The preprophase band is a localized center of clathrin-mediated endocytosis in late prophase cells of the onion cotyledon epidermis

Authors

  • Ichirou Karahara,

    1. Department of Biology, Graduate School of Science and Engineering, University of Toyama, Toyama 930-8555, Japan,
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  • Jinsuke Suda,

    1. Department of Biology, Graduate School of Science and Engineering, University of Toyama, Toyama 930-8555, Japan,
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    • Current address: Ishikawa Agricultural Research Center, 295-1 Bo, Saida, Kanazawa 920-3198, Japan.

  • Hiroshi Tahara,

    1. Department of Life Science, Graduate School of Life Science, University of Hyogo, 3-2-1 Kouto, Akou, Hyogo 678-1297, Japan,
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    • Current address: WORLD INTEC 13F Piass-Tower, 3-19-3 Toyosaki Kita-ku, Osaka 531-0072, Japan.

  • Etsuo Yokota,

    1. Department of Life Science, Graduate School of Life Science, University of Hyogo, 3-2-1 Kouto, Akou, Hyogo 678-1297, Japan,
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  • Teruo Shimmen,

    1. Department of Life Science, Graduate School of Life Science, University of Hyogo, 3-2-1 Kouto, Akou, Hyogo 678-1297, Japan,
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  • Kazuyo Misaki,

    1. RIKEN Center for Developmental Biology, 2-2-3 Minatojima-minamimachi, Chuou-ku, Kobe 650-0047, Japan,
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  • Shigenobu Yonemura,

    1. RIKEN Center for Developmental Biology, 2-2-3 Minatojima-minamimachi, Chuou-ku, Kobe 650-0047, Japan,
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  • Lucas Andrew Staehelin,

    1. MCD Biology, University of Colorado, Boulder, CO 80309-0347, USA,
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  • Yoshinobu Mineyuki

    Corresponding author
    1. Department of Biological Science, Hiroshima University, Higashi-Hiroshima 739-8526, and
    2. Department of Life Science, Graduate School of Life Science, University of Hyogo, 2167 Shosha, Himeji, Hyogo 671-2280, Japan
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*(fax +81 79 267 4920; e-mail mineyuki@sci.u-hyogo.ac.jp).

Summary

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.

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