Department of Biological Sciences, Vanderbilt University, Nashville, TN 37235, USA; Department of Molecular Microbiology, Washington University School of Medicine in St. Louis, St. Louis, MO 63110, USA.
Department of Biological Sciences, Vanderbilt University, Nashville, TN 37235, USA.
Curr Biol. 2018 Jun 4;28(11):1692-1702.e6. doi: 10.1016/j.cub.2018.04.010. Epub 2018 May 17.
Maternal transmission of intracellular microbes is pivotal in establishing long-term, intimate symbioses. For germline microbes that exert negative reproductive effects on their hosts, selection can theoretically favor the spread of host genes that counteract the microbe's harmful effects. Here, we leverage a major difference in bacterial (Wolbachia pipientis) titers between closely related wasp species with forward genetic, transcriptomic, and cytological approaches to map two quantitative trait loci that suppress bacterial titers via a maternal effect. Fine mapping and knockdown experiments identify the gene Wolbachia density suppressor (Wds), which dominantly suppresses bacterial transmission from mother to embryo. Wds evolved by lineage-specific non-synonymous changes driven by positive selection. Collectively, our findings demonstrate that a genetically simple change arose by positive Darwinian selection in less than a million years to regulate maternally transmitted bacteria via a dominant, maternal effect gene.
母系传播细胞内微生物对于建立长期、亲密共生关系至关重要。对于那些对宿主产生负面影响的生殖系微生物，理论上选择可以有利于宿主基因的传播，这些基因可以抵消微生物的有害影响。在这里，我们利用两种密切相关的黄蜂物种之间细菌（沃尔巴克氏体）滴度的主要差异，通过正向遗传、转录组学和细胞学方法来绘制两个通过母系效应抑制细菌滴度的数量性状位点。精细定位和敲低实验确定了基因沃尔巴克氏体密度抑制因子（Wds），它通过母系效应显性抑制细菌从母代向胚胎的传播。Wds 是由正选择驱动的谱系特异性非同义变化进化而来的。总的来说，我们的发现表明，在不到一百万年的时间里，一种遗传上简单的变化通过正达尔文选择产生，通过一个显性的母系效应基因来调节母系传播的细菌。
