Ants use a genetic trick to sharpen their sense of smell

Ants live in a world built on scent. Pheromones direct them to food, alert them to danger, and keep colony life in rhythm. This communication depends on a precise rule: one receptor, one neuron.

Each ant’s genome carries hundreds of odorant receptor genes, each tuned to a different chemical. If neurons expressed more than one receptor, the brain would receive scrambled signals, destroying the insect’s sharp sense of smell.

Solving the ant mystery

Researchers studying the clonal raider ant have uncovered how each neuron selects just one receptor from hundreds. Their findings, published in the journal Current Biology, solve a long-standing mystery of ant communication.

“We’re describing a new form of gene regulation,” said Daniel Kronauer, head of the Laboratory of Social Evolution and Behavior at The Rockefeller University.

“Our results demonstrate the importance of studying less conventional model species. We were able to discover new, fundamental molecular phenomena in clonal raider ants that we could not have seen in fruit flies.”

One receptor identity

The researchers noted that a central rule of smell is that every neuron must carry its own molecular signature.

“It’s a kind of dogma in the field of sensory neuroscience,” said Giacomo Glotzer, a graduate student in the Kronauer lab. “Each sensory neuron typically expresses one receptor – and that gives it its identity.”

Fruit flies manage this puzzle with molecular switches that turn single genes on or off. Mammals use a looser method, randomly reshuffling chromatin until only one receptor gene remains available. Until now, it was unclear which path ants followed.

Ant smell is complex

Ants require a far more complex way to manage their sense of smell. Unlike fruit flies, which rely on just 60 odorant receptors, ants have several hundred. These receptors are often grouped together in tight clusters of nearly identical genes.

Such an arrangement increases the risk of multiple receptors turning on accidentally, which could cause confusion in how ants process scent signals.

Because of this crowded genetic layout, ants cannot depend on the simpler strategies that work for fruit flies. Instead, they must employ a more sophisticated system to keep each neuron linked to only one specific receptor.

A deeper investigation

Building on earlier work, the team dissected ant antennae and mapped gene activity using RNA sequencing and localization tools. They discovered that when an ant neuron activates its chosen receptor, RNA polymerase does not stop at the gene’s boundary.

Instead, it reads through into downstream genes, producing transcripts that remain locked in the nucleus. These nonfunctional transcripts appear to silence neighboring genes.

At the same time, the neuron generates antisense RNAs upstream, acting as roadblocks to prevent unwanted activation. Together, these mechanisms create a protective shield around the chosen receptor.

How ants protect smell

“When we took the mechanism apart and dissected it into its constituent parts, we found that this strategy serves to silence the local genomic environment, giving that cell its singular receptor identity,” said Parviz Daniel Hejazi Pastor, a biomedical fellow in the Kronauer lab.

“Our findings center around transcriptional interference – that the neuron chooses one receptor by preventing the true transcription of other receptors both upstream and downstream.”

Shared across species

The researchers confirmed the same mechanism in the Indian jumping ant and the honeybee. This suggests transcriptional interference may be widespread among insects with large families of olfactory receptors.

“This mechanism may be even more broadly distributed than we thought, particularly among insect species with large repertoires of olfactory receptor genes” noted Kronauer. “It’s even possible that fruit flies are the odd ones out.”

Ants smell and evolution

The discovery reveals more than insect smell. By showing how genes can silence both upstream and downstream neighbors, the work outlines how genomes may control large families of similar genes.

It also offers clues to how ants rapidly expand their sensory toolkit. New receptor genes could be added without requiring fresh regulatory machinery, allowing ants to adapt more quickly to new environments. This adaptability may explain their evolutionary success, helping them survive in diverse habitats.

The findings also suggest similar genetic strategies could shape other organisms, offering a broader understanding of how complexity evolves in living systems over time.

“Once you have the system in place like this, you can allow it to become more complex without disrupting anything,” said Kronauer. “We speculate that this kind of gene regulatory system contributes to allowing the ants to evolve new olfactory receptors so quickly.”

The study is published in the journal Current Biology.

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