Department of Evolution, Ecology, and Behavior, University of Illinois, Urbana-Champaign, Illinois 61801.
Department of Biology, University of Puerto Rico, Rio Piedras Campus, San Juan, 00925, Puerto Rico.
Genetics. 2020 Apr;214(4):1059-1078. doi: 10.1534/genetics.120.303059. Epub 2020 Feb 4.
The underlying genetic changes that regulate the appearance and disappearance of repeated traits, or serial homologs, remain poorly understood. One hypothesis is that variation in genomic regions flanking master regulatory genes, also known as input-output genes, controls variation in trait number, making the locus of evolution almost predictable. Another hypothesis implicates genetic variation in up- or downstream loci of master control genes. Here, we use the butterfly , a species that exhibits natural variation in eyespot number on the dorsal hindwing, to test these two hypotheses. We first estimated the heritability of dorsal hindwing eyespot number by breeding multiple butterfly families differing in eyespot number and regressing eyespot numbers of offspring on midparent values. We then estimated the number and identity of independent genetic loci contributing to eyespot number variation by performing a genome-wide association study with restriction site-associated DNA sequencing from multiple individuals varying in number of eyespots sampled across a freely breeding laboratory population. We found that dorsal hindwing eyespot number has a moderately high heritability of ∼0.50 and is characterized by a polygenic architecture. Previously identified genomic regions involved in eyespot development, and novel ones, display high association with dorsal hindwing eyespot number, suggesting that homolog number variation is likely determined by regulatory changes at multiple loci that build the trait, and not by variation at single master regulators or input-output genes.
调控重复特征（或串联同源物）出现和消失的潜在遗传变化仍知之甚少。一种假设是，主调控基因（也称为输入-输出基因）侧翼的基因组区域的变异控制着特征数量的变化，从而使进化的基因座几乎可以预测。另一种假设涉及主控制基因上下游的遗传变异。在这里，我们使用蝴蝶作为研究对象，蝴蝶的后翅背部存在眼斑数量的自然变异，以此来检验这两种假设。我们首先通过繁殖具有不同眼斑数量的多个蝴蝶家族，并将后代的眼斑数量回归到中亲值，来估计后翅背部眼斑数量的遗传力。然后，我们通过对来自多个个体的限制酶相关 DNA 测序进行全基因组关联研究，对多个具有不同眼斑数量的个体进行采样，来估计对眼斑数量变化有贡献的独立遗传基因座的数量和身份。我们发现，后翅背部眼斑数量具有中等程度的遗传力，约为 0.50，并且具有多基因结构。先前鉴定的与眼斑发育有关的基因组区域，以及新的基因组区域，与后翅背部眼斑数量高度相关，这表明同源物数量的变化可能是由多个构建特征的调控变化决定的，而不是由单个主调控因子或输入-输出基因的变化决定的。
