Le Moan Alan, Panova Marina, De Jode Aurélien, Ortega-Martinez Olga, Duvetorp Mårten, Faria Rui, Butlin Roger, Johannesson Kerstin
Tjärnö Marine Laboratory, Department of Marine Sciences University of Gothenburg Strömstad Sweden.
InBIO Laboratório Associado, CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos Universidade do Porto Vairão Portugal.
Evol Appl. 2022 Jun 26;16(2):279-292. doi: 10.1111/eva.13427. eCollection 2023 Feb.
Understanding the genetic targets of natural selection is one of the most challenging goals of population genetics. Some of the earliest candidate genes were identified from associations between allozyme allele frequencies and environmental variation. One such example is the clinal polymorphism in the arginine kinase () gene in the marine snail . While other enzyme loci do not show differences in allozyme frequencies among populations, the alleles are near differential fixation across repeated wave exposure gradients in Europe. Here, we use this case to illustrate how a new sequencing toolbox can be employed to characterize the genomic architecture associated with historical candidate genes. We found that the alleles differ by nine nonsynonymous substitutions, which perfectly explain the different migration patterns of the allozymes during electrophoresis. Moreover, by exploring the genomic context of the gene, we found that the three main alleles are located on different arrangements of a putative chromosomal inversion that reaches near fixation at the opposing ends of two transects covering a wave exposure gradient. This shows is part of a large (3/4 of the chromosome) genomic block of differentiation, in which is unlikely to be the only target of divergent selection. Nevertheless, the nonsynonymous substitutions among alleles and the complete association of one allele with one inversion arrangement suggest that the gene is a strong candidate to contribute to the adaptive significance of the inversion.
了解自然选择的基因靶点是群体遗传学最具挑战性的目标之一。一些最早的候选基因是从等位酶等位基因频率与环境变异之间的关联中确定的。一个这样的例子是海蜗牛精氨酸激酶（）基因中的渐变多态性。虽然其他酶基因座在不同种群间的等位酶频率没有差异，但在欧洲，等位基因在反复的波浪暴露梯度中接近差异固定。在这里，我们用这个例子来说明如何使用一种新的测序工具箱来表征与历史候选基因相关的基因组结构。我们发现等位基因有九个非同义替换，这完美地解释了等位酶在电泳过程中的不同迁移模式。此外，通过探索基因的基因组背景，我们发现三个主要的等位基因位于一个假定的染色体倒位的不同排列上，该倒位在覆盖波浪暴露梯度的两个样带的相对两端接近固定。这表明是一个大的（染色体的3/4）分化基因组块的一部分，其中不太可能是趋异选择的唯一靶点。然而，等位基因之间的非同义替换以及一个等位基因与一种倒位排列的完全关联表明，基因是导致倒位适应性意义的有力候选基因。
