An ant’s brain changes when she takes on the role of queen. And one striking molecule underlies that transformation.

Although most ants are born either as workers or as queens, that is the case with the ant species Harpegnathos saltator different. When the queen dies, the workers fight among themselves to see who can take her coveted place. The winning ant then undergoes neural changes so that it does not show worker behavior, but queen behavior. And now researchers in a new study discovers exactly what orchestrates this complex social transition.

Plastic

In short, the ant’s brain changes when she takes on the role of queen. How is that possible? “Animal brains are plastic,” says researcher Roberto Bonasio. “This means that structure and function can change in response to the environment. Incidentally, this process also takes place in the human brain – think of the changes in behavior as you grow up. It is a crucial part for survival. But the molecular mechanisms that regulate it are not yet fully understood.”

ants

In an ant colony, the workers forage for food and chase away intruders, while the queen’s main job is to lay eggs. The big question, however, is what exactly ensures that a Harpegnathos saltatormaid lays down her duties and begins to reproduce. In their study, the researchers wanted to gain a better understanding of how turning certain genes on and off affects brain function and behaviour.

neurons

To study the underlying molecular developments that cause such a transformation, the researchers developed a method to isolate neurons from the ants and keep them alive in dishes in the lab. This allowed the team to examine how the cells respond to different simulated conditions. It leads to a remarkable conclusion. Because the research shows that only one single molecule determines whether an ant exhibits worker behavior or queen behavior.

Krüppel homologue 1

The molecule responsible for this is called Krüppel homolog 1, or Kr-h1. This protein responds to social hormones and then regulates the complex transition from worker to queen. Kr-h1 is thus a kind of light switch. It determines whether an ant acts as a worker or as a queen, depending on whether the light switch is on or off. “The protein regulates several genes and prevents the ants from exhibiting ‘socially inappropriate’ behaviour,” explains researcher Shelley Berger. “That means that Kr-h1 is needed to maintain the boundaries between social castes and keep workers working while transformed ants start acting like queens.”

Unexpected

However, it is quite surprising that only one molecule is responsible for this. “We didn’t expect that the same protein can silence different genes in the brains of different castes,” Bonasio says. It actually calms worker behavior in queens, while at the same time suppresses queen behavior in worker bees. “We previously thought this was caused by several factors, each of which would be present only in one brain or the other.”

To change gear

The findings reveal exactly how the animal brain’s extraordinary ability to switch from one genetic mode and social caste to another works. “The main message is that multiple behavioral patterns are specified simultaneously in the ant genome,” Berger concludes. “Then gene regulation has a major impact on what behavior that organism performs. In other words, anyone can play both roles, depending on which gene switches are on or off.”

This discovery may have far-reaching implications. “It’s tempting to speculate that related proteins may have similar functions in more complex brains, including our own,” Bonasio said. He plans to investigate the role of Kr-h1 in other organisms in future studies. The discovery that a single factor can suppress different sets of genes and behaviors in different brains raises important questions about how to regulate the dual function of this protein and other similar proteins. Hopefully, future research will show that.