Role of myosin in plant cells

细胞质流动通常在植物细胞中观察到，并参与细胞内的运输。有研究表明，肌动蛋白-肌球蛋白系统参与了细胞质流动动力的产生。我们成功地分离了烟草培养细胞和百合花粉管中参与胞质流动的肌球蛋白分子。在拟南芥中，已经报道了两种编码肌球蛋白分子的基因(肌球蛋白VIII和肌球蛋白XI)。然而，其功能仍有待阐明。据推测，肌球蛋白XI参与了细胞质的流动。有人认为，N端区具有沿肌动蛋白细丝滑动的功能，C端区具有结合细胞器的功能。在本研究中，我们试图鉴定Mysin XI携带的细胞器。在拟南芥中，已经鉴定了三类肌球蛋白XI基因。我们提出了一种针对MYA2肌球蛋白C末端的抗体。免疫细胞化学分析表明，该肌球蛋白与肌动蛋白细丝共存于叶、根毛细胞和培养细胞的表皮细胞中。该肌球蛋白在气孔细胞中的分布提示该肌球蛋白可能与过氧化物酶体有关。已有研究表明，肌动蛋白细丝与细胞内过氧化物酶的转运有关。然而，运动蛋白仍有待鉴定。因此，我们利用在过氧化体中表达GFP的转基因拟南芥植株进行了分析。ITR发现这种肌球蛋白确实与过氧化物酶体有关，并提示这种肌球蛋白负责过氧化物酶体的运输。

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.