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Keywords:

  • actin;
  • cytoplasmic organization;
  • cytoplasmic strand;
  • cytoskeleton;
  • myosin;
  • optical tweezers;
  • plant

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.