Riparbelli M G, Stouthamer R, Dallai R, Callaini G
Department of Evolutionary Biology, University of Siena, Via Mattioli 4, Siena, 53100, Italy.
Dev Biol. 1998 Mar 15;195(2):89-99. doi: 10.1006/dbio.1997.8841.
The origin of the zygotic centrosome is an important step in developmental biology. It is generally thought that sperm at fertilization plays a central role in forming the functional centrosome which subsequently organizes the first mitotic spindle. However, this view is not applicable in the case of parthenogenetic eggs which develop without the sperm contribution. To clarify the problem of the origin of the zygotic centrosome during parthenogenetic development, we studied a hymenopteran, Muscidifurax uniraptor. Antitubulin antibody revealed that after activation several asters assembled in the egg cytoplasm. The number of asters varied in relation to the cell cycle. They became visible from anaphase of the first meiotic division and increased in number as meiosis progressed, reaching a maximum at the first mitosis. From anaphase-telophase of the first mitosis they decreased in number and were no longer found during the third mitotic division. To elucidate the nature of these asters we performed an ultrastructural study with transmission electron microscopy and immunofluorescence with antibodies against anti-gamma-tubulin and CP190. In this way we showed the presence in these asters of centrosomal components and centrioles. Our observations suggest that the cytoplasm of Muscidifurax eggs contains a pool of inactive centrosomal precursor proteins becoming able to nucleate microtubules into well-defined asters containing centrioles after activation.
合子中心体的起源是发育生物学中的一个重要步骤。一般认为，受精时精子在形成功能性中心体过程中起核心作用，该中心体随后组织形成第一个有丝分裂纺锤体。然而，这种观点不适用于孤雌生殖的卵子，因为它们的发育无需精子参与。为了阐明孤雌生殖发育过程中合子中心体的起源问题，我们研究了一种膜翅目昆虫——独角蚁。抗微管蛋白抗体显示，激活后卵细胞质中组装形成了多个星体。星体的数量随细胞周期而变化。它们在第一次减数分裂后期开始可见，并随着减数分裂的进行而增加，在第一次有丝分裂时达到最多。从第一次有丝分裂的后期到末期，它们的数量减少，在第三次有丝分裂时不再出现。为了阐明这些星体的性质，我们用透射电子显微镜进行了超微结构研究，并用抗γ-微管蛋白和CP190抗体进行了免疫荧光研究。通过这种方式，我们证明了这些星体中存在中心体成分和中心粒。我们的观察结果表明，独角蚁卵子的细胞质中含有一群无活性的中心体前体蛋白，激活后这些蛋白能够将微管聚集成含有中心粒的明确星体。
