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）是一项至关重要的发育决策，对生态与进化过程具有深远影响。然而自然界中存在着极为多样的性别决定机制，而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，针对性别决定相关基因中突变的补偿性适应，可能在这些通路的演化中扮演重要角色。本研究以固定了两个关键性别决定基因突变的秀丽隐杆线虫（Caenorhabditis elegans）品系为材料，通过实验演化直接探究这一问题：这两个突变共同使性别决定过程具备温度敏感性，并在中间温度下引发间性表型（但仍具备弱至中等程度的可育性）。经过50代演化后，实验组品系的表型明显向野生型（wild-type）恢复。然而，演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（部分案例中近乎完全）恢复的表型，这意味着野生型表型的恢复可不依赖于这些突变的转录层面效应。我们的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相呼应。