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.

性别决定是一项具有重大生态与进化影响的关键发育决策，然而自然界中存在着种类繁多的性别决定机制，目前我们对其演化路径的认知仍较为有限。理论与实证研究均表明，针对性别决定通路相关基因的突变产生补偿性适应，可能在这些通路的演化过程中扮演重要角色。本研究以秀丽隐杆线虫（Caenorhabditis elegans）为实验材料，采用实验进化手段，对两类关键性别决定基因携带成对突变的品系展开研究：这类突变联合使性别决定具有温度敏感性，并在中间温度下引发间性表型（该表型个体仍具有弱至中等程度的可育性）。经过50代的进化后，进化品系的表型显著向野生型恢复。但值得注意的是，进化品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）恢复的表型，这表明野生型表型的恢复可不依赖于这些突变带来的转录调控效应。本研究结果凸显了性别决定通路的微进化灵活性，并指出对突变的补偿性适应可引发这些通路出现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契合。