title: Arrest of cytoplasmic streaming induces algal proliferation in green paramecia.
abstract: A green ciliate Paramecium bursaria, bearing several hundreds of endosymbiotic algae, demonstrates rotational microtubule-based cytoplasmic streaming, in which cytoplasmic granules and endosymbiotic algae flow in a constant direction. However, its physiological significance is still unknown. We investigated physiological roles of cytoplasmic streaming in P. bursaria through host cell cycle using video-microscopy. Here, we found that cytoplasmic streaming was arrested in dividing green paramecia and the endosymbiotic algae proliferated only during the arrest of cytoplasmic streaming. Interestingly, arrest of cytoplasmic streaming with pressure or a microtubule drug also induced proliferation of endosymbiotic algae independently of host cell cycle. Thus, cytoplasmic streaming may control the algal proliferation in P. bursaria. Furthermore, confocal microscopic observation revealed that a division septum was formed in the constricted area of a dividing paramecium, producing arrest of cytoplasmic streaming. This is a first report to suggest that cytoplasmic streaming controls proliferation of eukaryotic cells.
authors.affiliation: Graduate School of Biological Science, Hiroshima University, Higashi-Hiroshima, Hiroshima, Japan.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Takahashi
authors.forename: Yohji
authors.initials: Y
authors.lastname: Shirai
authors.forename: Toshikazu
authors.initials: T
authors.lastname: Kosaka
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Hosoya
mesh_terms: D000818:Animals; D003593:Cytoplasm / Q000187:drug effects; D056890:Eukaryota / Q000166:cytology* / Q000502:physiology; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D008870:Microtubules / Q000187:drug effects; D015739:Nocodazole / Q000494:pharmacology; D010247:Paramecium / Q000502:physiology*; D013559:Symbiosis
chemical_list: D015739:Nocodazole