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Massoz S, Larosa V, Horrion B, Matagne RF, Remacle C, Cardol P. Isolation of Chlamydomonas reinhardtii mutants with altered mitochondrial respiration by chlorophyll fluorescence measurement. J Biotechnol 2015; 215:27-34. [PMID: 26022424 DOI: 10.1016/j.jbiotec.2015.05.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Revised: 05/11/2015] [Accepted: 05/15/2015] [Indexed: 11/24/2022]
Abstract
The unicellular green alga Chlamydomonas reinhardtii is a model organism for studying energetic metabolism. Most mitochondrial respiratory-deficient mutants characterized to date have been isolated on the basis of their reduced ability to grow in heterotrophic conditions. Mitochondrial deficiencies are usually partly compensated by adjustment of photosynthetic activity and more particularly by transition to state 2. In this work, we explored the opportunity to select mutants impaired in respiration and/or altered in dark metabolism by measuring maximum photosynthetic efficiency by chlorophyll fluorescence analyses (FV/FM). Out of about 2900 hygromycin-resistant insertional mutants generated from wild type or from a mutant strain deficient in state transitions (stt7 strain), 22 were found to grow slowly in heterotrophic conditions and 8 of them also showed a lower FV/FM value. Several disrupted coding sequences were identified, including genes coding for three different subunits of respiratory-chain complex I (NUO9, NUOA9, NUOP4) or for isocitrate lyase (ICL1). Overall, the comparison of respiratory mutants obtained in wild-type or stt7 genetic backgrounds indicated that the FV/FM value can be used to isolate mutants severely impaired in dark metabolism.
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Affiliation(s)
- Simon Massoz
- Genetics and Physiology of Microalgae, PhytoSYSTEMS, Department of Life Sciences, University of Liège, B-4000 Liège, Belgium
| | - Véronique Larosa
- Genetics and Physiology of Microalgae, PhytoSYSTEMS, Department of Life Sciences, University of Liège, B-4000 Liège, Belgium
| | - Bastien Horrion
- Genetics and Physiology of Microalgae, PhytoSYSTEMS, Department of Life Sciences, University of Liège, B-4000 Liège, Belgium
| | - René F Matagne
- Genetics and Physiology of Microalgae, PhytoSYSTEMS, Department of Life Sciences, University of Liège, B-4000 Liège, Belgium
| | - Claire Remacle
- Genetics and Physiology of Microalgae, PhytoSYSTEMS, Department of Life Sciences, University of Liège, B-4000 Liège, Belgium
| | - Pierre Cardol
- Genetics and Physiology of Microalgae, PhytoSYSTEMS, Department of Life Sciences, University of Liège, B-4000 Liège, Belgium.
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Massoz S, Larosa V, Plancke C, Lapaille M, Bailleul B, Pirotte D, Radoux M, Leprince P, Coosemans N, Matagne RF, Remacle C, Cardol P. Inactivation of genes coding for mitochondrial Nd7 and Nd9 complex I subunits in Chlamydomonas reinhardtii. Impact of complex I loss on respiration and energetic metabolism. Mitochondrion 2014; 19 Pt B:365-74. [DOI: 10.1016/j.mito.2013.11.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2013] [Revised: 11/22/2013] [Accepted: 11/26/2013] [Indexed: 02/04/2023]
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Matagne RF, Beckers MC. Perturbation of chloroplast gene transmission in diploid and triploid zygotes of Chlamydomonas reinhardi by 5-fluorodeoxyuridine. Curr Genet 2013; 7:335-8. [PMID: 24173413 DOI: 10.1007/bf00445872] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/1983] [Indexed: 10/26/2022]
Abstract
Haploid cells or diploid cells homozygous (mt(+)/mt(+) or mt(-)/mt(-)) or heterozygous (mt(+)/mt(-) phenotypically mt(-)) for the mating-type locus and homoplasmic for a chloroplast marker conferring resistance to an antibiotic were crossed with haploid cells of opposite mating-type and carrying another chloroplast marker. Before mating, one or both of the parental strains were grown for 8 days on agar containing 1 mM 5-fluorodeoxyuridine (FUdR), which selectively reduces the amount of chloroplast DNA in Chlamydomonas. In all cases, the chloroplast allele of the treated parent was less frequently transmitted to the meiotic progeny of the zygote than in the corresponding control cross. The effect of FUdR was more pronounced on haploid cells than on diploid cells which initially contained a two-fold higher amount of chloroplast DNA.The results are discussed in relation to current models for uniparental inheritance of non-Mendelian genes.
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Affiliation(s)
- R F Matagne
- Genetics of Microorganisms, Department of Botany, University of Liege, B-4000, Liege, Belgium
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Ghysels B, Godaux D, Matagne RF, Cardol P, Franck F. Function of the chloroplast hydrogenase in the microalga Chlamydomonas: the role of hydrogenase and state transitions during photosynthetic activation in anaerobiosis. PLoS One 2013; 8:e64161. [PMID: 23717558 PMCID: PMC3662714 DOI: 10.1371/journal.pone.0064161] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2013] [Accepted: 04/10/2013] [Indexed: 01/12/2023] Open
Abstract
Like a majority of photosynthetic microorganisms, the green unicellular alga Chlamydomonas reinhardtii may encounter O2 deprived conditions on a regular basis. In response to anaerobiosis or in a respiration defective context, the photosynthetic electron transport chain of Chlamydomonas is remodeled by a state transition process to a conformation that favours the photoproduction of ATP at the expense of reductant synthesis. In some unicellular green algae including Chlamydomonas, anoxia also triggers the induction of a chloroplast-located, oxygen sensitive hydrogenase, which accepts electrons from reduced ferredoxin to convert protons into molecular hydrogen. Although microalgal hydrogen evolution has received much interest for its biotechnological potential, its physiological role remains unclear. By using specific Chlamydomonas mutants, we demonstrate that the state transition ability and the hydrogenase function are both critical for induction of photosynthesis in anoxia. These two processes are thus important for survival of the cells when they are transiently placed in an anaerobic environment.
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Affiliation(s)
- Bart Ghysels
- Laboratory of Bioenergetics, Institute of Plant Biology B22, University of Liège, Liège, Belgium
| | - Damien Godaux
- Laboratory of Genetics of Microorganisms, Institute of Plant Biology B22, University of Liège, Liège, Belgium
| | - René F. Matagne
- Laboratory of Genetics of Microorganisms, Institute of Plant Biology B22, University of Liège, Liège, Belgium
| | - Pierre Cardol
- Laboratory of Genetics of Microorganisms, Institute of Plant Biology B22, University of Liège, Liège, Belgium
| | - Fabrice Franck
- Laboratory of Bioenergetics, Institute of Plant Biology B22, University of Liège, Liège, Belgium
- * E-mail:
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Matagne RF, Mathieu D. Transmission of chloroplast genes in triploid and tetraploid zygospores of Chlamydomonas reinhardtii: Roles of mating-type gene dosage and gametic chloroplast DNA content. Proc Natl Acad Sci U S A 2010; 80:4780-3. [PMID: 16593351 PMCID: PMC384128 DOI: 10.1073/pnas.80.15.4780] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Diploid clones homozygous (mt(+)/mt(+) or mt(-)/mt(-)) or heterozygous (mt(+)/mt(-); phenotypically mt(-)) for the mating-type locus and homoplasmic for a chloroplast marker conferring resistance to an antibiotic were isolated by artificially induced cell fusion or sexual mating. These diploids were crossed with haploid or diploid strains of opposite mating type and carrying another chloroplast marker. The transmission of the chloroplast genes was analyzed in the triploid and tetraploid zygospores in comparison with diploid zygospores used as controls. The transmission was almost exclusively maternal (mt(+)) (>94%) in the crosses mt(+) x mt(-), mt(+)/mt(+) x mt(-), and mt(+)/mt(+) x mt(-)/mt(-). The transmission was preferentially maternal (>76%) in the crosses mt(+) x mt(-)/mt(-) whereas in the crosses mt(+) x mt(+)/mt(-), <50% of the zygospores transmitted the chloroplast allele of maternal (mt(+)) origin. The zygospores produced in crosses mt(+)/mt(+) x mt(+)/mt(-) transmitted the alleles from both parents in >60% of cases. The results show that (i) the presence of one mt(+) allele in the mt(+)/mt(-) (phenotypically mt(-)) diploid gametes and (ii) the higher amount of chloroplast DNA molecules (input) present in the diploid gametes versus the haploid ones favor the transmission of the chloroplast allele contributed by these gametes. Moreover, because the zygospores issued from crosses mt(+)/mt(+) x mt(-) and mt(+) x mt(+)/mt(-) were genotypically identical mt(+)/mt(+)/mt(-)) but behaved very differently in their chloroplast gene transmission, it was concluded that the molecular events leading to preferential elimination of paternal DNA copies must occur before the fusion of nuclei or chloroplasts in the newly formed zygotes.
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Affiliation(s)
- R F Matagne
- Genetics of Microorganisms, Department of Botany, University of Liège, Sart Tilman B-4000 Liège, Belgium
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Matagne RF, Hermesse MP. Modification of Chloroplast Gene Transmission in Somatic Fusion Products and Vegetative Zygotes of CHLAMYDOMONAS REINHARDI by 5-Fluorodeoxyuridine. Genetics 2010; 99:371-81. [PMID: 17249124 PMCID: PMC1214508 DOI: 10.1093/genetics/99.3-4.371] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Sexual crosses and somatic fusions were performed between complementing wall-less arg(-) mutant strains bearing chloroplast markers for resistance to antibiotics. The mode of chloroplast allele transmission was investigated in the diploid colonies developed from both vegetative zygotes and fusion products. Before mating or fusion, one or both of the parental strains were grown for 4 or 8 days on agar containing 5-fluorodeoxyuridine (FUdR, 0.1 to 1.0 mm), which selectively reduces the amount of chloroplast DNA in Chlamydomonas. When one parent was pregrown on FUdR, the frequency of vegetative zygotes transmitting chloroplast alleles of both parents (biparental or BP zygotes) decreased, the reduction being more drastic when the mt(-) parent was treated. Transmission was mainly uniparental maternal (UPm) or paternal (UPp) depending on whether the mt(-) or the mt(+) parent was pregrown for 8 days in the presence of 1.0 mm FUdR. Treatment of both parents led to a strong maternal transmission. In the experiments involving somatic fusion between parent 1 and parent 2 (same or opposite mt), the ratio UP(1)/UP(2), which was approximately equal to 1 in the control, decreased or increased according to whether the cells of parent 1 or 2 were pregrown on FUdR. In parallel, the frequency of BP fusion products always decreased. When both parental strains were treated with FUdR, the frequency of BP fusion products also decreased and the ratio UP(1)/UP(2) was roughly equal to 1. The effect of FUdR can be interpreted in terms of reduction of the input frequencies of parental chloroplast genomes at the time of gametic or somatic cell fusion, the bias in favor of the maternal parent being operational only in sexual crosses.
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Affiliation(s)
- R F Matagne
- Genetics of Microorganisms, Department of Botany, University of Liege, B-4000 Liege, Belgium
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Mathy G, Cardol P, Dinant M, Blomme A, Gérin S, Cloes M, Ghysels B, DePauw E, Leprince P, Remacle C, Sluse-Goffart C, Franck F, Matagne RF, Sluse FE. Proteomic and Functional Characterization of a Chlamydomonas reinhardtii Mutant Lacking the Mitochondrial Alternative Oxidase 1. J Proteome Res 2010; 9:2825-38. [DOI: 10.1021/pr900866e] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Grégory Mathy
- Laboratory of Bioenergetics and Cellular Physiology, Laboratory of Genetics of Microorganisms, Laboratory of Plant Biochemistry, Laboratory of Mass Spectrometry, and GIGA-Neuroscience, University of Liege, Belgium
| | - Pierre Cardol
- Laboratory of Bioenergetics and Cellular Physiology, Laboratory of Genetics of Microorganisms, Laboratory of Plant Biochemistry, Laboratory of Mass Spectrometry, and GIGA-Neuroscience, University of Liege, Belgium
| | - Monique Dinant
- Laboratory of Bioenergetics and Cellular Physiology, Laboratory of Genetics of Microorganisms, Laboratory of Plant Biochemistry, Laboratory of Mass Spectrometry, and GIGA-Neuroscience, University of Liege, Belgium
| | - Arnaud Blomme
- Laboratory of Bioenergetics and Cellular Physiology, Laboratory of Genetics of Microorganisms, Laboratory of Plant Biochemistry, Laboratory of Mass Spectrometry, and GIGA-Neuroscience, University of Liege, Belgium
| | - Stéphanie Gérin
- Laboratory of Bioenergetics and Cellular Physiology, Laboratory of Genetics of Microorganisms, Laboratory of Plant Biochemistry, Laboratory of Mass Spectrometry, and GIGA-Neuroscience, University of Liege, Belgium
| | - Marie Cloes
- Laboratory of Bioenergetics and Cellular Physiology, Laboratory of Genetics of Microorganisms, Laboratory of Plant Biochemistry, Laboratory of Mass Spectrometry, and GIGA-Neuroscience, University of Liege, Belgium
| | - Bart Ghysels
- Laboratory of Bioenergetics and Cellular Physiology, Laboratory of Genetics of Microorganisms, Laboratory of Plant Biochemistry, Laboratory of Mass Spectrometry, and GIGA-Neuroscience, University of Liege, Belgium
| | - Edwin DePauw
- Laboratory of Bioenergetics and Cellular Physiology, Laboratory of Genetics of Microorganisms, Laboratory of Plant Biochemistry, Laboratory of Mass Spectrometry, and GIGA-Neuroscience, University of Liege, Belgium
| | - Pierre Leprince
- Laboratory of Bioenergetics and Cellular Physiology, Laboratory of Genetics of Microorganisms, Laboratory of Plant Biochemistry, Laboratory of Mass Spectrometry, and GIGA-Neuroscience, University of Liege, Belgium
| | - Claire Remacle
- Laboratory of Bioenergetics and Cellular Physiology, Laboratory of Genetics of Microorganisms, Laboratory of Plant Biochemistry, Laboratory of Mass Spectrometry, and GIGA-Neuroscience, University of Liege, Belgium
| | - Claudine Sluse-Goffart
- Laboratory of Bioenergetics and Cellular Physiology, Laboratory of Genetics of Microorganisms, Laboratory of Plant Biochemistry, Laboratory of Mass Spectrometry, and GIGA-Neuroscience, University of Liege, Belgium
| | - Fabrice Franck
- Laboratory of Bioenergetics and Cellular Physiology, Laboratory of Genetics of Microorganisms, Laboratory of Plant Biochemistry, Laboratory of Mass Spectrometry, and GIGA-Neuroscience, University of Liege, Belgium
| | - René F. Matagne
- Laboratory of Bioenergetics and Cellular Physiology, Laboratory of Genetics of Microorganisms, Laboratory of Plant Biochemistry, Laboratory of Mass Spectrometry, and GIGA-Neuroscience, University of Liege, Belgium
| | - Francis E. Sluse
- Laboratory of Bioenergetics and Cellular Physiology, Laboratory of Genetics of Microorganisms, Laboratory of Plant Biochemistry, Laboratory of Mass Spectrometry, and GIGA-Neuroscience, University of Liege, Belgium
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Cardol P, Lapaille M, Minet P, Franck F, Matagne RF, Remacle C. ND3 and ND4L subunits of mitochondrial complex I, both nucleus encoded in Chlamydomonas reinhardtii, are required for activity and assembly of the enzyme. Eukaryot Cell 2006; 5:1460-7. [PMID: 16963630 PMCID: PMC1563589 DOI: 10.1128/ec.00118-06] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2006] [Accepted: 07/05/2006] [Indexed: 11/20/2022]
Abstract
Made of more than 40 subunits, the rotenone-sensitive NADH:ubiquinone oxidoreductase (complex I) is the most intricate membrane-bound enzyme of the mitochondrial respiratory chain. In vascular plants, fungi, and animals, at least seven complex I subunits (ND1, -2, -3, -4, -4L, -5, and -6; ND is NADH dehydrogenase) are coded by mitochondrial genes. The role of these highly hydrophobic subunits in the enzyme activity and assembly is still poorly understood. In the unicellular green alga Chlamydomonas reinhardtii, the ND3 and ND4L subunits are encoded in the nuclear genome, and we show here that the corresponding genes, called NUO3 and NUO11, respectively, display features that facilitate their expression and allow the proper import of the corresponding proteins into mitochondria. In particular, both polypeptides show lower hydrophobicity compared to their mitochondrion-encoded counterparts. The expression of the NUO3 and NUO11 genes has been suppressed by RNA interference. We demonstrate that the absence of ND3 or ND4L polypeptides prevents the assembly of the 950-kDa whole complex I and suppresses the enzyme activity. The putative role of hydrophobic ND subunits is discussed in relation to the structure of the complex I enzyme. A model for the assembly pathway of the Chlamydomonas enzyme is proposed.
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Affiliation(s)
- Pierre Cardol
- Biochemistry and Photobiology Laboratory, Department of Life Sciences, Université de Liège, B-4000, Liège, Belgium.
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Cardol P, González-Halphen D, Reyes-Prieto A, Baurain D, Matagne RF, Remacle C. The mitochondrial oxidative phosphorylation proteome of Chlamydomonas reinhardtii deduced from the Genome Sequencing Project. Plant Physiol 2005; 137:447-59. [PMID: 15710684 PMCID: PMC1065347 DOI: 10.1104/pp.104.054148] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2004] [Revised: 11/25/2004] [Accepted: 11/25/2004] [Indexed: 05/20/2023]
Affiliation(s)
- Pierre Cardol
- Genetics of Microorganisms , Institute of Plant Biology B22, University of Liege, B-4000 Liege, Belgium
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Cardol P, Vanrobaeys F, Devreese B, Van Beeumen J, Matagne RF, Remacle C. Higher plant-like subunit composition of mitochondrial complex I from Chlamydomonas reinhardtii: 31 conserved components among eukaryotes. Biochim Biophys Acta 2004; 1658:212-24. [PMID: 15450959 DOI: 10.1016/j.bbabio.2004.06.001] [Citation(s) in RCA: 98] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2004] [Revised: 05/31/2004] [Accepted: 06/08/2004] [Indexed: 11/16/2022]
Abstract
The rotenone-sensitive NADH:ubiquinone oxidoreductase (complex I) is the most intricate membrane-bound enzyme of the mitochondrial respiratory chain. Notably the bovine enzyme comprises up to 46 subunits, while 27 subunits could be considered as widely conserved among eukaryotic complex I. By combining proteomic and genomic approaches, we characterized the complex I composition from the unicellular green alga Chlamydomonas reinhardtii. After purification by blue-native polyacrylamide gel electrophoresis (BN-PAGE), constitutive subunits were analyzed by SDS-PAGE coupled to tandem mass spectrometry (MS) that allowed the identification of 30 proteins. We compared the known complex I components from higher plants, mammals, nematodes and fungi with this MS data set and the translated sequences from the algal genome project. This revealed that the Chlamydomonas complex I is likely composed of 42 proteins, for a total molecular mass of about 970 kDa. In addition to the 27 typical components, we have identified four new complex I subunit families (bovine ESSS, PFFD, B16.6, B12 homologues), extending the number of widely conserved eukaryote complex I components to 31. In parallel, our analysis showed that a variable number of subunits appears to be specific to each eukaryotic kingdom (animals, fungi or plants). Protein sequence divergence in these kingdom-specific sets is significant and currently we cannot exclude the possibility that homology between them exists, but has not yet been detected.
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Affiliation(s)
- Pierre Cardol
- Genetics of Microorganisms, Department of Life Sciences, University of Liège, B22, Institute of Botany, B4000 Liege, Belgium.
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Remacle C, Gloire G, Cardol P, Matagne RF. Impact of a mutation in the mitochondrial LSU rRNA gene from Chlamydomonas reinhardtii on the activity and the assembly of respiratory-chain complexes. Curr Genet 2004; 45:323-30. [PMID: 15014977 DOI: 10.1007/s00294-004-0490-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2003] [Revised: 01/21/2004] [Accepted: 01/24/2004] [Indexed: 10/26/2022]
Abstract
Two substitutions A1090G and A1098C (together called the m mutation) located in the conserved GTPase domain of the mitochondrial LSU rRNA gene were recently shown to weakly compensate for the phenotypical effect of a -1T frameshift mutation in the mitochondrial cox1 gene of C. reinhardtii. In order to analyze the impact of the m mutation on the mitochondrial translational machinery, a strain carrying the m mutation but wild-type for the cox1 gene was isolated. We found that the growth and the respiratory rate of the m mutant were affected and that the activities of complexes I, III, and IV, all containing mitochondria-encoded subunits, were lowered. In contrast the activities of complex II and of the alternative oxidase, both encoded exclusively by the nuclear genome, were not modified. The steady-state levels of complex I enzyme and of several components of the respiratory complexes I, III, and IV were also reduced in the mutant. We moreover showed that m did not suppress other frameshift or UGA stop mutations which affect mitochondrial genes.
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Affiliation(s)
- C Remacle
- Department of Life Sciences, Institute of Botany B22, University of Liège, Sart-Tilman, 4000, Liège, Belgium.
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Baurain D, Dinant M, Coosemans N, Matagne RF. Regulation of the alternative oxidase Aox1 gene in Chlamydomonas reinhardtii. Role of the nitrogen source on the expression of a reporter gene under the control of the Aox1 promoter. Plant Physiol 2003; 131:1418-30. [PMID: 12644691 PMCID: PMC166901 DOI: 10.1104/pp.013409] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2002] [Revised: 11/03/2002] [Accepted: 12/10/2002] [Indexed: 05/21/2023]
Abstract
In higher plants, various developmental and environmental conditions enhance expression of the alternative oxidase (AOX), whereas its induction in fungi is mainly dependent on cytochrome pathway restriction and triggering by reactive oxygen species. The AOX of the unicellular green alga Chlamydomonas reinhardtii is encoded by two different genes, the Aox1 gene being much more transcribed than Aox2. To analyze the transcriptional regulation of Aox1, we have fused its 1.4-kb promoter region to the promoterless arylsulfatase (Ars) reporter gene and measured ARS enzyme activities in transformants carrying the chimeric construct. We show that the Aox1 promoter is generally unresponsive to a number of known AOX inducers, including stress agents, respiratory inhibitors, and metabolites, possibly because the AOX activity is constitutively high in the alga. In contrast, the Aox1 expression is strongly dependent on the nitrogen source, being down-regulated by ammonium and stimulated by nitrate. Inactivation of nitrate reductase leads to a further increase of expression. The stimulation by nitrate also occurs at the AOX protein and respiratory levels. A deletion analysis of the Aox1 promoter region demonstrates that a short upstream segment (-253 to +59 with respect to the transcription start site) is sufficient to ensure gene expression and regulation, but that distal elements are required for full gene expression. The observed pattern of AOX regulation points to the possible interaction between chloroplast and mitochondria in relation to a potential increase of photogenerated ATP when nitrate is used as a nitrogen source.
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Affiliation(s)
- Denis Baurain
- Genetics of Microorganisms, Department of Life Sciences, B22, University of Liège, Sart Tilman, B-4000 Liège, Belgium
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Cardol P, Matagne RF, Remacle C. Impact of mutations affecting ND mitochondria-encoded subunits on the activity and assembly of complex I in Chlamydomonas. Implication for the structural organization of the enzyme. J Mol Biol 2002; 319:1211-21. [PMID: 12079358 DOI: 10.1016/s0022-2836(02)00407-2] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The mitochondrial rotenone-sensitive NADH:ubiquinone oxidoreductase (complex I) comprises more than 35 subunits, the majority of which are encoded by the nucleus. In Chlamydomonas reinhardtii, only five components (ND1, ND2, ND4, ND5 and ND6) are coded for by the mitochondrial genome. Here, we characterize two mitochondrial mutants (dum5 and dum17) showing strong reduction or inactivation of complex I activity: dum5 is a 1T deletion in the 3' UTR of nd5 whereas dum17 is a 1T deletion in the coding sequence of nd6. The impact of these mutations and of mutations affecting nd1, nd4 and nd4/nd5 genes on the assembly of complex I is investigated. After separation of the respiratory complexes by blue native (BN)-PAGE or sucrose gradient centrifugation, we demonstrate that the absence of intact ND1 or ND6 subunit prevents the assembly of the 850 kDa whole complex, whereas the loss of ND4 or ND4/ND5 leads to the formation of a subcomplex of 650 kDa present in reduced amount. The implications of our findings for the possible role of these ND subunits on the activity of complex I and for the structural organization of the membrane arm of the enzyme are discussed. In mitochondria from all the strains analyzed, we moreover detected a 160-210 kDa fragment comprising the hydrophilic 49 kDa and 76 kDa subunits of the complex I peripheral arm and showing NADH dehydrogenase activity.
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Affiliation(s)
- Pierre Cardol
- Genetics of Microorganisms, Department of Life Sciences, B22, University of Liège, Belgium
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Matagne RF, Baurain D. A mutation in the GTPase domain of the large subunit rRNA is involved in the suppression of a -1T frameshift mutation affecting a mitochondrial gene in Chlamydomonas reinhardtii. Mol Genet Genomics 2001; 266:103-8. [PMID: 11589566 DOI: 10.1007/s004380100526] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The dum19 mutation isolated in Chlamydomonas reinhardtii is due to the deletion of one T at codon 152 of the mitochondrial cox1 gene sequence. Phenotypically, the dum19 mutant is characterized by a lack of cytochrome c oxidase activity and is unable to grow under heterotrophic conditions. A spontaneous pseudo-revertant that grows slowly in the dark was isolated from the dum19 mutant strain. A genetic and molecular analysis allowed us to demonstrate that the revertant phenotype is the consequence of two additional mutations that together act as a frameshift suppressor: an m mutation affecting a mitochondrial gene other than cox1 and an n mutation affecting a nuclear gene. On its own the n mutation does not act as a suppressor, whereas the m mutation very slightly compensates for the effect of the -1T mutation. Sequencing analysis showed that the m mutation affects the GTPase-associated domain of the large subunit (LSU) ofmitochondrial rRNA. Surprisingly, two substitutions, A1090 to G and A1098 to C, were found in the LSU rRNA of the revertant, the latter one being already present in the dum19 mutant strain itself. The A1090 to G substitution is thus involved in the suppression of the frameshift mutation, but it is not clear whether the change at position 1098 is also required for the expression of the suppressed phenotype. To our knowledge, this is the first example of a mutation in the GTPase-associated domain acting as a suppressor of a frameshift mutation.
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Affiliation(s)
- R F Matagne
- Department of Plant Biology, University of Liège, Sart Tilman, Belgium.
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15
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Duby F, Cardol P, Matagne RF, Remacle C. Structure of the telomeric ends of mt DNA, transcriptional analysis and complex I assembly in the dum24 mitochondrial mutant of Chlamydomonas reinhardtii. Mol Genet Genomics 2001; 266:109-14. [PMID: 11589567 DOI: 10.1007/s004380100529] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The dum24 mutant of Chlamydomonas reinhardtii contains four types of altered mitochondrial linear genomes: two types of deleted monomers and two types of dimers resulting from fusions between some monomers via their deleted ends. All molecules lack at least cob, nd4 and the 3' end of nd5, three adjacent genes located in the left part of the genome. We present evidence showing that in dum24, as in other deletion mutants, the deletions extend to the left telomeric end, and propose that the only replicative forms in the mutants are the dimeric DNA molecules that possess intact telomeric structures at both ends. Two abnormally large transcripts produced from chimeric genes are detected in dum24, which throws some light on the location of potential promoter sequences and processing signals in the mitochondrial genome. Using BN-PAGE analysis and immunological methods to detect complex I, we further show that dum24 mitochondria do not possess the normal multimeric complex I (850 kDa), but produce a smaller, partially assembled, complex (650 kDa), demonstrating a role for ND4 and/or ND5 subunits(s) in complex I assembly.
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Affiliation(s)
- F Duby
- Department of Plant Biology, University of Liège, Belgium.
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16
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Abstract
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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Affiliation(s)
- C Remacle
- Genetics of Microorganisms, Department of Plant Biology B22, University of Liège, B-4000 Liège, Belgium.
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17
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Remacle C, Baurain D, Cardol P, Matagne RF. Mutants of Chlamydomonas reinhardtii deficient in mitochondrial complex I: characterization of two mutations affecting the nd1 coding sequence. Genetics 2001; 158:1051-60. [PMID: 11454754 PMCID: PMC1461730 DOI: 10.1093/genetics/158.3.1051] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The mitochondrial rotenone-sensitive NADH:ubiquinone oxidoreductase (complex I) comprises more than 30 subunits, the majority of which are encoded by the nucleus. In Chlamydomonas reinhardtii, only five components of complex I are coded for by mitochondrial genes. Three mutants deprived of complex I activity and displaying slow growth in the dark were isolated after mutagenic treatment with acriflavine. A genetical analysis demonstrated that two mutations (dum20 and dum25) affect the mitochondrial genome whereas the third mutation (dn26) is of nuclear origin. Recombinational analyses showed that dum20 and dum25 are closely linked on the genetic map of the mitochondrial genome and could affect the nd1 gene. A sequencing analysis confirmed this conclusion: dum20 is a deletion of one T at codon 243 of nd1; dum25 corresponds to a 6-bp deletion that eliminates two amino acids located in a very conserved hydrophilic segment of the protein.
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Affiliation(s)
- C Remacle
- Laboratory of Genetics of Microorganisms, Department of Plant Biology, University of Liège, B-4000 Liège Sart-Tilman, Belgium
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18
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Dinant M, Baurain D, Coosemans N, Joris B, Matagne RF. Characterization of two genes encoding the mitochondrial alternative oxidase in Chlamydomonas reinhardtii. Curr Genet 2001; 39:101-8. [PMID: 11405094 DOI: 10.1007/s002940000183] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Two cDNA clones (AOX1 and AOX2) and the corresponding genes encoding the alternative oxidases (AOXs) from Chlamydomonas reinhardtii were isolated and sequenced. The cDNAs, AOX1 and AOX2, contained open reading frames (ORFs) encoding putative proteins of 360 amino acids and 347 amino acids, respectively. For each of the ORFs, a potential mitochondrial-targeting sequence was found in the 5'-end regions. In comparison to AOX enzymes from plants and fungi, the predicted amino acid sequences of the ORFs showed their highest degree of identity with proteins from Aspergillus niger (38.1% and 37.2%) and Ajellomyces capsulatus (37% and 34.9%). Several residues supposed either to be Fe ligands or to be involved in the ubiquinol-binding site were fully conserved in both C. reinhardtii putative AOX proteins. In contrast, a cysteine residue conserved in the sequences of all higher plants and probably involved in the regulation of the enzyme activity was missing both from the AOX1 and AOX2 amino acid sequences and from protein sequences from various other microorganisms. The transcriptional expression of the AOX1 and AOX2 genes in wild-type cells and in mutant cells deficient in mitochondrial complex III activity was also investigated.
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Affiliation(s)
- M Dinant
- Génétique des Mícroorganismes, Département de Biologie Végétale, B22, Université de Liège, Sart Tilman, 4000 Liège, Belgium
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19
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Abstract
Insertional mutagenesis was used in Chlamydomonas reinhardtii to isolate original mutants hypersensitive to multiple drugs and physical agents. Out of 5200 transformants analyzed, 13 mutants belonging to seven phenotypic classes were isolated. Five were exclusively sensitive to cadmium and represented two loci. The other mutants were pleiotropic and presented a cross sensitivity to several (2--6) of the following agents: cadmium, copper, lead, paraquat, hydrogen peroxide, UVC and light. In all mutants analyzed, the hypersensitive phenotype was most probably due to a single mutational event. The sensitivity of several pleiotropic mutants to a broad range of physical and chemical agents suggests that the disrupted genes are involved in multiple stress responses.
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Affiliation(s)
- M Hanikenne
- Genetics of Microorganisms, Department of Plant Biology, B22, University of Liège, Sart-Tilman, B-4000 Liège, Belgium
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20
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Loppes R, Radoux M, Ohresser MC, Matagne RF. Transcriptional regulation of the Nia1 gene encoding nitrate reductase in Chlamydomonas reinhardtii: effects of various environmental factors on the expression of a reporter gene under the control of the Nia1 promoter. Plant Mol Biol 1999; 41:701-11. [PMID: 10645729 DOI: 10.1023/a:1006381527119] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
The NAD(P)H nitrate reductase (NR) from Chlamydomonas reinhardtii is encoded by the structural gene Nia1. Numerous data from the literature indicate that this enzyme is submitted to complex regulation mechanisms involving multiple controls at transcriptional and post-transcriptional levels. To specifically investigate the regulation of the Nia1 gene at the transcriptional level, NR+ and NR- transformed cells harbouring the Nia1:Ars construct (Nia1 promoter fused to the arylsulfatase (ARS)-encoding Ars reporter gene) were cultivated under various experimental conditions and the ARS activities were recorded. ARS levels were very low in cells grown in the presence of NH4Cl and dramatically increased on agar medium deprived of any nitrogen source or containing nitrate, nitrite, urea, arginine or glutamine. Compared to nitrogen-free medium, a slight positive effect of nitrate in the NR+ strain and a significant negative effect of nitrite in both NR+ and NR- strains were observed. The ARS activities were high in the light and very low in the dark or in the light in the presence of DCMU, indicating that Nia1 transcription is strikingly dependent on photosynthetic activity. Acetate used as a carbon source in the dark did not substitute for light in stimulating Nia1:Ars expression. Inactivation of NR by tungstate treatment of the NR+ strain resulted in a dramatic increase of ARS level suggesting that in Chlamydomonas, like in higher plants, active NR negatively regulates the transcription of the NR structural gene. Deleting the major part of the Nia1 leader sequence still present in the chimeric gene resulted in a decrease of ARS level but did not modify the regulation pattern.
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Affiliation(s)
- R Loppes
- Department of Plant Biology, University of Liège, Sart Tilman, Belgium.
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21
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Willem S, Srahna M, Devos N, Gerday C, Loppes R, Matagne RF. Protein adaptation to low temperatures: a comparative study of alpha-tubulin sequences in mesophilic and psychrophilic algae. Extremophiles 1999; 3:221-6. [PMID: 10484178 DOI: 10.1007/s007920050119] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
The alpha-tubulin genes from two psychrophilic algae belonging to the genus Chloromonas (here named ANT1 and ANT3) have been isolated and sequenced. The genes ant1 and ant3 contain 4 and 2 introns, respectively. The coding DNA sequences are 90% identical but the degree of isology is very high at the polypeptide level (more than 97% strict identities). The ANT1 and ANT3 alpha-tubulin amino acid sequences were compared to the corresponding sequence of the mesophilic alga Chlamydomonas reinhardtii. Of the 15 substitutions detected in ANT1 and/or ANT3, 5 are common to both psychrophilic algae. The recorded substitutions have been analyzed in terms of cold adaptation on the basis of the available three-dimensional structure of the alpha,beta-tubulin heterodimer from pig brain. Most of these are subtle changes, but two substitutions, M268V and A295V occurring in the region of interdimer contacts, could be of great significance for the cold stability of Antarctic algae microtubules due to the fact that the entropic control of microtubule assembly is particularly high in cold adaptes species.
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Affiliation(s)
- S Willem
- Department of Plant Biology, University of Liège, Belgium
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22
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Duby F, Matagne RF. Alteration of dark respiration and reduction of phototrophic growth in a mitochondrial DNA deletion mutant of Chlamydomonas lacking cob, nd4, and the 3' end of nd5. Plant Cell 1999; 11:115-25. [PMID: 9878636 PMCID: PMC144091 DOI: 10.1105/tpc.11.1.115] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
We describe here a new type of mitochondrial mutation (dum24; for dark uniparental minus inheritance) of the unicellular photosynthetic alga Chlamydomonas reinhardtii. The mutant fails to grow under heterotrophic conditions and displays reduced growth under both photoautotrophic and mixotrophic conditions. In reciprocal crosses between mutant and wild-type cells, the meiotic progeny only inherit the phenotype of the mating-type minus parent, indicating that the dum24 mutation exclusively affects the mitochondrial genome. Digestion with various restriction enzymes followed by DNA gel blot hybridizations with specific probes demonstrated that dum24 cells contain four types of altered mitochondrial genomes: deleted monomers lacking cob, nd4, and the 3' end of the nd5 gene; deleted monomers deprived of cob, nd4, nd5, and the 5' end of the cox1 coding sequence; and two types of dimers produced by end-to-end fusions between monomers similarly or differently deleted. Due to these mitochondrial DNA alterations, complex I activity, the cytochrome pathway of respiration, and presumably, the three phosphorylation sites associated with these enzyme activities are lacking in the mutant. The low respiratory rate of the dum24 cells results from the activities of rotenone-resistant NADH dehydrogenase, complex II, and alternative oxidase, with none of these enzymes being coupled to ATP production. To our knowledge, this type of mitochondrial mutation has never been described for photosynthetic organisms or more generally for obligate aerobes.
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Affiliation(s)
- F Duby
- Genetics of Microorganisms, Department of Plant Biology, B22, University of Liège, B4000 Liège, Belgium
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23
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Remacle C, Colin M, Matagne RF. Suppression of a +1 T mutation by a nearby substitution in the mitochondrial cox1 gene of Chlamydomonas reinhardtii: a new type of frameshift suppression in an organelle genome. Mol Gen Genet 1998; 259:294-8. [PMID: 9749672 DOI: 10.1007/s004380050815] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In Chlamydomonas reinhardtii, mutants defective in the cytochrome pathway of respiration lack the capacity to grow under heterotrophic conditions (in darkness on acetate). In the dark- strain duM18, a + 1 T addition in a run of four Ts, located at codon 145 of the mitochondrial cox1 gene encoding subunit I of cytochrome c oxidase, is responsible for the mutant phenotype. A leaky revertant (su11) that grows heterotrophically at a lower rate than wild-type cells was isolated from dum18. Its respiration sensitivity to cyanide was low and its cytochrome c oxidase activity was only 4% of that of the wild-type enzyme. Meiotic progeny obtained from crosses between revertant and wild-type cells inherited the phenotype of the mt- parent, showing that the suppressor mutation, like dum18 itself, is located in the mitochondrial genome. In order to map the su11 mutation relative to dum18, a recombinational analysis was performed on the diploid progeny. It demonstrated that su11 was very closely linked to the dum18 mutation less than 20-30 bp away. The cox1 gene of the su11 revertant was then sequenced. In addition to the + 1 T frameshift mutation still present at codon 145, an A-->C substitution was found at codon 146, leading to the replacement of a glutamic acid by an alanine in the polypeptide chain. No other mutations were detected in the cox1 coding sequence. As the new GCG codon (Ala) created at position 146 is very seldom used in the mitochondrial genome of C. reinhardtii, we suggest that the partial frameshift suppression by the nearby substitution is due to an occasional abnormal translocation of the ribosome (+ 1 base shift) facilitated both by the run of Ts and the low level of weak interaction of alanyl-tRNA.
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Affiliation(s)
- C Remacle
- Génétique des microorganismes, Département de Biologie végétale, Université de Liège, Belgium
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24
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Ohresser M, Matagne RF, Loppes R. Expression of the arylsulphatase reporter gene under the control of the nit1 promoter in Chlamydomonas reinhardtii. Curr Genet 1997; 31:264-71. [PMID: 9065390 DOI: 10.1007/s002940050204] [Citation(s) in RCA: 91] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
In Chlamydomonas reinhardtii, the expression of the nit1 gene encoding nitrate reductase is dependent on the nature of the nitrogen source and on other environmental factors. We have fused the nit1 promoter region to the arylsulphatase (ars) reporter gene lacking its own promoter and introduced this chimeric construction (nit1/ars) into a wall-less strain of C. reinhardtii. A new and sensitive method, based on the use of alpha-naphthylsulphate as a substrate and a diazonium salt as a chromogenic post-coupling agent, was developed to detect the activity of arylsulphatase (an enzyme which is almost completely secreted in the culture medium) both in vitro and in agar plates. The transformants carrying nit1/ars did not express arylsulphatase when grown in ammonium-sufficient medium but readily accumulated the enzyme in ammonium-free medium either supplemented, or not supplemented, with nitrate or nitrite. The nit1/ars construct, however, was not expressed in the nit2 mutant lacking a specific transcription regulator controlling the expression of nit1. These results, together with the observation that the transcription of nit1/ars is initiated at the same sites as the nit1 endogenous gene, confirms the hypothesis that the regulation of nit1 expression takes place mainly at the transcriptional level. The expression of the ars gene from the nit1 promoter was high enough to allow direct measurements of arylsulphatase activities in pools of transformants without prior isolation of nit1/ars clones. This original procedure has permitted the analysis of the effects of nested deletions in the nit1 promoter region on the expression of the reporter gene. The results indicate that the -282 to -198 sequence is required for transcription to occur and that the -751 to -282 region contains several elements mediating nit1 expression.
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Affiliation(s)
- M Ohresser
- Genetics of Microorganisms, Department of Botany, B22, University of Liège, Sart Tilman, B-4000 Liège, Belgium
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25
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Michaux JR, Filippucci MG, Libois RM, Fons R, Matagne RF. Biogeography and taxonomy of Apodemus sylvaticus (the woodmouse) in the Tyrrhenian region: enzymatic variations and mitochondrial DNA restriction pattern analysis. Heredity (Edinb) 1996; 76 ( Pt 3):267-77. [PMID: 8728987 DOI: 10.1038/hdy.1996.40] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
In the western Mediterranean area, the taxonomic status of the various forms of Apodemus sylvaticus is quite unclear. Moreover, though anthropogenic, the origins of the island populations remain unknown in geographical terms. In order to examine the level of genetic relatedness of insular and continental woodmice, 258 animals were caught in 24 localities distributed in Belgium, France, mainland Italy, Sardinia, Corsica and Elba. Electrophoresis of 33 allozymes and mtDNA restriction fragments were performed and a UPGMA dendrogram built from the indices of genetic divergence. The dendrogram based on restriction patterns shows two main groups: 'Tyrrhenian', comprising all the Italian and Corsican animals and 'North-western', corresponding to all the other mice trapped from the Pyrenees to Belgium. Since all the Tyrrhenian mice are similar and well isolated from their relatives living on the western edge of the Alpine chain, they must share a common origin. The insular populations are consequently derived from peninsular Italian ones. From a taxonomic point of view and taking the priority rules into account, we have to invalidate A. s. clanceyi Harrison, 1948 and to consider the Tyrrhenian woodmice as belonging to A. s. milleri de Beaux, 1926, whereas the North-western ones must be referred to as the nominal supspecies. As far as the Elban woodmouse is concerned, at the moment we prefer to keep its present subspecific status because we only studied one animal.
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Affiliation(s)
- J R Michaux
- Service d'Ethologie et de Psychologie Animale, Institut de Zoologie, Liège, Belgium
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26
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Roudyk SN, Moxhet A, Matagne RF, Aghion J. Evidence of singlet oxygen evolution by whole living cells of Chlamydomonas reinhardtii. Photosynth Res 1996; 47:99-102. [PMID: 24301711 DOI: 10.1007/bf00017757] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/1995] [Accepted: 11/20/1995] [Indexed: 06/02/2023]
Abstract
The oxygen evolved by Chlamydomonas reinhardtii in the light is measured simultaneously with a Clark electrode and with the nitrosodimethylaniline-imidazole colorimetric method which is specific for singlet oxygen. Experiments with wild-type and FuD7 mutant cells (unable to synthesize the D1 protein of Photosystem II), with dichlorophenyldimethylurea (which blocks electron transfer from Photosystem II to Photosystem I) and with dibromothymoquinone (which diverts electrons from their normal path between the two photosystems), as well as with hydroxylamine (an inactivator of the water-splitting part of Photosystem II and a competitor of water for electron donation to it), all point to the dependence of detected singlet oxygen on photolysis of water by Photosystem II.
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Affiliation(s)
- S N Roudyk
- Laboratory of Biochemistry, Département de Botanique (B22), University of Liège, B-4000, Liège, Belgium
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27
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Colin M, Dorthu MP, Duby F, Remacle C, Dinant M, Wolwertz MR, Duyckaerts C, Sluse F, Matagne RF. Mutations affecting the mitochondrial genes encoding the cytochrome oxidase subunit I and apocytochrome b of Chlamydomonas reinhardtii. Mol Gen Genet 1995; 249:179-84. [PMID: 7500939 DOI: 10.1007/bf00290364] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Mitochondrial mutants of the green alga Chlamydomonas reinhardtii that are inactivated in the cytochrome pathway of respiration have previously been isolated. Despite the fact that the alternative oxidase pathway is still active the mutants have lost the capacity to grow heterotrophically (dark + acetate) and display reduced growth under mixotrophic conditions (light + acetate). In crosses between wild-type and mutant cells, the meiotic progeny only inherit the character transmitted by the mt- parent, which indicates that the mutations are located in the 15.8 kb linear mitochondrial genome. Two new mutants (dum-18 and dum-19) have now been isolated and characterized genetically, biochemically and at the molecular level. In addition, two previously isolated mutants (dum-11 and dum-15) were characterized in more detail. dum-11 contains two types of deleted mitochondrial DNA molecules: 15.1 kb monomers lacking the subterminal part of the genome, downstream of codon 147 of the apocytochrome b (COB) gene, and dimers resulting from head-to-head fusion of asymmetrically deleted monomers (15.1 and 9.5 kb DNA molecules, respectively). As in the wild type, the three other mutants contain only 15.8 kb mitochondrial DNA molecules. dum-15 is mutated at codon 140 of the COB gene, a serine (TCT) being changed into a tyrosine (TAC). dum-18 and dum-19 both inactivate cytochrome c oxidase, as a result of frameshift mutations (addition or deletion of 1 bp) at codons 145 and 152, respectively, of the COX1 gene encoding subunit I of cytochrome c oxidase. In a total of ten respiratory deficient mitochondrial mutants characterized thus far, only mutations located in COB or COX1 have been isolated.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- M Colin
- Departement de Botanique, Université de Liège, Belgium
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28
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Remacle C, Colin M, Matagne RF. Genetic mapping of mitochondrial markers by recombinational analysis in Chlamydomonas reinhardtii. Mol Gen Genet 1995; 249:185-90. [PMID: 7500940 DOI: 10.1007/bf00290365] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The mitochondrial genome of Chlamydomonas reinhardtii is a 15.8 kb linear DNA molecule present in multiple copies. In crosses, the meiotic products only inherit the mitochondrial genome of the mating type minus (paternal) parent. In contrast mitotic zygotes transmit maternal and paternal mitochondrial DNA copies to their diploid progeny and recombinational events between molecules of both origins frequently occur. Six mitochondrial mutants unable to grow in the dark (dk- mutants) were crossed in various combinations and the percentages of wild-type dk+ recombinants were determined in mitotic zygotes when all progeny cells had become homoplasmic for the mitochondrial genome. In crosses between strains mutated in the COB (apocytochrome b) gene and strains mutated in the COX1 (subunit 1 of cytochrome oxidase) gene, the frequency of recombination was 13.7% (+/- 3.2%). The corresponding physical distance between the mutation sites was 4.3 kb. In crosses between strains carrying mutations separated by about 20 bp, a recombinational frequency of 0.04% (+/- 0.02%) was found. Two other mutants not yet characterized at the molecular level were also used for recombinational studies. From these data, a linear genetic map of the mitochondrial genome could be drawn. This map is consistent with the positions of the mutation sites on the mitochondrial DNA molecule and thereby validates the method used to generate the map. The frequency of recombination per physical distance unit (3.2% +/- 0.7% per kilobase) is compared with those obtained for other organellar genomes in yeasts and Chlamydomonas.
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Affiliation(s)
- C Remacle
- Département de Botanique, Université de Liège, Belgium
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29
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Remacle C, Matagne RF. Transmission, recombination and conversion of mitochondrial markers in relation to the mobility of a group I intron in Chlamydomonas. Curr Genet 1993; 23:518-25. [PMID: 8319312 DOI: 10.1007/bf00312645] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Mitochondrial DNA transmission has been analyzed in diploids produced from sexual crosses or artificial fusions between Chlamydomonas strains which differ by several genetic markers: a group I intron (Cs cob. 1 or alpha intron), three restriction sites (Nh, Nc and H markers) located 0.5-5 kb from the insertion site of the intron, and a MUD2 point mutation (27 bp from the insertion site) conferring resistance to myxothiazol. Recombination between mitochondrial markers is a general property of all crosses and fusions analyzed. In crosses between two intron-containing (alpha+) strains or two intron-less (alpha-) strains, the transmission is preferentially paternal (mt-), with a preponderance depending on the nature of the parental genomes. In crosses between alpha+ and alpha- strains, the conversion of intron-less molecules intron+ is frequent when the alpha+ parent is maternal (mt+) and nearly absolute when the alpha+ parent is paternal (mt-). In 94% of cases, the conversion is accompanied by the co-conversion of the MUD2 marker. In both crosses and artificial fusions, the conversion of alpha- into alpha+ also influences the transmission of the more distant Nh, Nc and H markers. It is hypothesized that the more frequent transmission of the genome containing the intron results from the elimination of alpha- molecules, as a result of a double-strand cut which is induced by an endonuclease encoded by the intron.
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Affiliation(s)
- C Remacle
- Department of Botany, University of Liège, Sart Tilman, Belgium
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30
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Randolph-Anderson BL, Boynton JE, Gillham NW, Harris EH, Johnson AM, Dorthu MP, Matagne RF. Further characterization of the respiratory deficient dum-1 mutation of Chlamydomonas reinhardtii and its use as a recipient for mitochondrial transformation. Mol Gen Genet 1993; 236:235-44. [PMID: 8437570 DOI: 10.1007/bf00277118] [Citation(s) in RCA: 92] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The respiratory deficient dum-1 mutant of Chlamydomonas reinhardtii fails to grow in the dark because of a terminal 1.5 kb deletion in the linear 15.8 kb mitochondrial genome, which affects the apocytochrome b (CYB) gene. In contrast to the wild type where only mitochondrial genomes of monomer length are observed, the dum-1 genomes are present as a mixture of monomer and dimer length molecules. The mutant dimers appear to result from head-to-head fusions of two deleted molecules. Furthermore, mitochondrial genomes of dum-1 were also found to be unstable, with the extent of the deletion varying among single cell clones from the original mutant population. The dum-1 mutant also segregates, at a frequency of ca. 4% per generation, lethal minute colonies in which the original deletion now extends at least into the adjacent gene encoding subunit four of NAD dehydrogenase (ND4). We have used the dum-1 mutant as a recipient to demonstrate stable mitochondrial transformation in C. reinhardtii employing the biolistic method. After 4 to 8 weeks dark incubation, a total of 22 respiratory competent colonies were isolated from plates of dum-1 cells bombarded with C. reinhardtii mitochondrial DNA (frequency 7.3 x 10(-7)) and a single colony was isolated from plates bombarded with C. smithii mitochondrial DNA (frequency 0.8 x 10(-7)). No colonies were seen on control plates (frequency < 0.96 x 10(-9)). All transformants grew normally in the dark on acetate media; 22 transformants were homoplasmic for the wild-type mitochondrial genome typical of the C. reinhardtii donor. The single transformant obtained from the C. smithii donor had a recombinant mitochondrial genome containing the donor CYB gene and the diagnostic HpaI and XbaI restriction sites in the gene encoding subunit I of cytochrome oxidase (COI) from the C. reinhardtii recipient. The characteristic deletion fragments of the dum-1 recipient were not detected in any of the transformants.
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31
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Abstract
After conjugation between Chlamydomonas gametes of opposite mating type, a transient dikaryon is formed. The two nuclei fuse within 4-6 hr after mating. The young diploid zygote differentiates into dormant zygospore competent to complete meiosis, or more rarely (2-10% of cases) it undergoes mitosis to produce a stable diploid progeny. We here bring genetical, biochemical, and cytological evidence that among the mitotic zygotes, a large proportion of them undergo cytokinesis without fusion of the nuclei-a process that has been termed "cytoduction." By using appropriate genetic markers, haploid cytoductants that possess the nuclear genotype of one parent and the chloroplast marker of the other parent can easily be isolated. Genetical analysis and hybridization experiments moreover show that many haploid cytoductants transmit the chloroplast DNA molecules of both parents and that, as in diploids, these DNA copies occasionally recombine. This process of cytoduction extends the life cycle of Chlamydomonas and provides new tools for its genetic analysis.
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Affiliation(s)
- R F Matagne
- Department of Botany, University of Liege, Sart Tilman, Belgium
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32
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Abstract
In order to study the mechanism responsible for the uniparental transmission of the mitochondrial genome in crosses between Chlamydomonas reinhardtii and C. smithii, we have analyzed the fate of mitochondrial DNA during gametogenesis, zygospore differentiation and sporulation by hybridization experiments. Both mt+ and mt- gametes contain the same amount of mitochondrial DNA and the two parental genomes persist for several days in the zygotes. The DNA of mt+ origin is slowly eliminated during the period of zygote maturation. Light is required for total elimination of mt+ mitochondrial DNA in the zygospores. Using appropriate restriction enzymes, we have been unable to detect methylation of the mitochondrial DNA during gametogenesis or zygospore formation. The possibility that the mt+ mitochondria themselves are specifically eliminated in the course of zygote maturation is discussed.
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Affiliation(s)
- M C Beckers
- Département de Botanique (B22), Université de Liège, Belgique
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Munaut C, Dombrowicz D, Matagne RF. Detection of chloroplast DNA by using fluorescent monoclonal anti-bromodeoxyuridine antibody and analysis of its fate during zygote formation in Chlamydomonas reinhardtii. Curr Genet 1990; 18:259-63. [PMID: 2249255 DOI: 10.1007/bf00318390] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
A monoclonal anti-bromodeoxyuridine antibody conjugated to fluorescein was used to detect the chloroplast nucleoids after specific incorporation of bromodeoxyuridine (BUdR) into the chloroplast DNA of Chlamydomonas reinhardtii. The incorporation of BUdR was enhanced by simultaneous treatment with fluorodeoxyuridine (FUdR). The method was applied to analyze the fate of chloroplast DNA in zygotes resulting from mating between BUdR-treated gametes (mt+ or mt-) and untreated gametes of opposite mating-type. In crosses between wild-type strains, the nucleoids of mt+ origin remained in the large majority of zygotes whereas those of mt- origin most often disappeared within the first hours following copulation. In crosses of the type mat-3 mt+ x wild-type mt- (the mat-3 mutation permits a high transmission of chloroplast genes from the mt- parent), the nucleoids of mt- origin were generally not eliminated which indicates that the mat-3 mutation prevents the selective destruction of paternal chloroplast DNA in the zygote.
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Affiliation(s)
- C Munaut
- Department of Botany, University of Liège, Sart Tilman, Belgium
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34
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Remacle C, Bovie C, Michel-Wolwertz MR, Loppes R, Matagne RF. Mitochondrial genome transmission in Chlamydomonas diploids obtained by sexual crosses and artificial fusions: role of the mating type and of a 1 kb intron. Mol Gen Genet 1990; 223:180-4. [PMID: 2250646 DOI: 10.1007/bf00265051] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The linear mitochondrial DNAs of the two infertile algal species Chlamydomonas smithii and C. reinhardtii are co-linear with the exception of a 1 kb intron (alpha intron) located in the cytochrome b gene of C. smithii. C. smithii also possesses an additional HpaI restriction site (H marker) located in the COXI gene, about 5 kb from the intron. In reciprocal crosses, C. smithii (H+ alpha +) x C. reinhardtii (H- alpha -), the alpha intron is transmitted to all diploid progeny, whereas the H marker is frequently transmitted either biparentally or paternally depending on whether the C. smithii parent is maternal (mt+) or paternal (mt-). In diploids resulting from artificial fusion between vegetative cells, the absolute transmission of alpha is accompanied by the frequent transmission of the H+ marker, irrespective of the mating type of the parental strains. Finally, in reciprocal crosses between C. smithii (H+ alpha +) and recombinant H- alpha + clones, the transmission of the H marker is predominantly paternal or biparental. These results allow us to conclude that (1) the alpha intron behaves as a group I intron whose unidirectional conversion influences the transmission of the H marker; and (2) the mt- paternal mitochondrial genome is transmitted more often than the mt+. The mating type has no effect in diploids obtained by artificial fusion.
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Affiliation(s)
- C Remacle
- Department of Botany, University of Liège, Belgium
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35
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Colleaux L, Michel-Wolwertz MR, Matagne RF, Dujon B. The apocytochrome b gene of Chlamydomonas smithii contains a mobile intron related to both Saccharomyces and Neurospora introns. Mol Gen Genet 1990; 223:288-96. [PMID: 1701210 DOI: 10.1007/bf00265065] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The mitochondrial DNA of the two interfertile algal species Chlamydomonas smithii and Chlamydomonas reinhardtii are co-linear with the exception of ca. 1 kb insertion (the alpha insert) present in C. smithii DNA only. In vegetative diploids resulting from interspecific crosses, mitochondrial genomes are transmitted biparentally except for the alpha insert which is transmitted to all C. reinhardtii molecules in a manner reminiscent of the intron-mediated conversion event that occurs at the omega locus in yeast mitochondria, under the action of the I-SceI endonuclease. Here we report that the alpha insert corresponds to a typical group I intron of 1075 bp, inserted within the gene for apocytochrome b and containing a 237 codon open reading frame (ORF). We also report the complete sequence of the apocytochrome b gene of C. smithii. Comparison with the sequence of the same gene in C. reinhardtii reveals the precise intron insertion site. These data, together with the previous genetic data provide the first example of intron mobility in mitochondria of the plant kingdom. The product of the intronic ORF shows 36% amino acid identity with the I-SceI endonuclease whereas the intron ribozyme shows a 60% identity at the nucleotide level with the Neurospora crassa cob.1 intron. The possibility of a recent horizontal transfer of introns between fungi and algae is discussed.
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Affiliation(s)
- L Colleaux
- Département de Biologie Moléculaire, Institut Pasteur, Paris, France
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36
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Abstract
In Chlamydomonas reinhardtii, cadmium induces reduction of growth, reduction of chlorophyll content, and lethality. The toxicity was higher in a cell wall-deficient strain than in the wild type. By growing the cells on agar medium containing cadmium at concentrations inducing high lethality, stable resistant clones were isolated. The resistance was due to a nuclear mutation (cadAR) which probably preexisted in the wild-type cell population, as suggested by the fluctuation test. A double mutant (cadAR cadBR) was selected on media containing higher concentrations of cadmium. The cadBR mutation, which is unlinked to cadAR, determines a resistance intermediate between the CadAR mutant and the wild-type strain. Both cadAR and cadBR mutations are partially dominant.
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Affiliation(s)
- J M Collard
- Laboratoire de Génétique des Microorganismes, Université de Liège, Belgium
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Matagne RF, Michel-Wolwertz MR, Munaut C, Duyckaerts C, Sluse F. Induction and characterization of mitochondrial DNA mutants in Chlamydomonas reinhardtii. J Cell Biol 1989; 108:1221-6. [PMID: 2925784 PMCID: PMC2115516 DOI: 10.1083/jcb.108.4.1221] [Citation(s) in RCA: 60] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
In addition to lethal minute colony mutations which correspond to loss of mitochondrial DNA, acriflavin induces in Chlamydomonas reinhardtii a low percentage of cells that grow in the light but do not divide under heterotrophic conditions. Two such obligate photoautotrophic mutants were shown to lack the cyanide-sensitive cytochrome pathway of the respiration and to have a reduced cytochrome c oxidase activity. In crosses to wild type, the mutations are transmitted almost exclusively from the mating type minus parent. A same pattern of inheritance is seen for the mitochondrial DNA in crosses between the two interfertile species C. reinhardtii and Chlamydomonas smithii. Both mutants have a deletion in the region of the mitochondrial DNA containing the apocytochrome b gene and possibly the unidentified URFx gene.
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Affiliation(s)
- R F Matagne
- Département de Botanique, Université de Liège, Sart Tilman, Belgium
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38
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Abstract
In vivo complementation between different wild and mutant strains defective for nitrate assimilation has been performed by isolating diploid strains from the appropriate crosses. Twenty-two diploids homozygous or heterozygous with respect to nitrate reduction and able to grow on nitrate medium were obtained and their diploid character demonstrated from analyses of mating type, cell volume, nuclear size and progeny of crosses with haploid wild-type. All diploids were assayed for overall- and terminal-nitrate reductase (NR) activity and for the occurrence of the NR-diaphorase subunit. Data on NR activities in heterozygotes carrying mutation(s) in structural gene(s) (nit-1 or nit-1a, nit-1b) agree with the heteromultimeric nature of the enzyme complex previously described (Franco et al. (1984) EMBO J 3: 1403-1407), and indicate that subunits are exchangeable to form hybrid enzymes. In addition, in vitro complementation tests with mutant nit-1 of C. reinhardtii indicate that this mutant has defective NR-diaphorase subunits but intact terminal subunits. Super-repression caused by the mutant allele nit-2 is suppressed by the wild allele in heterozygotes, which suggests a positive control by the nit-2 product on structural gene(s) transcription. Mutant alleles of genes for the biosynthesis of molybdenum-containing cofactor, either nit-4 or nit-5 and nit-6, were recessive in diploids carrying them. The mutant allele of nit-3, from strain 307, was codominant in all heterozygotes suggesting that nit-3 codes for a protein whose activity is limiting for the molybdenum-cofactor biosynthetic pathway.
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Affiliation(s)
- E Fernández
- Departamento de Bioquímica, Facultad de Ciencias, Universidad de Córdoba, Spain
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39
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Matagne RF, Vincenzotto C. Study of the argininosuccinate lyase produced by triallelic complementation in triploids of Chlamydomonas reinhardi [proceedings]. Arch Int Physiol Biochim 1979; 87:832-3. [PMID: 93932] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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40
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Matagne RF. Fine structure of the arg-7 ciston in chlamydomonas reinhardi. Complementation between arg-7 mutants defective in argininosuccinate lyase. Mol Gen Genet 1978; 160:95-9. [PMID: 642927] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
In Chlamydomonas reinhardi, the arg-7 cistron is the structural gene for the enzyme argininosuccinate lyase which catalyzes the last reaction in the biosynthesis of arginine. Fourteen mutants (nine previously analyzed and five new mutants) defective in the lyase have been investigated so far: they all map within a cistron (length: 1.0--1.6 recombination units) of the linkage group I and fall within six groups of complementation. The enzyme activity found in the diploids formed by intragenic complementation was always lower than in wild-type haploid or diploid strains. The study of the denaturation curves obtained by heat treatment of the lyase indicates that in some diploids, several enzyme varieties can be present. These results and those previously obtained with diploids formed by intragenic and intergenic complementation (Matagne and Loppes, 1972; Matagne, 1976) are discussed in relation to the recent data showing that the argininosuccinate lyase is a multimeric enzyme probably composed of five identical polypeptide chains (Matagne and Schlösser, 1977).
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Loppes R, Braipson J, Matagne RF, Sassen A, Ledoux L. Regulation of the neutral phosphatase in Chlamydomonas reinhardi: an immunogenetic study of wild-type and mutant strains. Biochem Genet 1977; 15:1147-57. [PMID: 203266 DOI: 10.1007/bf00484505] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
In Chlamydomonas reinhardi, the activity of the neutral phosphatase considerably increases when the cells are grown in the absence of inorganic phosphate (Pi). A comparative immunological study of cells grown on media containing Pi or not indicated that the neutral phosphatase was synthesized de novo. Ten mutants lacking the neutral phosphatase and distributed among three genetic loci (PD2, PD3, PD24) were investigated for their ability to produce cross-reacting material (CRM) antigenically related to the wild enzyme. All mutants were shown to form much less CRM than the wild-type strain. It is proposed that the three genes are involved in the regulation of neutral phosphatase synthesis.
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Ledoux L, Huart R, Ryngaert-Adriaenssens A, Matagne RF, Schlösser JP, Jacobs M. Does DNA correct Arabidopsis thiamin mutants? [proceedings]. Arch Int Physiol Biochim 1977; 85:992-4. [PMID: 79403 DOI: 10.3109/13813457709053324] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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43
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Abstract
Argininosuccinate lyase (EC 4.3.2.1) was purified by (NH4)2SO4 fractionation, chromatography on DEAE-cellulose and gel filtration on Sephadex G-200. The final enzyme preparation was purified 46-fold compared with the crude extract. Electrophoresis of this preparation revealed three bands, the major one having the enzyme activity. Analysis of the enzyme by gel filtration and by disc electrophoresis (in two different concentrations of acrylamide) gave mol.wts. of 200000 (+/- 15000) and 190000 (+/- 20000) respectively. Treatment with sodium dodecyl sulphate and mercaptoethanol dissociated the enzyme into subunits of mol.wt. 39000 (+/-2000). The results are indicative of the multimeric structure of the enzyme, which is composed of five (perhaps four or six) identical subunits.
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Matagne RF. Arg-7 mutant X wild-type crosses in Chlamydomonas reinhardi: study of the enzyme produced in diploid strains. Mol Gen Genet 1976; 146:209-14. [PMID: 958202 DOI: 10.1007/bf00268090] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The arg-7 locus is the structural gene for the argininosuccinate lyase (ASL). Interallelic complementation was previously found to occur between several mutants of the locus: this is indicative for the homomultimeric nature of ASL. Two complementing (arg-7-5 and arg-7-7) and two non-complementing (arg-7-1 and arg-7-6) mutants of the arg-7 locus were crossed to the pab-2 strain (which is wild-type for the arg-7 locus). In each cross, heterozygote phenotypically wild-type strains were isolated; their diploid pattern was demonstrated by various criteria: mating type, cell volume, nuclear size. The four heterozygotes were compared to the haploid wild-type and in some experiments, to the diploid strain arg-1 X pab-2 homozygous for the arg-7 locus. No difference was found in growth rate and in the Michaelis constant values for ASL. The specific activity of the enzyme produced in the heterozygotes was about 50 percent of the activity found in haploid or diploid wild-type. The heat sensitivity of ASL was also investigated in the different strains: two (containing the complementing mutations arg-7-5 and arg-7-7) of the four heterozygotes produce ASL varieties different from the wild-type enzyme as far as the thermolability is concerned. These results suggest that hybrid ASL can be formed by interaction between the products of wild-type and mutant genes. A clear dominance of the wild-type allele is expected only when the mutant allele has no product of the gene: this could be the case for arg-7-1 and arg-7-6.
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Abstract
The unicellular alga Chlamydomonas reinhardi produces two constitutive acid phosphatases and three depressible phosphatases (a neutral and two alkaline ones) that can utilize napthyl phosphate as a substrate. Specific mutants depressible phosphatase were used to investigate biochemical properties and the cytochemical localization of these enzymes. The two constitutive phosphatases show similar pH optima (about 5.0) and Km values (2 x 10(-3) to 3.3 x 10(-3) M) but differ in their heat sensitivity and affinity for glycerophosphate.
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Loppes R, Matagne RF, Deltour R. Proceedings: Biochemical and cytochemical study of the two constitutive acid phosphatases in Chlamydomonas reinhardi. Arch Int Physiol Biochim 1976; 84:172-3. [PMID: 60946] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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47
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Matagne RF, Loppes R, Deltour R. Proceedings: Biochemical and cytochemical study of the derepressible phosphatases in Chlamydomonas reinhardi. Arch Int Physiol Biochim 1976; 84:173-4. [PMID: 60947] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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48
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Abstract
In the green alga Chlamydomonas reinhardi, removal of inorganic phosphate from the culture medium results in the increase of phosphatase activity (derepression) in the wild-type (WT) strain as well as in a double mutant (P2Pa)) lacking the two main constitutive acid phosphatases. Following treatment of WT and P2Pa with N-methyl-N-nitro-N-nitrosoguanidine (MNNG), mutants were recovered which display very low phosphatase activities when grown in the absence of phosphate; as shown by electrophoresis, they lack one non-migrating phosphatase (PD mutants). This enzyme is active over a wide range of pH with an optimum at pH 7.5. The comparison of elctropherograms form WT and mutants grown on media with or without phosphate allowed us to provide a tentative definition of the pool of derepressible phosphatases in Chlamydomonas: in addition tothe neutral phosphatase lacking in PD mutants, Chlamydomonas produces two electrophoretic forms of alkaline phosphatase showing an optimal activity at pH 9.5.
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Konvalinkova V, Matagne RF, Loppes R. Induction and analysis of revertants from various arg-7 mutants lacking argininosuccinate lyase in Chlamydomonas reinhardi. Mutat Res 1974; 24:69-72. [PMID: 4843978 DOI: 10.1016/0027-5107(74)90048-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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50
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Lurquin PF, Delaunoit G, Loppes R, Matagne RF, Konvalinkova V. Uptake of bacterial DNA by Chlamydomonas reinhardi. Arch Int Physiol Biochim 1973; 81:979. [PMID: 4133557] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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