DNA methylation and chromatin organization in insects: insights from the Ant Camponotus floridanus

Epigenetic information regulates gene function and has important effects on development in eukaryotic organisms. DNA methylation, one such form of epigenetic information, has been implicated in the regulation of gene function in diverse metazoan taxa. In insects, DNA methylation has been shown to play a role in the regulation of gene expression and splicing. However, the functional basis for this role remains relatively poorly understood, and other epigenetic systems likely interact with DNA methylation to affect gene expression. We investigated associations between DNA methylation and histone modifications in the genome of the ant Camponotus floridanus in order to provide insight into how different epigenetic systems interact to affect gene function. We found that many histone modifications are strongly predictive of DNA methylation levels in genes, and that these epigenetic signals are more predictive of gene expression when considered together than when considered independently. We also found that peaks of DNA methylation are associated with the spatial organization of chromatin within active genes. Finally, we compared patterns of differential histone modification enrichment to patterns of differential DNA methylation to reveal that several histone modifications significantly covary with DNA methylation between C. floridanus phenotypes. As the first genomic comparison of DNA methylation to histone modifications within a single insect taxon, our investigation provides new insight into the regulatory significance of DNA methylation.