Worker bees switch jobs via their epigenomes

The life of a worker honeybee is mostly a predictable one: Grow up a nurse, helping to feed the larvae in the hive, and then transition to a forager, heading out from the hive, traveling to find sources of nectar and pollen to bring back.

Scientists have long been interested in the life trajectory of these worker bees because there are many differences, both physical and behavioral, between nurses and foragers. But because single bees transition from one to the other, they obviously have the same DNA. In fact, forager bees can even regress to the role of nurse if the situation calls for it.

So how do bees undergo such incredible transformations so rapidly? The answer appears to be epigenetics — a biological process whose name means, roughly, “above the genome.”

Epigenetics refers to chemical markers attached to genes that help regulate how those genes are expressed. Epigenetic processes can turn a gene on or off, or simply make the gene more or less likely to be expressed.

The researchers discovered the role of epigenetics in the life-course of the worker bee by carrying out a clever experiment. First, they looked to see whether there were epigenetic differences between groups of nurse bees and forager bees. They identified epigenetic differences in over 150 genes.

The researchers then played what some might consider a cruel trick. When the foragers were away, they removed all the nurse bees — an act which they knew would cause some of the foragers to revert to being nurses after they returned. When the researchers analyzed the bees’ epigenetic markers again, they found that around 50 of the genes they had previously identified as being epigenetically different had changed back. This suggests that the changes to the epigenome were largely responsible for the changes that occurred when a bee changed roles.

When the researchers looked more closely at what the modified genes actually do, they discovered something surprising: The genes regulate other genes. This actually makes quite a bit of sense, as modifying gene-regulating genes is an efficient way to have an outsized impact on overall gene expression.

While the study is groundbreaking for bee researchers — it provides a strong explanation for just how the bees make their rapid switch in roles — it is also big news for behavioral scientists of all stripes.

That’s because it is the first clear evidence of a reversible change in behavior that is controlled by epigenetic modifications to the genome.

You can read a summary of the study here.

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