Articles de revues : « Chlamydomonas reinhardtii mutant »

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Llamas, Ángel, Manuel Tejada-Jimenez, David González-Ballester, José Javier Higuera, Guenter Schwarz, Aurora Galván et Emilio Fernández. « Chlamydomonas reinhardtii CNX1E Reconstitutes Molybdenum Cofactor Biosynthesis in Escherichia coli Mutants ». Eukaryotic Cell 6, n^o 6 (6 avril 2007) : 1063–67. http://dx.doi.org/10.1128/ec.00072-07.

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ABSTRACT We have isolated and characterized the Chlamydomonas reinhardtii genes for molybdenum cofactor biosynthesis, namely, CNX1G and CNX1E, and expressed them and their chimeric fusions in Chlamydomonas and Escherichia coli. In all cases, the wild-type phenotype was restored in individual mutants as well as in a CNX1G CNX1E double mutant. Therefore, CrCNX1E is the first eukaryotic protein able to complement an E. coli moeA mutant.

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Posewitz, M. C., P. W. King, S. L. Smolinski, R. Davis Smith, A. R. Ginley, M. L. Ghirardi et M. Seibert. « Identification of genes required for hydrogenase activity in Chlamydomonas reinhardtii ». Biochemical Society Transactions 33, n^o 1 (1 février 2005) : 102–4. http://dx.doi.org/10.1042/bst0330102.

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The eukaryotic green alga, Chlamydomonas reinhardtii, produces H2 under anaerobic conditions, in a reaction catalysed by an [FeFe]-hydrogenase. To identify genes that influence H2 production in C. reinhardtii, a library of 6000 colonies on agar plates was screened with sensitive chemochromic H2-sensor films for clones defective in H2 production. Two mutants of particular interest were fully characterized. One mutant, hydEF-1, is unable to assemble an active [FeFe]-hydrogenase. This is the first reported C. reinhardtii mutant that is not capable of producing any H2. The second mutant, sta7-10, is not able to accumulate insoluble starch and has significantly lowered H2-photoproduction rates in comparison with the wild-type. In hydEF-1, anaerobiosis induces transcription of the two reported C. reinhardtii hydrogenase genes, HydA1 and HydA2, indicating a normal transcriptional response to anaerobiosis. In contrast, the transcription of both hydrogenase genes in sta7-10 is significantly attenuated.

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Suzuki, Kensaku, Laura Fredrick Marek et Martin H. Spalding. « A Photorespiratory Mutant of Chlamydomonas reinhardtii ». Plant Physiology 93, n^o 1 (1 mai 1990) : 231–37. http://dx.doi.org/10.1104/pp.93.1.231.

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Remacle, C., F. Duby, P. Cardol et R. F. Matagne. « Mutations inactivating mitochondrial genes in Chlamydomonas reinhardtii ». Biochemical Society Transactions 29, n^o 4 (1 août 2001) : 442–46. http://dx.doi.org/10.1042/bst0290442.

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Chlamydomonas reinhardtii is now becoming a useful model for the study of mitochondrial genetics in a photosynthetic organism. The small (15.8 kb) mitochondrial genome C. reinhardtii has been sequenced completely and all the genes have been identified. Several mutants inactivated in mitochondrial genes encoding components of the respiratory complexes I, III and IV have been characterized at the molecular level. Assembly of complex I in several mutant strains and mapping of mitochondrial mutations by recombinational analysis are also described.

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Kuchka, Michael R., et Jonathan W. Jarvik. « Short-Flagella Mutants of Chlamydomonas reinhardtii ». Genetics 115, n^o 4 (1 avril 1987) : 685–91. http://dx.doi.org/10.1093/genetics/115.4.685.

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ABSTRACT Six short-flagella mutants were isolated by screening clones of mutagenized Chlamydomonas for slow swimmers. The six mutants identify three unlinked Mendelian genes, with three mutations in gene shf-1, two in shf-2 and one in shf-3. shf-1 and shf-2 have been mapped to chromosomes VI and I, respectively. Two of the shf-1 mutations have temperature-sensitive flagellar-assembly phenotypes, and one shf-2 mutant has a cold-sensitive phenotype. shf shf double mutants were constructed; depending on the alleles present they showed either flagellaless or short-flagella phenotypes. Phenotypic revertants of shf-1 and shf-2 mutants were isolated, and certain of them were found to carry extragenic suppressors, some dominant and some recessive. We suspect that the shf mutations affect components of a specific flagellar size-control system, the existence of which has been suggested by a variety of physiological experiments.

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Tam, L. W., et P. A. Lefebvre. « Cloning of flagellar genes in Chlamydomonas reinhardtii by DNA insertional mutagenesis. » Genetics 135, n^o 2 (1 octobre 1993) : 375–84. http://dx.doi.org/10.1093/genetics/135.2.375.

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Abstract Chlamydomonas is a popular genetic model system for studying many cellular processes. In this report, we describe a new approach to isolate Chlamydomonas genes using the cloned nitrate reductase gene (NIT1) as an insertional mutagen. A linearized plasmid containing the NIT1 gene was introduced into nit1 mutant cells by glass-bead transformation. Of 3000 Nit+ transformants examined, 74 showed motility defects of a wide range of phenotypes, suggesting that DNA transformation is an effective method for mutagenizing cells. For 13 of 15 such motility mutants backcrossed to nit- mutant strains, the motility phenotype cosegregated with the Nit+ phenotype, indicating that the motility defects of these 13 mutants may be caused by integration of the plasmid. Further genetic analysis indicated that three of these mutants contained alleles of previously identified loci: mbo2 (move backward only), pf13 (paralyzed flagella) and vfl1 (variable flagellar number). Three other abnormal-flagellar-number mutants did not map to any previously described loci at which mutations produce similar phenotypes. Genomic sequences flanking the integrated plasmid in the mbo2 and vfl1 mutants were isolated and used as probes to obtain wild-type genomic clones, which complemented the motility defects upon transformation into cells. Our results demonstrate the potential of this new approach for cloning genes identified by mutation in Chlamydomonas.

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Dutcher, S. K., R. E. Galloway, W. R. Barclay et G. Poortinga. « Tryptophan analog resistance mutations in Chlamydomonas reinhardtii. » Genetics 131, n^o 3 (1 juillet 1992) : 593–607. http://dx.doi.org/10.1093/genetics/131.3.593.

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Abstract Forty single gene mutations in Chlamydomonas reinhardtii were isolated based on resistance to the compound 5'-methyl anthranilic acid (5-MAA). In other organisms, 5-MAA is converted to 5'-methyltryptophan (5-MT) and 5-MT is a potent inhibitor of anthranilate synthase, which catalyzes the first committed step in tryptophan biosynthesis. The mutant strains fall into two phenotypic classes based on the rate of cell division in the absence of 5-MAA. Strains with class I mutations divide more slowly than wild-type cells. These 17 mutations map to seven loci, which are designated MAA1 to MAA7. Strains with class II mutations have generation times indistinguishable from wild-type cells, and 7 of these 23 mutations map to loci defined by class I mutations. The remainder of the class II mutations map to 9 other loci, which are designated MAA8-MAA16. The maa5-1 mutant strain excretes high levels of anthranilate and phenylalanine into the medium. In this strain, four enzymatic activities in the tryptophan biosynthetic pathway are increased at least twofold. These include the combined activities of anthranilate phosphoribosyl transferase, phosphoribosyl anthranilate isomerase, indoleglycerol phosphate synthetase and anthranilate synthase. The slow growth phenotypes of strains with class I mutations are not rescued by the addition of tryptophan, but the slow growth phenotype of the maa6-1 mutant strain is partially rescued by the addition of indole. The maa6-1 mutant strain excretes a fluorescent compound into the medium, and cell extracts have no combined anthranilate phosphoribosyl transferase, phosphoribosyl anthranilate isomerase and indoleglycerol phosphate synthetase activity. The MAA6 locus is likely to encode a tryptophan biosynthetic enzyme. None of the other class I mutations affected these enzyme activities. Based on the phenotypes of double mutant strains, epistatic relationships among the class I mutations have been determined.

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Lin, Huawen, Zhengyan Zhang, Carlo Iomini et Susan K. Dutcher. « Identifying RNA splicing factors using IFT genes in Chlamydomonas reinhardtii ». Open Biology 8, n^o 3 (mars 2018) : 170211. http://dx.doi.org/10.1098/rsob.170211.

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Intraflagellar transport moves proteins in and out of flagella/cilia and it is essential for the assembly of these organelles. Using whole-genome sequencing, we identified splice site mutations in two IFT genes, IFT81 ( fla9 ) and IFT121 ( ift121-2 ), which lead to flagellar assembly defects in the unicellular green alga Chlamydomonas reinhardtii . The splicing defects in these ift mutants are partially corrected by mutations in two conserved spliceosome proteins, DGR14 and FRA10. We identified a dgr14 deletion mutant, which suppresses the 3′ splice site mutation in IFT81 , and a frameshift mutant of FRA10 , which suppresses the 5′ splice site mutation in IFT121 . Surprisingly, we found dgr14-1 and fra10 mutations suppress both splice site mutations. We suggest these two proteins are involved in facilitating splice site recognition/interaction; in their absence some splice site mutations are tolerated. Nonsense mutations in SMG1 , which is involved in nonsense-mediated decay, lead to accumulation of aberrant transcripts and partial restoration of flagellar assembly in the ift mutants. The high density of introns and the conservation of noncore splicing factors, together with the ease of scoring the ift mutant phenotype, make Chlamydomonas an attractive organism to identify new proteins involved in splicing through suppressor screening.

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Spalding, Martin H., Kyujung Van, Yingjun Wang et Yoshiko Nakamura. « Acclimation of Chlamydomonas to changing carbon availability ». Functional Plant Biology 29, n^o 3 (2002) : 221. http://dx.doi.org/10.1071/pp01182.

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Aquatic organisms, including Chlamydomonas reinhardtii, are faced with a variable supply of dissolved inorganic carbon (Ci). Accordingly, C. reinhardtii has the ability to acclimate to the changing Ci supply through a variety of responses, including induction of a CO2 concentrating mechanism (CCM) when Ci is limiting. The CCM uses active Ci uptake to accumulate a high internal concentration of bicarbonate, which is dehydrated by a specific thylakoid carbonic anhydrase to supply CO2, the substrate used in photosynthesis. In addition to the changes demonstrably related to the function of the CCM, C. reinhardtii exhibits several other acclimation responses to limiting Ci, such as changes in cellular organization and induction or upregulation of several genes. A key area currently under investigation is how C. reinhardtii cells recognize the change in Ci or CO2 concentration, and transduce that signal into needed gene expression changes. Mutational analyses are proving very useful for learning more about the CCM and about the acclimation response to changes in Ci availability. Cloning of the gene disrupted in cia5, a mutant apparently unable to acclimate to limiting Ci, has opened opportunities for more rapid progress in understanding the signal transduction pathway. The Cia5 gene appears to encode a transcription factor that may control, either directly or indirectly, much of the gene expression responses to limiting Ci in C. reinhardtii. Several additional new mutants with potential defects in the signal transduction pathway have been isolated, including three new alleles of cia5.

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Unal, Dilek, et Fazilet Ozlem Cekic. « Cold acclimation of SnRK2.2 kinases mutant Chlamydomonas reinhardtii ». Phycological Research 67, n^o 3 (19 mars 2019) : 202–7. http://dx.doi.org/10.1111/pre.12371.

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Ferris, P. J., J. P. Woessner et U. W. Goodenough. « A sex recognition glycoprotein is encoded by the plus mating-type gene fus1 of Chlamydomonas reinhardtii. » Molecular Biology of the Cell 7, n^o 8 (août 1996) : 1235–48. http://dx.doi.org/10.1091/mbc.7.8.1235.

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Sexual fusion between plus and minus gametes of the unicellular green alga Chlamydomonas reinhardtii entails adhesion between plus-specific and minus-specific "fringe" proteins displayed on the plasma membrane of gametic mating structures. We report the identification of the gene (fus1) encoding the plus fringe glycoprotein, which resides in a unique domain of the mating-type plus (mt+) locus, and which was identified by transposon insertions in three fusion-defective mutant strains. Transformation with fus1+ restores fringe and fusion competence to these mutants and to the pseudo-plus mutant imp11 mt-, defective in minus differentiation. The fus1 gene is remarkable in lacking the codon bias found in all other nuclear genes of C. reinhardtii.

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Bray, Douglas F., John R. Bagu et Kazuo Nakamura. « Ultrastructure of Chlamydomonas reinhardtii following exposure to paraquat : comparison of wild type and a paraquat-resistant mutant ». Canadian Journal of Botany 71, n^o 1 (1 janvier 1993) : 174–82. http://dx.doi.org/10.1139/b93-020.

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A mutant (NL-51) of the unicellular green alga Chlamydomonas reinhardtii Dangeard isolated from a wild-type strain (137c+) was shown to be resistant to the bipyridilium herbicide paraquat at the concentration at which growth of the wild type was inhibited. Tetrad analysis from a cross between the mutant and the wild type showed 2:2 segregation, indicating that the resistance is under control of a single gene. Cross-resistance of the mutant to methionine and to methionine combined with riboflavin suggested that the resistance is due to increased levels of one of the enzymes capable of detoxifying active oxygens. Ultrastructural examination of mutant and wild-type cells exposed to paraquat revealed that the mutant cells were 3 to 4 times more resistant, but both strains showed the same sequence of deterioration. Damage was first manifested as swelling of the mitochondria and dilation of the perinuclear space. This was followed by disintegration of the nuclear matrix and the chloroplast thylakoids. Key words: Chlamydomonas reinhardtii, methionine resistance, paraquat, paraquat-resistant mutant, ultrastructure.

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Nelson, J. A., et P. A. Lefebvre. « Targeted disruption of the NIT8 gene in Chlamydomonas reinhardtii. » Molecular and Cellular Biology 15, n^o 10 (octobre 1995) : 5762–69. http://dx.doi.org/10.1128/mcb.15.10.5762.

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We have used homologous recombination to disrupt the nuclear gene NIT8 in Chlamydomonas reinhardtii. This is the first report of targeted gene disruption of an endogenous locus in C. reinhardtii and only the second for a photosynthetic eukaryote. NIT8 encodes a protein necessary for nitrate and nitrite assimilation by C. reinhardtii. A disruption vector was constructed by placing the CRY1-1 selectable marker gene, which confers emetine resistance, within the NIT8 coding region. nit8 mutants are unable to grow on nitrate as their sole nitrogen source (Nit-) and are resistant to killing by chlorate. One of 2,000 transformants obtained after selection on emetine-chlorate medium contained a homologous insertion of five copies of the disruption plasmid into the NIT8 gene, producing an emetine-resistant, chlorate-resistant Nit- phenotype. The mutant phenotype was rescued by the wild-type NIT8 gene upon transformation. Seven other mutations at the nit8 locus, presumably resulting from homologous recombination with the disruption plasmid, were identified but were shown to be accompanied by deletions of the surrounding genomic region.

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Barsel, S. E., D. E. Wexler et P. A. Lefebvre. « Genetic analysis of long-flagella mutants of Chlamydomonas reinhardtii. » Genetics 118, n^o 4 (1 avril 1988) : 637–48. http://dx.doi.org/10.1093/genetics/118.4.637.

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Abstract The length of the flagella of Chlamydomonas reinhardtii cells is tightly regulated; both short-flagella and long-flagella mutants have been described. This report characterizes ten long-flagella mutants, including five newly isolated mutants, to determine the number of different loci conferring this phenotype, and to study interactions of mutants at different loci. The mutants, each of which was recessive in heterozygous diploids with wild type, fall into three unlinked complementation groups. One of these defines a new gene, lf3, which maps near the centromere of linkage group I. The flagellar length distributions in populations of each mutant were broad, with the longest flagella measuring four times the length of the longest flagella seen on wild-type cells. Each of the ten mutants had defective flagellar regrowth after amputation. Some of the mutants showed no regrowth within the time required for wild-type cells to regenerate flagella completely. Other mutants had subpopulations with rapid regeneration kinetics, and subpopulations with no observable regeneration. The mutants were each crossed to wild type to form temporary quadriflagellate, dikaryon cells; in each case the long flagella were rapidly shortened in the presence of the wild-type cytoplasm, demonstrating that the mutants were recessive, and that length control could be exerted on already assembled flagella.

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Matsuura, Kumi, Paul A. Lefebvre, Ritsu Kamiya et Masafumi Hirono. « Bld10p, a novel protein essential for basal body assembly in Chlamydomonas ». Journal of Cell Biology 165, n^o 5 (1 juin 2004) : 663–71. http://dx.doi.org/10.1083/jcb.200402022.

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How centrioles and basal bodies assemble is a long-standing puzzle in cell biology. To address this problem, we analyzed a novel basal body-defective Chlamydomonas reinhardtii mutant isolated from a collection of flagella-less mutants. This mutant, bld10, displayed disorganized mitotic spindles and cytoplasmic microtubules, resulting in abnormal cell division and slow growth. Electron microscopic observation suggested that bld10 cells totally lack basal bodies. The product of the BLD10 gene (Bld10p) was found to be a novel coiled-coil protein of 170 kD. Immunoelectron microscopy localizes Bld10p to the cartwheel, a structure with ninefold rotational symmetry positioned near the proximal end of the basal bodies. Because the cartwheel forms the base from which the triplet microtubules elongate, we suggest that Bld10p plays an essential role in an early stage of basal body assembly. A viable mutant having such a severe basal body defect emphasizes the usefulness of Chlamydomonas in studying the mechanism of basal body/centriole assembly by using a variety of mutants.

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Vartak, Varsha, et Sujata Bhargava. « Characterization of a norflurazon-resistant mutant of Chlamydomonas reinhardtii ». Weed Science 45, n^o 3 (juin 1997) : 374–77. http://dx.doi.org/10.1017/s0043174500093000.

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A norflurazon-resistant mutant has been isolated from Chlamydomonas reinhardtii that showed a three-fold factor of resistance over wild type cultures. In comparison to wild type cultures, the mutant showed better retention of chlorophylls and carotenoids when grown in light in the presence of norflurazon. When grown in the dark, chlorophyll losses were similar, while carotenoid losses were lower than in the wild type cultures. Higher levels of phytoene accumulated in the wild type cultures in the presence of norflurazon than in the resistant cultures. The resistant cultures also showed cross tolerance to EMD-IT 5914, a herbicide with a similar mode of action. Norflurazon resistance in this alga appears to arise from alterations in the target enzyme phytoene desaturase.

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Nakamura, Shogo, Haruo Ogihara, Kinue Jinbo, Midori Tateishi, Tetsuo Takahashi, Kenjiro Yoshimura, Mamoru Kubota, Masakatsu Watanabe et Soichi Nakamura. « Chlamydomonas reinhardtii Dangeard (Chlamydomonadales, Chlorophyceae) mutant with multiple eyespots ». Phycological Research 49, n^o 2 (juin 2001) : 115–21. http://dx.doi.org/10.1111/j.1440-1835.2001.tb00241.x.

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Li, Xiaobo, Christoph Benning et Min-Hao Kuo. « Rapid Triacylglycerol Turnover in Chlamydomonas reinhardtii Requires a Lipase with Broad Substrate Specificity ». Eukaryotic Cell 11, n^o 12 (5 octobre 2012) : 1451–62. http://dx.doi.org/10.1128/ec.00268-12.

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ABSTRACT When deprived of nitrogen (N), the photosynthetic microalga Chlamydomonas reinhardtii accumulates large quantities of triacylglycerols (TAGs), making it a promising source of biofuel. Prominent transcriptional changes associated with the conditions leading to TAG accumulation have been found, suggesting that the key enzymes for TAG metabolism might be among those that fluctuate in their expression during TAG synthesis and breakdown. Using a Saccharomyces cerevisiae lipase null mutant strain for functional complementation, we identified the CrLIP1 gene from Chlamydomonas based on its ability to suppress the lipase deficiency-related phenotypes of the yeast mutant. In Chlamydomonas , an inverse correlation was found between the CrLIP1 transcript level and TAG abundance when Chlamydomonas cultures were reversibly deprived of N. The CrLIP1 protein expressed and purified from Escherichia coli exhibited lipolytic activity against diacylglycerol (DAG) and polar lipids. The lipase domain of CrLIP1 is most similar to two human DAG lipases, DAGLα and DAGLβ. The involvement of CrLIP1 in Chlamydomonas TAG hydrolysis was corroborated by reducing the abundance of the CrLIP1 transcript with an artificial micro-RNA, which resulted in an apparent delay in TAG lipolysis when N was resupplied. Together, these data suggest that CrLIP1 facilitates TAG turnover in Chlamydomonas primarily by degrading the DAG presumably generated from TAG hydrolysis.

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Grovenstein, Phillip B., Darryel A. Wilson, Cameron G. Lennox, Katherine P. Smith, Alisha A. Contractor, Jonathan L. Mincey, Kathryn D. Lankford, Jacqueline M. Smith, Tashana C. Haye et Mautusi Mitra. « Identification and molecular characterization of a novel Chlamydomonas reinhardtii mutant defective in chlorophyll biosynthesis ». F1000Research 2 (10 juin 2013) : 138. http://dx.doi.org/10.12688/f1000research.2-138.v1.

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The green micro-alga Chlamydomonas reinhardtii is an elegant model organism to study all aspects of oxygenic photosynthesis. Chlorophyll (Chl) and heme are major tetrapyrroles that play an essential role in energy metabolism in photosynthetic organisms and are synthesized via a common branched tetrapyrrole biosynthetic pathway. One of the enzymes in the pathway is Mg chelatase (MgChel) which inserts Mg2+ into protoporphyrin IX (PPIX, proto) to form magnesium-protoporphyrin IX (MgPPIX, Mgproto), the first biosynthetic intermediate in the Chl branch. MgChel is a multimeric enzyme that consists of three subunits designated CHLD, CHLI and CHLH. Plants have two isozymes of CHLI (CHLI1 and CHLI2) which are 70%-81% identical in protein sequences. Although the functional role of CHLI1 is well characterized, that of CHLI2 is not. We have isolated a non-photosynthetic light sensitive mutant 5A7 by random DNA insertional mutagenesis that is devoid of any detectable Chl. PCR based analyses show that 5A7 is missing the CHLI1 gene and at least eight additional functionally uncharacterized genes. 5A7 has an intact CHLI2 gene. Complementation with a functional copy of the CHLI1 gene restored Chl biosynthesis, photo-autotrophic growth and light tolerance in 5A7. We have identified the first chli1 mutant of Chlamydomonas reinhardtii and in green algae. Our results show that in the wild type Chlamydomonas CHLI2 protein amount is lower than that of CHLI1 and the chli1 mutant has a drastic reduction in CHLI2 protein levels although it possesses the CHLI2 gene. Our chli1 mutant opens up new avenues to explore the functional roles of CHLI1 and CHLI2 in Chl biosynthesis and chloroplast to nucleus retrograde signaling in Chlamydomonas, which has never been studied before.

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Grovenstein, Phillip B., Darryel A. Wilson, Cameron G. Lennox, Katherine P. Smith, Alisha A. Contractor, Jonathan L. Mincey, Kathryn D. Lankford, Jacqueline M. Smith, Tashana C. Haye et Mautusi Mitra. « Identification and molecular characterization of a novel Chlamydomonas reinhardtii mutant defective in chlorophyll biosynthesis ». F1000Research 2 (29 juillet 2013) : 138. http://dx.doi.org/10.12688/f1000research.2-138.v2.

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The green micro-alga Chlamydomonas reinhardtii is an elegant model organism to study all aspects of oxygenic photosynthesis. Chlorophyll (Chl) and heme are major tetrapyrroles that play an essential role in energy metabolism in photosynthetic organisms and are synthesized via a common branched tetrapyrrole biosynthetic pathway. One of the enzymes in the pathway is Mg chelatase (MgChel) which inserts Mg2+ into protoporphyrin IX (PPIX, proto) to form magnesium-protoporphyrin IX (MgPPIX, Mgproto), the first biosynthetic intermediate in the Chl branch. MgChel is a multimeric enzyme that consists of three subunits designated CHLD, CHLI and CHLH. Plants have two isozymes of CHLI (CHLI1 and CHLI2) which are 70%-81% identical in protein sequences. Although the functional role of CHLI1 is well characterized, that of CHLI2 is not. We have isolated a non-photosynthetic light sensitive mutant 5A7 by random DNA insertional mutagenesis that is devoid of any detectable Chl. PCR based analyses show that 5A7 is missing the CHLI1 gene and at least eight additional functionally uncharacterized genes. 5A7 has an intact CHLI2 gene. Complementation with a functional copy of the CHLI1 gene restored Chl biosynthesis, photo-autotrophic growth and light tolerance in 5A7. We have identified the first chli1 (chli1-1) mutant of Chlamydomonas reinhardtii and in green algae. Our results show that in the wild type Chlamydomonas CHLI2 protein amount is lower than that of CHLI1 and the chli1-1 mutant has a drastic reduction in CHLI2 protein levels although it possesses the CHLI2 gene. Our chli1-1 mutant opens up new avenues to explore the functional roles of CHLI1 and CHLI2 in Chl biosynthesis in Chlamydomonas, which has never been studied before.

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Baroli, Irene, et Krishna K. Niyogi. « Molecular genetics of xanthophyll–dependent photoprotection in green algae and plants ». Philosophical Transactions of the Royal Society of London. Series B : Biological Sciences 355, n^o 1402 (29 octobre 2000) : 1385–94. http://dx.doi.org/10.1098/rstb.2000.0700.

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The involvement of excited and highly reactive intermediates in oxygenic photosynthesis inevitably results in the generation of reactive oxygen species. To protect the photosynthetic apparatus from oxidative damage, xanthophyll pigments are involved in the quenching of excited chlorophyll and reactive oxygen species, namely 1 Chl*, 3 Chl*, and 1 1O 2 *. Quenching of 1 Chl* results in harmless dissipation of excitation energy as heat and is measured as non–photochemical quenching (NPQ) of chlorophyll fluorescence. The multiple roles of xanthophylls in photoprotection are being addressed by characterizing mutants of Chlamydomonas reinhardtii and Arabidopsis thaliana . Analysis of Arabidopsis mutants that are defective in 1 Chl* quenching has shown that, in addition to specific xanthophylls, the psbS gene is necessary for NPQ. Double mutants of Chlamydomonas and Arabidopsis that are deficient in zeaxanthin, lutein and NPQ undergo photo–oxidative bleaching in high light. Extragenic suppressors of the Chlamydomonas npq1 lor1 double mutant identify new mutations that restore varying levels of zeaxanthin accumulation and allow survival in high light.

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van Hunnik, Eddy, et Dieter Sültemeyer. « A possible role for carbonic anhydrase in the lumen of chloroplast thylakoids in green algae ». Functional Plant Biology 29, n^o 3 (2002) : 243. http://dx.doi.org/10.1071/pp01196.

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In order to understand the function of the lumen carbonic anhydrase (CA) which is bound to PSII at the lumenal side of the thylakoids in chloroplasts of eukaryotic algae, thylakoids were isolated from chloroplasts of Tetraedron minimum, Chlamydomonas noctigama, the cell wall-less mutant Chlamydomonas reinhardtii CW15, and a C. reinhardtii CW15/CIA3 mutant which lacks the lumen CA. The isolated thylakoids produced O2 on illumination and exhibited electron flow between PSII and PSI, indicating that the thylakoids were intact and the photosynthetic apparatus were functional. We could not detect any uptake of HCO3–,nor efflux of CO2, from the thylakoids upon illumination, making it improbable that the CA present in the lumen of the thylakoids would play a role in furnishing CO2 for Rubisco. We were able to determine ATP production upon illumination in isolated thylakoids. Under high inorganic carbon (Ci; 5 mM), all species showed significant amounts of ATP being produced. Under low Ci (200 M), we could not detect ATP formation from C. reinhardtii CW15/CIA3 upon illumination. This mutant was not able to survive more then 4 h of low Ci in culture. We therefore suggest that the lumen CA is not involved in the CO2 concentrating mechanism, but might play a role in the formation of a proton gradient across the thylakoid membranes.

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Van, Kyujung, et Martin H. Spalding. « Periplasmic Carbonic Anhydrase Structural Gene (Cah1) Mutant in Chlamydomonas reinhardtii ». Plant Physiology 120, n^o 3 (1 juillet 1999) : 757–64. http://dx.doi.org/10.1104/pp.120.3.757.

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Suzuki, K., T. G. Mamedov et T. Ikawa. « A Mutant of Chlamydomonas reinhardtii with Reduced Rate of Photorespiration ». Plant and Cell Physiology 40, n^o 8 (1 janvier 1999) : 792–99. http://dx.doi.org/10.1093/oxfordjournals.pcp.a029607.

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Scoma, Alberto, Danuta Krawietz, Cecilia Faraloni, Luca Giannelli, Thomas Happe et Giuseppe Torzillo. « Sustained H2 production in a Chlamydomonas reinhardtii D1 protein mutant ». Journal of Biotechnology 157, n^o 4 (février 2012) : 613–19. http://dx.doi.org/10.1016/j.jbiotec.2011.06.019.

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Ladygin, Vladimir G. « Efficient transformation of mutant cells of Chlamydomonas reinhardtii by electroporation ». Process Biochemistry 39, n^o 11 (juillet 2004) : 1685–91. http://dx.doi.org/10.1016/j.procbio.2003.07.001.

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PICCIONI, Richard G., Nam-Hai CHUA et Pierre BENNOUN. « A Nuclear Mutant of Chlamydomonas reinhardtii Defective in Photosynthetic Photophosphorylation ». European Journal of Biochemistry 117, n^o 1 (3 mars 2005) : 93–102. http://dx.doi.org/10.1111/j.1432-1033.1981.tb06307.x.

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Fargo, David C., John E. Boynton et Nicholas W. Gillham. « Mutations Altering the Predicted Secondary Structure of a Chloroplast 5′ Untranslated Region Affect Its Physical and Biochemical Properties as Well as Its Ability To Promote Translation of Reporter mRNAs Both in the Chlamydomonas reinhardtii Chloroplast and in Escherichia coli ». Molecular and Cellular Biology 19, n^o 10 (1 octobre 1999) : 6980–90. http://dx.doi.org/10.1128/mcb.19.10.6980.

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ABSTRACT Random mutations were generated in the sequence for the 5′ untranslated region (5′UTR) of the Chlamydomonas reinhardtii chloroplast rps7 mRNA by PCR, the coding sequence for the mutant leaders fused upstream of the lacZ′ reporter in pUC18, and transformed into Escherichia coli, and white colonies were selected. Twelve single base pair changes were found at different positions in the rps7 5′UTR in 207 white colonies examined. Seven of the 12 mutant leaders allowed accumulation of abundant lacZ′ message. These mutant rps7leaders were ligated into an aadA expression cassette and transformed into the chloroplast of C. reinhardtii and intoE. coli. In vivo spectinomycin-resistant growth rates and in vitro aminoglycoside adenyltransferase enzyme activity varied considerably between different mutants but were remarkably similar for a given mutant expressed in the Chlamydomonas chloroplast and in E. coli. The variable effect of the mutants onaadA reporter expression and their complete abolition oflacZ′ reporter expression in E. coli suggests differences in the interaction between the 5′UTR of rps7and aadA or lacZ′ coding regions. Severalrps7 5′UTR mutations affected the predicted folding pattern of the 5′UTR by weakening the stability of stem structures. Site-directed secondary mutations generated to restore these structures in the second stem suppressed the loss of reporter activity caused by the original mutations. Additional site-directed mutations that were predicted to further strengthen (A-U→G-C) or weaken (G-C→A-U) the second stem of the rps7 leader both resulted in reduced reporter expression. This genetic evidence combined with differences between mutant and wild-type UV melting profiles and RNase T1 protection gel shifts further indicate that the predicted wild-type folding pattern in the 5′UTR is likely to play an essential role in translation initiation.

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Lechtreck, Karl-Ferdinand, Eric C. Johnson, Tsuyoshi Sakai, Deborah Cochran, Bryan A. Ballif, John Rush, Gregory J. Pazour, Mitsuo Ikebe et George B. Witman. « The Chlamydomonas reinhardtii BBSome is an IFT cargo required for export of specific signaling proteins from flagella ». Journal of Cell Biology 187, n^o 7 (28 décembre 2009) : 1117–32. http://dx.doi.org/10.1083/jcb.200909183.

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In humans, seven evolutionarily conserved genes that cause the cilia-related disorder Bardet-Biedl syndrome (BBS) encode proteins that form a complex termed the BBSome. The function of the BBSome in the cilium is not well understood. We purified a BBSome-like complex from Chlamydomonas reinhardtii flagella and found that it contains at least BBS1, -4, -5, -7, and -8 and undergoes intraflagellar transport (IFT) in association with a subset of IFT particles. C. reinhardtii insertional mutants defective in BBS1, -4, and -7 assemble motile, full-length flagella but lack the ability to phototax. In the bbs4 mutant, the assembly and transport of IFT particles are unaffected, but the flagella abnormally accumulate several signaling proteins that may disrupt phototaxis. We conclude that the BBSome is carried by IFT but is an adapter rather than an integral component of the IFT machinery. C. reinhardtii BBS4 may be required for the export of signaling proteins from the flagellum via IFT.

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Wakao, Setsuko, Patrick M. Shih, Katharine Guan, Wendy Schackwitz, Joshua Ye, Dhruv Patel, Robert M. Shih et al. « Discovery of photosynthesis genes through whole-genome sequencing of acetate-requiring mutants of Chlamydomonas reinhardtii ». PLOS Genetics 17, n^o 9 (7 septembre 2021) : e1009725. http://dx.doi.org/10.1371/journal.pgen.1009725.

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Large-scale mutant libraries have been indispensable for genetic studies, and the development of next-generation genome sequencing technologies has greatly advanced efforts to analyze mutants. In this work, we sequenced the genomes of 660 Chlamydomonas reinhardtii acetate-requiring mutants, part of a larger photosynthesis mutant collection previously generated by insertional mutagenesis with a linearized plasmid. We identified 554 insertion events from 509 mutants by mapping the plasmid insertion sites through paired-end sequences, in which one end aligned to the plasmid and the other to a chromosomal location. Nearly all (96%) of the events were associated with deletions, duplications, or more complex rearrangements of genomic DNA at the sites of plasmid insertion, and together with deletions that were unassociated with a plasmid insertion, 1470 genes were identified to be affected. Functional annotations of these genes were enriched in those related to photosynthesis, signaling, and tetrapyrrole synthesis as would be expected from a library enriched for photosynthesis mutants. Systematic manual analysis of the disrupted genes for each mutant generated a list of 253 higher-confidence candidate photosynthesis genes, and we experimentally validated two genes that are essential for photoautotrophic growth, CrLPA3 and CrPSBP4. The inventory of candidate genes includes 53 genes from a phylogenomically defined set of conserved genes in green algae and plants. Altogether, 70 candidate genes encode proteins with previously characterized functions in photosynthesis in Chlamydomonas, land plants, and/or cyanobacteria, 14 genes encode proteins previously shown to have functions unrelated to photosynthesis. Among the remaining 169 uncharacterized genes, 38 genes encode proteins without any functional annotation, signifying that our results connect a function related to photosynthesis to these previously unknown proteins. This mutant library, with genome sequences that reveal the molecular extent of the chromosomal lesions and resulting higher-confidence candidate genes, will aid in advancing gene discovery and protein functional analysis in photosynthesis.

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Mitchell, David R., et Masako Nakatsugawa. « Bend propagation drives central pair rotation in Chlamydomonas reinhardtii flagella ». Journal of Cell Biology 166, n^o 5 (30 août 2004) : 709–15. http://dx.doi.org/10.1083/jcb.200406148.

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Regulation of motile 9+2 cilia and flagella depends on interactions between radial spokes and a central pair apparatus. Although the central pair rotates during bend propagation in flagella of many organisms and rotation correlates with a twisted central pair structure, propulsive forces for central pair rotation and twist are unknown. Here we compared central pair conformation in straight, quiescent flagella to that in actively beating flagella using wild-type Chlamydomonas reinhardtii and mutants that lack radial spoke heads. Twists occur in quiescent flagella in both the presence and absence of spoke heads, indicating that spoke–central pair interactions are not needed to generate torque for twisting. Central pair orientation in propagating bends was also similar in wild type and spoke head mutant strains, thus orientation is a passive response to bend formation. These results indicate that bend propagation drives central pair rotation and suggest that dynein regulation by central pair–radial spoke interactions involves passive central pair reorientation to changes in bend plane.

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Remacle, Claire, Sara Cline, Layla Boutaffala, Stéphane Gabilly, Véronique Larosa, M. Rosario Barbieri, Nadine Coosemans et Patrice P. Hamel. « The ARG9 Gene Encodes the Plastid-Resident N-Acetyl Ornithine Aminotransferase in the Green Alga Chlamydomonas reinhardtii ». Eukaryotic Cell 8, n^o 9 (17 juillet 2009) : 1460–63. http://dx.doi.org/10.1128/ec.00108-09.

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ABSTRACT Here we report the characterization of the Chlamydomonas reinhardtii gene ARG9, encoding the plastid resident N-acetyl ornithine aminotransferase, which is involved in arginine synthesis. Integration of an engineered ARG9 cassette in the plastid chromosome of the nuclear arg9 mutant restores arginine prototrophy. This suggests that ARG9 could be used as a new selectable marker for plastid transformation.

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Subrahmanian, Nitya, Andrew David Castonguay, Claire Remacle et Patrice Paul Hamel. « Assembly of Mitochondrial Complex I Requires the Low-Complexity Protein AMC1 in Chlamydomonas reinhardtii ». Genetics 214, n^o 4 (19 février 2020) : 895–911. http://dx.doi.org/10.1534/genetics.120.303029.

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Complex I is the first enzyme involved in the mitochondrial electron transport chain. With >40 subunits of dual genetic origin, the biogenesis of complex I is highly intricate and poorly understood. We used Chlamydomonas reinhardtii as a model system to reveal factors involved in complex I biogenesis. Two insertional mutants, displaying a complex I assembly defect characterized by the accumulation of a 700 kDa subcomplex, were analyzed. Genetic analyses showed these mutations were allelic and mapped to the gene AMC1 (Cre16.g688900) encoding a low-complexity protein of unknown function. The complex I assembly and activity in the mutant was restored by complementation with the wild-type gene, confirming AMC1 is required for complex I biogenesis. The N terminus of AMC1 targets a reporter protein to yeast mitochondria, implying that AMC1 resides and functions in the Chlamydomonas mitochondria. Accordingly, in both mutants, loss of AMC1 function results in decreased abundance of the mitochondrial nd4 transcript, which encodes the ND4 membrane subunit of complex I. Loss of ND4 in a mitochondrial nd4 mutant is characterized by a membrane arm assembly defect, similar to that exhibited by loss of AMC1. These results suggest AMC1 is required for the production of mitochondrially-encoded complex I subunits, specifically ND4. We discuss the possible modes of action of AMC1 in mitochondrial gene expression and complex I biogenesis.

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Suzuki, Kensaku, Hidenobu Uchida et Tarlan G. Mamedov. « The phosphoglycolate phosphatase gene and the mutation in the phosphoglycolate phosphatase-deficient mutant (pgp1-1) of Chlamydomonas reinhardtii ». Canadian Journal of Botany 83, n^o 7 (1 juillet 2005) : 842–49. http://dx.doi.org/10.1139/b05-071.

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The sequences of the phosphoglycolate phosphatase (PGPase) gene Pgp1 and the 5′-upstream region from Chlamydomonas reinhardtii wildtype 2137 and the pgp1-1 mutant N142 that lacks the activity of PGPase (PGP1) were determined. The comparison revealed the alteration of a G to A at position 98 relative to the start codon. This destroyed the "GT" splice donor site at the beginning of the first intron of this gene, resulting in an extension of the first exon to 49 translatable codons followed by a stop codon, containing the codons corresponding to whole transit peptide for the chloroplast stroma and the first four N-terminal amino-acid residues of the PGP1 subunit. The comparison of the upstream nucleotide sequence of Pgp1 with those of 37 other genes including those involved in the CO2-concentrating mechanism and (or) photorespiration showed the high similarity of Pgp1 upstream to a periplasmic carbonic anhydrase gene Cah1; the motifs RAGGTCAGN8-9CCR and TTGGCAG were found only within the low-CO2 responsive genes, including Pgp1 and Cah1. GAN7CGNTTGGAAN2AG, TTGGAAGGAG, and CAGAGGTCAGN8CCG were found only with Pgp1 and Cah1, and ACGCTTGGCAGT and CATTACCAT were found only with Pgp1 and alanine aminotransferase gene Aat1. The possibility of functional PGPase isozyme(s) in C. reinhardtii is also discussed.Key words: Chlamydomonas reinhardtii, CO2-concentrating mechanism, low-CO2 responsive gene, pgp1-1 mutation, phosphoglycolate phosphatase.

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Sirikhachornkit, Anchalee, Jai W. Shin, Irene Baroli et Krishna K. Niyogi. « Replacement of α-Tocopherol by β-Tocopherol Enhances Resistance to Photooxidative Stress in a Xanthophyll-Deficient Strain of Chlamydomonas reinhardtii ». Eukaryotic Cell 8, n^o 11 (novembre 2009) : 1648–57. http://dx.doi.org/10.1128/ec.00124-09.

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ABSTRACT Tocopherols (vitamin E) comprise a class of lipid-soluble antioxidants synthesized only in plants, algae, and some cyanobacteria. The majority of tocopherols in photosynthetic cells is in the α form, which has the highest vitamin E activity in humans, whereas the β, γ, and δ forms normally account for a small percentage of total tocopherols. The antioxidant activities of these forms of tocopherol differ depending on the experimental system, and their relative activities in vivo are unclear. In a screen for suppressors of the xanthophyll-deficient npq1 lor1 double mutant of Chlamydomonas reinhardtii, we isolated a vte3 mutant lacking α-tocopherol but instead accumulating β-tocopherol. The vte3 mutant contains a mutation in the homolog of a 2-methyl-6-phytyl-1,4-benzoquinone methyltransferase gene found in plants. The vte3 npq1 lor1 triple mutant with β-tocopherol survived better under photooxidative stress than did the npq1 lor1 mutant, but the vte3 mutant on its own did not have an obvious phenotype. Following transfer from low light to high light, the triple mutant showed a higher efficiency of photosystem II, a higher level of cell viability, and a lower level of lipid peroxide, a marker for oxidative stress, than did the npq1 lor1 mutant. After high-light transfer, the level of the photosystem II reaction center protein, D1, was also higher in the vte3 npq1 lor1 mutant, but the rate of D1 photodamage was not significantly different from that of the npq1 lor1 mutant. Taken together, these results suggest that the replacement of α-tocopherol by β-tocopherol in a xanthophyll-deficient strain of Chlamydomonas reinhardtii contributes to better survival under conditions of photooxidative stress.

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Nakamura, Yoshiko, Saradadevi Kanakagiri, Kyujung Van, Wei He et Martin H. Spalding. « Disruption of the glycolate dehydrogenase gene in the high-CO2-requiring mutant HCR89 of Chlamydomonas reinhardtii ». Canadian Journal of Botany 83, n^o 7 (1 juillet 2005) : 820–33. http://dx.doi.org/10.1139/b05-067.

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One of the most notable contrasts between the photorespiratory pathway of higher plants and that of many of the green algae including Chlamydomonas reinhardtii lies in the enzymes that serve for oxidation of glycolate to glyoxylate. The gene disrupted by insertional mutagenesis in a high-CO2-requiring mutant, HCR89, of C. reinhardtii was determined to encode glycolate dehydrogenase (EC 1.1.99.14), which serves as the counterpart of glycolate oxidase (EC 1.1.3.15) in classical higher plant photorespiration. Neither glycolate nor D-lactate oxidation from the membrane fraction of HCR89 was detected. Excretion of over-accumulated glycolate into media due to the absence of glycolate dehydrogenase activity was observed for HCR89 under both high- and low-CO2 conditions. Chlamydomonas glycolate dehydrogenase, CrGDH, with a molecular mass of 118 851 Da, comprises a relatively hydrophobic N-terminal region, a FAD-containing domain homologous to the D subunit of the glycolate oxidase complex from Escherischia coli, and an ironsulfur cluster containing domain homologous to the C subunit of anaerobic glycerol-3-phosphate dehydrogenase complex from Escherichia coli. The second Cys residue in the second ironsulfur cluster motif of CrGDH is replaced by Asp, as CxxDxxCxxxCP, indicating the second ironsulfur cluster coordinates most likely 3Fe4S instead of 4Fe4S. The membrane association of the glycolate dehydrogenase activity agrees with three predicted transmembrane regions on the ironsulfur domain.Key words: algae, Chlamydomonas, CO2, glycolate, lactate, mitochondria, photorespiration, photosynthesis.

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Yun, Eun Ju, Guo-Chang Zhang, Christine Atkinson, Stephan Lane, Jing-Jing Liu, Donald R. Ort et Yong-Su Jin. « Glycolate production by a Chlamydomonas reinhardtii mutant lacking carbon-concentrating mechanism ». Journal of Biotechnology 335 (juillet 2021) : 39–46. http://dx.doi.org/10.1016/j.jbiotec.2021.06.009.

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Formighieri, Cinzia, Mauro Ceol, Giulia Bonente, Jean-David Rochaix et Roberto Bassi. « Retrograde Signaling and Photoprotection in a gun4 Mutant of Chlamydomonas reinhardtii ». Molecular Plant 5, n^o 6 (novembre 2012) : 1242–62. http://dx.doi.org/10.1093/mp/sss051.

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Wu, Shuangxiu, Lili Xu, Rongrong Wang, Xiaolei Liu et Quanxi Wang. « A high yield mutant of Chlamydomonas reinhardtii for photoproduction of hydrogen ». International Journal of Hydrogen Energy 36, n^o 21 (octobre 2011) : 14134–40. http://dx.doi.org/10.1016/j.ijhydene.2011.05.001.

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Jang, Sunghoon, Yasuyo Yamaoka, Dong-hwi Ko, Tomokazu Kurita, Kyungyoon Kim, Won-Yong Song, Jae-Ung Hwang, Byung-Ho Kang, Ikuo Nishida et Youngsook Lee. « Characterization of a Chlamydomonas reinhardtii mutant defective in a maltose transporter ». Journal of Plant Biology 58, n^o 5 (octobre 2015) : 344–51. http://dx.doi.org/10.1007/s12374-015-0377-1.

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Johanningmeier, Udo, et Silvia Heiss. « Construction of a Chlamydomonas reinhardtii mutant with an intronless psbA gene ». Plant Molecular Biology 22, n^o 1 (avril 1993) : 91–99. http://dx.doi.org/10.1007/bf00038998.

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Collard, Jean-Marc, et Rene F. Matagne. « Cd2+ resistance in wild-type and mutant strains of Chlamydomonas reinhardtii ». Environmental and Experimental Botany 34, n^o 2 (avril 1994) : 235–44. http://dx.doi.org/10.1016/0098-8472(94)90044-2.

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Purton, Saul, et Jean-David Rochaix. « Complementation of a Chlamydomonas reinhardtii mutant using a genomic cosmid library ». Plant Molecular Biology 24, n^o 3 (février 1994) : 533–37. http://dx.doi.org/10.1007/bf00024121.

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Lee, Jihyeon, Yasuyo Yamaoka, Fantao Kong, Caroline Cagnon, Audrey Beyly-Adriano, Sunghoon Jang, Peng Gao, Byung-Ho Kang, Yonghua Li-Beisson et Youngsook Lee. « The phosphatidylethanolamine-binding protein DTH1 mediates degradation of lipid droplets in Chlamydomonas reinhardtii ». Proceedings of the National Academy of Sciences 117, n^o 37 (31 août 2020) : 23131–39. http://dx.doi.org/10.1073/pnas.2005600117.

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Lipid droplets (LDs) are intracellular organelles found in a wide range of organisms and play important roles in stress tolerance. During nitrogen (N) starvation, Chlamydomonas reinhardtii stores large amounts of triacylglycerols (TAGs) inside LDs. When N is resupplied, the LDs disappear and the TAGs are degraded, presumably providing carbon and energy for regrowth. The mechanism by which cells degrade LDs is poorly understood. Here, we isolated a mutant (dth1-1, Delayed in TAG Hydrolysis 1) in which TAG degradation during recovery from N starvation was compromised. Consequently, the dth1-1 mutant grew poorly compared to its parental line during N recovery. Two additional independent loss-of-function mutants (dth1-2 and dth1-3) also exhibited delayed TAG remobilization. DTH1 transcript levels increased sevenfold upon N resupply, and DTH1 protein was localized to LDs. DTH1 contains a putative lipid-binding domain (DTH1LBD) with alpha helices predicted to be structurally similar to those in apolipoproteins E and A–I. Recombinant DTH1LBD bound specifically to phosphatidylethanolamine (PE), a major phospholipid coating the LD surface. Overexpression of DTH1LBD in Chlamydomonas phenocopied the dth1 mutant’s defective TAG degradation, suggesting that the function of DTH1 depends on its ability to bind PE. Together, our results demonstrate that the lipid-binding DTH1 plays an essential role in LD degradation and provide insight into the molecular mechanism of protein anchorage to LDs at the LD surface in photosynthetic cells.

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Zhang, Ningning, Leila Pazouki, Huong Nguyen, Sigrid Jacobshagen, Brae M. Bigge, Ming Xia, Erin M. Mattoon et al. « Comparative Phenotyping of Two Commonly Used Chlamydomonas reinhardtii Background Strains : CC-1690 (21gr) and CC-5325 (The CLiP Mutant Library Background) ». Plants 11, n^o 5 (22 février 2022) : 585. http://dx.doi.org/10.3390/plants11050585.

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The unicellular green alga Chlamydomonas reinhardtii is an excellent model organism to investigate many essential cellular processes in photosynthetic eukaryotes. Two commonly used background strains of Chlamydomonas are CC-1690 and CC-5325. CC-1690, also called 21gr, has been used for the Chlamydomonas genome project and several transcriptome analyses. CC-5325 is the background strain for the Chlamydomonas Library Project (CLiP). Photosynthetic performance in CC-5325 has not been evaluated in comparison with CC-1690. Additionally, CC-5325 is often considered to be cell-wall deficient, although detailed analysis is missing. The circadian rhythms in CC-5325 are also unclear. To fill these knowledge gaps and facilitate the use of the CLiP mutant library for various screens, we performed phenotypic comparisons between CC-1690 and CC-5325. Our results showed that CC-5325 grew faster heterotrophically in dark and equally well in mixotrophic liquid medium as compared to CC-1690. CC-5325 had lower photosynthetic efficiency and was more heat-sensitive than CC-1690. Furthermore, CC-5325 had an intact cell wall which had comparable integrity to that in CC-1690 but appeared to have reduced thickness. Additionally, CC-5325 could perform phototaxis, but could not maintain a sustained circadian rhythm of phototaxis as CC1690 did. Finally, in comparison to CC-1690, CC-5325 had longer cilia in the medium with acetate but slower swimming speed in the medium without nitrogen and acetate. Our results will be useful for researchers in the Chlamydomonas community to choose suitable background strains for mutant analysis and employ the CLiP mutant library for genome-wide mutant screens under appropriate conditions, especially in the areas of photosynthesis, thermotolerance, cell wall, and circadian rhythms.

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Sültemeyer, Dieter F., Heinrich P. Fock et David T. Canvin. « Active uptake of inorganic carbon by Chlamydomonas reinhardtii : evidence for simultaneous transport of HCO3− and CO2 and characterization of active CO2 transport ». Canadian Journal of Botany 69, n^o 5 (1 mai 1991) : 995–1002. http://dx.doi.org/10.1139/b91-128.

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Washed protoplasts of low CO2 grown cells of Chlamydomonas reinhardtii were used to further characterize the ability for active CO2 transport. The CO2 transport mechanism and the high affinity for dissolved inorganic carbon were completely induced within 4 h after transferring 5% CO2 grown cells to ambient air (0.035% CO2). Net O2 evolution and CO2 uptake were saturable processes showing saturation between 100 and 200 μM DIC (1.6–3.2 μM CO2) at pH 8.0. For both O2 evolution in whole cells and CO2 uptake in the protoplasts the concentration of dissolved inorganic carbon required for 50% of the maximal rates was about 12 μM (= 0.20 μM CO2). Studies with 3-(3,4-dichloro-phenyl)-1,1 dimethylurea, dibromo-thymoquinone, tetramethyl phenylenediamine and protoplasts of a cytochrome c oxidase deficient mutant of C. reinhardtii indicated the CO2 transport was driven by cyclic or pseudocyclic ATP formation and oxidative phosphorylation was not involved. These studies also show that CO2 transport and CO2 fixation are distinct mechanisms and that active CO2 uptake may occur in the absence of CO2 fixation. Key words: Chlamydomonas reinhardtii; CO2–HCO3− concentrating mechanism, CO2 transport, cyclic photophosphorylation, pseudocyclic photophosphorylation.

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Hotter, Vivien, David Zopf, Hak Joong Kim, Anja Silge, Michael Schmitt, Prasad Aiyar, Johanna Fleck et al. « A polyyne toxin produced by an antagonistic bacterium blinds and lyses a Chlamydomonad alga ». Proceedings of the National Academy of Sciences 118, n^o 33 (13 août 2021) : e2107695118. http://dx.doi.org/10.1073/pnas.2107695118.

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Algae are key contributors to global carbon fixation and form the basis of many food webs. In nature, their growth is often supported or suppressed by microorganisms. The bacterium Pseudomonas protegens Pf-5 arrests the growth of the green unicellular alga Chlamydomonas reinhardtii, deflagellates the alga by the cyclic lipopeptide orfamide A, and alters its morphology [P. Aiyar et al., Nat. Commun. 8, 1756 (2017)]. Using a combination of Raman microspectroscopy, genome mining, and mutational analysis, we discovered a polyyne toxin, protegencin, which is secreted by P. protegens, penetrates the algal cells, and causes destruction of the carotenoids of their primitive visual system, the eyespot. Together with secreted orfamide A, protegencin thus prevents the phototactic behavior of C. reinhardtii. A mutant of P. protegens deficient in protegencin production does not affect growth or eyespot carotenoids of C. reinhardtii. Protegencin acts in a direct and destructive way by lysing and killing the algal cells. The toxic effect of protegencin is also observed in an eyeless mutant and with the colony-forming Chlorophyte alga Gonium pectorale. These data reveal a two-pronged molecular strategy involving a cyclic lipopeptide and a conjugated tetrayne used by bacteria to attack select Chlamydomonad algae. In conjunction with the bloom-forming activity of several chlorophytes and the presence of the protegencin gene cluster in over 50 different Pseudomonas genomes [A. J. Mullins et al., bioRxiv [Preprint] (2021). https://www.biorxiv.org/content/10.1101/2021.03.05.433886v1 (Accessed 17 April 2021)], these data are highly relevant to ecological interactions between Chlorophyte algae and Pseudomonadales bacteria.

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Baek, Jaewon, et Jong-il Choi. « Effect of Nutrient Limitation on Lipid Content and Fatty Acid Composition of Mutant Chlamydomonas reinhardtii ». KSBB Journal 30, n^o 2 (27 avril 2015) : 91–95. http://dx.doi.org/10.7841/ksbbj.2015.30.2.91.

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Förster, Britta, Peter B. Heifetz, Anita Lardans, John E. Boynton et Nicholas W. Gillham. « Herbicide Resistance and Growth of D1 Ala251 Mutants in Chlamydomonas ». Zeitschrift für Naturforschung C 52, n^o 9-10 (1 octobre 1997) : 654–64. http://dx.doi.org/10.1515/znc-1997-9-1013.

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We elucidated the effects of substituting seven amino acids for Ala at residue 251 of the Chlamydomonas reinhardtii D1 protein on herbicide resistance and photoautotrophic growth. Ala251 has been suggested to play a key role in the structural integrity and function of the stromal loop between transmembrane helices IV and V of D1 and has previously been shown to affect resistance to “classical” PSII specific herbicides. Sensitive and rapid microtiter assays were employed to compare herbicide resistance and photoautotrophic growth in the various mutants. Substitution of Ala251 by Ile, Leu or Val conferred resistance to the PSII herbicides atrazine, bromacil and metribuzin but not to DCMU, and impaired photoautotrophic growth in high and low light. Compared to an otherwise isogenic wildtype strain, the lie and Val mutants exhibited nearly identical levels of herbicide resistance and reduced growth while the Leu mutant had even slower growth and higher levels of herbicide resistance. In contrast Cys, Pro, Ser and Gly mutants were phenotypically indistinguishable from wildtype in terms of herbicide sensitivity and photoautotrophic doubling times. Collectively the seven Ala251 mutations differed markedly from an Ala mutant (dr-1) at the well characterized Ser264 D1 residue in terms of herbicide resistance and photoautotrophic growth

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Hou, Yuqing, Hongmin Qin, John A. Follit, Gregory J. Pazour, Joel L. Rosenbaum et George B. Witman. « Functional analysis of an individual IFT protein : IFT46 is required for transport of outer dynein arms into flagella ». Journal of Cell Biology 176, n^o 5 (20 février 2007) : 653–65. http://dx.doi.org/10.1083/jcb.200608041.

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Intraflagellar transport (IFT), which is the bidirectional movement of particles within flagella, is required for flagellar assembly. IFT particles are composed of ∼16 proteins, which are organized into complexes A and B. We have cloned Chlamydomonas reinhardtii and mouse IFT46, and show that IFT46 is a highly conserved complex B protein in both organisms. A C. reinhardtii insertional mutant null for IFT46 has short, paralyzed flagella lacking dynein arms and with central pair defects. The mutant has greatly reduced levels of most complex B proteins, indicating that IFT46 is necessary for complex B stability. A partial suppressor mutation restores flagellar length to the ift46 mutant. IFT46 is still absent, but levels of the other IFT particle proteins are largely restored, indicating that complex B is stabilized in the suppressed strain. Axonemal ultrastructure is restored, except that the outer arms are still missing, although outer arm subunits are present in the cytoplasm. Thus, IFT46 is specifically required for transporting outer arms into the flagellum.

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