DNA base modifications in honey bee and fruit fly genomes suggest an active demethylation machinery with species- and tissue-specific turnover rates

• Reporting cytosine modifications in uncharacterized tissues, phenotypes and species.
• Quantification of 5mC and 5hmC suggests species-specific roles and turnover.​
• Low levels of 5hmC relative to 5mC and cytosine in honey bees compared to mammals.
• Honey bee abdominal tissues are richer in5hmC than the brain.
• We found a higher 5hmC to 5mC ratio in fruit flies as compared to the honey bee.

Well-known epigenetic DNA modifications in mammals include the addition of a methyl group and a hydroxyl group to cytosine, resulting in 5-methylcytosine (5mC) and 5-hydroxymethylcytosine (5hmC) respectively. In contrast, the abundance and the functional implications of these modifications in invertebrate model organisms such as the honey bee (Apis mellifera) and the fruit fly (Drosophila melanogaster) are not well understood. Here we show that both adult honey bees and fruit flies contain 5mC and also 5hmC. Using a highly sensitive liquid chromatography/tandem mass spectrometry (LC/MS/MS) technique, we quantified 5mC and 5hmC in different tissues of adult honey bee worker castes and in adult fruit flies. A comparison of our data with reports from human and mouse shed light on notable differences in 5mC and 5hmC levels between tissues and species.