Mu Huawei, Sun Jin, Heras Horacio, Chu Ka Hou, Qiu Jian-Wen
Department of Biology, Hong Kong Baptist University, Hong Kong, China.
Division of Life Science, Hong Kong University of Science and Technology, Hong Kong, China.
J Proteomics. 2017 Feb 23;155:22-30. doi: 10.1016/j.jprot.2017.01.006. Epub 2017 Jan 14.
Proteins of the egg perivitelline fluid (PVF) that surrounds the embryo are critical for embryonic development in many animals, but little is known about their identities. Using an integrated proteomic and transcriptomic approach, we identified 64 proteins from the PVF of Pomacea maculata, a freshwater snail adopting aerial oviposition. Proteins were classified into eight functional groups: major multifunctional perivitellin subunits, immune response, energy metabolism, protein degradation, oxidation-reduction, signaling and binding, transcription and translation, and others. Comparison of gene expression levels between tissues showed that 22 PVF genes were exclusively expressed in albumen gland, the female organ that secretes PVF. Base substitution analysis of PVF and housekeeping genes between P. maculata and its closely related species Pomacea canaliculata showed that the reproductive proteins had a higher mean evolutionary rate. Predicted 3D structures of selected PVF proteins showed that some nonsynonymous substitutions are located at or near the binding regions that may affect protein function. The proteome and sequence divergence analysis revealed a substantial amount of maternal investment in embryonic nutrition and defense, and higher adaptive selective pressure on PVF protein-coding genes when compared with housekeeping genes, providing insight into the adaptations associated with the unusual reproductive strategy in these mollusks.
There has been great interest in studying reproduction-related proteins as such studies may not only answer fundamental questions about speciation and evolution, but also solve practical problems of animal infertility and pest outbreak. Our study has demonstrated the effectiveness of an integrated proteomic and transcriptomic approach in understanding the heavy maternal investment of proteins in the eggs of a non-model snail, and how the reproductive proteins may have evolved during the transition from laying underwater eggs to aerial eggs.
包围胚胎的卵周质液（PVF）中的蛋白质对许多动物的胚胎发育至关重要，但对其身份了解甚少。我们采用蛋白质组学和转录组学相结合的方法，从淡水蜗牛黄斑苹果螺（Pomacea maculata）的PVF中鉴定出64种蛋白质。这些蛋白质被分为八个功能组：主要多功能卵黄磷蛋白亚基、免疫反应、能量代谢、蛋白质降解、氧化还原、信号传导与结合、转录与翻译以及其他。组织间基因表达水平的比较表明，22个PVF基因仅在分泌PVF的雌性器官蛋白腺中表达。黄斑苹果螺与其近缘物种福寿螺（Pomacea canaliculata）之间PVF和管家基因的碱基替换分析表明，生殖蛋白具有更高的平均进化速率。所选PVF蛋白的预测三维结构表明，一些非同义替换位于可能影响蛋白质功能的结合区域或其附近。蛋白质组和序列分歧分析揭示了母体在胚胎营养和防御方面的大量投入，以及与管家基因相比，PVF蛋白质编码基因受到更高的适应性选择压力，这为了解这些软体动物与异常生殖策略相关的适应性提供了见解。
研究与生殖相关的蛋白质一直备受关注，因为此类研究不仅可能回答有关物种形成和进化的基本问题，还可能解决动物不育和害虫爆发的实际问题。我们的研究证明了蛋白质组学和转录组学相结合的方法在理解非模式蜗牛卵中蛋白质的大量母体投入以及生殖蛋白在从水下产卵向气生产卵转变过程中可能如何进化方面的有效性。
