The fate of mitochondrial DNAs of mt + and mt ? origin in gametes and zygotes of Chlamydomonas

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.

Mitochondria inherit its DNA from male parents in Chlamydomonas

“…The experiments described above raise questions as to whether they accurately represent the process of paternal inheritance, as they were based on crosses between interspecific strains , Beckers et al 1991, respiration-deficient mutants (Matagne et al 1989, Dorthu et al 1992, Colin et al 1995, or haploid cells derived from artificially produced diploid cells (Bennoun et al 1991). To answer these questions, Nakamura et al However, the mating efficiency was always less than 1% following any backcross to C. smithii.…”

“…The period of maternal mtDNA disappearance Beckers et al (1991) crossed interspecific strains of C. reinhardtii with C. smithii, and followed the fate of mtDNA by the hybridization of restriction digestion bands from gametogenesis until sporulation to determine when maternal mtDNA disappears. The fragment derived from mt+ C. reinhardtii decreased progressively from day 2 of zygote maturation in the dark.…”

“…Following the modification-restriction system proposed for the maternal inheritance of cpDNA by Sager and Lane (1972), Beckers et al (1991) analyzed the methylation of mtDNA to explain the slow elimination of mt+ mtDNA Figure 6 Main events occurring during the period between zygote formation and zoospore formation. a About 1 h after zygote formation, only mt-chloroplast nucleoids had disappeared.…”

Paternal inheritance of mitochondrial DNA in <i>Chlamydomonas reinhardtii</i> and dynamic morphological changes in mitochondria, mitochondrial nucleoids, and the cell nucleus during its life cycle

“…The above experiments raise questions about whether the process of paternal inheritance proceeds accurately in crosses between strains from different species (Boynton et al 1987, Beckers et al 1991, in crosses using respiration-deficient mutants (Matagne et al 1989, Dorthu et al 1992, Colin et al 1995, or in haploid cells derived from artificially produced diploid cells (Bennoun et al 1991).…”

Degenerated recognition property of a mitochondrial homing enzyme in the unicellular green alga Chlamydomonas smithii

“…Maternal mitochondrial genomes are subjected to degradation in the course of meiosis (Beckers et al, 1991) preceding the fusion of mt + and mt -mitochondria (Nakamura et al, 2003). However, in the diploid cells, which are rare zygotes and account for about 5% of the mated cells, inheritance of the mitochondrial genome i s no longer strictly uniparental.…”