PDF(Pubmed)
Abstract：
Ovaries play key roles in fitness and evolution: they are essential female reproductive structures that develop and house the eggs in sexually reproducing animals. In Drosophila, the mature ovary contains multiple tubular egg-producing structures known as ovarioles. Ovarioles arise from somatic cellular structures in the larval ovary called terminal filaments (TFs), formed by TF cells and subsequently enclosed by sheath (SH) cells. As in many other insects, ovariole number per female varies extensively in Drosophila. At present, however, there is a striking gap of information on genetic mechanisms and evolutionary forces that shape the well-documented rapid interspecies divergence of ovariole numbers. To address this gap, here we studied genes associated with Drosophila melanogaster ovariole number or functions based on recent experimental and transcriptional datasets from larval ovaries, including TFs and SH cells, and assessed their rates and patterns of molecular evolution in five closely related species of the melanogaster subgroup that exhibit species-specific differences in ovariole numbers. From comprehensive analyses of protein sequence evolution (dN/dS), branch-site positive selection, expression specificity (tau), and phylogenetic regressions (phylogenetic generalized least squares), we report evidence of 42 genes that showed signs of playing roles in the genetic basis of interspecies evolutionary change of Drosophila ovariole number. These included the signaling genes upd2 and Ilp5 and extracellular matrix genes vkg and Col4a1, whose dN/dS predicted ovariole numbers among species. Together, we propose a model whereby a set of ovariole-involved gene proteins have an enhanced evolvability, including adaptive evolution, facilitating rapid shifts in ovariole number among Drosophila species.
摘要：
卵巢在健身和进化中起着关键作用：它们是重要的雌性生殖结构，在有性繁殖的动物中发育和容纳卵。在果蝇中,成熟的卵巢包含多个管状产卵结构，称为卵巢。卵巢起源于幼虫卵巢中的体细胞结构，称为终丝，由末端细丝细胞形成，随后被鞘细胞包围。和许多其他昆虫一样，果蝇中每个雌性的卵巢数量差异很大。然而，目前，关于遗传机制和进化力的信息存在惊人的差距，这些信息形成了有据可查的卵巢数量的种间快速差异。为了解决这个差距，在这里，我们根据最近的幼虫卵巢的实验和转录数据集研究了与D.melanogaster卵巢数量或功能相关的基因，包括末端细丝和鞘细胞，并评估了它们在黑腹亚组的五个密切相关物种中的分子进化速率和模式，这些物种在卵巢数量上表现出物种特异性差异。通过对蛋白质序列进化(dN/dS)的综合分析，分支位点阳性选择，表达特异性(tau)和系统发育回归(PGLS)，我们报告了42个基因的证据，这些基因显示出在果蝇卵巢数量的种间进化变化的遗传基础中发挥作用的迹象。其中包括信号基因upd2和Ilp5以及细胞外基质基因vkg和Col4a1，其dN/dS预测了物种之间的卵巢数量。一起,我们提出了一个模型，其中一组卵巢相关基因蛋白具有增强的进化能力，包括适应性进化，促进果蝇种类中卵巢数量的快速变化。
