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 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 nontraditional 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，需要依赖差异化的发育程序并引入切换机制。由于学界对多型现象切换的遗传基础的认知仅刚刚起步，其具体起源机制尚未明晰。针对具有适配差异化食性的口器多型现象的线虫——太平洋普里什昂线虫（Pristionchus pacificus），近期研究将执行多型现象切换的eud-1基因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形成过程中的作用。我们通过反向遗传学与群体遗传学分析，对三类竞争性演化假说进行了验证：退化与互补、中性进化以及功能特化。在所有子基因中，仅eud-1获得了对口器多型现象的类开关调控功能。在良性环境中对单、双、三硫酸酯酶突变体的生活史性状进行测定后，并未发现eud-1旁系同源基因存在替代或互补功能。尽管其潜在功能仍未明确，对其姊妹物种及104株太平洋普里什昂线虫自然分离株的选择分析显示存在纯化选择（负选择），表明这些基因通过固定与进化维持实现了功能保留。
本研究证实，在非传统模式生物系统中，借助反向遗传学探究基因重复驱动的演化过程具备可操作性。