Department of Biology, University of Victoria, Victoria, British Columbia, Canada; The Deeley Research Centre, BC Cancer, Victoria, British Columbia, Canada.
Department of Biology, University of Victoria, Victoria, British Columbia, Canada; Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, UK.
Curr Biol. 2018 Dec 3;28(23):3864-3870.e4. doi: 10.1016/j.cub.2018.10.035. Epub 2018 Nov 15.
Diverse selfish genetic elements have evolved the ability to manipulate reproduction to increase their transmission, and this can result in highly distorted sex ratios [1]. Indeed, one of the major explanations for why sex determination systems are so dynamic is because they are shaped by ongoing coevolutionary arms races between sex-ratio-distorting elements and the rest of the genome [2]. Here, we use genetic crosses and genome analysis to describe an unusual sex ratio distortion with striking consequences on genome organization in a booklouse species, Liposcelis sp. (Insecta: Psocodea), in which two types of females coexist. Distorter females never produce sons but must mate with males (the sons of nondistorting females) to reproduce [3]. Although they are diploid and express the genes inherited from their fathers in somatic tissues, distorter females only ever transmit genes inherited from their mothers. As a result, distorter females have unusual chimeric genomes, with distorter-restricted chromosomes diverging from their nondistorting counterparts and exhibiting features of a giant non-recombining sex chromosome. The distorter-restricted genome has also acquired a gene from the bacterium Wolbachia, a well-known insect reproductive manipulator; we found that this gene has independently colonized the genomes of two other insect species with unusual reproductive systems, suggesting possible roles in sex ratio distortion in this remarkable genetic system.
多种多样的自私遗传因子进化出了操纵繁殖的能力，以增加它们的传播，这可能导致高度扭曲的性别比例[1]。事实上，性别决定系统如此动态的主要原因之一是，它们受到性别比例扭曲因子与基因组其余部分之间持续的共同进化军备竞赛的影响[2]。在这里，我们使用遗传杂交和基因组分析来描述一种不寻常的性别比例扭曲现象，这种现象对一种书虱物种（昆虫纲：Psocodea）的基因组组织产生了显著影响，在该物种中存在两种类型的雌性。扭曲雌性从不产生雄性，但必须与雄性（非扭曲雌性的雄性后代）交配才能繁殖[3]。尽管它们是二倍体，并在体细胞中表达从父亲那里继承的基因，但扭曲雌性只传递从母亲那里继承的基因。结果，扭曲雌性具有不寻常的嵌合基因组，扭曲限制染色体与非扭曲对应染色体分离，并表现出巨型非重组性染色体的特征。扭曲限制的基因组还从细菌沃尔巴克氏体获得了一个基因，沃尔巴克氏体是一种著名的昆虫生殖操纵因子；我们发现，这个基因独立地在另外两个具有不寻常生殖系统的昆虫物种的基因组中定植，这表明在这个显著的遗传系统中，它可能在性别比例扭曲中发挥作用。
