Allele specific expression and methylation in the bumblebee,Bombus terrestris

Abstract

The social hymenoptera are emerging as models for epigenetics. DNA methylation, the addition of a methyl group, is a common epigenetic marker. In mammals and flowering plants methylation affects allele specific expression. There is contradictory evidence for the role of methylation on allele specific expression in social insects. The aim of this paper is to investigate allele specific expression and monoallelic methylation in the bumblebee, Bombus terrestris. We found nineteen genes that were both monoallelically methylated and monoallelically expressed in a single bee. Fourteen of these genes express the hypermethylated allele, while the other five express the hypomethylated allele. We also searched for allele specific expression in twenty-nine published RNA-seq libraries. We found 555 loci with allele-specific expression. We discuss our results with reference to the functional role of methylation in gene expression in insects and in the as yet unquantified role of genetic cis effects in insect allele specific methylation and expression.

Parent of origin gene expression in the bumblebee, Bombus terrestris, supports Haig’s kinship theory for the evolution of genomic imprinting

“…The identification of genes showing parent-of-origin expression in this study lays the ground work for future research to identify potential epigenetic mechanisms of allele specific expression in social insects. Genes showing allele specific expression and DNA methylation have been previously identified in B. terrestris (Lonsdale et al, 2017), and genes involved in the reproductive process have been shown to be differentially methylated between reproductive castes (Amarasinghe et al, 2014; Marshall et al, 2019). DNA methylation is the mechanism by which some genes are imprinted in mammals and plants (Scott and Spielman, 2006) and so investigation of parent-of-origin methylation in B. terrestris may be fruitful.…”

Methylation and gene expression differences between reproductive and sterile bumblebee workers

“…A competition phase then occurs between queens and workers, where some workers will become reproductive and produce their own haploid sons (Alaux et al 2006); this results in distinct reproductive worker castes within the colony. Multiple recent studies have highlighted B. terrestris as an ideal organism to assess methylation as a potential regulatory mechanism for reproductive caste determination (Amarasinghe et al 2014;Lonsdale et al 2017;Li et al 2018).…”

Methylation and Gene Expression Differences Between Reproductive Castes of Bumblebee Workers

“…A competition phase then occurs between queens and workers, where some workers will become reproductive and produce their own haploid sons (Alaux et al , 2006), this results in distinct reproductive worker castes within the colony. Multiple recent studies have highlighted B. terrestris as an ideal organism to assess methylation as a potential regulatory mechanism for reproductive caste determination (Li et al , 2018; Lonsdale et al , 2017; Amarasinghe et al , 2014).…”

“…Methylation regulatory genes were identified in the bumblebee genome and have since been shown to have varying expression levels between queens, workers and drones (Li et al , 2018). Additionally, genes showing allele-specific methylation and gene expression have been identified and are enriched in reproductive related processes (Lonsdale et al , 2017). Most importantly, experimental changes in methylation in B. terrestris workers has been shown to alter levels of reproductive behaviour (Amarasinghe et al , 2014).…”