McNew Sabrina M, Boquete M Teresa, Espinoza-Ulloa Sebastian, Andres Jose A, Wagemaker Niels C A M, Knutie Sarah A, Richards Christina L, Clayton Dale H
School of Biological Sciences University of Utah Salt Lake City UT USA.
Cornell Lab of Ornithology Cornell University Ithaca NY USA.
Ecol Evol. 2021 May 3;11(12):7713-7729. doi: 10.1002/ece3.7606. eCollection 2021 Jun.
Anthropogenic changes to the environment challenge animal populations to adapt to new conditions and unique threats. While the study of adaptation has focused on genetic variation, epigenetic mechanisms may also be important. DNA methylation is sensitive to environmental stressors, such as parasites and pesticides, which may affect gene expression and phenotype. We studied the effects of an invasive ectoparasite, , on DNA methylation of Galápagos mockingbirds (). We used the insecticide permethrin to manipulate presence in nests of free-living mockingbirds and tested for effects of parasitism on nestling mockingbirds using epiGBS, a reduced-representation bisulfite sequencing (RRBS) approach. To distinguish the confounding effects of insecticide exposure, we conducted a matching experiment exposing captive nestling zebra finches () to permethrin. We used zebra finches because they were the closest model organism to mockingbirds that we could breed in controlled conditions. We identified a limited number of differentially methylated cytosines (DMCs) in parasitized versus nonparasitized mockingbirds, but the number was not more than expected by chance. In contrast, we saw clear effects of permethrin on methylation in captive zebra finches. DMCs in zebra finches paralleled documented effects of permethrin exposure on vertebrate cellular signaling and endocrine function. Our results from captive birds indicate a role for epigenetic processes in mediating sublethal nontarget effects of pyrethroid exposure in vertebrates. Environmental conditions in the field were more variable than the laboratory, which may have made effects of both parasitism and permethrin harder to detect in mockingbirds. RRBS approaches such as epiGBS may be a cost-effective way to characterize genome-wide methylation profiles. However, our results indicate that ecological epigenetic studies in natural populations should consider the number of cytosines interrogated and the depth of sequencing in order to have adequate power to detect small and variable effects.
人为的环境变化对动物种群适应新环境和独特威胁构成了挑战。虽然对适应的研究主要集中在基因变异上，但表观遗传机制可能也很重要。DNA甲基化对环境应激源敏感，如寄生虫和杀虫剂，这可能会影响基因表达和表型。我们研究了一种入侵性体外寄生虫对加拉帕戈斯模仿鸟DNA甲基化的影响。我们使用氯菊酯来控制自由生活的模仿鸟巢中该寄生虫的存在，并使用epiGBS（一种简化代表性亚硫酸氢盐测序方法）测试寄生虫感染对雏鸟模仿鸟的影响。为了区分接触杀虫剂的混杂效应，我们进行了一项配对实验，将圈养的雏鸟斑胸草雀暴露于氯菊酯中。我们使用斑胸草雀是因为它们是我们能够在可控条件下饲养的与模仿鸟最接近的模式生物。我们在受寄生虫感染和未受感染的模仿鸟中鉴定出数量有限的差异甲基化胞嘧啶，但数量不超过偶然预期。相比之下，我们看到氯菊酯对圈养斑胸草雀的甲基化有明显影响。斑胸草雀中的差异甲基化胞嘧啶与记录的氯菊酯暴露对脊椎动物细胞信号传导和内分泌功能的影响相似。我们对圈养鸟类的研究结果表明，表观遗传过程在介导拟除虫菊酯暴露对脊椎动物的亚致死非靶标效应中发挥作用。野外的环境条件比实验室更具变化性，这可能使得在模仿鸟中检测寄生虫感染和氯菊酯的影响更加困难。像epiGBS这样的简化代表性亚硫酸氢盐测序方法可能是一种经济有效的方式来表征全基因组甲基化图谱。然而，我们的结果表明，自然种群中的生态表观遗传研究应考虑所检测的胞嘧啶数量和测序深度，以便有足够的能力检测微小和可变的效应。
