title: The preprophase band is a localized center of clathrin-mediated endocytosis in late prophase cells of the onion cotyledon epidermis.
abstract: The preprophase band (PPB) marks the site on the plant cell cortex where the cell plate will fuse during the final stage of cytokinesis. Recent studies have shown that several cytoskeletal proteins are depleted at the PPB site, but the processes that bring about these changes are still unknown. We have investigated the membrane systems associated with the PPB regions of epidermal cells of onion cotyledons by means of serial thin sections and electron tomograms. In contrast with specimens preserved by chemical fixatives, our high-pressure frozen cells demonstrated the presence of large numbers of clathrin-coated pits and vesicles in the PPB regions. The vesicles were of two types: clathrin-coated and structurally related, non-coated vesicles. Quantitative analysis of the data revealed that the number of clathrin-coated pits and vesicles is higher in the PPB regions than outside of these regions. Immunofluorescent microscopy using anti-plant clathrin-antibody confirmed this result. In contrast, no differences in secretory activities were observed. We postulate that the removal of membrane proteins by endocytosis plays a role in the formation of PPB 'memory' structures.
authors.affiliation: Department of Biology, Graduate School of Science and Engineering, University of Toyama, Toyama, Japan.
authors.forename: Ichirou
authors.initials: I
authors.lastname: Karahara
authors.forename: Jinsuke
authors.initials: J
authors.lastname: Suda
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Tahara
authors.forename: Etsuo
authors.initials: E
authors.lastname: Yokota
authors.forename: Teruo
authors.initials: T
authors.lastname: Shimmen
authors.forename: Kazuyo
authors.initials: K
authors.lastname: Misaki
authors.forename: Shigenobu
authors.initials: S
authors.lastname: Yonemura
authors.forename: Lucas Andrew
authors.initials: LA
authors.lastname: Staehelin
authors.forename: Yoshinobu
authors.initials: Y
authors.lastname: Mineyuki
mesh_terms: D002966:Clathrin / Q000378:metabolism*; D022163:Clathrin-Coated Vesicles / Q000378:metabolism; D003034:Coated Pits, Cell-Membrane / Q000378:metabolism / Q000648:ultrastructure; D048749:Cytokinesis; D055032:Electron Microscope Tomography; D004705:Endocytosis; D019697:Onions / Q000166:cytology / Q000254:growth & development*; D019441:Plant Epidermis / Q000166:cytology / Q000254:growth & development* / Q000648:ultrastructure; D011418:Prophase
chemical_list: D002966:Clathrin