Data from: Recurrent and recent selective sweeps in the piRNA pathway

Uncontrolled transposable element (TE) insertions and excisions can cause chromosome breaks and mutations with dramatic deleterious effects. The PIWI interacting RNA (piRNA) pathway functions as an adaptive TE silencing system during germline development. Several essential piRNA pathway proteins appear to be rapidly evolving, suggesting that TEs and the silencing machinery may be engaged in a classical “evolutionary arms race.” Using a variety of molecular evolutionary and population genetic approaches, we find that the piRNA pathway genes rhino, krimper, and aubergine show patterns suggestive of extensive recurrent positive selection across Drosophila species. We speculate that selection on these proteins reflects crucial roles in silencing unfamiliar elements during vertical and horizontal transmission of TEs into naïve populations and species, respectively.失控转座因子（transposable element, TE）的插入与切离可引发染色体断裂与突变，进而造成极具破坏性的有害效应。PIWI互作RNA（PIWI interacting RNA, piRNA）通路在生殖系发育过程中，作为适应性转座因子沉默系统发挥功能。多个核心piRNA通路蛋白呈现快速进化特征，这提示转座因子与其沉默机制可能陷入了经典的“进化军备竞赛”。本研究通过多种分子进化与群体遗传学研究手段，发现果蝇属物种中piRNA通路基因rhino、krimper与aubergine的演化模式显示其经历了广泛的周期性正向选择。我们推测，对这些蛋白的选择压力，源于转座因子分别通过垂直传播进入未接触该因子的种群、通过水平传播进入未接触该因子的物种时，这些蛋白在沉默陌生转座因子过程中所发挥的关键作用。