How epigenetics can affect ants’ behavior
By applying compounds that cause epigenetic changes to ants, researchers were able to change the insects' behavior. Epigenetics is a process whereby environmental factors can affect DNA and the mechanism by which DNA is transcribed and translated into proteins, and now, results by Daniel Simola et al. demonstrate how epigenetic changes can have lasting effects on behavior. Colonies of ants have a structured workforce where individuals have specialized responsibilities, though how this caste-based system is regulated at the molecular level has not been fully understood. Epigenetic regulation, including modification of proteins called histones that package DNA, has been proposed as a possible mechanism. This study looks at two social groups of Camponotus floridanus, or Florida carpenter ants. Minor ants are smaller and tend to forage for food, while major ants, which are larger, act as brawny soldiers. Genetically, these two types of ants are very similar, but epigenetic processes cause the ants to differentiate. In particular, chemical modifications to histone H3 (H3K27ac) are known to increase the foraging behavior of Camponotus floridanus. To test the effects of H3K27ac, Simola and colleagues fed minor ants a compound that increases acetylation of H3K27ac, noting a subsequent increase in foraging behavior. The team then tested the power of epigenetic changes in major ants using a more potent compound, trichostatin A (TSA), to increase acetylation of H3K27ac. They injected TSA directly into the brains of developing majors at a very young age, just before the establishment of molecular barriers in the brain that restrict behavioral plasticity. They noticed a significant increase in foraging behavior in these major ants. Remarkably, 30 to 50 days after the single-injection treatments, TSA-injected majors still displayed significantly increased foraging activity, suggesting that these epigenetic changes can have lasting effects. Interestingly, these pharmacological treatments were effective only for very young majors, implying that the epigenetic landscape regulating worker behavior is plastic in young ant brains but quickly assumes a more rigid conformation with age. The findings of this study may be generalizable to other eusocial insects, like honeybees.