Groningen Institute for Evolutionary Life Sciences, University of Groningen, Groningen, The Netherlands.
Department of Molecular Biosciences, University of Kansas, Lawrence, KS, USA.
Mol Ecol. 2021 May;30(9):1979-1992. doi: 10.1111/mec.15863. Epub 2021 Mar 15.
During the transition from sexual to asexual reproduction, a suite of reproduction-related sexual traits become superfluous, and may be selected against if costly. Female functional virginity refers to asexual females resisting to mate or not fertilizing eggs after mating. These traits appear to be among the first that evolve during transitions from sexual to asexual reproduction. The genetic basis of female functional virginity remains elusive. Previously, we reported that female functional virginity segregates as expected for a single recessive locus in the asexual parasitoid wasp Asobara japonica. Here, we investigate the genetic basis of this trait by quantitative trait loci (QTL) mapping and candidate gene analyses. Consistent with the segregation of phenotypes, we found a single QTL of large effect, spanning over 4.23 Mb and comprising at least 131 protein-coding genes, of which 15 featured sex-biased expression in the related sexual species Asobara tabida. Two of the 15 sex-biased genes were previously identified to differ between related sexual and asexual population/species: CD151 antigen and nuclear pore complex protein Nup50. A third gene, hormone receptor 4, is involved in steroid hormone mediated mating behaviour. Overall, our results are consistent with a single locus, or a cluster of closely linked loci, underlying rapid evolution of female functional virginity in the transition to asexuality. Once this variant, causing rejection to mate, has swept through a population, the flanking region does not get smaller owing to lack of recombination in asexuals.
在有性繁殖到无性繁殖的转变过程中，一系列与繁殖相关的性特征变得多余，如果代价高昂，这些特征可能会被选择淘汰。雌性功能性贞洁是指无性雌性在交配后拒绝交配或不使卵子受精。这些特征似乎是在从有性繁殖向无性繁殖的转变过程中首先进化的特征之一。雌性功能性贞洁的遗传基础仍然难以捉摸。以前，我们报道了在无性寄生蜂日本金小蜂（Asobara japonica）中，雌性功能性贞洁作为单个隐性基因座分离，符合预期。在这里，我们通过数量性状基因座（QTL）作图和候选基因分析来研究该特征的遗传基础。与表型分离一致，我们发现了一个单一的大效应 QTL，跨越超过 4.23Mb，包含至少 131 个编码蛋白质的基因，其中 15 个在相关的有性物种日本金小蜂中表现出性别偏向表达。这 15 个性别偏向表达的基因中的两个先前被鉴定为在相关的有性和无性种群/物种之间存在差异：CD151 抗原和核孔复合物蛋白 Nup50。第三个基因，激素受体 4，参与类固醇激素介导的交配行为。总体而言，我们的结果与单个基因座或紧密连锁的基因座一致，这些基因座是在向无性繁殖的转变过程中，雌性功能性贞洁的快速进化的基础。一旦这种导致拒绝交配的变异在一个种群中传播开来，由于无性生殖中缺乏重组，侧翼区域就不会因缺乏重组而变小。
