Baerwald Melinda R, Meek Mariah H, Stephens Molly R, Nagarajan Raman P, Goodbla Alisha M, Tomalty Katharine M H, Thorgaard Gary H, May Bernie, Nichols Krista M
Department of Animal Science, University of California - Davis, Davis, CA, 95616.
School of Natural Sciences, University of California - Merced, Merced, CA, 95343.
Mol Ecol. 2016 Apr;25(8):1785-1800. doi: 10.1111/mec.13231. Epub 2015 Jun 5.
Migration is essential for the reproduction and survival of many animals, yet little is understood about its underlying molecular mechanisms. We used the salmonid Oncorhynchus mykiss to gain mechanistic insight into smoltification, which is a morphological, physiological and behavioural transition undertaken by juveniles in preparation for seaward migration. O. mykiss is experimentally tractable and displays intra- and interpopulation variation in migration propensity. Migratory individuals can produce nonmigratory progeny and vice versa, indicating a high degree of phenotypic plasticity. One potential way that phenotypic plasticity might be linked to variation in migration-related life history tactics is through epigenetic regulation of gene expression. To explore this, we quantitatively measured genome-scale DNA methylation in fin tissue using reduced representation bisulphite sequencing of F2 siblings produced from a cross between steelhead (migratory) and rainbow trout (nonmigratory) lines. We identified 57 differentially methylated regions (DMRs) between smolt and resident O. mykiss juveniles. DMRs were high in magnitude, with up to 62% differential methylation between life history types, and over half of the gene-associated DMRs were in transcriptional regulatory regions. Many of the DMRs encode proteins with activity relevant to migration-related transitions (e.g. circadian rhythm pathway, nervous system development, protein kinase activity). This study provides the first evidence of a relationship between epigenetic variation and life history divergence associated with migration-related traits in any species.
洄游对许多动物的繁殖和生存至关重要，但其潜在的分子机制却鲜为人知。我们利用鲑科鱼类虹鳟（Oncorhynchus mykiss）来深入了解银化过程，这是幼鱼为准备向海洋洄游而经历的一种形态、生理和行为上的转变。虹鳟在实验上易于操作，并且在洄游倾向方面表现出种群内和种群间的差异。洄游个体可以产生非洄游后代，反之亦然，这表明其具有高度的表型可塑性。表型可塑性可能与洄游相关生活史策略的变化相关联的一种潜在方式是通过基因表达的表观遗传调控。为了探究这一点，我们使用由钢头鳟（洄游型）和虹鳟（非洄游型）品系杂交产生的F2代同胞的简化代表性亚硫酸氢盐测序，对鳍组织中的全基因组DNA甲基化进行了定量测量。我们在银化虹鳟和定居型虹鳟幼鱼之间鉴定出57个差异甲基化区域（DMR）。DMR的差异程度很高，生活史类型之间的甲基化差异高达62%，并且超过一半的与基因相关的DMR位于转录调控区域。许多DMR编码的蛋白质具有与洄游相关转变相关的活性（例如昼夜节律途径、神经系统发育、蛋白激酶活性）。这项研究首次证明了表观遗传变异与任何物种中与洄游相关性状的生活史差异之间的关系。
