Germ Cell Specification Requires Zygotic Mechanisms Rather Than Germ Plasm in a Basally Branching Insect
Germ Cell Specification Requires Zygotic Mechanisms Rather Than Germ Plasm in a Basally Branching Insect
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DOI：
10.1016/j.cub.2013.03.063
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发表时间：
2013-05-20
期刊：
影响因子：
9.2
通讯作者：
Extavour, Cassandra G.
中科院分区：
文献类型：
--
作者：
Ewen-Campen, Ben;Donoughe, Seth;Extavour, Cassandra G.
背景资料：原始生殖细胞（PGC）的特化是一个跨动物的普遍过程，但指定PGC的分子机制是非常不同的。在果蝇中，PGCs由母体提供的、不对称定位的细胞质因子（生殖质）指定。相反，大多数其他节肢动物的历史文献报道，PGCs出现在nidembryogenesis中胚层，这表明节肢动物最后的共同祖先可能有特定的PGCs通过合子机制。然而，迄今为止，没有直接的实验证据，为种质独立的节肢动物PGC specification.Results：在这里，我们表明，在一个基部分支的昆虫，蟋蟀Gryllus bimaculatus，保守的种质分子是无处不在的，而不是不对称的，定位在卵子发生和早期胚胎发生。分子和细胞学分析表明，在卵裂过程中，蟋蟀PGCs来自腹部中胚层，而缺乏中胚层的扭曲RNAi胚胎不能形成PGCs。使用RNA干扰，我们表明，瓦萨和piwi不需要母系或合子PGC的形成，而是需要初级精原细胞分裂在成年male.Conclusions：这些观察表明，蟋蟀缺乏母系遗传的种质，与许多holometabolous昆虫，包括果蝇。Gtyllus PGC的中胚层起源和缺乏指导作用的vasa和piwi在PGC的形成是让人想起小鼠PGC的规范，并建议合子细胞信号可能直接PGC规范Gtyllus和其他Hemimetroa。
Background: Primordial germ cell (PGC) specification is a universal process across animals, but the molecular mechanisms specifying PGCs are remarkably diverse. In Drosophila, PGCs are specified by maternally provided, asymmetrically localized cytoplasmic factors (germ plasm). In contrast, historical literature on most other arthropods reports that PGCs arise from mesoderm during nnidembryogenesis, suggesting that an arthropod last common ancestor may have specified PGCs via zygotic mechanisms. However, there has been no direct experimental evidence to date for germ plasm-independent arthropod PGC specification.Results: Here we show that in a basally branching insect, the cricket Gryllus bimaculatus, conserved germ plasm molecules are ubiquitously, rather than asymmetrically, localized during oogenesis and early embryogenesis. Molecular and cytological analyses suggest that Gryllus PGCs arise from abdominal mesoderm during segmentation, and twist RNAi embryos that lack mesoderm fail to form PGCs. Using RNA interference we show that vasa and piwi are not required maternally or zygotically for PGC formation but rather are required for primary spermatogonial divisions in adult males.Conclusions: These observations suggest that Gryllus lacks a maternally inherited germ plasm, in contrast with many holometabolous insects, including Drosophila. The mesodermal origin of Gtyllus PGCs and absence of instructive roles for vasa and piwi in PGC formation are reminiscent of mouse PGC specification and suggest that zygotic cell signaling may direct PGC specification in Gtyllus and other Hemimetabola.