A pair of invertedly repeated genes in Chlamydomonas reinhardtii encodes azygote-specific protein whose expression is UV-sensitive

Uniparental inheritance of the chloroplast genome has been observed in a wi de variety of green plants. In Chlamydomonas this phenomenon, which can be selectively inhibited by UV irradiation of mrt gametes, has been shown cyto logically to be due to the preferential degradation of mt(-)-derived chloro plast nucleoids in young zygotes. The zygote-specific pair of zys1 genes, z ys1A and zys1B, is expressed earliest among five genes isolated from a "10- min" zygote library. We report here that the ZYS1 protein, which is encoded by the invertedly duplicated zys1 gene, accumulates in zygotes and is loca lized in nuclei. In addition, when mtf gametes (but not mt(-) gametes) are UV-irradiated before mating, only very limited accumulation of ZYS1 protein can be detected in the resulting zygotes.