Poster: Organelle Biogenesis

Abs # 1171: Recruitment of dynamin for the final mitochondrial severance in a primitive red alga Cyanidioschyzon merolae

Presenter:	Nishida, Keiji , keiji@platz.or.jp
Authors	Nishida, Keiji  (A) (B)  Miyagishima, Shin-ya  (B)   Takahara, Manabu  (C)   Kuroiwa, Haruko  (B)   Matsuzaki, Motomichi  (A)   Kuroiwa, Tsuneyoshi  (B)
Affiliations:	(A): University of Tokyo (B): Rikkyo University (C): The Ministry of Agriculture, Forestry and Fisheries of Japan

Dynamins are a eukaryote-specific family of GTPases. Some family members are involved in diverse and varied cellular activities. Here, we report that the primitive red alga Cyanidioschyzon merolae retains dynamin homolog, CmDnm1, belonging to the mitochondrial division subfamily. Previously, the bacterial cell division protein, FtsZ was shown to localize at the mitochondrial division site in the alga. We showed that FtsZ and dynamin coexist as mitochondrial division-associated proteins that act during different phases of division. CmDnm1 was recruited from 10 to 20 cytoplasmic patches (dynamin patches) to the midpoint of the constricted mitochondrion-dividing ring (MD ring), which was observed as an electron-dense structure on the cytoplasmic side. CmDnm1 is probably not required for early constriction; it forms a ring or spiral when the outer mitochondrial membrane is finally severed, while the FtsZ and MD rings are formed before constriction. It is thought that the FtsZ, MD, and dynamin rings are involved in scaffolding, constriction, and final separation, respectively. This model is common to the division of the other endosymbiont organelle, plastid, which also involves FtsZ, plastid-dividing ring and dynamin. In eukaryotes, mitochondrial severance is probably the most conserved role for the dynamin family. For further study, we are now searching binding partners of CmDnm1, to reveal what causes mitochondrial constriction, what regulates the recruitment of dynamin, and what is the functional meaning of dynamin patch, which is not associated with mitochondria.