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  • 學位論文

由 vasa 基因表現探討豌豆蚜生殖細胞發育之可塑性

Developmental plasticity of germline development in the pea aphid Acyrthosiphon pisum: implicated by vasa expressions

指導教授 : 張俊哲
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摘要


在昆蟲中,生殖細胞在胚胎發育的過程中與體細胞分離,是生殖細胞特化相當重要的一步。部分的物種如黃果蠅,生殖細胞在發育早期即與體細胞分離。黃果蠅胚後端的核在細胞化時,囊括了聚集於胚後端的生殖細胞決定物質,而被特化成為生殖前驅細胞;其他的物種如蝗蟲,生殖前驅細胞在原腸胚形成後才與體細胞分離,且推測生殖細胞的特化是透過其鄰近的體細胞釋放出訊息誘導而成。上述生殖細胞的研究成果,都是透過偵測 vasa 基因的表現,因為 vasa 基因保守表現於各種動物的生殖細胞中,成為最好的生殖細胞標記基因。 本論文的研究當中,我選殖出豌豆蚜的四個 vasa 同源基因,製備分別辨識其蛋白的四個抗體,偵測四個 vasa 基因訊息 RNA 以及蛋白在發育過程中的表現。旨在探討無性和有性的豌豆蚜胚胎,其生殖細胞如何特化。以及同一基因體在不同光週期的刺激之下,能產生無性胚胎或有性胚胎的可塑性,是否受到四個 vasa 基因差異性的表現來調控。 研究結果顯示,無性胚胎和有性胚胎都是藉由同一個 Vasa 蛋白來特化其生殖細胞。不過,無性胚胎中,Vasa 蛋白聚集於胚後端,並會在生殖細胞特化之前向前端位移。Vasa 蛋白聚集的位移可能是現今無性且胎生的蚜蟲才出現的特徵。這個假設需透過分析較原始的蚜蟲物種,其具有無性生殖且卵生的世代才能驗證。除此之外,蚜蟲 Vasa 蛋白在胚後端聚集的分子機制是否和其它昆蟲有共通性,以及蚜蟲四個 vasa 基因的功能性分析,都需要繼續探討。

並列摘要


Segregation of germline from soma during embryogenesis is critical to the specification of germ cells in insects. In some species such as the fruit fly Drosophila melanogaster, germ cells are segregated during early development. It has been reported that in D. melanogaster the posterior syncytial nuclei are associated with the maternally inherited germline determinants in the egg posterior to form the primordial germ cells (PGCs) at the beginning of embryogenesis. In some other species like the grasshopper Schistocerca gregaria, segregation of PGCs is first identified after gastrulation and germline specification may be achieved via signal induction from neighboring somatic cells. Discoveries of germline segregation mentioned above were all evidenced by the expression of vasa, a highly conserved germline marker in insects and other animals. In this study, I cloned four vasa genes (Apvasa1-4) in the pea aphid Acyrthosiphon pisum, made antibodies against ApVasa1-4, and detected the developmental expressions of Apvasa mRNAs and ApVasa proteins. My ultimate goals are to understand how germline is specified in asexual and sexual pea aphids and whether reproductive plasticity of the pea aphid is regulated by differential expressions of four vasa genes from the same genome. My results show that only one germline specific Vasa protein to specify PGCs in asexual and sexual embryos. The localization of germline specific Vasa protein is dymanic in asexual embryo, in which accumulated Vasa protein shifts its position toward anterior of embryo. I suggest that the dynamic localization of Vasa protein in asexual embryo is a derived feature in modern aphids, which are viviparous in asexual phase. This hypothesis has to be confirmed by analyzing the localization of Vasa protein in ancient asexual and oviparous aphids. Besides, the conserved mechanism for the localization of germline specifc Vasa in aphids across other insects, and the functional assay of four vasa genes are also necessary to be done.

參考文獻


Abdelhaleem, M. (2005). RNA helicases: regulators of differentiation. Clin Biochem 38, 499-503.
Andersen, C. L., Jensen, J. L. and Orntoft, T. F. (2004). Normalization of real-time quantitative reverse transcription-PCR data: A model-based variance estimation approach to identify genes suited for normalization, applied to bladder and colon cancer data sets. Cancer Res 64, 5245-5250.
Anderson, R., Copeland, T. K., Scholer, H., Heasman, J. and Wylie, C. (2000). The onset of germ cell migration in the mouse embryo. Mech Dev 91, 61-68.
Anne, J. (2010). Targeting and anchoring Tudor in the pole plasm of the Drosophila oocyte. PLoS One 5, e14362.
Asaoka-Taguchi, M., Yamada, M., Nakamura, A., Hanyu, K. and Kobayashi, S. (1999). Maternal Pumilio acts together with Nanos in germline development in Drosophila embryos. Nat Cell Biol 1, 431-437.

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