Identification of the plastid division gene PDR1

Abstract

For energy, food, and oxygen, almost all organisms depend on photosynthesis by chloroplasts (plastids), which proliferate by division. In chloroplast division, the plastid-dividing (PD) ring is a main structure of the PD machinery and is a universal structure in the plant kingdom. However, the components and formation of the PD ring have been enigmatic. By proteomic analysis of PD machineries isolated from Cyanidioschyzon merolae, we identified the glycosyltransferase protein plastid-dividing ring 1 (PDR1), which constructs the PD ring and is widely conserved from red alga to land plants. Electron microscopy showed that the PDR1 protein forms a ring with carbohydrates at the chloroplast-division site. Fluorometric saccharide ingredient analysis of purified PD ring filaments showed that only glucose was included. Thus, the chloroplasts are divided by the PD ring, which is a bundle of PDR1-mediated polyglucan filaments.