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Lown, Felicity Jane. "Respiratory mutants of chlamydomonas." Thesis, University College London (University of London), 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271247.
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Matika, Andreas. "Die Regulation der Photosynthese durch Proteinphosphatasen in Chlamydomonas reinhardtii." [S.l. : s.n.], 1999. http://deposit.ddb.de/cgi-bin/dokserv?idn=959084630.
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Chan, Chun Tat. "Characterization of CrMRP2 and CrPMA2 genes involved in heavy metals resistances in chlamydomonas reinhardtii /." View abstract or full-text, 2007. http://library.ust.hk/cgi/db/thesis.pl?BIOL%202007%20CHAN.
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Koblenz, Bettina. "Centrin-RNAi in Chlamydomonas reinhardtii." [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=972406301.
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Ligr, Martin. "Ubiquitin metabolism in Chlamydomonas reinhardtii." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1995. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/MQ33407.pdf.
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Kulsam, Ali. "Photosystem I in 'Chlamydomonas reinardtii'." Thesis, University College London (University of London), 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.405499.
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Ali, K. "Photosystem I in Chlamydomonas reinhardtii." Thesis, University College London (University of London), 2004. http://discovery.ucl.ac.uk/1446558/.
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Photosystem I (PSI) catalyses the light driven electron transfer from plastocyanin/ cytochrome c6 on the luminal side of the thylakoid membrane to ferredoxin/ flavodoxin at the stromal side via a chain of electron carriers. PSI is a multi-protein membrane complex composed of a large number of polypeptide subunits, designated PsaA to PsaO. There are key differences in subunit composition between prokaryotic and eukaryotic PSI complexes. For example, PsaG, PsaH, PsaN and PsaO are all absent from cyanobacterial PSI. In eukaryotes the genes for the PSI subunits are distributed between the nuclear and chloroplast genomes. This thesis describes a series of molecular-genetic studies using the model photosynthetic eukaryote Chlamydomonas reinhardtii, aimed at understanding various aspects of the eukaryotic PSI. The nuclear gene encoding the PsaN subunit from C. reinhardtii was cloned and characterised. The psaN gene was shown to be present as a single copy in the genome and northern analysis indicated that the expression of this gene is light-induced. Antibodies were raised to the mature PsaN protein and attempts were made to down- regulate psaN gene expression using an RNA antisense approach. Several PSI mutants were investigated using western analysis. A mutant lacking PsaJ showed significantly reduced levels of PsaN protein accumulation, while a mutant lacking PsaF showed no detectable levels of PsaN, indicating that these two subunits may interact with PsaN on the lumenal side of the PSI complex. The role of the 22 ?-carotene molecules associated with the PSI complex was investigated. Molecular and biophysical analysis of a carotenoid deficient mutant established that the PSI complex is assembled and functional despite the loss of carotenoids and the PsaN protein from the complex. The crystal structure of cyanobacterial PSI reveals two possible electron transfer branches bound to the PsaA and PsaB subunits, which display a remarkable symmetry. However, a key difference is a tryptophan residue located between the PsaB-bound phylloquinone and the iron-sulphur centre Fx, which is not conserved in PsaA. The tryptophan residue was substituted with a glycine using site-directed mutagenesis. The mutant was unable to grow photoautotrophically and biophysical analysis revealed that electron transfer on the PsaB branch was partially blocked.
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Gangl, Doris. "Biotechnological exploitation of Chlamydomonas reinhardtii." Thesis, University of Kent, 2016. https://kar.kent.ac.uk/56648/.
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Microalgae have become increasingly important in the biotech sector and are currently exploited for their natural products. In recent years efforts have also been directed towards establishing them as production platforms for recombinant proteins. The aim of this thesis is to investigate the feasibility of Chlamydomonas reinhardtii as a production platform for highvalue products expressed in the chloroplast of the alga. A cytochrome P450 was introduced into the chloroplast of C. reinhardtii as a proof-of-concept study. The model enzyme CYP79A1 was successfully targeted into the chloroplast membranes and was found to be active. A bifunctional diterpene synthase, TPS4, was also expressed in the chloroplast of C. reinhardtii. TPS4 could be purified to homogeneity and is the largest enzyme expressed in the chloroplast to date. The two transgenic strains expressing CYP79A1 and TPS4 were investigated for their ability to withstand industrial growth conditions. The cell wall deficient strains were successfully cultivated in 100 L photobioreactors using a mixotrophic growth regime. They reached dry weights of 0.3 g/L and the expression of CYP79A1 and TPS4 was detected over the entire growth period. Taken together these data suggest that C. reinhardtii could be an attractive platform for recombinant protein production. Two enzymes with biotechnological relevance were expressed in the chloroplast of the alga and the transgenic cell wall deficient strains were successfully cultivated on a semi-industrial scale.
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Gallagher, Victoria Nicole. "Photosynthetic hydrogen production by Chlamydomonas reinhardtii." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 72 p, 2007. http://proquest.umi.com/pqdweb?did=1338926921&sid=3&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Smith, Annette Clare. "The transcriptional apparatus of Chlamydomonas chloroplasts." Thesis, University College London (University of London), 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368097.
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Kirchmayr, Anna. "Optimierung nukleärer Promotoren in Chlamydomonas reinhardtii." Doctoral thesis, Humboldt-Universität zu Berlin, Lebenswissenschaftliche Fakultät, 2015. http://dx.doi.org/10.18452/17391.
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Die einzellige Grünalge C. reinhardtii dient als Modellorganismus und ist aufgrund des GRAS-Status, des schnellen, kostengünstigen Wachstums und der Möglichkeit posttranslationaler Modifikationen im Kerngenom, als Expressionssystem für beispielsweise orale Impfstoffe sehr interessant. Herausforderungen sind die im Vergleich zu konventionell verwendeten Expressionssystemen sehr geringen Expressionsraten im Kerngenom. Daher sollten in dieser Arbeit neuartige, teils induzierbare, Promotorkonstrukte verwendet und mittels Luciferase-Reporter auf ihre Expressionssteigerung hin getestet werden. Zunächst wurden ausgewählte Promotoren des Chlorella-Virus-1 (PBCV-1) gewählt, diese führten allerdings zu keiner Expression. Außerdem wurden synthetische, aneinandergereihte Hitzeschockelemente mit dem endogenen RBCS2-Promotor fusioniert und die Expressionsraten analysiert. Dabei ergab sich bei der Kombination aus dem synthetischen Hitzeschockelement in achtfacher Wiederholung (HSE8x) mit RBCS2 nach der Hitzeinduktion eine Steigerung der Expressionsrate um das bis zu dreifache. Die Basalexpression war hierbei bei HSE1x-RBCS2 am höchsten und erreichte Expressionslevels, welche um das fünffache höher lagen als die Positivkontrolle HSP70A-RBCS2. Mittels Chromatinimmunopräzipitation mit dem Antikörper gegen HSF1 konnte gezeigt werden, dass eine Bindung an das synthetische Hitzeschockelement vorliegt und deshalb die Expression über die konventionelle Hitzeschockantwort in Chlamydomonas reinhardtii funktioniert. Im Gegensatz zur Luciferase benötigen Fluoreszenzproteine als Reporter kein Substrat. Infolge dieses Vorteils und der Möglichkeiten der FACS-Analyse und Fluoreszenzmikroskopie wurde tagRFP als neuer Reporter in C. reinhardtii etabliert. Die Erhöhung der Expressionsrate durch neue Promotorkombinationen und die Anwendung von tagRFP als neuen Fluoreszenzreporter bedeuten wichtige Schritte in der Etablierung von C.reinhardtii als Expressionssystem für Produkte in der Biotechnologie.The unicellular green alga C.reinhardtii which is used as a model organism could be an interesting expression system for oral vaccines. This is because the alga is generally regarded as safe, it shows fast growth rates and culturing is cheap. Furthermore it offers the possibility of posttranslational modifications. Challenges lie in the low expression rates in the nuclear genome when compared to other expression systems. Therefore the first step in this work was to test whether selected Chlorella virus PBCV-1 promoters, do lead to enhanced expression rates, but there was no detectable expression. Furthermore synthetic repeats of heat shock elements were used in combination with the endogenous RBCS2-promoter and analysed for expression rates via reporter measurements. The combination of synthetic heat shock elements in eightfold repeats in combination with RBCS2 enhanced expression rates of luciferase after heat shock up to threefold in comparison with the up to now strongest known promoter combination HSP70A-RBCS2. Basalexpression turned out to be best for the HSE1x-RBCS2 promoter and reached expression levels fivefold higher compared to HSP70A-RBCS2. To examine if the artificial heat shock elements (HSEs) are bound by the heat shock factor 1 in C. reinhardtii a ChIP assay with HSE8x-RBCS2 and the antibody of HSF1 of C. reinhardtii was done. It could be shown that HSF1 binds HSEs and therefore one can explain the heat shock inducibility of HSEs is regulated via the conserved heat shock response. In contrast to luciferase fluorescence reporters do not need substrate. Because of this advantage and the possibility of FACS analyses and fluorescence microscopy tagRFP was established as new reporter in C.reinhardtii. Enhancement of expression rates through new constitutive and inducible promoter combinations and the possible use of tagRFP as new fluorescence reporter are significant steps in establishing C.reinhardtii as expression system for products in biotechnology.
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Zhang, Yizhi. "Intrinsically disordered proteins in Chlamydomonas reinhardtii." Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0290/document.
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Les objectifs de cette thèse étaient d'apporter une percée conceptuelle pour une compréhension en profondeur des mécanismes moléculaires des protéines intrinsèquement désordonnées (IDPs) et de leurs rôles dans la physiologie cellulaire de Chlamydomonas reinhardtii. La combinaison d’approches expérimentale et bioinformatique m’a permis d’identifier 682 protéines thermorésistantes chez C. reinhardtii. Parmi celles-ci, 299 protéines sont systématiquement prédites comme potentielles IDP par quatre algorithmes de prédiction de désordre. Nos résultats indiquent que le pourcentage désordonné moyen de ces protéines prédites comme étant des IDPs est d'environ 20%, et la plupart d'entre elles (~70%) sont adressées à d'autres compartiments que la mitochondrie et le chloroplaste. Leur composition en acides aminés est biaisée par rapport à d'autres IDPs de la base de données de protéines désordonnées (DisProt). Ces IDPs potentielles jouent des fonctions moléculaires diverses, et 54% d'entre elles sont des cibles de phosphorylation.Notre travail a également augmenté l’état des connaissances sur l'adénylate kinase 3 (ADK3), une enzyme contenant une région intrinsèquement désordonnée (IDR). Cette enzyme a été isolée par notre approche globale pour caractériser les IDPs de l’algue verte. L’extension C-terminale désordonnée (CTE) de cette enzyme lui confère de nouvelles fonctions comme par exemple, la formation d’un complexe bi-enzymatique avec la glycéraldéhyde-3-phosphate déshydrogénase (GAPDH), la régulation (négative) de l'activité GAPDH avec le NADPH comme cofacteur, et le rôle de chaperon pour la GAPDH en la protégeant de la dénaturation par traitement thermique et de l’agrégationThe objectives of this work were to bring a conceptual breakthrough for an in-depth understanding of the molecular mechanisms of intrinsically disordered proteins (IDPs) and their roles in the cellular physiology of Chlamydomonas reinhardtii. Using experimental approaches, 682 heat-resistant proteins were identified as putative IDPs. Among them, 299 proteins were consistently predicted as IDPs by all four disordered predictors. The mean percentage of disordered residues content of these IDPs is about 20%, and most of them (~70%) are addressed to other compartments than mitochondrion and chloroplast. These newly identified IDPs from C. reinhardtii have a biased amino acid composition as regard to other IDPs from the Database of protein disorder (DisProt). Furthermore, they play diverse molecular functions, and 54% of them are the targets for phosphorylation. Our work also revealed more knowledge of the IDR-containing protein adenylate kinase 3 (ADK3) that was extracted by heat-treatment. Its disordered C-terminal extension (CTE) brought new functions to this protein. For instance, via its CTE, ADK3 can form a bi-enzyme complex with glyceraldehyde-3-phosphate dehydrogenase (GAPDH), down-regulates the NADPH-dependent GAPDH activity, and behaves as a chaperone for GAPDH against its aggregation and inactivation under heat-treatment
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Goho, Shaun. "The accumulation of variance in fitness in clonal populations of Chlamydomonas reinhardtii in normal and stressful environments /." Thesis, McGill University, 1997. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=27328.
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The work presented here investigates two basic properties of mutation rates in the unicellular chlorophyte Chlamydomonas reinhardtii. The first chapter is devoted to an investigation of the mutational heritability $ rm (V sb{M})$ of fitness in asexually propagated populations. This is the rate at which novel variation for fitness accumulates in a population. In two trials, values of $ rm V sb{M}$ = 4.5 and $4.7 times 10 sp{-3}$ of the environmental variance $ rm (V sb{E})$ were obtained. These values were at least an order of magnitude greater than estimates from other organisms of $ rm V sb{M}/V sb{E}$ for fitness or for quasineutral variation. The possibility that this was due to disruptive selection for types specialized for different parts of the culturing environment was investigated, and rejected. Other possible explanations, and future avenues for research, are discussed.The second chapter extends the investigation from normal culturing conditions into stressful ones. Specifically, it considers the hypothesis that C. reinhardtii might increase its mutation rate as a general response to environmental stress. Stressed lines were found to display reduced mean fitness and an increased variance of fitness after being returned to normal culturing conditions. This was interpreted as evidence for increased mutation rates in treated lines relative to controls. Possible mechanisms underlying this phenomenon are discussed, along with suggestions for further research.
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Chao, Vincent 1973. "Ecological and sexual divergence in experimental populations of Chlamydomonas." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=32982.
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Laboratory studies on speciation have revealed that selection must be disruptively applied on traits related to the mating system in order to produce deviations from random mating in experimental populations. One problem with these experiments, however, has been the complexity of the model organism used, most frequently Drosophila species. Due to the multi genic nature of the mating systems of such organisms, it has been difficult to obtain the necessary gene combinations that result in complete sexual isolation. In the present study, I have used a simple sexual organism, the unicellular green algae Chlamydomonas reinhardtii, as a model for ecological and sexual differentiation. Disruptive selection was applied on the flagella, by selecting simultaneously for photo taxis and mating, behaviours for which these organelles are of fundamental importance. An asymmetric response to selection for photo taxis and zygote production was obtained in populations selected for conditions at opposite ends of the environmental spectrum used, differentiating these two populations in both movement capacity and mating efficiency. These results are discussed in relation to previous experiments on speciation and to the implications of future experimental studies on the same subject.
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Ciol, Heloísa. "Septina de Chlamydomonas reinhardtii: estudos com foco em sua expressão e função." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/76/76132/tde-11092017-084455/.
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Septinas fazem parte de uma família de proteínas de ligação ao nucleotídeo guanina e já foram encontradas em diversos eucariontes, mas nunca em plantas. Essas proteínas têm sido descritas como atuantes na citocinese, estruturação celular e exocitose, mas pouco se conhece do seu modo de ação. Além disso, as septinas mostraram-se capazes de se polimerizar em heterofilamentos altamente organizados, a partir da interação com outras septinas, mas as referências à existência e funcionalidade de homofilamentos de septinas permanecem escassas e controversas. Este trabalho visou caracterizar a função da septina da alga unicelular Chlamydomonas reinhardtii, um eucarionte modelo que divergiu há muito de um ancestral comum a plantas e metazoários, e que possui uma única septina, diferente dos demais eucariontes estudados até o momento. Para tal, foram realizados ensaios de duplo híbrido para detecção de possíveis proteínas parceiras à septina de C. reinhardtii, além de análise de expressão gênica em diferentes pontos do ciclo celular por PCR quantitativo (qPCR), silenciamento gênico por micro-RNA artificial de interferência e imunolocalização por microscopia confocal. Os ensaios de duplo híbrido retornaram duas possíveis proteínas parceiras de interação à septina de Chalmydomonas reinhardtii (CrSept) – S-Adenosyl-Homocysteine-Hydrolase (CrSAHH) e Subtilase-like-Serino-Protease (esporangina) – ambas relacionada à estrutura flagelar. A interação entre CrSept e CrSAHH não foi validada através das técnicas de pulldown e crosslinking, porém, os experimentos de imunolocalização da proteína in situ mostraram uma grande concentração de CrSept na base flagelar durante as fases G0, e G1, com mudança no perfil de localização para o citoplasma durante as fases S e M do ciclo celular, evidenciando uma participação da septina na estrutura flagelar e não excluindo a possibilidade de uma interação in vivo entre CrSept e CrSAHH. Análises do nível de expressão gênica de CrSept mostraram uma tendência de maior expressão do gene da septina durante o período claro, com redução na fase escura do ciclo celular, resultados que se assemelham aos observados pela análise qualitativa, por western blot, da expressão da proteína ao longo do ciclo celular. Os experimentos de silenciamento gênico, por fim, mostraram um possível fenótipo relacionado à redução de mRNA de CrSept, não observado no grupo controle. Estes resultados mostram que a CrSept possui caráter estrutural na alga verde C. reinhardtii, podendo atuar como suporte para outras proteínas durante a fase de crescimento celular. Além disso, localizações pontuais por toda a célula durante a fase de divisão celular sugerem que a CrSept desempenha um importante papel na manutenção da estrutura celular para a conclusão da divisão celular.Septins belong to a family of proteins that bind guanine nucleotide and have been found in many eukaryotes, but never in plants. These proteins have been described in cytokinesis process, cell structure and exocytosis, but little is known about their way of action. Besides, septins are capable of polymerize in high organized heterofilaments when interacting with other septins, but references and functional studies of septins homofilaments remain controversial. This work aimed to characterize the function of the unique septin from the green alga Chlamydomonas reinhardtii, a model eukaryote organism that long diverged from a common ancestor to plants and Metazoans and that has a single septin. For that, yeast two-hybrid assays were conducted in search of possible partner proteins to C.reinhardtii, septin (CrSept); also, gene expression analyses by qPCR of different points of the cell cycle helped characterize the expression profile of the CrSept gene and gene silencing by artificial micro-RNA (amiRNA) and immunolocalization by confocal microscopy were used to enrich functional and localization studies. The yeast two-hybrid assays returned two possible partner proteins to CrSept - S-Adenosyl-Homocysteine-Hydrolase (CrSAHH) e Subtilase-like-Serino-Protease (sporangin) – both related to the flagella structure. The interaction among CrSept and CrSAHH could not be validated in vitro by pulldown or crosslink assays, however, the in situ immunostaining showed CrSept can mostly be found in punctual concentrated spots close to the base of the flagella during G0 and G1 phases of the cell cycle, which differs from the profile observed during phases S and M, where the protein can be observed as punctual spots through the whole cell. These results strengths CrSept role on the flagellar structure and do not exclude the possibility of an in vivo interaction between CrSept and CrSAHH. Gene expression analyses showed that septin is mostly expressed during the light part of the cycle, which is also observed at the protein quantitative analysis by western blot. Gene silencing experiments showed a possible phenotype in clones expressing amiRNA against CrSept, which was not observed on control group. Together, these results suggest CrSept has a structural role in C. reinhardtii and might work as a scaffold to other proteins during cell growth stage. Besides, punctual staining observed during mitosis suggests CrSept might help maintaining cell structure until cell division is completed.
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Lu, Yinghong. "Functional analysis of phototropin in Chlamydomonas reinhardtii." Doctoral thesis, [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=981277802.
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Roberts, Susan Penelope Sara. "Low temperature injuries in Chlamydomonas reinhardtii (CW15+)." Thesis, University of Plymouth, 1988. http://hdl.handle.net/10026.1/1110.
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The responses of Chlamydomonas reinhardtii CW15+ (a wall-less mutant) to freezing stress have been examined: Tests following freezing of bulk (0.5ml) samples reveal the existence of an optimum cooling rate f o r preservation of viability, close to l*C min-1. Direct observation of cells during freezing and thawing on a cryo light microscope have allowed different forms of injury to be classified. At suboptimal cooling rates, reduction in surface area during shrinkage can be achieved by severe distortion or by the formation of layered stacks of membrane. Lethal injury is not evident until thawing takes place. The manifestation of injury depends upon the severity of the freezing treatment. The first symptom of injury is membrane blebbing at the cell surface, leading to swelling of the entire cell, followed by collapse. The membrane involved in the swelling might originate i n the mitochondrion and chloroplast envelope. Regions of fusion between membrane of these organelles and the plasma membrane have been observed during rewarming by electron microscopy. Fluorescent markers of the mitochondrial membrane have been detected i n the membrane involved in blebbing. Further damage during slow cooling contributes to rapid lysis on re-expansion. If the freezing treatment is still more severe, osmotic unresponsiveness will result. At supraoptimal cooling rates loss inviability is associated with intra cellular freezing. These responses have been examined in the light of available data regarding the freeze-thaw responses of higher plant protoplasts . The first symptom of damage seen in 'C reinhardtii ie. that of blebbing and massive swelling, is not common to both systems. Thus general rules concerning the responses of plant cells to freezing stresses cannot be made by using either of these protoplasts as a model system, although each may be useful for study of particular aspects of higher plant and algal cell freezing as separate investigations.
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Balia, Yusof Zetty Norhana. "Regulation of thiamine biosynthesis in Chlamydomonas reinhardtii." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610616.
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Boyd, Joseph Samuel. "Eyespot Assembly and Positioning in Chlamydomonas reinhardtii." Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/145298.
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The eyespot of the biflagellate unicellular green alga Chlamydomonas reinhardtii is a complex organelle that facilitates directional responses of the cell to environmental light stimuli. The eyespot, which assembles de novo after every cell division and retains a distinctive association with the microtubule cytoskeleton, comprises an elliptical patch of rhodopsin photoreceptors in the plasma membrane and stacks of carotenoid-rich pigment granule arrays in the chloroplast and serves as a model for understanding how organelles are formed and placed asymmetrically in the cell. This study describes the roles of several factors in the assembly and positioning of the eyespot. Two loci, EYE2 and EYE3, define factors involved in the formation and organization of the eyespot pigment granule arrays. Whereas EYE3, a serine/threonine kinase of the ABC1 family, localizes to pigment granules, EYE2 localization corresponds to an area of the chloroplast envelope in the eyespot. These proteins play interdependent roles: EYE2 and the ChR1 photoreceptor co-position in the absence of pigment granules, and the pigment granules are required to maintain the shape and integrity of the EYE2/ChR1 patch. The miniature-eyespot locus MIN2 affects eyespot size and likely regulates the amount of material available for eyespot assembly. The MLT2 locus regulates eyespot size, number, and asymmetry. A novel locus, PEY1, modulates the position of the eyespot on the anterior-posterior axis by affecting microtubule rootlet length. A working model is developed wherein rootlet microtubule-directed photoreceptor localization establishes connections in the chloroplast envelope with EYE2, which directs the site for pigment granule array assembly, and MLT2 is proposed to negatively regulate the levels of eyespot proteins.
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Wietrzynski, Wojciech. "Rubisco biogenesis and assembly in Chlamydomonas reinhardtii." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066336/document.
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La nécessité de coordonner l’expression des gènes provenant de génomes différents chez les plantes a conduit à l’émergence de mécanismes imposant un contrôle nucléaire sur l’expression génétique de l’organelle. Des signaux antérogrades, exercés par des protéines reconnaissant des séquences spécifiques, existent en parallèle avec un contrôle des synthèses chloroplastiques dépendant de l’assemblage (CES). Ensemble, ils coordonnent la formation stoichiométrique des complexes photosynthétiques.La Ribulose bisphosphate carboxylase/oxygénase (Rubisco) est une enzyme localisée dans le chloroplaste qui contient deux sous-unités. La grande sous-unité (LSU) et la petite sous-unité (SSU) sont codées par les génomes chloroplastique et nucléaire respectivement. Elles s’assemblent dans le stroma du chloroplaste pour former une holoenzyme hexadécamérique (LSU8SSU8). Pendant mon travail au laboratoire, j’ai tenté de décrire les étapes régulatrices majeures de la synthèse de la Rubisco chez Chlamydomonas reinhardtii en me focalisant sur la régulation post-transcriptionelle de la LSU.J’ai montré que la protéine PPR – MRL1 est un facteur limitant pour l’accumulation de l’ARN messager de rbcL. Bien qu’il ait été décrit précédemment comme un facteur stabilisateur du transcrit susnommé, MRL1 s’est révélé avoir un rôle dans la traduction.J’ai par ailleurs démontré que chez Chlamydomonas, l’expression de la Rubisco est contrôlée par la présence de la SSU. En son absence, la traduction de rbcL est inhibée par son propre produit – la grande sous-unité non assemblée. J’ai pu montrer qu’un intermédiaire d’assemblage, constitué de LSU en complexe avec sa chaperonne RAF1, est nécessaire pour cette régulation, ce qui prouve que ce processus dépend de l’état d’oligomérisation de la LSU. Parallèlement, j’ai caractérisé le devenir de la LSU non assemblée quand la régulation CES est perturbée, et grâce à cela ait contribué à améliorer la connaissance de son processus de repliement et d’assemblageThe necessity to coordinate the expression of genes originating from different genomes within the plant cell resulted in the appearance of mechanisms imposing nuclear control over organelle gene expression. Anterograde signaling through sequence-specific trans-acting proteins (OTAFs) coexists in the chloroplast with an assembly dependent control of chloroplast synthesis (CES process) that coordinates the stoichiometric formation of photosynthetic complexes.Ribulose bisphosphate carboxylase/oxygenase (Rubisco) is a chloroplast-located carbon fixing enzyme constituted of two subunits. Large subunit (LSU) and small subunit (SSU) are encoded in the chloroplast and nuclear genomes respectively. In the stroma they assemble to form a hexadecameric holoenzyme (LSU8SSU8). In this study I tried to highlight major regulatory points of its synthesis in Chlamydomonas reinhardtii focusing on the posttranscriptional regulation of LSU.I showed that the MRL1 PPR protein is a limiting factor for rbcL mRNA accumulation. Whereas it has been previously designated as a stabilization factor for the abovementioned transcript, MRL1 appeared also to have a function in rbcL translation.Most notably, I have demonstrated that in Chlamydomonas reinhardtii Rubisco expression is controlled by the small subunit (SSU) presence. In its absence rbcL undergoes an inhibition of translation through its own product – the unassembled Rubisco large subunit. This process depends on LSU-oligomerization state as I was able to show that the presence of a high order LSU assembly intermediate bound to the RAF1 assembly chaperone is essential for the regulation to occur. In parallel I shed light on the fate of unassembled LSU in a deregulated CES context, thereby improving our understanding of the process of its folding and assembly
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Wietrzynski, Wojciech. "Rubisco biogenesis and assembly in Chlamydomonas reinhardtii." Electronic Thesis or Diss., Paris 6, 2017. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2017PA066336.pdf.
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La nécessité de coordonner l’expression des gènes provenant de génomes différents chez les plantes a conduit à l’émergence de mécanismes imposant un contrôle nucléaire sur l’expression génétique de l’organelle. Des signaux antérogrades, exercés par des protéines reconnaissant des séquences spécifiques, existent en parallèle avec un contrôle des synthèses chloroplastiques dépendant de l’assemblage (CES). Ensemble, ils coordonnent la formation stoichiométrique des complexes photosynthétiques.La Ribulose bisphosphate carboxylase/oxygénase (Rubisco) est une enzyme localisée dans le chloroplaste qui contient deux sous-unités. La grande sous-unité (LSU) et la petite sous-unité (SSU) sont codées par les génomes chloroplastique et nucléaire respectivement. Elles s’assemblent dans le stroma du chloroplaste pour former une holoenzyme hexadécamérique (LSU8SSU8). Pendant mon travail au laboratoire, j’ai tenté de décrire les étapes régulatrices majeures de la synthèse de la Rubisco chez Chlamydomonas reinhardtii en me focalisant sur la régulation post-transcriptionelle de la LSU.J’ai montré que la protéine PPR – MRL1 est un facteur limitant pour l’accumulation de l’ARN messager de rbcL. Bien qu’il ait été décrit précédemment comme un facteur stabilisateur du transcrit susnommé, MRL1 s’est révélé avoir un rôle dans la traduction.J’ai par ailleurs démontré que chez Chlamydomonas, l’expression de la Rubisco est contrôlée par la présence de la SSU. En son absence, la traduction de rbcL est inhibée par son propre produit – la grande sous-unité non assemblée. J’ai pu montrer qu’un intermédiaire d’assemblage, constitué de LSU en complexe avec sa chaperonne RAF1, est nécessaire pour cette régulation, ce qui prouve que ce processus dépend de l’état d’oligomérisation de la LSU. Parallèlement, j’ai caractérisé le devenir de la LSU non assemblée quand la régulation CES est perturbée, et grâce à cela ait contribué à améliorer la connaissance de son processus de repliement et d’assemblageThe necessity to coordinate the expression of genes originating from different genomes within the plant cell resulted in the appearance of mechanisms imposing nuclear control over organelle gene expression. Anterograde signaling through sequence-specific trans-acting proteins (OTAFs) coexists in the chloroplast with an assembly dependent control of chloroplast synthesis (CES process) that coordinates the stoichiometric formation of photosynthetic complexes.Ribulose bisphosphate carboxylase/oxygenase (Rubisco) is a chloroplast-located carbon fixing enzyme constituted of two subunits. Large subunit (LSU) and small subunit (SSU) are encoded in the chloroplast and nuclear genomes respectively. In the stroma they assemble to form a hexadecameric holoenzyme (LSU8SSU8). In this study I tried to highlight major regulatory points of its synthesis in Chlamydomonas reinhardtii focusing on the posttranscriptional regulation of LSU.I showed that the MRL1 PPR protein is a limiting factor for rbcL mRNA accumulation. Whereas it has been previously designated as a stabilization factor for the abovementioned transcript, MRL1 appeared also to have a function in rbcL translation.Most notably, I have demonstrated that in Chlamydomonas reinhardtii Rubisco expression is controlled by the small subunit (SSU) presence. In its absence rbcL undergoes an inhibition of translation through its own product – the unassembled Rubisco large subunit. This process depends on LSU-oligomerization state as I was able to show that the presence of a high order LSU assembly intermediate bound to the RAF1 assembly chaperone is essential for the regulation to occur. In parallel I shed light on the fate of unassembled LSU in a deregulated CES context, thereby improving our understanding of the process of its folding and assembly
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Clowez, Sophie. "Conséquences Fonctionnelles de l’Organisation Supramoléculaire de la Chaîne Photosynthétique et Commutation Entre Transferts d’Electrons Cyclique et Linéaire." Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066525/document.
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Le processus photosynthétique se traduit par un flux d’électron impliquant différents complexes de la membrane thylacoïdale. Ce flux peut adopter deux chemins différents : le transfert d’électron linéaire (Merchant, Prochnik et al. 2007) à travers lequel les électrons sont transférés de l’eau oxydée au niveau du Photosystème II (PSII), au NADPH réduit par le PSI ; et le transfert d’électron cyclique autour du Photosystème I (PSI) et du complexe cytochrome b6f. Ces flux d’électrons sont couplés à un pompage de proton du stroma vers le lumen générant une différence de potentiel transmembranaire, permettant la synthèse d’ATP (Allen 2002). La coexistence de ces deux flux est considéré comme nécessaire à la fixation et la métabolisation des molécules de dioxyde de carbone (Seelert, Poetsch et al. 2000 ; Munekage, Hashimoto et al. 2004) dans un rapport stricte ATP / NADPH. Cette coexistence qui semble essentiel soulève la question des mécanismes qui prévalent à l’implication des mêmes acteurs photosynthétiques, dans une même membrane, dans l’un ou l’autre mode de transfert d’électron. Chez l’algue verte Chlamydomonas reinhardtii, nous avons démontré que la commutation entre les deux transferts était dépendante de l’état redox des cellules, mais contrairement à ce qui avait été suggéré dans les études précédentes (Bulté, Rebeillé et al. 1990 ; Finazzi, Rappaport et al. 2002) indépendante du phénomène de transition d’état (Takahashi, Clowez et al. 2013), qui implique la migration latérale des complexes antennaires au sein de la membrane. L’association de ces antennes au Photosystème I conduirait à la séquestration, dans une même entité biochimique, des différents acteurs du mode cyclique. Cette formation de supercomplexe dans les conditions anoxiques, à fait l’objet d’une étude fonctionnelle in vitro, laissant quelques questions ouvertes sur leurs capacités fonctionnelles. Ce travail de thèse présente aussi la caractérisation d’une limitation transitoire des accepteurs du Photosystème I, en début d’anoxie pendant laquelle il n’est pas possible d’observer d’oxydation de P700, à 705 nm. Ce phénomène dû à la recombinaison de charge est créé par un engorgement du pool de NADPH. L’oxydation spontanée du PSI au bout d’un certain temps d’anoxie implique l’induction de l’hydrogénase, acceptant les électrons du PSI. Il reste possible d’induire cette évolution de l’oxydation de P700 lorsque les cellules sont constamment sous illumination dans les conditions anoxiques, impliquant cette fois ci, la voie de l’ATP chloroplastique. L’ATP synthétisé à la lumière permettrait la consommation de NADPH via le cycle de Benson CalvinThe photosynthetic process relies on an electron flow involving several complexes in the thylakoid membranes of photosynthetic organisms. This flux can follow two possibly competing pathways: the linear electron transfer through which electrons are transferred from water (which is oxidized) to NADP+ (which is reduced), which is coupled to the generation of a transmembrane potential difference allowing the synthesis of ATP (Allen 2002); the cyclic pathway (around PSI and Cytochrome b6f complex) which only allows the production of ATP. These two pathways are thought to be essential for the reduction of CO2 and must likely coexist to allow the photosynthetic ATP/NADPH ratio to meet the requirement of the reduction of CO2 into carbohydrates (Seelert, Poetsch et al. 2000 ; Munekage, Hashimoto et al. 2004). This mere statement raises the question of the mechanisms that prevail in the implication of the same actors, within the same membrane, in either one of the two functional modes. In the green algae Chlamydomonas reinhardtii, our results show that the regulation of cyclic electron transfer is controlled by the redox poise and not by the lateral migration of antennae (Takahashi, Clowez et al. 2013), and disprove with the conclusion drawn from previous studies (Bulté, Rebeillé et al. 1990 ; Finazzi, Rappaport et al. 2002) according to which state transition would determine this switch. The association of these antennae to Photosystem I would promote the sequestration, within a single unit, of all the actors of the cyclic mode. Functional studies, in vitro, of supercomplex formation under anoxic conditions, questions on their functional capacities. This PhD work presents also the characterization of transient ‘’acceptor side limitation’’ of PSI, upon the onset of anoxia where it is not possible to observe an oxidation of P700 in 705 nm. This phenomenon due to the charge recombination is created by an accumulation of NADPH. The spontaneous oxidation of the PSI acceptor pool, after some time under anoxia, involves the hydrogenase induction, accepting the electrons from NADPH. It’s also possible to induce this PSI oxidation as soon as cells are constantly under illumination, involving chloroplast ATP pathway. ATP synthesised in the light, allow the consumption of NADPH through Benson-Calvin cycle
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Schoppmeier, Jutta. "GFP-Markierung von Cytoskelettproteinen in Chlamydomonas reinhardtii (Chlorophyceae)." [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=972195637.
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Weitnauer, Stefanie. "Kartierung des Periodik-Gens Uhr1 aus Chlamydomonas reinhardtii." [S.l. : s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=968797024.
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Zaoui, Amel. "OPR-RAP proteins and nucleotidyl transferases : role in organellar gene expression in Chlamydomonas reinhardtii." Electronic Thesis or Diss., Sorbonne université, 2024. http://www.theses.fr/2024SORUS624.
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Chez l'algue verte Chlamydomonas reinhardtii, une famille de protéines liant l'ARN, appelées protéines à répétitions OctotricoPeptides (OPR), jouent un rôle dans le contrôle de l'expression des gènes au sein des organelles. Ces protéines, codées par le noyau, se caractérisent par une séquence répétée de 38 acides aminés qui se replient en une structure ressemblant à une spirale. Les protéines OPR sont impliquées dans de nombreux processus, tels que la stabilisation et la maturation des ARNm, leur traduction en protéines, et même leur épissage. Deux mutations dominantes indépendantes dans les gènes nucléaires ncc1 et ncc2 ont été découvertes. Ces mutations permettent aux protéines de reconnaître et de déstabiliser de nouvelles cibles d'ARN, en particulier deux ARNm chloroplastiques : atpA et petA, qui codent des composants essentiels dans deux complexes de photosynthèse. Fait intéressant, les protéines NCC1 et NCC2 possèdent un domaine RAP à leur extrémité C-terminale, une caractéristique également présente dans les protéines mitochondriales humaines, ce qui suggère qu'elles pourraient agir comme des endonucléases—des enzymes capables de couper l'ARN.NCC1 et NCC2 font partie d'un groupe de gènes étroitement apparentés, propres à C. reinhardtii, connus sous le nom de gènes NCL. Ces gènes, situés sur le chromosome 15, sont très similaires en séquence et semblent évoluer rapidement, notamment dans une partie clé des répétitions OPR qui détermine la spécificité de la cible ARN. Nous proposons que ces gènes NCL pourraient être adaptés pour éviter de couper leur propre ARN chloroplastique, mais pourraient le faire lors d'un croisement avec une souche éloignée. Cette fonction pourrait être cruciale pour assurer que l'ADN chloroplastique soit hérité du bon parent lors de la reproduction. Dans ma thèse, j'ai exploré le rôle du domaine RAP dans ces protéines, en cherchant à démontrer qu'elles fonctionnent comme des endonucléases en créant différents variants du domaines RAP, qui s'avère être l'élément clef de cette coupure, qui dépend de sa présence, et de son bon fonctionnementIn the green alga Chlamydomonas reinhardtii, a family of RNA-binding proteins called OctotricoPeptide Repeat (OPR) proteins plays a role in controlling gene expression within organelles. These proteins, which are encoded in the nucleus, are characterized by a repeated sequence of 38 amino acids that fold into a structure resembling a spiral. OPR proteins are involved in many processes, such as stabilizing and maturing mRNA, translating it into proteins, and even splicing. Two separate dominant mutations in the nuclear genes ncc1 and ncc2 have been discovered. These mutations enable the proteins to recognize and destabilize new RNA targets, specifically two chloroplast mRNAs: atpA and petA, which encode essential components of the cell's photosynthetic chains. Interestingly, the NCC1 and NCC2 proteins have a RAP domain at their C-terminus, a feature also found in human mitochondrial proteins, which suggests they might act as endonucleases—enzymes that can cut RNA.NCC1 and NCC2 are part of a closely related group of genes unique to C. reinhardtii, known as the NCL genes. These genes, located on chromosome 15, are highly similar in sequence and appear to be evolving rapidly, particularly in a key part of the OPR repeats that determine RNA target specificity. We propose that these NCL genes may be adapted to avoid cutting their own chloroplast RNA but could potentially do so when crossed with a distantly related strain. This function might be crucial in ensuring that the chloroplast DNA is inherited from the correct parent during reproduction. In my thesis, I explored the role of the RAP domain in these proteins, aiming to demonstrate that they function as endonucleases by creating several variants of the RAP domains, that shows that the protein's ability to cut totally dependes on the presence of a functional RP domain
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Balczun, Carsten. "Nuklear kodierte Plastidenproteine bei der Grünalge Chlamydomonas reinhardtii: molekulargenetische Analyse eines RNA-Prozessierungsfaktors." [S.l.] : [s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=975328840.
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Ossenbühl, Friedrich. "Zur post-transkriptionellen Regulation der plastidären Genexpression in Chlamydomonas reinhardtii Analyse von RNA-Protein-Interaktionen mit der 5'nicht-translatierten Region der psbD mRNA /." [S.l. : s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=961934239.
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Orawski, Grazyna. "Struktur-Funktionsanalyse der QB-Bindenische im Photosystem II von Chlamydomonas reinhardtii." [S.l. : s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=962781991.
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Balczun, Carsten. "Nukleär kodierte Plastidenproteine bei der Grünalge Chlamydomonas reinhardtii: molekulargenetische Analyse eines RNA-Prozessierungsfaktors." [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=975328840.
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Teplitski, Maxim I. "Quorum sensing in Sinorhizobium meliloti and effect of plant signals on bacterial quorum sensing." Columbus, Ohio : Ohio State University, 2002. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1029777185.
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Thesis (Ph. D.)--Ohio State University, 2002.Title from first page of PDF file. Document formatted into pages; contains xi, 148 p.; also includes graphics (some col.). Includes abstract and vita. Advisor: Wolfgang D. Bauer, Dept. of Horticulture and Crop Science. Includes bibliographical references (p. 127-148).
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Bollig, Klaus. "Hydroxyprolin gebundene Glykane der Zellwand von Chlamydomonas reinhardtii." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=98265491X.
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Jalal, Abdullah. "Molecular analysis of PPR proteins in Chlamydomonas reinhardtii." Diss., lmu, 2012. http://nbn-resolving.de/urn:nbn:de:bvb:19-150800.
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Haji, Taha Hussein. "Genetic manipulation of fermentative metabolism in Chlamydomonas reinhardtii." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/38619.
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Photobiological hydrogen production by green algae, such as Chlamydomonas reinhardtii is an attractive approach to generate renewable energy, but is currently not economically viable. It has been suggested that hydrogen yields could potentially be improved by eliminating or down-regulating competing fermentative pathways. However, at present fermentative metabolism is not completely understood in C. reinhardtii, such as the nature of the ill-defined D-lactate dehydrogenase (D-LDH) activity responsible for the production of D-lactate. To characterise the D-LDH activity, a bioinformatics analysis identified a candidate nucleus-encoded D-LDH in the C. reinhardtii genome (Phytozome v9.1 ID: Cre07.g324550), which was predicted to be localised to the chloroplast. The putative protein without its predicted chloroplast transit peptide was overexpressed in Escherichia coli as a C-terminal His6-tagged protein to confirm its function and assess its structure. Enzyme assays confirmed that the protein was an NAD+-dependent D-LDH, favouring the reduction of pyruvate to D-lactate with an estimated Km value of 1.85 ± 0.05 mM and kcat value of 415 ± 18 s-1. Size-exclusion chromatography suggests the holoenzyme was tetrameric with a molecular mass of about 202 kDa. Artificial microRNA technology was used to reduce the amount of D-LDH protein to less than 20% of WT levels. D-lactate was still produced in the mutant either from residual D-LDH activity or from other routes such as from methylglyoxal. Both NMR and HPLC confirmed that the knockdown did not have any substantial impact on dark anaerobic metabolite production except in slightly increasing the pyruvate levels. Additionally, the knockdown did not improve hydrogen yields under sulphur-deprived conditions. To assess the impact of eliminating fermentative pathways on metabolism, a series of mutants was isolated through cell mating, targeting the enzymes D-LDH, pyruvate decarboxylase (PDC3), pyruvate formate lyase (PFL1) and a bifunctional acetaldehyde/alcohol dehydrogenase (ADH1). Dark anaerobic metabolite production in the quadruple mutant confirmed the re-routing of metabolic flux from ethanol and formate towards glycerol and D-lactate. There was also a reduced flux towards acetate production. Pyruvate and glucose levels were found to be elevated in this mutant. Gas chromatography analysis suggested that downregulation of the fermentative pathways did not improve hydrogen production under sulphur-deprived conditions, in part because of reduced cell viability. These mutants are promising tools for future studies probing the metabolism of C. reinhardtii.
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Davis, Maria. "An evaluation of metabolic photoacclimation in Chlamydomonas reinhardtii." Thesis, Fredericton: University of New Brunswick, 2011. http://hdl.handle.net/1882/35383.
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Green algae have evolved several photo-protective responses to cope with high-light
stress. The present study examines the metabolic changes during photoacclimation
to high-light in Chlamydomonas reinhardtii using nuclear magnetic resonance and mass spectrometry. Using principal component analysis, a clear metabolic response to highlight intensity was observed on global metabolite pools in Chlamydomonas, with major changes in the levels of amino acids and related nitrogen metabolites. Amino acid biosynthesis was induced during short-term photoacclimation presumably to alleviate excess excitation pressure in the plastid. An increase in mitochondrial metabolism through downstream photorespiratory and glyoxylate metabolism, pathways thought to act in a photo-protective capacity, was also observed. Long-term light stress resulted in a significant increase in antioxidant metabolites, ascorbate and dehydroascorbate. These results suggest that metabolism plays a direct role in coping with the imbalance in the excess excitation pressure generated during high-light stress; however, this metabolomics survey has generated additional questions about the roles of nitrogen assimilation associated metabolites in photoacclimatory responses to high-light in Chlamydomonas.
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Moser, Chase. "Experimental evolution of «Chlamydomonas reinhardtii » under salt stress." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=94916.
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Abstract The environment is now changing much faster than in recent geological time, causing increasing population extinctions. Experiments have shown that extinction can be avoided by adaptation through natural selection leading to evolutionary rescue. I first determined the response of Chlamydomonas to stressful environments by growing populations over a range of salinity. The population growth is halved at 5 g/L salt (NaCl), and 8 g/L is lethal. In this experiment, the genetic correlation between environments increases with environmental similarity. I then manipulated the genotypic diversity in experimental populations and cultured them by serial transfer at 5 g/L salt. The outcome of adaptation is not influenced by initial genetic variation. Instead, populations adapted mainly through the spread of new beneficial mutations. These results suggest that populations have a greater chance of adapting when new environments are similar to current conditions and that adaptation is sometimes dominated by the spread of new mutations, even in the presence of a substantial amount of standing genetic variation.Résumé Notre environnement change maintenant beaucoup plus rapidement que dans le passé géologique récent, précipitant l'extinction de plus en plus d'espèces. Des chercheurs ont démontré que, grâce à l'adaptation par la sélection naturelle, des espèces peuvent éviter l'extinction, un processus nommé sauvetage évolutif. J'ai d'abord étudié la capacité de Chlamydomonas à croitre dans des environnements dont la salinité augmente. J'ai trouvé que 5 g/L de sel diminue la croissance de moitié tandis que 8 g/L est suffisant pour empêcher toute croissance. Ici, la corrélation génétique entre environnement augmente avec la similarité des environnements comparés. J'ai ensuite soumis des populations contenant différentes quantités de diversité génétique initiale à une salinité de 5 g/L. La diversité génétique initiale ne semble pas influencer la capacité d'adaptation. Cependant, les populations semblent plutôt s'adapter en utilisant de nouvelles mutations dont l'effet est bénéfique. Ces résultats suggèrent que les populations s'adapteront plus facilement à des environnements similaires aux conditions présentes. De plus, ce processus sera dominé par la fixation de nouvelles mutations, même dans des populations contenant de la diversité génétique.
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Collins, Douglas. "Competition between the mating types of Chlamydomonas reinhardtii." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=68160.
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Heterothallic, facultatively sexual populations are vulnerable to the loss of a mating type by natural selection during periods of asexual reproduction. Experiments are described which demonstrate a competitive difference between the mating types of Chlamydomonas reinhardtii, a unicellular green alga with two isogamous mating types, mt + and mt $-.$ When grown vegetatively under phototrophic (light) conditions, mt + outcompetes mt $-.$ Assays of the growth parameters of isolated spores suggest that mt + has a higher growth rate than mt $-$ in the light, and that mt $-$ has a higher growth rate than mt + in heterotrophic (dark) growth conditions.A literature review shows that sampling from natural populations of heterothallic, facultatively sexual species often yields only one mating type or significantly skewed mating-type distributions. This indicates that competition between mating types and the consequent loss of one mating type may be common in these populations.
A discussion of current theories on the evolution of heterothallism as well as the results of a simulation model reveal that heterothallism will spread if any fitness reduction is suffered by in-crossing homothallic individuals. However, fitness differences between the heterothallic alleles allow the invasion of a homothallic allele into a heterothallic population.
The implications of mating type competition on the maintenance and distribution of heterothallic populations in nature are discussed. It is argued that heterothallic, facultatively sexual populations commonly lose the potential for sex because of the loss of one mating-type allele. The prediction is made that homothallism is more common among facultatively sexual organisms than it is among obligately sexual organisms.
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Berry, James Thomas. "Hydrogen production in the green alga Chlamydomonas reinhardtii." Thesis, Imperial College London, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.429038.
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Morais, Francisco Silverio. "Mutagenesis of cytochrome b-559 in Chlamydomonas reinhardtii." Thesis, Imperial College London, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.484183.
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Jenkins, H. A. "Circadian and ultradian rhythms in Chlamydomonas and Euglena." Thesis, Bucks New University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233011.
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Patel, Vaishali. "Analysis of photosystem 1 mutants in Chlamydomonas reinhardtii." Thesis, University College London (University of London), 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266592.
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Stevens, David Roy. "Nuclear transformation and gene expression in Chlamydomonas reinhardtii." Thesis, University College London (University of London), 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362931.
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McLaughlin, Linda Frances. "Glycoproteins of the cell wall of Chlamydomonas reinhardtii." Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329282.
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Godman, James Edward. "Iron-sulphur cluster assembly factors in Chlamydomonas reinhardtii." Thesis, University of Cambridge, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608760.
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Lagator, Mato. "Experimental evolution of herbicide resistance in Chlamydomonas reinhardtii." Thesis, University of Warwick, 2012. http://wrap.warwick.ac.uk/56830/.
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Our understanding of the evolutionary dynamics of selection for herbicide resistance is limited by the time and space required to conduct meaningful selection experiments in higher plants. This constrains the study of the dynamics of resistance evolution predominantly to mathematical models. The primary goal of this thesis was to overcome these limitations, and to study the evolutionary phenomena underpinning several management strategies. To do so, a series of experimental evolution studies were conducted using Chlamydomonas reinhardtii, a single-‐cell green chlorophyte susceptible to a range of commercial herbicides. In particular, this thesis explored the impact of herbicide sequences, rotations and mixtures, as well the impact of herbicide dose, on evolution of resistance. Applying herbicides in sequence allowed the study of the impact of environmental perturbation on the dynamics of resistance and the associated fitness costs, finding more rapid selection for resistance to a second and third mode of action in some populations. Cycling between herbicides creates conditions of temporal environmental heterogeneity, the outcomes of which are not easily predictable as resistance was slowed down in some cycling regimes, while in others it accelerated the evolution of resistance or gave rise to cross-‐resistance. Herbicide mixtures are a management strategy relying on increases in environmental complexity to provide better control of resistance. The results presented show that mixtures were effective at slowing the evolution of resistance when all mixture components were used at fully effective doses, while low doses of mixtures accelerated resistance evolution and led to more cross-‐resistance. Finally, modifications of the applied herbicide dose allowed the study of local adaptation along an environmental gradient, where the differences in outcomes based on the specific herbicides used were again evident. Overall, the work presented here uses applied scenarios to study the underlying evolutionary phenomena, in order to feed back into the applied thinking.
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Lipońska, Anna Danuta. "Etude de la Ribonuclease J de Chlamydomonas reinhardtii." Sorbonne Paris Cité, 2016. http://www.theses.fr/2016USPCC064.
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Nous avons surproduit et purifié différentes formes de la RNase J de Chlamydomonas reinhardtii (CrRNase J). Nous avons testé les protéines dans un test d'activité avec la séquence de l'ARN "leader" de thrS. Cet ARN a permis de mettre en évidence aussi bien l'activité 5' exonucléolytique que l'activité endonucléolytique de la RNase J de B. Subtilis. Nous avons alors mis en évidence une activité endonucléolytique pour les différentes constructions de la CrRNAse J, mais une activité 5'-3'exonucléolytique très faible. Pour confirmer ce résultat, nous avons testé si la CrRNase J, pouvait compenser in vivo l'absence des RNases J de B. Subtilis (BsRNase J). Nous avons constaté que la CrRNase J n'était pas capable de compenser la perte de la RNase JI de B. Subtilis. L'absence de complémentation de la RNase. 11 n'indique pas une absence d'activité 5' exonucléolytique de la CrRNase J. Nous avons décidé de tester l'activité 5' exonucléase in vivo (chez B. Subtilis) sur des substrats pour lesquels cette activité a été bien caractérisée (16S rRNA and glmS). Nous n'avons pas pu observer la moindre activité 5'-3' exonucléolytique pour la CrRNase J in vivo. Nous avons aussi entamé des expériences de double hybride dans la levure (Y2H), dans le but d'identifier les partenaires potentiels de la CrRNase J. Nous avons mis en évidence des partenaires potentiels pour la CrRNase J (NDA3, EF3 ou HP4). Nos résultats montrent que même en présence de ces proteines, indépendamment de la nature du nucléotide à l'extrémité 5' de l'ARN cible ou de la présence d'ions dans le mélange réactionnel, CrRNase J montre seulement une activité endoribonucléolytiqueWe overproduced and purified different forms of RNase J from Chlamydomonas reinhardtii (CrRNase J). Proteins were tested for the presence of endonucleolytic and 5'-3' exonucleolytic activity with the B. Subtilis thrS leader model substrate. This substrate is routinely used to test the double activity of the B. Subtilis RNase J (BsRNase J1). CrRNase J proteins showed high endo- but no significant 5'-3' exonucleolytic activity. The lack of strong exonucleolytic activity in vitro prompted us to verify if CrRNase J could compensate for a deletion of BsRNase J. The expression of CrRNase J had no effect on growth of a wild type strain, but could not compensate for the severe growth defect caused by the lack of BsRNase JI. The absence of complementation of BsRNase J1 is no proof that it is due to the lack of the 5'-3' exonucleolytic activity. We further analysed two well-studied processing/degradation events that require the 5'-3' exonucleolytic activity of the B. Subtilis enzyme (16S rRNA and glmS) in these recombinant strains. We found that CrRNase J was unable to provide the 5' exonuclease activity required for these processes in B. Subtilis. We performed a yeast double-hybrid (Y2H) screen to look for potential partners of the CrRNase J. In this study we tested some of them (FTT2, NDA3, EF3 or HP4), in the in vitro test with CrRNase J. None of those proteins was able to stimulate the 5'-3' exonucleolytic activity of C. Reinhardtii enzyme. Together these results show that, despite our efforts with different substrates, modification of the test system and the presence of potential activating factors, CrRNase J shows only an endoribonucleolytic activity
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Raj, Kumar Praveen Kumar. "BIOINFORMATICS ANALYSIS OF ALTERNATIVE SPLICING IN CHLAMYDOMONAS REINHARDTII." Miami University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=miami1281124967.
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Amaral, Joana Sofia Constantino. "SnRK families in Chlamydomonas: promising targets for bioproduction." Master's thesis, Universidade de Aveiro, 2015. http://hdl.handle.net/10773/14762.
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Mestrado em Biologia AplicadaGiven the great world energy demand and the environmental costs associated to fossil fuels use, it is imperative to find a CO2 neutral, sustainable, and renewable energy source. Microalgae are one of the most studied biofuel feedstock, mainly because they produce considerable amounts of energetic compounds (TAG and starch) and other valuable secondary metabolites (such as pigments, vitamins, and bioplastic). Currently, a two-phase cultivation strategy including a stress imposition step is used to accumulate interesting compounds for biofuel production. However, microalgae cell growth is often reduced, requiring longer cultivation times, and stress imposition techniques are still expensive, which represent high costs for the microalgal biofuel production process. In order to make it profitable, a biorefinery approach must be used, combining the extraction of energetic molecules and high value-added by-products. However, biomass supply continues to represent a major limiting factor. To overcome this limitation, the study of the metabolic and regulatory networks involved in stress response is essential so that potential targets for bioengineering can be identified. This would allow either the maintenance of cell growth under stress conditions or the mimicking of a stress condition by coupling a gene of interest to a promoter induced by a simple stimulus, reducing production costs. Therefore, the model microalga Chlamydomonas reinhardtti was used to study the involvement of SnRK protein kinases in stress response. This family is highly associated to plant stress response mechanisms. A few studies also report its involvement in Chlamydomonas stress response, although little is known about it. We identified and classified Chlamydomonas SnRK based on sequence and domain structure similarities with the SnRK sequences described in Arabidopsis using bioinformatic tools. Moreover, its expression patterns were evaluated by RT-qPCR under a wide range of stress conditions in order to look for target genes that might be involved in Chlamydomonas stress response pathways. By using bioinformatic tools 19 SnRK genes coding for 20 proteins from 4 subfamilies (SnRK1, its regulatory subunits, and two groups of SnRK2 proteins) were identified. Surprisingly, the plant-specific SnRK3 subfamily was not found in Chlamydomonas. The analysis of SnRK expression patterns under a wide range of stresses by RT-qPCR identified SnRK2.9 as a potential candidate for future studies as its response was specific to heat stress. Also SnRK2.12 and SnRK2.7 seem to have an important role in mediating Iron deficiency and oxidative stress, respectively, according to the mining of available RNA-seq data. Furthermore, from the stresses studied, UV radiation showed interesting results as it led to lipid accumulation and it is a stimulus that can be applied inexpensively. This work represents a great advance in microalgal and stress biology research since that, although SnRK are a key group of protein kinases for biotechnology, this family was never described before in microalgae.
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Malnoë, Alizée. "A genetic suppressor approach to the biogenesis, quality control and function of photosynthetic complexes in Chlamydomonas reinhardtii." Phd thesis, Université Paris Sud - Paris XI, 2011. http://tel.archives-ouvertes.fr/tel-01057821.
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Central in oxygenic photosynthesis, the cytochrome b6f complex, couples electron transfer to proton translocation across the thylakoid membrane via its quinol:plastocyanin oxidoreductase activity, contributing to ATP formation. Cytochrome b6f complex differs from its respiratory homolog, the bc1 complex, by the presence of an additional heme, heme ci located within the quinone reduction site Qi and attached by a unique thioether bond. Mutants lacking heme ci show low accumulation of partially functional b6f complex and, hence, cannot grow phototrophically. This grounded a screen for suppressor mutations that would restore higher accumulation of b6f complexes whose function, even if compromised, would sustain phototrophic growth.The genetic suppressor approach undertook in Chlamydomonas reinhardtii during this PhD thesis led to the isolation and characterisation of the ftsh1-1 protease mutant (mutation R420C which should affect ATP hydrolysis). The mutant ftsh1-1 proved to be a versatile tool for the functional study of otherwise degraded proteins. The combination of genetic, biochemical, physiological and biophysical experiments demonstrated notably that: (i) a QiKO mutant, whose b6f complexes are devoid of both bh and ci hemes, can grow phototrophically despite a broken Q-cycle, (ii) the absence of covalently bound heme ci, in the Rccb2 mutant, triggers photosensivity enhanced in the presence of O2 supporting a role for heme ci in oxygen rich environment, (iii) FtsH is involved in the maintenance of the main photosynthetic complexes.
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Mitchell, Madeline Claire. "Regulation of the carbon-concentrating mechanism in Chlamydomonas reinhardtii." Thesis, University of Cambridge, 2015. https://www.repository.cam.ac.uk/handle/1810/263885.
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Despite accounting for approximately half of global primary productivity, photosynthesis in aquatic environments is often limited by the availability of dissolved carbon dioxide (CO$_{2(aq)}$). To overcome the slow diffusion of CO$_{2(aq)}$ as well as kinetic limitations of the primary photosynthetic carboxylase, Rubisco, carbon concentrating mechanisms (CCMs) have evolved in many aquatic photosynthetic organisms to improve photosynthetic efficiency and growth in CO2- limited environments. In the model eukaryotic green alga Chlamydomonas reinhardtii, the CCM is induced under low CO2 in the light and comprises: active inorganic carbon transport systems, carbonic anhydrases and the localisation of Rubisco to a central chloroplast microcompartment called the pyrenoid. In addition to changes in gene expression, acclimation to low CO2 is accompanied by alterations to metabolism, physiology and even cellular ultrastructure. However, mechanisms governing the regulation and interaction of these molecular components to increase CCM activity remain poorly understood. The overall aim of this study was to investigate regulation of the CCM in wild-type and mutant Chlamydomonas strains at both the whole cell and molecular level. Firstly, investigation of CCM induction in synchronised cultures of wild-type cells identified changes in CCM activity that were uncoupled from accumulation of CCM-related mRNA and protein, contrasting with the coordinated response to low CO2 observed in asynchronous control cultures. Pre-dawn induction of the CCM was coincident with preferential localisation of Rubisco and a thylakoid-lumenal carbonic anhydrase (CAH3) to the pyrenoid, highlighting the possible role of endogenous signals and post-translational modifications in modulating CCM activity. Secondly, in order to probe the relationship between pyrenoid formation and CCM induction and activity, CCM expression was investigated in pyrenoid-negative mutants with substituted Rubisco small subunits (RBCS). Low CO2-adapted pyrenoid-less RBCS mutants had impaired growth and low photosynthetic affinity for inorganic carbon (Ci). These pyrenoid-negative strains also showed a specific reduction in the accumulation of several CCM mRNAs, compared to pyrenoid- positive wild-type. Two-dimensional difference in gel electrophoresis (2D-DIGE) was used to compare the soluble proteome of one low CO2-adapted pyrenoid-less RBCS mutant compared to the pyrenoid-positive wild-type. This analysis identified only a few differentially expressed proteins, none of which were directly involved in CCM activity. Two primary metabolic enzymes were more abundant in the wild- type while eight proteins associated with protein synthesis and photosynthesis were more abundant in the pyrenoid-less mutant, suggesting that pyrenoid loss is accompanied by global metabolic, as well as CCM-specific, changes. A shotgun proteomics approach (LC-MS/MS) was used to extend the analysis of the pyrenoid-less RBCS mutant proteome to the whole genome level. Approximately 10% of the total proteins detected using this method were identified as differentially expressed between pyrenoid-negative and pyrenoid-positive strains. Increased abundance of photosynthetic proteins was found in the pyrenoid-less RBCS mutant, confirming the results of 2D-DIGE. In contrast, increased accumulation of CCM and primary metabolic enzymes was detected in the pyrenoid-positive wild-type. Overall, detailed investigation of the phenotype of pyrenoid-negative RBCS mutants indicates that pyrenoid loss leads to impaired induction of the CCM as well as altered metabolism under low CO2 conditions, perhaps as a result of decreased carbon fixation. The results of these studies are explored in the context of the identification of additional CCM components and regulatory mechanisms as well as possible connections between Rubisco aggregation and CCM activity.
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Goold, Hugh Douglas. "Lipid metabolism and storage in the microalga Chlamydomonas reinhardtii." Thesis, The University of Sydney, 2015. http://hdl.handle.net/2123/13317.
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Neutral lipid accumulation by microalgae has recently regained considerable interest as these organisms are considered as a promising feedstock for the production of renewable biodiesel. Nitrogen deprivation is well described as a trigger for neutral lipid accumulation in various species of microalgae including Chlamydomonas.However nitrogen deprivation provokes a stop in protein synthesis and cell division, therefore limiting microalgal biomass productivity. In order to elucidate mechanisms of lipid accumulation in Chlamydomonas reinhardtii, a mutant exhibiting elevated TAG levels is characterized. The mutant exhibits reduced chlorophyll but elevated starch and neutral lipids under strong illumination in replete medium. Genetic characterization has revealed 41 missing genes whose detailed study is beyond the scope of this thesis. However this mutant has highlighted the link between luminosity and TAG biosynthesis. High light has also previously been reported as a trigger to induce oil accumulation. To gain insights into the differences in molecular mechanisms behind oil accumulation processes under nitrogen starvation to that of high light, lipidomic changes in separate cultures subjected to the either stress condition was performed. Results showed that despite intracellular TAGs were found to accumulate to lower levels in response to high light in comparison to nitrogen deprivation; the TAGs productivity was higher due to a persistent biomass production. Furthermore differences in both the lipid and protein composition were observed in lipidomes and proteomes determined by pure extracts of lipid bodies isolated from both conditions revealing differences in lipid bodies isolated from different conditions.