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 RNAseq 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.

Methylation and gene expression differences between reproductive and sterile bumblebee workers

“…Additionally, genes showing allele‐specific methylation and gene expression have been identified and are enriched in reproductive‐related processes (Lonsdale et al. ). Finally, experimental changes in methylation in B. terrestris workers has been shown to alter levels of reproductive behavior (Amarasinghe et al.…”

A novel method for using RNA‐seq data to identify imprinted genes in social Hymenoptera with multiply mated queens

“…With a solid theoretical basis for expecting genomic imprinting in the social Hymenoptera with physically differentiated castes, the search for parent‐of‐origin effects consistent with the kinship theory has indeed been accumulating suggestive evidence (reviewed in Pegoraro et al., 2017). Consistent with the kinship theory, disruption of DNA methylation associated with imprinting promotes worker reproduction in a bumblebee, leading to increased aggression and ovary size (Amarasinghe et al., 2014), whereas the genes involved appear mono‐allelically methylated and expressed (Amarasinghe et al., 2015; Lonsdale et al., 2017). In an ant, parent‐of‐origin effects influence development into queens rather than workers (Libbrecht et al., 2011) and brood care behaviour in workers (Libbrecht & Keller, 2013).…”

“…Under such mono‐allelic expression, the frequency of a SNP allele in the colony RNA will then reflect either the genotype of the queen or the weighted average of the genotypes of the males she mated with. Many imprinted genes in mammals (Haig, 2004), and a smaller number of genes in bumblebees (Lonsdale et al., 2017), show mono‐allelic expression, but it is unclear whether the ‘loudest‐voice’ principle is universally applicable as incomplete ASE biases are often found, particularly in the social insects (e.g. Galbraith et al., 2016; Kocher et al., 2015; Smith et al., 2020).…”

“…Only five social insect studies have attempted to directly identify putatively imprinting‐induced ASE with genome‐wide searches based on high‐throughput sequencing: three in the honeybee (Galbraith et al., 2016; Kocher et al, 2015; Smith et al., 2020) and two in a bumblebee (Lonsdale et al., 2017; Marshall et al., 2020). These studies adopted techniques successfully applied in other (diploid) organisms, where two genotypes are reciprocally crossed and offspring RNA sequenced to find genes where the relative proportion of the two RNA alleles is dependent on the direction of the cross while differing significantly from the 1:1 null expectation (Babak et al, 2015, Coolon et al, 2012, Gehring et al, 2011, Gregg et al, 2010, Wang et al., 2008).…”

10-hydroxy-2E-decenoic Acid (10HDA) is not a Caste-differentiation Factor in Melipona Scutellaris Stingless Bees

“…Currently, it is largely recognized that epigenetic mechanisms are associated with caste polyphenisms regulation [16][17][18][19][20][21][22][23][24][25][26][27][28][29] . Honeybees and bumblebees present different sets of microRNAs [30][31][32][33][34][35] as well as differences in methylation [16,21,[36][37][38][39][40][41] according to the caste. Also, in Apis mellifera, histone posttranslation modifications were described [42,43] .…”