DNA Methylation in the Red Harvester Ant

Red Harvester ants (Pogonomyrmex barbatus) are hymenoptera where workers and queens in a colony are much more genetically similar, but show extreme phenotypic differences such as size and the ability to reproduce. Other research groups show other hymenoptera exhibit methylated cytosine (C) residues in CG dinucleotides. Methylated residues act as 'switches,' hindering access to promoters using transcription machinery. Over evolutionary time, methylated C can degrade into a uracil (read in DNA as thymine (T)) , resulting in fewer observed CG pairs than expected (CpG-OE). This allows us to predict which genome regions are methylated with bioinformatics. We hypothesize that P. barbatus have CG sites in their genome that are methylated. To test this, we first selected genes based on their predicted CpG-OE values from preliminary genome data. We chose three apoptosis and three reproductive genes, since these pathways are used by queens and not workers. To find methylated sites, we treated genomic DNA with with sodium bisulfite, converting non-methylated C’s into T’s, and designed primers to putatively methylated regions. We then sequenced the treated DNA and compared it to the reference genome. We have found four genes which show evidence for methylation. Locating areas of methylation in P. barbatus will help us understand the differences of these genes in the development of the different ant castes and will shed light on how a single genome can be 'read' in multiple ways to produce individuals that have very different lifespans, body shapes, and behavior.