ABSTRACT

Temperature is a key environmental parameter affecting both the phenotypes and distributions of organisms, particularly ectotherms. Rapid organismal responses to thermal environmental changes have been described for several ectotherms; however, the underlying molecular mechanisms often remain unclear. Here, we studied whole genome cytosine methylation patterns of European grayling (Thymallus thymallus) embryos from five populations with contemporary adaptations of early life history traits at either ‘colder’ or ‘warmer’ spawning grounds. We reared fish embryos in a common garden experiment using two temperatures that resembled the ‘colder’ and ‘warmer’ conditions of the natal natural environments. Genome-wide methylation patterns were similar in populations originating from colder thermal origin subpopulations, whereas single nucleotide polymorphisms uncovered from the same data identified strong population structure among isolated populations, but limited structure among interconnected populations. This was surprising because the previously studied gene expression response among populations was mostly plastic, and mainly influenced by the developmental temperature. These findings support the hypothesis of the magnified role of epigenetic mechanisms in modulating plasticity. The abundance of consistently changing methylation loci between two warmer-to-colder thermal origin population pairs suggests that local adaptation has shaped the observed methylation patterns. The dynamic nature of the methylomes was further highlighted by genome-wide and site-specific plastic responses. Our findings support both the presence of a plastic response in a subset of CpG loci, and the evolutionary role of methylation divergence between populations adapting to contrasting thermal environments.

摘要

温度是影响生物表型和分布的关键环境参数，尤其是等温动物。已经描述了几种等温动物对热环境变化的快速有机体反应；然而，潜在的分子机制通常仍不清楚。在这里，我们研究了欧洲河豚 ( Thymallus thymallus ) 的全基因组胞嘧啶甲基化模式。) 来自五个种群的胚胎，这些种群在“较冷”或“较热”产卵场具有当代适应早期生活史特征。我们在一个普通的花园实验中使用类似于出生自然环境的“较冷”和“较暖”条件的两种温度来饲养鱼胚胎。全基因组甲基化模式在源自较冷热起源亚群的种群中相似，而从相同数据中发现的单核苷酸多态性在孤立种群中确定了强烈的种群结构，但在相互关联的种群中结构有限。这是令人惊讶的，因为先前研究的群体之间的基因表达反应大多是可塑性的，主要受发育温度的影响。这些发现支持表观遗传机制在调节可塑性中的放大作用的假设。两个从暖到冷的热源种群对之间不断变化的甲基化基因座的丰度表明，局部适应塑造了观察到的甲基化模式。全基因组和位点特异性塑料反应进一步突出了甲基化组的动态特性。我们的研究结果支持在 CpG 基因座子集中存在塑性反应，以及适应不同热环境的种群之间甲基化差异的进化作用。全基因组和位点特异性塑料反应进一步突出了甲基化组的动态特性。我们的研究结果支持在 CpG 基因座子集中存在塑性反应，以及适应不同热环境的种群之间甲基化差异的进化作用。全基因组和位点特异性塑料反应进一步突出了甲基化组的动态特性。我们的研究结果支持在 CpG 基因座子集中存在塑性反应，以及适应不同热环境的种群之间甲基化差异的进化作用。