title: The kinesin-like protein TOP promotes Aurora localisation and induces mitochondrial, chloroplast and nuclear division.
abstract: The cell cycle usually refers to the mitotic cycle, but the cell-division cycle in the plant kingdom consists of not only nuclear but also mitochondrial and chloroplast division cycle. However, an integrated control system that initiates division of the three organelles has not been found. We report that a novel C-terminal kinesin-like protein, three-organelle division-inducing protein (TOP), controls nuclear, mitochondrial and chloroplast divisions in the red alga Cyanidioschyzon merolae. A proteomics study revealed that TOP is a member of a complex of mitochondrial-dividing (MD) and plastid-dividing (PD) machineries (MD/PD machinery complex) just prior to constriction. After TOP localizes at the MD/PD machinery complex, mitochondrial and chloroplast divisions occur and the components of the MD/PD machinery complexes are phosphorylated. Furthermore, we found that TOP downregulation impaired both mitochondrial and chloroplast divisions. MD/PD machinery complexes were formed normally at each division site but they were neither phosphorylated nor constricted in these cells. Immunofluorescence signals of Aurora kinase (AUR) were localized around the MD machinery before constriction, whereas AUR was dispersed in the cytosol by TOP downregulation, suggesting that AUR is required for the constriction. Taken together our results suggest that TOP induces phosphorylation of MD/PD machinery components to accomplish mitochondrial and chloroplast divisions prior to nuclear division, by relocalization of AUR. In addition, given the presence of TOP homologs throughout the eukaryotes, and the involvement of TOP in mitochondrial and chloroplast division may illuminate the original function of C-terminal kinesin-like proteins.
authors.affiliation: Graduate School of Science, Rikkyo University, 3-34-1 Nishiikebukuro, Toshima-ku, Tokyo 171-8501, Japan.
authors.forename: Yamato
authors.initials: Y
authors.lastname: Yoshida
authors.forename: Takayuki
authors.initials: T
authors.lastname: Fujiwara
authors.forename: Yuuta
authors.initials: Y
authors.lastname: Imoto
authors.forename: Masaki
authors.initials: M
authors.lastname: Yoshida
authors.forename: Mio
authors.initials: M
authors.lastname: Ohnuma
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Hirooka
authors.forename: Osami
authors.initials: O
authors.lastname: Misumi
authors.forename: Haruko
authors.initials: H
authors.lastname: Kuroiwa
authors.forename: Shoichi
authors.initials: S
authors.lastname: Kato
authors.forename: Sachihiro
authors.initials: S
authors.lastname: Matsunaga
authors.forename: Tsuneyoshi
authors.initials: T
authors.lastname: Kuroiwa
mesh_terms: D064127:Aurora Kinases; D048750:Cell Nucleus Division / Q000502:physiology*; D060365:Chloroplast Proteins / Q000235:genetics / Q000378:metabolism*; D002736:Chloroplasts / Q000235:genetics / Q000378:metabolism*; D016547:Kinesins / Q000235:genetics / Q000378:metabolism*; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D021381:Protein Transport / Q000502:physiology; D000461:Rhodophyta / Q000235:genetics / Q000378:metabolism*
chemical_list: D060365:Chloroplast Proteins; D024101:Mitochondrial Proteins; D064127:Aurora Kinases; D017346:Protein Serine-Threonine Kinases; D016547:Kinesins
keywords: Cell-division cycle; Cyanidioschyzon merolae; Kinesin; Mitochondrial division; Plastid division