川百合花粉管的生殖细胞分裂过程中微管骨架的分布变化

应用透射电镜辅以免疫荧光定位技术研究了川百合 (Lilium davidii Duch.)花粉管中生殖细胞分裂过程中染色体动态和微管分布的关系。在生殖细胞分裂前和有丝分裂前期 ,电镜观察一直未见微管结构 ,但免疫荧光图象显示生殖细胞中有微管蛋白存在。直到分裂的前中期—中期 ,染色体出现 ,它们沿花粉管的长轴前后排列 ,横向的着丝点对相应地一对对地纵向排列。这时 ,生殖细胞中才出现大量微管 ,它们分布于细胞周质区和染色体之间 ,并跨越染色体的整个长度。前中期—中期开始时 ,只有 1～ 2对着丝点从横向转为纵向 ,微管垂直插入着丝点形成着丝点微管 ,而非前人用免疫荧光方法观察到的微管与着丝点侧向联接的图象。随着横向的着丝点对逐渐转变成纵向的过程 ,着丝点微管数量逐渐增多 ,但不形成典型的纺锤体。分裂后期 ,染色体交错分离 ,微管的分布与前中期—中期的基本相同。晚后期 ,染色体呈明显的两群 ,除极区和细胞中央区有微管残余外 ,大部分微管消失。通过染色体长度的测量 ,间接证明了分裂后期 B的存在。分裂末期的晚期 ,核膜形成后 ,在两精核之间的区域 ,微管数量开始增多。此区可能代表用免疫荧光所观察到的微管重叠区。细胞板出现后 ,微管消失

CHANGES OF MICROTUBULAR SKELETON IN THE GENERATIVE CELL IN POLLEN TUBE DURING MITOSIS OF LILIUM DAVIDII

Previous observations indicated that division of the generative cell (GC) in some plant genura such as Lilium and Tradescantia is characterized by several unusual features,including persistence of surrounding microtubule (MT) bundles during mitosis,lacking a matephase plate,the cytokinesis is completed with furrow.The authors have further studied the changes of MT organizations and the chromosome (CHs) behavior in the GC during mitosis using electron microscopy and method of tubulin localizations. No MTs in the GC before GC division and during prophase was seen under electron microscopy.However,there was tubulin in the GC with antitubulin staining.During promatephase to matephase,the CHs appeared and arranged in a complexed tangled pattern lengthwise along the cell.Correspondingly,transverse pairs of kinetochores were located along the length and depth of the cell.They stacked successively like the rungs of a ladder.In this phase,a large mount of MTs appeared in the GC,which distributed in the cortex of the cell and among the CHs and along the whole length of the CHs.In the beginning,one or two kinetochore pairs changed from transversely to longitudinally situated in each cell.MTs ended on the kinetochore to form kinetochore MTs (KMTs).With the electron microscopy,authors did not find the image of lateral connection between the MTs and the kinetochores as previous reported with immunofluorescent method.As karyokinesis proceeded,more transverse kinetochore pairs gradually became longitudinal, and KMTs gradually increased in number.However,a distinct spindle was not evidenced.During anaphase, CHs seperation started at various positions along the length of the cell. The distribution of MTs in the GC was similar to that of promatephase to matephase.In late anaphase,the CHs segregated as two groups. Most MTs disappeared but only some remained in the polar regions and the interzone.Authors also measured and compared the lengths of the CHs and indirectly identified the existing anaphase B.During late tolephase,the MTs increased in number gradually in the region between the two newly formed sperm nuclei.The region might be the MT interdigitating zone visualized with antitubulin localization.The MTs disappeared after the cell plate (CP) appeared.