Actin and myosin regulate cytoplasm stiffness in plant cells: a study using optical tweezers

Authors

  • Hannie S. van der Honing,

    1. Laboratory of Plant Cell Biology, Wageningen University, Building 107, Radix W1, Droevendaalsesteeg 1, 6708PB Wageningen, The Netherlands
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  • Norbert C. A. de Ruijter,

    1. Laboratory of Plant Cell Biology, Wageningen University, Building 107, Radix W1, Droevendaalsesteeg 1, 6708PB Wageningen, The Netherlands
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  • Anne Mie C. Emons,

    1. Laboratory of Plant Cell Biology, Wageningen University, Building 107, Radix W1, Droevendaalsesteeg 1, 6708PB Wageningen, The Netherlands
    2. Department of Biomolecular Systems, FOM Institute for Atomic and Molecular Physics, Science Park 113, 1098 SG Amsterdam, The Netherlands
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  • Tijs Ketelaar

    1. Laboratory of Plant Cell Biology, Wageningen University, Building 107, Radix W1, Droevendaalsesteeg 1, 6708PB Wageningen, The Netherlands
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Author for correspondence:
Tijs Ketelaar
Tel: +31 317 484329
Email: tijs.ketelaar@wur.nl

Summary

  •  Here, we produced cytoplasmic protrusions with optical tweezers in mature BY-2 suspension cultured cells to study the parameters involved in the movement of actin filaments during changes in cytoplasmic organization and to determine whether stiffness is an actin-related property of plant cytoplasm.
  •  Optical tweezers were used to create cytoplasmic protrusions resembling cytoplasmic strands. Simultaneously, the behavior of the actin cytoskeleton was imaged.
  •  After actin filament depolymerization, less force was needed to create cytoplasmic protrusions. During treatment with the myosin ATPase inhibitor 2,3-butanedione monoxime, more trapping force was needed to create and maintain cytoplasmic protrusions. Thus, the presence of actin filaments and, even more so, the deactivation of a 2,3-butanedione monoxime-sensitive factor, probably myosin, stiffens the cytoplasm. During 2,3-butanedione monoxime treatment, none of the tweezer-formed protrusions contained filamentous actin, showing that a 2,3-butanedione monoxime-sensitive factor, probably myosin, is responsible for the movement of actin filaments, and implying that myosin serves as a static cross-linker of actin filaments when its motor function is inhibited. The presence of actin filaments does not delay the collapse of cytoplasmic protrusions after tweezer release.
  •  Myosin-based reorganization of the existing actin cytoskeleton could be the basis for new cytoplasmic strand formation, and thus the production of an organized cytoarchitecture.

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