2017 Volume 29 Issue 1 Pages 63-71
Generally, eukaryotic cell has a set of organelles: three types of double-membrane-bound organelles (the cell nucleus, mitochondrion, and plastid), and four types of single-membrane-bound organelles [endoplasmic reticulum (ER), Golgi apparatus, peroxisome (microbody), and lysosome]. These organelles are essential for fulfilling the functions of eukaryotic cells. In textbooks, cell nuclei have been the focus of the study of cell proliferation, whereas division and proliferation of other six organelles have not been described much. This is because large number and complex shapes of these six organelles in cells of most of organisms from the amoeba to the higher animals and plants, making detailed structural study difficult. The primitive unicellular red alga Cyanidioschyzon merolae offers unique advantages for studying organelle division, because each cell contains a minimal set of basic eukaryotic organelles, the divisions of which occur in order and can be synchronized by light/dark cycles. In addition, the complete sequence of its genome has enabled proteomic analyses. As a result, we have discovered the plastid- (chloroplast) dividing apparatus (ring), the mitochondrion-dividing-apparatus (ring) and the peroxisome-dividing apparatus (ring), apparatuses that are essential for the survival of almost all the eukaryotic cells, ahead of the rest of the world, and then solved their structures and functions at the molecular level. This discovery also brought a new understanding of the birth of eukaryotic cells and organelles. The next work is to search smaller eukaryotic organisms to answer questions such as how such splitting devices were born, how much eukaryotes could be made smaller, and so on. We recently discovered the green alga Medakamo hakoo (Medakamo), which could possibly answer those questions. Here, I describe the research history of C. merolae as its foundation and discuss about future research of Medakamo.
