Bilinski Szczepan M, Jaglarz Mariusz K, Tworzydlo Waclaw
Department of Developmental Biology and Morphology of Invertebrates, Institute of Zoology and Biomedical Research, Jagiellonian University, Gronostajowa 9, 30-387, Krakow, Poland.
Results Probl Cell Differ. 2017;63:103-126. doi: 10.1007/978-3-319-60855-6_5.
Animal germline cells are specified either through zygotic induction or cytoplasmic inheritance. Zygotic induction takes place in mid- or late embryogenesis and requires cell-to-cell signaling leading to the acquisition of germline fate de novo. In contrast, cytoplasmic inheritance involves formation of a specific, asymmetrically localized oocyte region, termed the germ (pole) plasm. This region contains maternally provided germline determinants (mRNAs, proteins) that are capable of inducing germline fate in a subset of embryonic cells. Recent data indicate that among insects, the zygotic induction represents an ancestral condition, while the cytoplasmic inheritance evolved at the base of Holometabola or in the last common ancestor of Holometabola and its sister taxon, Paraneoptera.In this chapter, we first describe subsequent stages of morphogenesis of the pole plasm and polar granules in the model organism, Drosophila melanogaster. Then, we present an overview of morphology and cytoarchitecture of the pole plasm in various holometabolan and paraneopteran insect species. Finally, we focus on phylogenetic hypotheses explaining the known distribution of two different strategies of germline specification among insects.
动物生殖系细胞通过合子诱导或细胞质遗传来确定。合子诱导发生在胚胎发育的中期或后期，需要细胞间信号传导，从而从头获得生殖系命运。相比之下，细胞质遗传涉及形成一个特定的、不对称定位的卵母细胞区域，称为生殖质（极质）。该区域包含母源提供的生殖系决定因子（mRNA、蛋白质），这些决定因子能够在一部分胚胎细胞中诱导生殖系命运。最近的数据表明，在昆虫中，合子诱导代表一种祖先状态，而细胞质遗传是在全变态昆虫基部或在全变态昆虫及其姐妹类群副新翅类的最后一个共同祖先中进化而来的。在本章中，我们首先描述模式生物黑腹果蝇中极质和极颗粒形态发生的后续阶段。然后，我们概述各种全变态昆虫和副新翅类昆虫物种中极质的形态和细胞结构。最后，我们重点关注系统发育假说，这些假说解释了昆虫中两种不同生殖系确定策略的已知分布情况。
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