A novel role for Eip74EF in male reproduction in promoting sperm elongation at the cost of fecundity

Spermatozoa are the most morphologically variable cell type, yet little is known about genes controlling natural variation in sperm shape. Drosophila fruit flies have evolved the longest sperm known, which are evolving under postcopulatory sexual selection, driven by sperm competition and cryptic female choice. Long sperm outcompete short sperm but primarily when females have long seminal receptacles (SRs), the primary sperm storage organ. Thus, selection on sperm length is mediated by SR length, and the two traits are coevolving across the Drosophila lineage, driven by a genetic correlation and fitness advantage of long sperm and long SR genotypes in both males and females. Ecdysone induced protein 74EF (Eip74EF) is rapidly evolving under positive selection in Drosophila, and it is expressed during post-meiotic stages of spermatogenesis, when spermatid elongation occurs. Partial knockdown of Eip74EF leads to shorter sperm but does not affect SR length, suggesting that Eip74EF is involv...精子细胞是形态变异程度最高的细胞类型，但目前对于调控精子形态自然变异的基因仍知之甚少。果蝇（Drosophila）演化出了已知最长的精子，这类精子处于交配后性选择的作用之下，该选择由精子竞争和隐性雌性选择驱动。长精子在竞争中优于短精子，但该优势仅在雌性拥有较长的受精囊（seminal receptacles, SRs）——这一主要的精子储存器官——时才会体现。因此，对精子长度的选择由受精囊长度介导，这两个性状在果蝇类群中处于协同演化状态，其驱动力来自遗传相关性，以及雌雄个体中长精子与长受精囊基因型所带来的适合度优势。蜕皮激素诱导蛋白74EF（Ecdysone induced protein 74EF, Eip74EF）在果蝇属中处于正向选择下的快速演化状态，且其在精子发生的减数后阶段——即精细胞伸长发生的时期——中表达。对Eip74EF的部分敲低会导致精子长度变短，但不会影响受精囊长度，这表明Eip74EF参与……