Protein switch lets ants achieve ‘queen-like status,’ study finds

Ants can switch from a worker bee to a ‘queen-like status’ thanks to a small adjustment in a single protein in their brains, a new study reveals.

Biologists in Philadelphia isolated nerve cells from the brain of the Indian jumping ant (Harpegnathos saltator), which gets its name from their ability to jump a few inches.

The experts found that the protein, called Kr-h1, orchestrates the transition of ants from a standard worker, tasked with finding food, and a queen-like “gamergate.”

Gamergates are described as ‘queen-like’, even though they are not queens. They are actually workers that can reproduce in the absence of a queen in a colony.

Harpegnathos saltator (also called the Indian jumping ant) ​​is found in India. Here a worker is depicted in an aggressive display (jaws open) aimed at the photographer. Gamergates can reproduce, while workers cannot

WHAT ARE GAME GATES?

A gamergate is a worker ant that can reproduce sexually. Gamergates are described as ‘queen-like’, even though they are not queens.

In the Indian jumping ant, workers have the potential to become reproductive gamergates, but this transition is inhibited by the presence of the queen.

When the queen dies, a period of intense fighting ensues, after which a few individuals are given reproductive rights.

These individuals, called gamergates, show dramatic changes in social behavior within the colony.

However, these changes can be undone and a newly formed gamergate can be turned back into a worker.

The study was conducted by biologists from the University of Pennsylvania’s Perelman School of Medicine and published in the journal Cell.

‘Animal brains are made of plastic; that is, they can change their structure and function in response to the environment,” said study co-author Professor Roberto Bonasio.

‘This process, which also takes place in the human brain – think of behavioral changes during adolescence – is crucial for survival, but the molecular mechanisms controlling it are not fully understood.’

In an ant colony, worker bees maintain the colony by finding food and fighting invaders, while the queen’s main job is to lay eggs.

In H. saltator workers have the potential to become reproductive gamergates, but this transition is inhibited by the presence of the queen.

When the queen dies, a period of intense combat ensues, after which a few individuals earn reproductive rights and become gamergates.

These gamergates show dramatic changes in social behavior within the colony.

However, these changes can be undone and a newly formed gamergate can be turned back into a worker.

“Queens are born queens,” Professor Bonasio told MailOnline. ‘If they close’ [emerge as an adult from the pupa or as a larva from the egg] they have wings.

Harpegnathos saltator is pictured here with its prey in Wynaad, India.  Any female adult worker of Harpegnathos can be turned into a 'queen-like' gamergate in the absence of the queen

Harpegnathos saltator is pictured here with its prey in Wynaad, India. Any female adult worker of Harpegnathos can be turned into a ‘queen-like’ gamergate in the absence of the queen

“Gamergates are born workers (no wings) and become queens after a change in their social circumstances.”

ANTS USE THEIR MEMORY TO AVOID THE SECOND FALLS

Ants can learn to avoid danger after just one risky experience, according to a 2020 study.

The insects can link visual cues to negative experiences and remember potentially dangerous routes, the team of authors from the University of Toulouse found.

Two species of ants were tested in experiments: Melophorus bagoti from Australia and Cataglyphis fortis from the Sahara.

During a second attempt to reach their nest, the insects were found to change their behavior to avoid falling into a pit.

As they approached the trap, some of the ants stopped to scan their surroundings before detouring around the pit and safely reaching the nest.

Read more: Ants use their memory to avoid pitfalls of the past

It’s already known that Harpegnathos adults can switch from a worker to a gamergate, but how they do this has been more of a mystery.

To find out more, the team developed a method to isolate neurons — nerve cells — from the ants and store them in plastic dishes in the lab.

By isolating neurons in this way, the team was able to study how they responded to two hormones, juvenile hormone (JH3) and ecdysone (20E).

Both hormones are present at different levels in the bodies of both workers and gamergates.

The researchers found that JH3 and 20E produced different patterns of gene activation in the brains of workers and gamergates.

More JH3 and less 20E make ants act like workers, while less JH3 and more 20E make ants act like gamergates.

But the biggest surprise was that both hormones affected nerve cells by activating Kr-h1.

The protein suppresses employee behavior in gamergates and gamergate behavior in employees.

In this way, the Kr-h1 protein is a bit like a light switch, and the hormones are the forces that turn it on or off.

“This protein regulates several genes in workers and gamergates and prevents the ants from exhibiting ‘socially inappropriate’ behavior,” said study author Shelley Berger, also at the University of Pennsylvania.

“That is, Kr-h1 is needed to maintain boundaries between social castes and keep workers working while gamergates continue to act like queens.”

If Kr-h1 were removed from ant neurons, gamergates would behave like workers and worker ants would behave like gamergates.

“We did not expect that the same protein could silence different genes in the brains of different castes and, as a result, suppress employee behavior in gamergates and gamergate behavior in employees,” said Professor Bonasio.

Graphic summary of the paper illustrates the process.  On the left is a worker ant (which finds food and fights invaders);  to the right is a 'queen-like' gamergate (propagating).  More JH3 and less 20E make ants act like workers, while less JH3 and more 20E make ants act like gamergates

Graphic summary of the paper illustrates the process. On the left is a worker ant (which finds food and fights invaders); to the right is a ‘queen-like’ gamergate (propagating). More JH3 and less 20E make ants act like workers, while less JH3 and more 20E make ants act like gamergates

“We thought that these jobs would be assigned to two or more different factors, each of which is only present in one brain or the other.

‘The core message is that, at least in ants, several behavioral patterns are specified simultaneously in the genome and that gene regulation can have a major influence on what behavior that organism performs.

‘In other words, the parts of both Dr Jekyll and Mr Hyde are already written into the genome; everyone can play both roles, depending on which gene switches are on or off.’

Professor Bonasio thinks other similar proteins may have similar functions in more complex brains, such as human brains.

“By discovering these proteins, we may one day restore the plasticity of brains that have lost it, for example, aging brains,” he said.

In future studies, the researchers plan to investigate the role of Kr-h1 in other organisms, as well as how the environment affects gene regulation and, in turn, brain plasticity and behavior.

GENETICALLY-TWEAKED INDIAN JUMPING ANTS BECOME ‘SPACE CADETS’

In 2017, scientists genetically engineered ants to lack their sense of smell.

This affected the insects’ ability to communicate, forage or compete to be queens, as their antennae and brain circuitry did not fully develop.

Ants communicate through pheromones (secreted chemicals that trigger reactions).

Such scents are used to sound the alarm when a predator approaches, leave a trail for food, indicate social status and indicate willingness to mate.

Ants can receive such signals because they have proteins called odor receptors on their antennae, with each protein being the correct shape to bind to a specific odorant.

However, to process any odor or pheromone in an ant’s brain, both the correct odor receptor protein and a shared, common partner protein called Orco must be present.

The team successfully engineered the genetic loss of Orco protein, resulting in ants that could no longer perform some, if not all, pheromone-based social interactions.

In particular, unlike their nestmates without the changes, the altered young ants spent much of their time wandering out of the nest. They failed to interact with other members of the colony (a behavior called “space cadet”), and were unable to forage and return food to the nest.

Also, mutated females no longer nursed males, a pre-mating behavior. The current study focused on the Indian jumping ant, Harpegnathos saltator, which is unlike many ant species where only the queen can mate and pass genes on to the next generation.

Any female adult worker of Harpegnathos can be turned into a ‘queen-like’ gamergate in the absence of the queen. This is because the queen secretes a pheromone that suppresses workers’ ability to mate and lay eggs.

If the queen is removed, after winning a series of aerial duels, the most aggressive females undergo this transition and can continue to produce offspring, which is essential for colony survival.

The 2017 study found that the females without Orco cannot process pheromones, making them much less likely to duel.

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