Cellular structure of Cyanidioschyzon merolae: A minimum set of organelles

The cell of the unicellular red alga Cyanidioschyzon merolae is composed of a very small number of membranous organelles: one cell nucleus, one mitochondrion, one chloroplast (plastid), a simple-shaped ER, one Golgi body with two cisternae, a few vacuoles (lysosomes), and one peroxisome. During the last two decades, numerous electron and fluorescence microscopic studies, combined with synchronous culture, have demonstrated spatial organization andmorphological information of these organelles in each cell cycle phase of C. merolae cells. These explorations have revealed that the timing and manner of the organelle behaviors are strictly determined by the progression of the cell division cycle. In addition, the simplicity of the cell structure assists researchers to directly address the biological processes in each organelle. Concurrently, given the completely sequenced genome and various genetic technologies, the simple composition of C. merolae cells provides considerable opportunities to clarify long-standing biological questions, including cell cycle regulation, organelle biogenesis, and various types of metabolic pathways.