16 October 2023

From soldier to gatherer

Researchers have discovered an enzyme in the "blood-brain barrier" of ants that controls whether the insect becomes a soldier or a gatherer.

Scientists have found that ants' complex caste system may be partially controlled by the insects' version of the blood-brain barrier (BBB), a gatekeeper that allows only certain substances into the brain.

In the study, the scientists figured out which genes and proteins are expressed differently in two classes of ants (Camponotus floridanus). They found that the enzyme that breaks down juvenile hormone, known as juvenile hormone esterase, is only present in the cells that make up the ants' GEB.

Their analysis showed that soldier ants were characterized by higher levels of juvenile hormone esterase than gatherers, and therefore less of the hormone reached the soldiers' brains.

When the researchers injected juvenile hormone directly into the soldier ants' brains, bypassing the GEB, the ants abandoned their "mercenary" role and began searching for food. The insects showed a similar shift in social behavior when the researchers reduced the supply of juvenile hormone esterase by manipulating the gene that produces it. Without an enzyme to break it down, juvenile hormone reached the ants' brains and reprogrammed their behavior.

An ant hill is a carefully organized community of insects with a clear division of labor that ensures smooth operations. While the queen lays eggs, worker ants either forage for food or defend the nest as soldiers, and ant hormones, including the so-called juvenile hormone, determine what role each ant plays.

However, researchers knew little about the underlying molecular control mechanisms that regulate these hormones to shape social behavior.

The findings are published in the journal Cell.
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