A Single Protein Can Switch Some Ants From a Worker Into a Queen

Changing the expression of a one protein in the brains of Jerdon’s jumping ants is enough to launch the biological transition

Two red Jerdon's jumping ants with large mandibles fighting each other against a tan backdrop
When the queen dies, Jerdon's jumping ants duel to select their next leader. Kalyanvarma via Wikimedia Commons [CC BY-SA 4.0]

Most ants will spend their lives working to support the colony and their queen, born into their roles. But if their queen dies, the other ants have a rare opportunity to claim her position. Now, scientists discovered a slight tweak to a single protein could determine whether some ants become workers or ascend to royalty, according to a new study published last week in Cell.

Like many ant species, a colony of Jerdon's jumping ant (Harpegnathos saltator) is comprised of dutiful workers who gather food and fight invaders, and a single reigning queen gives birth to more workers. But Jerdon's jumping ants take a different approach to selecting their leader compared to most ants. When the queen dies, the worker ants of this species duel over who gets to take her place. The contending ants turn into “gamergates,” ants with queen-like qualities to prep for their new potential role, including shrinking venom sacs and expanding ovaries. The eager ants abandon their usually foraging work and begin reproducing and laying eggs like a queen ant. But what triggers this transformation has been largely a mystery until now.

Earlier studies have shown the ant’s transition to a gamergate comes with increasing changes in the brain, including different gene expressions, hormone levels, and a 5-fold lifespan. The researchers behind the recent study were curious how the insects’ brains changed in response to their environment, like the death of their colony's queen.

"Animal brains are plastic; that is, they can change their structure and function in response to the environment," explains study author Roberto Bonasio, a molecular biologist at the University of Pennsylvania. "This process, which also takes place in human brains – think about the changes in behavior during adolescence – is crucial to survival, but the molecular mechanisms that control it are not fully understood."

To test what role brain changes might be playing, Bonasio and his colleagues conducted a series of experiments on the jumping ants, in which scientists exported the ant's neurons to different levels of hormones, according to Carly Cassella for Science Alert. The team focused their attention on two specific hormones believed to regulate social behavior in ants and other social insects like bees. The team found switching the expression of just a single protein, Kr-h1, in the brains of ants is enough to elevate an ant from worker to queen.

Kr-h1’s responds to two hormones: one found more in workers, and one found in greater abundance in queens. When they gave a ten-day old ant more of the hormone found in workers, Kr-h1 shut down genes related to queenliness. Give an ant the hormone found in the queen, and Kr-h1 will instead promote queen-like characteristics and behaviors. The researchers also found that if they deleted the Kr-h1 protein from ant neurons, worker ants started to behave more like gamergates, and gamergates acted more like workers. They concluded that the protein acts as a sort of light switch, with hormone flicking specific signals on or off to generate a worker brain or the gamergate brain state, reports Hannah Seo for Popular Science.

"In other words, the parts of both Dr. Jekyll and Mr. Hyde are already written into the genome; everyone can play either role, depending on which gene switches are turned on or off," says epigeneticist Shelley Berger from the University of Pennsylvania who co-authored the study.

Though the results of the recent study suggest there is a single protein controlling Jerdon's jumping ants behavior in a colony, researchers say more research to definitively prove that’s the case. Next, they want to investigate whether the protein Kr-h1 exists in other social organisms beyond Jerdon's jumping ants.

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