A single molecule can switch certain ants from workers to a queen

PHILADELPHIA, Pa. — All hail — the worker ant? It may sound like a Cinderella story, but a new study finds a species of ant can transform from a worker to a queen thanks to “flipping the switch” of a single molecule. Scientists from the University of Pennsylvania say ants of the Harpegnathos saltator species have the “Jekyll and Hyde” ability to switch from a worker to a queen-like status, which researchers call gamergate.

The new findings reveal that a single protein, called Kr-h1, responds to hormones to orchestrate the “complex” social transition.

Animal brains are plastic; that is, they can change their structure and function in response to the environment,” says study leader Professor Roberto Bonasio from Penn’s Perelman School of Medicine in a media release. “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. We determined that, in ants, Kr-h1 curbs brains’ plasticity by preventing inappropriate gene activation.”

Prof. Bonasio explains that a worker’s job in the colony is to find food and fight off invaders. As for the queen, their main task is to lay eggs. However, researchers find the same genetic instructions trigger these very different social roles and behavior.

Finding the royal switch in the brain

Ant with eggs
Illustration showing ant with eggs. (Credit:
Illustration by Tim Christopher based on photography by Brigitte Baella and Karl Glastad)

The team wanted to understand how turning certain genes “on” or “off” affects brain function and behavior. Bonasio considers Harpegnathos adults as the perfect ant for the study because they switch from workers to gamergates.

Study authors developed a method for isolating neurons from the ants, keeping them alive in lab experiments. That allowed them to explore how the cells responded to changes in their environment, including hormone levels.

From there, the team identified that two hormones, juvenile hormone and ecdysone, which are present at different levels in the bodies of workers and the queen. These hormones produced distinct patterns of gene activation in the brains of both classes of insects. The researchers explain that the biggest surprise is that both hormones appear to influence the cells by activating Kr-h1.

“This protein regulates different genes in workers and gamergates and prevents the ants from performing ‘socially inappropriate’ behaviors,” explains Professor Shelley Berger. “That is to say, Kr-h1 is required to maintain the boundaries between social castes and to ensure that workers continue to work while gamergates continue to act like queens.”

“We had not anticipated that the same protein could silence different genes in the brains of different castes and, as a consequence, suppress worker behavior in gamergates and gamergate behavior in workers,” Bonasio adds. “We thought that these jobs would be assigned to two or more different factors, each of them only present in one or the other brain.”

Anyone can be queen?

The researchers say their findings reveal important roles for socially regulated hormones and gene regulation in the ability of animal brains to switch from one genetic mode and social caste to another.

“The key message is that, at least in ants, multiple behavioral patterns are simultaneously specified in the genome and that gene regulation can have a great impact on which behavior that organism carries out,” Prof. Berger notes. “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.”

The researchers believe the implications may go much further than understanding behavioral plasticity in ants and other insects.

“It is tempting to speculate that related proteins might have comparable functions in more complex brains, including our own. Discovering these proteins might allow us to one day restore plasticity to brains that have lost it, for example aging brains,” Bonasio concludes.

The findings appear in the journal Cell.

South West News Service writer Stephen Beech contributed to this report.