Poster: Organelle Biogenesis

Abs # 1136: Sequential formation of the plastid division complex: FtsZ, plastid-dividing, and dynamin rings participates with plastid division by distinct modes.

Presenter:	Miyagishima, Shin-ya , miyagi@biol.s.u-tokyo.ac.jp
Authors	Miyagishima, Shin-ya  (A)   Nishida, Keiji  (A)   Kuroiwa, Haruko  (A)   Kuroiwa, Tsuneyoshi  (A)
Affiliations:	(A): Department of Life Science, College of Science, Rikkyo (St.Paul's) University

Chloroplasts have retained the bacterial FtsZ for division, while mitochondria lack FtsZ, except some lower eukaryotes. Instead, mitochondrial division involves a dynamin-related protein, suggesting that chloroplasts retained the bacterial division system, while a dynamin-based system replaced the bacterial system in mitochondria during evolution. In this study, we identified a novel plant-specific group of dynamins from the primitive red alga Cyanidioschyzon merolae. Synchronization of chloroplast division and immunoblot analyses showed that the protein (CmDnm2) associates with the chloroplast only during division. Immunocytochemical analyses showed that CmDnm2 appears in cytoplasmic patches just before chloroplast division, and is recruited to the cytosolic side of the chloroplast division site to form a ring in the late stage of division. The ring constricts until division is complete, and then disappears. These results show that a dynamin-related protein also participates in chloroplast division, and that FtsZ, plastid-dividing (PD) and dynamin rings forms in this order. Combined with the results of a recent study of mitochondrial division in C. merolae, we hypothesized that when first established in lower eukaryotes, mitochondria and chloroplasts divided using a very similar system, including the FtsZ ring, PD/mitochondrion-dividing (MD) ring, and dynamin ring.