Perturbation of chloroplast gene transmission in diploid and triploid zygotes of Chlamydomonas reinhardi by 5-fluorodeoxyuridine.

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.