Cytosine modifications in the honey bee (Apis mellifera) worker genome

Abstract

Epigenetic changes enable genomes to respond to changes in the environment, such as altered nutrition, activity, or social setting. Epigenetic modifications, thereby, provide a source of phenotypic plasticity in many species. The honey bee (Apis mellifera) uses nutritionally sensitive epigenetic control mechanisms in the development of the royal caste (queens) and the workers. The workers are functionally sterile females that can take on a range of distinct physiological and/or behavioral phenotypes in response to environmental changes. Honey bees have a wide repertoire of epigenetic mechanisms which, as in mammals, include cytosine methylation, hydroxymethylated cytosines, together with the enzymatic machinery responsible for these cytosine modifications. Current data suggests that honey bees provide an excellent system for studying the "social repertoire" of the epigenome. In this review, we elucidate what is known so far about the honey bee epigenome and its mechanisms. Our discussion includes what may distinguish honey bees from other model animals, how the epigenome can influence worker behavioral task separation, and how future studies can answer central questions about the role of the epigenome in social behavior.

Keywords: 5-hydroxymethylcytosine; demethylation; honey bee; methylation; social behavior.

FIGURE 1

General features of the 5-methylcytosine distribution in DNA from mammals, honey bees and fruit flies. Red circles indicate 5-mC. Mammalian genomes are typically methylated in transposon and repeat elements, and at some promoter regions. Intergenic DNA methylation occurs albeit at lower levels. Honey bee genomes are typically methylated in exons close to the exon-intron borders. Non-CpG methylation occurs in introns. Methylation outside of transposons has not been mapped in fruit fly genomes.