Nagasato C, Motomura T, Ichimura T
Institute of Algological Research, Faculty of Science, Hokkaido University, Muroran, 051-0003, Japan.
Dev Biol. 1999 Apr 1;208(1):200-9. doi: 10.1006/dbio.1998.9183.
The influence of centrioles, derived from the sperm flagellar basal bodies, and the centrosomal material (MTOCs) on spindle formation in the brown alga Fucus distichus (oogamous) was studied by immunofluorescence microscopy using anti-centrin and anti-beta-tubulin antibodies. In contrast to a bipolar spindle, which is formed after normal fertilization, a multipolar spindle was formed in polyspermic zygote. The number of mitotic poles in polyspermic zygotes was double the number of sperm involved in fertilization. As an anti-centrin staining spot (centrioles) was located at these poles, the multipolar spindles in polyspermic zygotes were produced by the supplementary centrioles. When anucleate egg fragments were fertilized, chromosome condensation and mitosis did not occur in the sperm nucleus. Two anti-centrin staining spots could be detected, microtubules (MTs) radiated from nearby, but the mitotic spindle was never produced. When a single sperm fertilized multinucleate eggs (polygyny), abnormal spindles were also observed. In addition to two mitotic poles containing anti-centrin staining spots, extra mitotic poles without anti-centrin staining spots were also formed, and as a result multipolar spindles were formed. When karyogamy was blocked with colchicine, it became clear that the egg nucleus proceeded independently into mitosis accompanying chromosome condensation. A monoastral spindle could be frequently observed, and in rare cases a barrel-shaped spindle was formed. However, when a sperm nucleus was located near an egg nucleus, the two anti-centrin staining spots shifted to the egg nucleus from the sperm nucleus. In this case, a normal spindle was formed, the egg chromosomes arranged at the equator, and the associated MTs elongated from one pole of the egg spindle toward the sperm chromosomes which were scattered. From these results, it became clear that paternal centrioles derived from the sperm have a crucial role in spindle formation in the brown algae, such as they do during animal fertilization. However, paternal centrioles were not adequate for the functional centrosome during spindle formation. We speculated that centrosomal materials from the egg cytoplasm aggregate around the sperm centrioles and are needed for centrosomal activation.
利用抗中心蛋白和抗β-微管蛋白抗体，通过免疫荧光显微镜研究了源自精子鞭毛基体的中心粒和中心体物质（微管组织中心，MTOCs）对褐藻鹿角菜（卵式生殖）纺锤体形成的影响。与正常受精后形成的双极纺锤体不同，多精合子中形成了多极纺锤体。多精合子中有丝分裂极的数量是参与受精的精子数量的两倍。由于抗中心蛋白染色点（中心粒）位于这些极上，多精合子中的多极纺锤体是由额外的中心粒产生的。当无核卵片段受精时，精子核中不会发生染色体凝聚和有丝分裂。可以检测到两个抗中心蛋白染色点，微管从附近发出，但从未形成有丝分裂纺锤体。当单个精子使多核卵受精（多雌受精）时，也观察到了异常纺锤体。除了含有抗中心蛋白染色点的两个有丝分裂极外，还形成了没有抗中心蛋白染色点的额外有丝分裂极，结果形成了多极纺锤体。当用秋水仙碱阻断核配时，很明显卵核伴随着染色体凝聚独立进入有丝分裂。经常可以观察到单星体纺锤体，在极少数情况下会形成桶状纺锤体。然而，当精子核位于卵核附近时，两个抗中心蛋白染色点从精子核转移到卵核。在这种情况下，形成了正常的纺锤体，卵染色体排列在赤道上，相关的微管从卵纺锤体的一极向分散的精子染色体延伸。从这些结果可以清楚地看出，源自精子的父本中心粒在褐藻纺锤体形成中起着关键作用，就像它们在动物受精过程中所起的作用一样。然而，父本中心粒在纺锤体形成过程中对于功能性中心体来说是不够的。我们推测，来自卵细胞质的中心体物质聚集在精子中心粒周围，是中心体激活所必需的。
