Chloroplast Genetics

The most successfully studied in the Chlamydomonas alga. C. reinhardtii has only one chloroplast with about 80 cpDNA molecules of 196 kbp each. The transmission of the cpDNA genome is largely uniparental, i.e., inherited most commonly through the mt⁺ (comparable to egg) cytoplasm although in 1–10% of the cases biparental transmission may take place (alfalfa, Oenothera). The chloroplast nucleoid (DNA) transmitted by the mt⁻ mate is usually completely digested in Chlamydomonas within 10 minutes after zygote formation, whereas the mitochondrial nucleoid still remained intact. Specially, e.g., in conifers, uniparental male transmission may also exist. The uniparental mt⁺ transfer may sometimes be spurious in cases when the coding of the subunits of a particular protein is under the control of nuclear and organelle genes, respectively. In diploid vegetative zygotes of Chlamydomonasthe biparental transmission of the extranuclear genes is most likely. Incubation in dark or postponing the...