title: Myosin-dependent endoplasmic reticulum motility and F-actin organization in plant cells.
abstract: Plants exhibit an ultimate case of the intracellular motility involving rapid organelle trafficking and continuous streaming of the endoplasmic reticulum (ER). Although it was long assumed that the ER dynamics is actomyosin-driven, the responsible myosins were not identified, and the ER streaming was not characterized quantitatively. Here we developed software to generate a detailed velocity-distribution map for the GFP-labeled ER. This map revealed that the ER in the most peripheral plane was relatively static, whereas the ER in the inner plane was rapidly streaming with the velocities of up to approximately 3.5 microm/sec. Similar patterns were observed when the cytosolic GFP was used to evaluate the cytoplasmic streaming. Using gene knockouts, we demonstrate that the ER dynamics is driven primarily by the ER-associated myosin XI-K, a member of a plant-specific myosin class XI. Furthermore, we show that the myosin XI deficiency affects organization of the ER network and orientation of the actin filament bundles. Collectively, our findings suggest a model whereby dynamic three-way interactions between ER, F-actin, and myosins determine the architecture and movement patterns of the ER strands, and cause cytosol hauling traditionally defined as cytoplasmic streaming.
authors.affiliation: Department of Botany, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
authors.forename: Haruko
authors.initials: H
authors.lastname: Ueda
authors.forename: Etsuo
authors.initials: E
authors.lastname: Yokota
authors.forename: Natsumaro
authors.initials: N
authors.lastname: Kutsuna
authors.forename: Tomoo
authors.initials: T
authors.lastname: Shimada
authors.forename: Kentaro
authors.initials: K
authors.lastname: Tamura
authors.forename: Teruo
authors.initials: T
authors.lastname: Shimmen
authors.forename: Seiichiro
authors.initials: S
authors.lastname: Hasezawa
authors.forename: Valerian V
authors.initials: VV
authors.lastname: Dolja
authors.forename: Ikuko
authors.initials: I
authors.lastname: Hara-Nishimura
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism; D000199:Actins / Q000378:metabolism; D017360:Arabidopsis / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000737:chemistry; D018613:Microscopy, Confocal / Q000379:methods; D008954:Models, Biological; D009218:Myosins / Q000737:chemistry / Q000502:physiology*; D010944:Plants / Q000378:metabolism*; D030821:Plants, Genetically Modified; D012984:Software; D013347:Subcellular Fractions
chemical_list: D000199:Actins; D049452:Green Fluorescent Proteins; D009218:Myosins