Role of myosin in plant cells

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Cytoplasmic streaming is generally observed in plant cells and involved in intracellular transport. It has been suggested that actin-myosin system is involved in generation of the motive force of cytoplasmic streaming. We had succeeded in isolating myosin molecules involved in cytoplasmic streaming in tobacco cultured cells and lily pollen tubes. In Arabidopsis thaliana, two kinds of genes supposed to code myosin molecule had been reported (myosin VIII and myosin XI). However, the function of had been remained to be elucidated. It was supposed that myosin XI is involved in cytoplasmic streaming. It has been suggested that the N terminal region has a function to slide along actin filaments and that C terminal region has a function to bind organelles. In the present study, we tried to identify the organlles carried by mysin XI.In Arabidopsis thaliana, three classes of myosin XI gene have been identified. We raised an antibody against C terminal region of MYA2 myosin. Immunocytochemical analysis revealed that this myosin is co-localized with actin filaments in epidermal cells of leaf, root hair cells and cultured cells. Distribution of this myosin in stomatal cell suggested that this myosin may associated with peroxisomes. It has been suggested that actin filament is concerned with intracellular transport of peroxisomes. However, the moter protein was remained to be identified. Therefore, we carried out an analysis using transgenic Arabidopsis plants expressing GFP in peroxisomes. Itr was found that this myosin is really associated with peroxisomes, and suggested that this myosin is responsible for transport of peroxisomes.