Gene Duplication in the Evolution of Sex and Caste Biased Gene Expression

Social insects are among the most dominant organisms on earth. The success of social insects arises from the caste system, whereby different individuals, which often exhibit drastically different morphologies, physiologies, and behaviors, are each responsible for certain tasks within the colony. The development of insect castes has been linked to differential gene expression and epigenetic variation.  However, little is known about the role of new genes, generated by gene duplication, in the evolution of different castes. Gene duplication is important for evolution because it can provide novel genetic material. We hypothesize that genetic redundancy provided by gene duplication could be used to facilitate differential gene expression which promotes the evolution of different phenotypes. We approached this hypothesis by investigating the genome of the honey bee, Apis mellifera, using biased gene expression as a proxy for phenotype specific gene function. Duplicate genes have a higher level of sex biased expression compared to singletons. However, this was not true for caste biased gene expression. We found that gene expression patterns amongst duplicate pairs diverge over time. By studying the interaction between gene duplication and gene expression, we can further our understanding of the genomic factors involved in evolution of social insect castes.