FIGURE 1.

Honeybee castes are distinguished by methylation except at the time of emergence. (A) Summary of multiple studies show that DNA methylation separates queens and workers during larval development, but this difference disappears by the time they emerge as adults. Number of differentially methylated genes (DMGs) and differentially methylated regions (DMRs) are from the following studies – larvae: (Foret et al., 2012), emergent queens and workers and adult nurses and foragers: (Herb et al., 2012) and adult queens and workers: (Lyko et al., 2010). (B) Reversible differences between nurses and foragers show that DNA methylation is used to temporarily lock in sub-caste phenotypes within the life time of workers as they transition between tasks. Intra-caste changes in DNA methylation between nurses and foragers during adulthood could explain inter-caste differences observed between adult queens and workers. Since queens and workers are the same at emergence, it is possible that DNA methylation is no longer needed to maintain the irreversible morphological difference between queens and workers, and any difference in DNA methylation observed between adult queens and workers are simply a result of intra-caste changes in adults.