Mitochondrial genome transmission in Chlamydomonas diploids obtained by sexual crosses and artificial fusions: role of the mating type and of a 1 kb intron.
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.
Remacle
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Department of Botany, University of Liège, Belgium.
Bovie
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Michel-Wolwertz
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Loppes
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Matagne
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D002696:Chlamydomonas / Q000235:genetics*; D003001:Cloning, Molecular; D003433:Crosses, Genetic; D003573:Cytochrome b Group / Q000235:genetics*; D004272:DNA, Mitochondrial / Q000235:genetics*; D004171:Diploidy; D007438:Introns; D015183:Restriction Mapping
D003573:Cytochrome b Group; D004272:DNA, Mitochondrial