Transcription and Translation involved in Uniparental Inheritance and Cell Nuclei Fusion in the Chlamydomonas reinhardtii Zygote

Abstract

The preferential digestion of male-derived chloroplast-DNA (cp-DNA) and fusion of the cell nuclei were observed in zygotes of the alga Chlamydomonas reinhardtii, when transcription (actinomycin D) and translation (cycloheximide) inhibitors were given at various times after mating. The minimum periods required to complete cytoplasmic transcription and translation were estimated. Genes playing a role in uniparental inheritance are transcribed from the moment the gametes fuse until about 1 hr after mating, but fusion of the cell nuclei requires a longer period of gene expression. Observations of two cell types indicating the beginning and completion of the preferential digestion of male-derived cp-DNA suggested two possibilities. (1) Expression of additional genes after expression of the first zygotic genes is required to complete the process. (2) The presence of a continuous signal promoting cp-DNA digestion is necessary for completion.