Honeybees make for a versatile workforce. They start as nurses, tending the larvae and the queen; after several weeks, however, many become foragers, searching for pollen, nectar, and water. All workers in a beehive are sisters that are genetically very similar, yet they perform one of two types of jobs that require very distinct skills—and they can switch roles if the hive needs more of the other. How is that possible?
Gro V. Amdam of Arizona State University and a team of geneticists suspected that the answer involved DNA methylation, small epigenetic changes—chemical tags on the DNA—that can profoundly affect gene expression while leaving the genetic sequence unchanged.
The researchers compared DNA extracted from the brain cells of nurses and foragers and found differences in the methylation levels in 155 genetic regions, at least some of which presumably account for the differences in behavior between the two types of workers. They then removed all the nurse bees from the hive, leaving the queen and larvae bereft of care. When foragers were confronted with the hive under those conditions, some continued foraging but others reverted to their former nursing roles. Those reverted nurse bees showed DNA methylation changes in more than a third of the same gene regions.
Amdam’s team is currently trying to identify which areas in the bee brain, which has been extensively mapped, are associated with those epigenetic changes. They hope that their research will help clarify complex behavioral issues in humans and perhaps one day lead to ways to reverse the brain-changing effects of psychological trauma. (Nature Neuroscience)