Cyanidioschyzon merolae is one of the photosynthetic eukaryotes that have simplest cell architecture. The cell contains a single nucleus, a single mitochondrion and a single chloroplast. The genome size is as small as 16 Mbp, which is about 1/7 of that of thale cress Arabidopsis thaliana, about 1/27 of that of rice Oryza sativa, and 1/100 of that of wheat Triticum aestivum. The sequencing of the chloroplast genome (Ohta et al. 1999) that preceded the current project has revealed that the chloroplast genome of this organism retains many genes that are not present in the chloroplast genomes of other algae and plants. We consider this chloroplast represents one of the most ancestral ones, and will shed a new light on the evolution of chloroplast.
The three DNA-containing organelles divide synchronously during the cell division cycle under photoperiodic growth conditions with light and dark. This organism provides a good model for the study of organellar division.