Intragenomic conflicts and their epigenetic basis in honey bees

Much attention is directed to studying the proximate mechanisms underlying phenotypic variation, including its genetic and epigenetic basis. Little attention has been given to the contribution of intragenomic conflicts, which occur when different genes within the same organism have different inclusive fitness agendas. For example, the alleles of genes involved in regulating resources received by an embryo/juvenile from its mother/siblings can be under divergent selection, because maternal alleles (“matrigenes”) are inherited by each offspring at equal frequency, whereas paternal alleles (“patrigenes”) are not. This conflict manifests as parent-specific gene expression (PSGE) and is predicted to occur frequently in eusocial species. Additionally, conflict between transposable elements (TEs) and their regulation by PIWI-interacting RNAs (piRNAs) can influence gene expression during embryonic development, potentially contributing to caste differentiation, sex determination, and anti-viral response in various insect species. Honey bees offer an excellent model to investigate these intragenomic conflicts and their contribution to phenotypic variation. In these studies, we generated reciprocal crosses of European honey bees and used genomic tools to investigate matrigene/patrigene and TE/host genome conflicts in behavior and development. Specifically, we tested whether variation in an altruistic, pheromone-mediated behavior in worker bees is influenced by matrigene/patrigene conflict through analysis of PSGE and began to explore its epigenetic basis through analysis of parent-specific histone posttranslational modifications across tissues and developmental stages. Additionally, we investigated matrigene/patrigene and TE/host genome conflicts in early embryonic development to determine whether caste differentiation is associated with PSGE and/or parent-specific piRNA expression and TE regulation.