigma factors genes in Anabaena PCC 7120 during heterocyst differentiation, and we found that the expression of sigC, sigG and sigE is localized primarily in heterocysts. Expression studies using sigE mutant showed that nifH is under the control of this specific sigma factor.
| Author | : Todd Alan Black |
| Publisher | : |
| Total Pages | : 346 |
| Release | : 1993 |
| Genre | : Anabaena |
| ISBN | : |
| Author | : D.A. Bryant |
| Publisher | : Springer |
| Total Pages | : 916 |
| Release | : 1995-02-28 |
| Genre | : Science |
| ISBN | : 9780792332220 |
The Molecular Biology of Cyanobacteria summarizes more than a decade of progress in analyzing the taxonomy, biochemistry, physiology, cellular differentiation and developmental biology of cyanobacteria by modern molecular methods, especially molecular genetics. During this period cyanobacterial molecular biologists have been `studying those things that cyanobacteria do well', and they have made cyanobacteria the organisms of choice for detailed molecular analyses of oxygenic photosynthesis. Part 1 contains chapters describing the molecular evolution and taxonomy of the cyanobacteria, as well as chapters describing cyanelles and the origins of algal and higher plant chloroplasts. Also included are chapters describing the picoplanktonic, oceanic cyanobacteria and prochlorophytes, `the other cyanobacteria'. Part 2 is devoted to a detailed description of structural and functional aspects of the cyanobacterial photosynthetic apparatus. Included are chapters on thylakoid membrane organization, phycobiliproteins, and phycobilisomes, Photosystem I, Photosystem II, the cytochrome b6f complex, ATP synthase, and soluble electron carriers associated with photosynthetic electron transport. Structure, as it relates to biological function, is heavily emphasized in this portion of the book. Part 3 describes other important biochemical processes, including respiration, carbon metabolism, inorganic carbon uptake and concentration, nitrogen metabolism, tetrapyrrole biosynthesis, and carotenoid biosynthesis. Part 4 describes the cyanobacterial genetic systems and gene regulatory phenomena in these organisms. Emphasis is placed on responses to environmental stimuli, such as light intensity, light wavelength, temperature, and nutrient availability. Cellular differentiation and development phenomena, including the formation of heterocysts for nitrogen fixation and hormogonia for dispersal of organisms in the environment, are described. The book comprises 28 chapters written by leading experts from Europe, Israel, Japan, and the United States. The book is intended for graduate students and researchers in the fields of photosynthesis, microbiology, plant molecular biology, biochemistry, and biotechnology.
| Author | : |
| Publisher | : |
| Total Pages | : 12 |
| Release | : 2015 |
| Genre | : |
| ISBN | : |
Heterocysts are specialized cells that establish a physiologically low oxygen concentration; they function as the sites of oxygen-sensitive nitrogen fixation and hydrogen metabolism in certain filamentous cyanobacteria. They are present at a frequency of less than 10% of the cells and singly in a nonrandom spacing pattern in the filaments. The extent of differential gene expression during heterocyst differentiation was defined by DNA microarray analysis in wild type and mutant cultures of Nostoc punctiforme. The results in wild-type cultures identified two groups of genes; approximately 440 that are unique to heterocyst formation and function, and 500 that respond positively and negatively to the transient stress of nitrogen starvation. Nitrogen fixation is initiated within 24 h after induction, but the cultures require another 24 h before growth is reinitiated. Microarray analyses were conducted on strains with altered expression of three genes that regulate the presence and spacing of heterocysts in the filaments; loss of function or over expression of these genes increases the heterocyst frequency 2 to 3 fold compared to the wild-type. Mutations in the genes hetR and hetF result in the inability to differentiate heterocysts, whereas over expression of each gene individually yields multiple contiguous heterocysts at sites in the filaments; they are positive regulatory elements. Mutation of the gene patN results in an increase in heterocysts frequency, but, in this case, the heterocysts are singly spaced in the filaments with a decrease in the number of vegetative cells in the interval between heterocysts; this is a negative regulatory element. However, over expression of patN resulted in the wild-type heterocyst frequency and spacing pattern. Microarray results indicated HetR and HetF influence the transcription of a common set of about 395 genes, as well as about 350 genes unique to each protein. HetR is known to be a transcriptional regulator and HetF is predicted to be a protease, perhaps operating thorough stability of HetR; thus, the influence of HetF on transcription of a unique set of genes was unanticipated. These two proteins are also found in non-heterocyst-forming filamentous cyanobacteria and the results have implications on their other physiological role(s). The PatN protein is unique to heterocyst-forming cyanobacteria. Cytological analysis indicated PatN is present in only one of the two daughter cells following division, but is present in both cell less than 8 h after division. Microarray analysis indicated only five genes were differentially transcribed in the patN mutant compared to the wild type; three up-regulated genes that are known to influence heterocyst differentiation and two down-regulated genes that have an unassigned function. Mutational analyses indicted the two down-regulated genes do not have a distinct role in heterocyst differentiation. Thus, PatN only indirectly impacts transcription. These databases provide lists of differentially transcribed genes involved in nitrogen starvation and cellular differentiation that can be mined for detailed genetic analysis of the regulation of heterocyst formation and function for subsequent photo-biohydrogen production.
| Author | : |
| Publisher | : Academic Press |
| Total Pages | : 409 |
| Release | : 2012-12-26 |
| Genre | : Science |
| ISBN | : 0123946034 |
Advances in Botanical Research publishes in-depth and up-to-date reviews on a wide range of topics in plant sciences. The series features a wide range of reviews by recognized experts on all aspects of plant genetics, biochemistry, cell biology, molecular biology, physiology and ecology. This thematic volume features reviews on The Genomics of Cyanobacteria. Chapters by internationally renowned researchers share the most up-to-date knowledge on cyanobacteria Even if you have no previous background in the subject, the book's clear language and illustrations tell you what you need to know about the biology and genomics of cyanobacteria and it highlights important directions for future research An essential book for students and researchers
| Author | : T. A. Sarma |
| Publisher | : CRC Press |
| Total Pages | : 814 |
| Release | : 2012-12-18 |
| Genre | : Science |
| ISBN | : 1578088003 |
This handbook acquaints readers with the exciting developments in various areas of cyanobacterial research in the backdrop of the publication of complete genome sequence of the cyanobacterium Synechocystis sp. strain PCC 6803 in 1996. It begins with a summary of the current knowledge on the taxonomy, phylogeny and evolution of cyanobacteria followed by the sequenced genomes, differentiation of akinetes and heterocyst. The book considers mechanisms of cellular movements (gliding, swimming and twitching motions) exhibited by various cyanobacteria in order to adjust to their environmental niches and the operation of the circadian rhythms. It covers cyanobacterial symbiosis, cyanophages and cyanobacterial toxins, followed by a discussion on stress responses (salinity, temperature, desiccation and oxidation). A comprehensive account on the developments in all these spheres has been presented in a lucid style with the required background information, molecular techniques employed and models proposed. This handbook constitutes the first such book written by a single author at a level and depth for graduate and research students in botany and microbiology.
| Author | : N. G. Carr |
| Publisher | : Univ of California Press |
| Total Pages | : 708 |
| Release | : 1982-01-01 |
| Genre | : Science |
| ISBN | : 9780520047174 |
| Author | : Ritu Garg |
| Publisher | : |
| Total Pages | : 0 |
| Release | : 2022 |
| Genre | : |
| ISBN | : |
The planktonic freshwater filamentous cyanobacterium Anabaena variabilis ATCC 29413 (syn. Trichormus variabilis) grows as filaments of hundreds of cells and is capable of differentiating nitrogen fixing heterocysts, motile hormogonia and dormant akinetes from vegetative cells in response to different stress conditions. Under conditions of nitrogen limitation, heterocysts form in a semi-regular pattern and provide the filaments with organic nitrogen by fixing N2. Akinetes are transient spore-like cells enabling these bacteria to withstand harsh environmental conditions. When suitable growth conditions are available, the akinetes can germinate and produce new vegetative filaments, thereby providing cyanobacteria with a means of survival in changing habitats. Heterocysts and akinetes are characterized by the presence of a thick multilayered envelope, including an outermost polysaccharide and an inner glycolipid layer. Until now, the role of a glycolipid layer, which reduces the entry of oxygen into the heterocysts for the maintenance of a microoxic environment and nitrogen fixation, was unknown in spore-like akinetes. Therefore, in this work, the function of the gene Ava_2595 in A. variabilis, which is homolog to the known hglB gene, that encodes a putative polyketide synthase involved in heterocyst glycolipid synthesis in Anabaena sp. PCC 7120, a species which does not form akinetes, was elucidated. The hglB mutant was created and its phenotype was characterized and further investigated for the functionality of heterocysts and akinetes. This work revealed that the hglB mutant strain formed aberrant heterocysts and akinete-like cells, in which the specific glycolipid layers were absent demonstrating the requirement of HglB in glycolipid layer formation in both heterocyst and akinete envelope. Consequently, the mutant was unable to fix N2 under aerobic condition and to grow diazotrophically. This study also confirmed that both cell types use a glycolipid of identical chemical composition in their special envelopes. Furthermore, we unraveled the role of the glycolipids in protecting the akinetes against harsh conditions, like freezing, desiccation, oxidative stress and lytic enzymes. Severely reduced tolerance to stress conditions was exhibited by the akinetes lacking the glycolipids but under standard conditions, they could germinate normally. Our study established the dual role of the glycolipid layer in fulfilling different functions in the evolutionary-related specialized cells of cyanobacteria and indicated the existence of a common biosynthetic pathway for glycolipid synthesis in heterocysts and akinetes involving the same gene hglB. Akinetes accumulate large quantities of cytoplasmic reserve products, mainly glycogen and the nitrogen storage polymer cyanophycin during their differentiation. In this work, the physiological function of cyanophycin in akinete differentiation and germination was investigated which showed that the cyanophycin production is not required for these cellular processes. This study also summarized the significant morphological and physiological changes that occur during formation and germination of the akinetes in A. variabilis ATCC 29413. Further analysis of changes occurring during akinete formation and germination using scanning electron microscopy (SEM) found that the mature akinetes have a wrinkled envelope and during germination, the surface of the envelope smoothens upon increase in the cell size, and finally, the akinete envelope ruptures to release the short emerging filament. Also, in this work, the akinete envelope architecture of different layers, the exopolysaccharide and glycolipid layer, could be visualized and showed that this multilayered envelope helps to withstand the osmotic stress and to maintain the structural integrity. Finally, we demonstrated that the intercellular communication decreased during akinete formation as compared to the vegetative cells. In contrast, the cell communication was restored in freshly germinating filaments.
