University of Groningen, Center for Ecological and Evolutionary Studies, Evolutionary Genetics, Groningen, The Netherlands.
PLoS One. 2013 May 22;8(5):e63618. doi: 10.1371/journal.pone.0063618. Print 2013.
Although sex determination is a universal process in sexually reproducing organisms, sex determination pathways are among the most highly variable genetic systems found in nature. Nevertheless, general principles can be identified among the diversity, like the central role of transformer (tra) in insects. When a functional TRA protein is produced in early embryogenesis, the female sex determining route is activated, while prevention of TRA production leads to male development. In dipterans, male development is achieved by prevention of female-specific splicing of tra mRNA, either mediated by X-chromosome dose or masculinizing factors. In Hymenoptera, which have haplodiploid sex determination, complementary sex determination and maternal imprinting have been identified to regulate timely TRA production. In the parasitoid Nasonia, zygotic transformer (Nvtra) expression and splicing is regulated by a combination of maternal provision of Nvtra mRNA and silencing of Nvtra expression in unfertilized eggs. It is unclear, however, if this silencing is directly on the tra locus or whether it is mediated through maternal silencing of a trans-acting factor. Here we show that in Nasonia, female sex determination is dependent on zygotic activation of Nvtra expression by an as yet unknown factor. This factor, which we propose to term womanizer (wom), is maternally silenced during oogenesis to ensure male development in unfertilized eggs. This finding implicates the upstream recruitment of a novel gene in the Nasonia sex determining cascade and supports the notion that sex determining cascades can rapidly change by adding new components on top of existing regulators.
虽然性别决定是有性繁殖生物中普遍存在的过程，但性别决定途径是自然界中遗传系统最具多样性的途径之一。然而，在多样性中可以识别出一般原则，例如在昆虫中转化器（tra）的核心作用。当早期胚胎发生中产生功能性 TRA 蛋白时，激活雌性性别决定途径，而阻止 TRA 产生则导致雄性发育。在双翅目昆虫中，通过阻止 tra mRNA 的雌性特异性剪接来实现雄性发育，这种剪接要么由 X 染色体剂量介导，要么由雄性化因子介导。在膜翅目昆虫中，具有单倍体二倍体性别决定，已经确定互补性别决定和母体印记来调节 TRA 的适时产生。在寄生蜂 Nasonia 中，合子转化器（Nvtra）的表达和剪接受到母体提供 Nvtra mRNA 和在未受精卵中沉默 Nvtra 表达的组合调控。然而，尚不清楚这种沉默是否直接在 tra 基因座上发生，还是通过母体沉默转录因子来介导。在这里，我们表明在 Nasonia 中，雌性性别决定依赖于未知因子对 Nvtra 表达的合子激活。我们提议将这个因子称为“女人迷”（wom），它在卵子发生过程中被母体沉默，以确保未受精卵中的雄性发育。这一发现暗示了在 Nasonia 性别决定级联中招募了一个新基因，支持了性别决定级联可以通过在现有调节剂之上添加新成分来快速改变的观点。
