Allele-specific expression is when one allele of a gene shows higher levels of expression compared with the other allele, in a diploid organism. Recent work has identified allele-specific expression in a number of Hymenopteran species. However, the molecular mechanism which drives this allelic expression bias remains unknown. In mammals, DNA methylation is often associated with genes which show allele-specific expression. DNA methylation systems have been described in species of Hymenoptera, providing a candidate mechanism. Using previously generated RNA-Seq and whole-genome bisulfite sequencing from reproductive and sterile bumblebee (Bombus terrestris) workers, we have identified genome-wide allele-specific expression and allele-specific DNA methylation. The majority of genes displaying allele-specific expression are common between reproductive and sterile workers and the proportion of allele-specific expression bias generally varies between genetically distinct colonies. We have also identified genome-wide allele-specific DNA methylation patterns in both reproductive and sterile workers, with reproductive workers showing significantly more genes with allele-specific methylation. Finally, there is no significant overlap between genes showing allele-specific expression and allele-specific methylation. These results indicate that cis-acting DNA methylation does not directly drive genome-wide allele-specific expression in this species.

中文翻译：

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大黄蜂工蜂在等位基因特异性 DNA 甲基化和等位基因特异性表达方面表现出差异。

等位基因特异性表达是指在二倍体生物中，基因的一个等位基因与其他等位基因相比表现出更高水平的表达。最近的工作已经确定了许多膜翅目物种中的等位基因特异性表达。然而，驱动这种等位基因表达偏差的分子机制仍然未知。在哺乳动物中，DNA 甲基化通常与显示等位基因特异性表达的基因相关。膜翅目物种中的 DNA 甲基化系统已被描述，提供了候选机制。利用先前生成的来自繁殖和不育熊蜂（Bombus terrestris）工蜂的 RNA-Seq 和全基因组亚硫酸氢盐测序，我们已经确定了全基因组等位基因特异性表达和等位基因特异性 DNA 甲基化。大多数显示等位基因特异性表达的基因在生殖工蚁和不育工蚁之间是常见的，并且等位基因特异性表达偏差的比例通常在遗传不同的菌落之间有所不同。我们还在生殖工蚁和不育工蚁中发现了全基因组等位基因特异性 DNA 甲基化模式，其中生殖工蚁显示出更多具有等位基因特异性甲基化的基因。最后，显示等位基因特异性表达和等位基因特异性甲基化的基因之间不存在显着重叠。这些结果表明顺式作用DNA甲基化并不直接驱动该物种中的全基因组等位基因特异性表达。