The Origin and Structure of Centrosomes in Embryos derived from Haplodiploid Parthenogenetic Insects

在大多数动物细胞中，中心体或微管组织中心（MTOC）在核分裂过程中染色体分离中起关键作用。它们由一对中心粒组成，被复杂的蛋白质基质包围。在大多数生物体中，中心粒是父系来源于精子基体，周围的成分主要来自母体细胞质。经历孤雌生殖发育的生物体提供了一个研究中心体形成和结构的自然变异的机会。蜂目昆虫（包括蚂蚁、蜜蜂和黄蜂）的特征是单倍二倍体单性生殖，即未受精的卵发育为雄性，受精的卵发育为雌性。尽管这一目中物种的遗传学、行为和生态学已经被深入研究，但令人惊讶的是，很少有研究直接关注与中心体有关的问题。对该目中一种宝石蜂Nasoniavitripennis的初步研究表明，尽管没有精子来源的基体，但中心体仍能形成，在减数分裂完成后，受精卵和未受精卵中都能形成大量的细胞质星形细胞。在未受精的卵中，两个细胞质星形细胞被雌原核捕获，它们作为合子中心体发挥功能，而不相关的星形细胞消失。在受精胚中，精子源中心体起合子中心体的作用，细胞质星状体消失。因为未受精的卵发育成雄性，而受精卵发育成雌性，这是第一个描述中心体非遗传的系统。该项目旨在进一步表征Nasonia的中心体遗传和结构。这些研究可能会产生新的MTOC组织机制，也提供了有关单性生殖的进化和发育后果的新见解。该项目的三个具体目标是：1。通过活体荧光显微镜进一步研究受精和未受精胚中细胞质星状体的行为.研究未受精卵和受精卵发育受到特异性破坏的纳氏虫株的中心体遗传模式.通过免疫荧光分析和厚切片电镜观察，对受精和未受精胚胎的星状体和中心体的组成和结构进行了研究。

In most animal cells, the centrosomes, or microtubule organizing centers (MTOC), play akey role in chromosome segregation during nuclear division. They consist of a pair of centriolesencompassed by a complex protein matrix. In most organisms, the centrioles are paternallyderived from the sperm basal body and the surrounding components are primarily derived fromthe maternal cytoplasm. Organisms that undergo parthenogenetic development provide anopportunity to study natural variants in centrosome formation and structure. The insect orderHymenoptera (this includes ants, bees, and wasps) is characterized by haplodiploidparthenogenesis, whereby unfertilized eggs develop as males and fertilized eggs develop asfemales. Although the genetics, behavior, and ecology of species within this order have beenintensively studied, surprisingly few studies have directly focused on issues pertaining to thecentrosome. Preliminary results for one species within this order, the jewel wasp Nasoniavitripennis, demonstrate that centrosomes form despite the lack of a sperm-derived basal body.Numerous cytoplasmic asters form in both fertilized and unfertilized eggs after the completion ofmeiosis. In unfertilized eggs, two of these cytoplasmic asters are captured by the femalepronucleus and these function as the zygotic centrosomes while the unassociated astersdisappear. In fertilized embryos, the sperm derived centrosomes function as the zygoticcentrosomes and the cytoplasmic asters disappear. Because unfertilized eggs develop into malesand fertilized eggs into females, this is the first system described in which centrosomes arereciprocally inherited. This project seeks to further characterize centrosome inheritance andstructure in Nasonia. These studies are likely to yield novel mechanisms of organizingMTOCs and also provide new insights concerning the evolution and developmental consequencesof parthenogenesis. The three specific aims of this project are:1. To further characterize the behavior of the cytoplasmic asters in fertilized and unfertilizedembryos through live fluorescent microscopy.2. To characterize the centrosome inheritance pattern in Nasonia strains in which developmentof unfertilized or fertilized eggs is specifically disrupted.3. To characterize the composition and structure of the asters and centrosomes in fertilized andunfertilized embryos through immunofluorescent analysis and thick section electronmicroscopy.