Species with a circannual life cycle need to match the timing of their life history events to the environment to maximize fitness. However, our understanding of how circannual traits such as timing of reproduction are regulated on a molecular level remains limited. Recent studies have implicated that epigenetic mechanisms can be an important part in the processes that regulate circannual traits. Here, we explore the role of DNA methylation in mediating reproductive timing in a seasonally breeding bird species, the great tit (Parus major), using genome-wide DNA methylation data from individual females that were blood sampled repeatedly throughout the breeding season. We demonstrate rapid and directional changes in DNA methylation within the promoter region of several genes, including a key transcription factor (NR5A1) known from earlier studies to be involved in the initiation of timing of reproduction. Interestingly, the observed changes in DNA methylation at NR5A1 identified here are in line with earlier gene expression studies of reproduction in chicken, indicating that the observed shifts in DNA methylation at this gene can have a regulatory role. Our findings provide an important step towards elucidating the genomic mechanism that mediates seasonal timing of a key life history traits and provide support for the idea that epigenetic mechanisms may play an important role in circannual traits.

中文翻译：

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与小型鸣禽繁殖开始相关的 DNA 甲基化的快速变化

具有圆形生命周期的物种需要将其生活史事件的时间与环境相匹配，以最大限度地提高适应度。然而，我们对如何在分子水平上调节诸如繁殖时间等周期性特征的理解仍然有限。最近的研究表明，表观遗传机制可能是调节昼夜性状过程中的重要组成部分。在这里，我们探索了 DNA 甲基化在调节季节性繁殖鸟类——大山雀（Parus major）繁殖时间中的作用。)，使用来自个体雌性的全基因组 DNA 甲基化数据，这些数据在整个繁殖季节重复进行血液采样。我们证明了几个基因的启动子区域内 DNA 甲基化的快速和定向变化，包括早期研究中已知的一个关键转录因子 ( NR5A1 ) ，该因子参与繁殖时间的开始。有趣的是，观察到的NR5A1 DNA 甲基化变化这里确定的与早期鸡繁殖的基因表达研究一致，表明观察到的该基因 DNA 甲基化的变化可能具有调节作用。我们的研究结果为阐明介导关键生活史特征的季节性时间的基因组机制迈出了重要一步，并为表观遗传机制可能在周期性特征中发挥重要作用的观点提供了支持。