Analysis of reorganization of cortical microtubules in cell morphogenesis at M/G_1 interface.

我们通过免疫荧光显微镜发现，在同步烟草by -2细胞从M期到G_1期的细胞周期转变过程中，mt被组织在核周区域。MT向上延伸至细胞皮层，接着是平行于细胞长轴的进一步延伸。当延长的MTs尖端到达分割面远端时，横向定向的MTs在分割面近端形成。虽然核表面是MT组织的部位，但有组织的MT并不是皮质MT的直接前体。为了检查MT重组的部位，by -2细胞的MT被冷和丙酰胺联合处理完全破坏。细胞洗涤培养后，M/G_1界面的MT重组位点仅在核周区或核周区和细胞皮层上被鉴定出来（Hasezawa et al.1997）。在细胞周期从M期到G_1期的转变过程中，观察到更多的MT组织类型。仅在核周区域的MT重组反映了早期类型的模式，而核周区域和细胞皮层的MT重组反映了后期类型的模式。我们还发现EF-1 α（一种49 kDa的蛋白）与烟草BY-2细胞中的MTs组织有关，并且这种关联只发生在细胞周期从M期过渡到G_1期的核周区域的MTs组织中（Kumagai et al.1995）。我们从BY-2细胞的疏散原生质体中制备了具有微管组织中心（MTOC）活性和EF-1 α的部分纯化蛋白。利用这些馏分，我们开发了一个系统，其中添加纯化的微管蛋白导致形成小的星形结构。我们称它们为“aster”。我们努力寻找影响“aster”形成的因素，预计将为进一步了解植物细胞中的MT组织提供帮助。少

We have shown by immunofluorescence microscopy that, during the cell cycle transition from M to G_1 phase in synchronized tobacco BY-2 cells, MTs were organized on the perinuclear region. MT elongation up to the cell cortex was followed by further elongation parallel to the long axis of cells. As soon as the tips of the elongated MTs reached the distal end of the division plane, the transversely oriented MTs were formed proximal to the division plane. Although the nuclear surface is the site of MT organization, the organized MTs are not the direct precursors of the cortical MTs. To examine the sites of MT reorganization, the MTs of BY-2 cells were completely destroyed by a combination of cold and propyzamide treatment. After the cells were washed and cultured, the sites of MT reorganization at M/G_1 interface were identified solely on the perinuclear region or on the perinuclear region and on the cell cortex(Hasezawa et al.1997). These patterns of MT organization correspond to the five … More types observed during the cell cycle transition from M to G_1 phase ; reorganization of MTs solely on the perinuclear region reflecting earlier types of the patterns and MT reorganization on both the perinuclear region and the cell cortex reflecting later types of them.We have also shown that EF-1 alpha(a 49 kDa protein)is associated with organizing MTs in tobacco BY-2 cells, and this association occurs exclusively with organizing MTs on the perinuclear region during the cell cycle transition from M to G_1 phase(Kumagai et al.1995). We prepared partially purified protein fractions which had a microtubule organizing center(MTOC)activity and involved EF-1 alpha, from evacuolated protoplasts of BY-2 cells. Using these fractions, we developed a system, in which the addition of purified tubulin caused the formation of small aster-like structure. We called them"aster". Our efforts to find factors affecting the formation of the"aster"would be expected to provide further insight into MT organization in plant cells. Less