Like father like daughter? Investigating epigenetic inheritance in honeybees

A project undertaken at The University of Sydney, and supervised by Ben Oldroyd, Emily Remnant and Boris Yagound

Besides their value for plant pollination, honeybees are an important model organism for studying how cooperation and conflicts are balanced in social systems. Honeybee queens mate with multiple males (drones), so each colony is comprised of up to 30 worker ‘patrilines’, each sired by a different father. Patriline-specific traits in worker physiology and behaviour are well documented, and are often interpreted as evidence of genetic task specialisation – the adaptive phenomenon in which workers with particular fathers perform specific tasks like guarding or pollen foraging. Yet the genetics of such traits are complex and the underlying causal genes are largely unknown. An underexplored avenue by which each drone could influence his worker progeny involves epigenetic mechanisms, DNA methylation being the best candidate.

DNA methylation is an epigenetic modification that alters gene expression by adding methyl marks to cytosines. DNA methylation is involved in developmental and phenotypic plasticity, and could be responsible for parent-of-origin effects. Previous results showed that male honeybees produce semen with unique DNA methylation profiles, indicating that they have the potential to epigenetically influence their worker daughters, ultimately leading to patriline-specific traits. Honeybees thus give us the unique opportunity to investigate the existence of epigenetic inheritance and its impacts on societies.

Our objective is to investigate if male honeybees can epigenetically influence their daughters through DNA methylation. Using instrumental inseminations of queens with the semen of different drones, combined with next-generation sequencing of each father and his daughters, we will test the hypothesis that each drone carries unique DNA methylation profiles that are transmitted through their semen to their daughter workers. We will further test whether these epigenetic patterns are associated with the workers’ reproductive phenotype. The results should deepen our understanding of inheritance and the functional outcomes of epigenetic mechanisms, and could be valuable for breeding programs in the beekeeping industry.

 

Figure 1. (a) A drone with his endophallus everted ready for semen collection. (b) A queen in an instrumental insemination apparatus. Syringe containing semen is indicated with an arrow. (c) Marked workers inside a hive. Credits: B. Oldroyd and B. Yagound.