Data from: Specialization of a polyphenism switch gene following serial duplications in Pristionchus nematodes

Polyphenism is an extreme manifestation of developmental plasticity, requiring distinct developmental programs and the addition of a switch mechanism. Because the genetic basis of polyphenism switches has only begun to be understood, how their mechanisms arise is unclear. In the nematode Pristionchus pacificus, which has a mouthpart polyphenism specialized for alternative diets, a gene (eud-1) executing the polyphenism switch was recently identified as the product of lineage-specific duplications. Here we infer the role of gene duplications in producing a switch gene. Using reverse genetics and population genetic analyses, we examine evidence for competing scenarios of degeneration and complementation, neutral evolution, and functional specialization. Of the daughter genes, eud-1 alone has assumed switch-like regulation of the mouth polyphenism. Measurements of life-history traits in single, double, and triple sulfatase mutants did not, given modest sample sizes and a benign environment, identify alternative or complementary roles for eud-1 paralogs. Although possible roles are still unknown, selection analyses of the sister species and 104 natural isolates of P. pacificus detected purifying selection on the genes, suggesting their functionality by their fixation and evolutionary maintenance. Our approach shows the tractability of reverse genetics in a non-traditional model system to study evolution by gene duplication.多型现象（polyphenism）是发育可塑性的极端表现形式，其发生依赖于专属的发育程序与开关调控机制。由于学界仅在近年才开始解析多型现象开关的遗传基础，其机制的起源仍未明确。在具备针对差异化饮食特化口器多型现象的线虫——太平洋拟杆线虫（Pristionchus pacificus）中，执行多型现象开关功能的基因eud-1，近期被鉴定为谱系特异性基因重复的产物。本研究旨在推断基因重复在开关基因演化形成过程中的作用。通过反向遗传学与群体遗传学分析，我们对退化与互补、中性进化以及功能特化这三类竞争性演化假说进行了检验。在该基因重复产生的子代同源基因中，仅eud-1承担了口器多型现象的开关调控功能。在实验环境温和且样本量有限的条件下，对单、双及三硫酸酯酶（sulfatase）突变体的生活史性状检测，并未发现eud-1旁系同源基因存在替代性或互补性功能。尽管其潜在功能仍有待探明，但对该物种的姊妹物种以及104株太平洋拟杆线虫自然分离株的选择分析显示，该类基因受到纯化选择（purifying selection），表明它们通过序列固定与进化维持而具备生物学功能。本研究证实了在非传统模式生物体系中，利用反向遗传学手段探究基因重复驱动的进化过程具有可操作性。