Data from: Experimental evolution of the Caenorhabditis elegans sex determination pathway

Sex determination is a critical developmental decision with major ecological and evolutionary consequences, yet a large variety of sex determination mechanisms exist and we have a poor understanding of how they evolve. Theoretical and empirical work suggest that compensatory adaptations to mutations in genes involved in sex determination may play a role in the evolution of these pathways. Here, we directly address this problem using experimental evolution in Caenorhabditis elegans lines fixed for a pair of mutations in two key sex-determining genes that jointly render sex determination temperature-sensitive and cause intersexual (but still weakly to moderately fertile) phenotypes at intermediate temperatures. After fifty generations, evolved lines clearly recovered towards wild-type phenotypes. However, changes in transcript levels of key sex-determining genes in evolved lines cannot explain their partially (or in some cases, nearly completely) rescued phenotypes, implying that wild-type phenotypes can be restored independently of the transcriptional effects of these mutations. Our findings highlight the microevolutionary flexibility of sex determination pathways, and suggest that compensatory adaptation to mutations can elicit novel and unpredictable evolutionary trajectories in these pathways, mirroring the phylogenetic diversity and macroevolutionary dynamics of sex determination mechanisms.性别决定（sex determination）是一项关键的发育决策，对生态与进化进程具有重大影响。然而现存性别决定机制种类繁多，我们对其演化路径的认知仍较为匮乏。理论与实证研究表明，对性别决定通路相关基因突变产生的补偿性适应，可能在这些通路的演化过程中发挥作用。本研究以携带有两个关键性别决定基因双突变的纯合品系秀丽隐杆线虫（Caenorhabditis elegans）为实验材料，通过实验进化手段直接探究该问题：该双突变可使性别决定过程呈现温度敏感性，并在中间温度下诱导出间性表型（该表型下个体仍具备弱至中等程度的可育性）。经过50代进化后，进化株系的表型明显向野生型恢复。然而，进化株系中关键性别决定基因的转录水平变化，无法解释其部分（部分案例中甚至近乎完全）被挽救的表型，这意味着野生型表型的恢复可不依赖于这些突变带来的转录效应。本研究结果凸显了性别决定通路的微进化灵活性，并表明针对突变的补偿性适应可引发这些通路产生新颖且难以预测的演化轨迹，这与性别决定机制的系统发育多样性及宏进化动态特征相呼应。