Biochemical,genetic and molecular characterization of new respiratory-deficient mutants inChlamydomonas reinhardtii |
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Authors: | Marie-Pierre Dorthu Suzanne Remy Marie-Rose Michel-Wolwertz Laurence Colleaux Didier Breyer Marie-Claire Beckers Serge Englebert Claire Duyckaerts Francis E. Sluse René F. Matagne |
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Affiliation: | (1) Laboratoire de Génétique des microorganismes, Département de Botanique, B22, Université de Liège, Sart-Tilman, B-4000 Liège, Belgium;(2) Laboratoire de Bioénergétique, Centre Interdisciplinaire de Biochimie normale et pathologique de l'Oxygène, B6, Université de Liège, Sart-Tilman, B-4000 Liège, Belgium;(3) Unité de génétique moléculaire des Levures, Département de Biologie Moléculaire, Institut Pasteur, 25 rue du Docteru Roux, F-75724 Paris Cedex 15, France |
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Abstract: | Eight respiratory-deficient mutants ofChlamydomonas reinhardtii have been isolated after mutagenic treatment with acriflavine or ethidium bromide. They are characterized by their inability to grow or their very reduced growth under heterotrophic conditions. One mutation (Class III) is of nuclear origin whereas the seven remaining mutants (Classes I and II) display a predominantly paternalmt- inheritance, typical of mutations residing in the mitochondrial DNA. Biochemical analysis has shown that all mutants are deficient in the cyanide-sensitive cytochrome pathway of the respiration whereas the alternative pathway is still functional. Measurements of complexes II + III (antimycin-sensitive succinate-cytochromec oxido-reductase) and complex IV (cytochromec oxidase) activities allowed to conclude that six mutations have to be localized in the mitochondrial apocytochromeb (COB) gene, one in the mitochondrial cytochrome oxidase subunit I (COI) gene and one in a nuclear gene encoding a component of the cytochrome oxidase complex. By using specific probes, we have moreover demonstrated that five mutants (Class II mutants) contain mitochondrial DNA molecules deleted in the terminal end containing the COB gene and the telomeric region; they also possess dimeric molecules resulting from end-to-end junctions of deleted monomers. The two other mitochondrial mutants (Class I) have no detectable gross alteration. Class I and Class II mutants can also be distinguished by the pattern of transmission of the mutation in crosses.Anin vivo staining test has been developed to identify rapidly the mutants impaired in cyanide-sensitive respiration. |
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Keywords: | Chlamydomonas cytochromeb gene cytochrome oxidase gene mitochondrial genome respiratory-deficient mutants |
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