Summary: Researchers investigating clonal raider ants have uncovered how each sensory neuron expresses a single odorant receptor gene from hundreds available in the genome. Unlike mechanisms seen in fruit flies or mammals, ants use a distinctive form of transcriptional interference: once one receptor gene is activated, neighboring genes are silenced by readthrough and antisense transcription.
This creates a localized molecular shield that secures a neuron’s single identity. The discovery resolves a long-standing question in insect olfaction and suggests a general genomic strategy for regulating large gene families.
Key Facts
- Single-Receptor Rule: Ant sensory neurons express one odorant receptor each to ensure clear, unambiguous signaling.
- Protective Shield: Transcriptional interference silences nearby receptor genes whenever one is chosen.
- Broad Significance: This mechanism likely applies to other social insects and could be used by genomes to control diverse gene families.
Source: Rockefeller University
Ant societies rely on scent. Pheromones direct foraging, signal danger, and coordinate colony life. This chemical communication depends on a strict rule: one receptor per sensory neuron.
Ant genomes contain hundreds of odorant receptor genes, each tuned to particular chemical cues. If a single neuron expressed multiple receptors, the brain would receive mixed signals and the ant’s sense of smell would be compromised.
A research team working with the clonal raider ant has now revealed how each neuron selects a single odorant receptor from a very large gene repertoire. The results, published in Current Biology, clarify how ants preserve precise olfactory signaling despite having receptor families comparable in size to those of mammals.
“We’re describing a new form of gene regulation,” says Daniel Kronauer, head of the Laboratory of Social Evolution and Behavior at Rockefeller. “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, one neuron
A fundamental principle of olfaction is that each sensory neuron must carry a unique molecular identity. “It’s a kind of dogma in the field of sensory neuroscience,” says Giacomo Glotzer, a graduate student in the Kronauer lab. “Each sensory neuron typically expresses one receptor—and that gives it its identity.”
Different animals achieve this 1:1 mapping by different means. Fruit flies use discrete molecular switches to turn individual genes on or off. Mammals use stochastic chromatin remodeling so that, over time, only one receptor gene remains accessible. Ants, however, present a distinct challenge: many receptor genes exist in tight clusters of similar sequences. In such crowded genomic neighborhoods, activating one gene could easily activate its neighbors, so a more robust strategy is required.
To observe this mechanism, the team dissected antennal tissue from clonal raider ants and applied RNA sequencing to define active genes, along with RNA fluorescence in situ hybridization to map their locations in antennal cells. Combining molecular and computational methods, the researchers produced a detailed picture of a single active receptor surrounded by silent neighbors.
They discovered that when a neuron activates its chosen receptor gene, RNA polymerase does not stop neatly at the gene boundary. Instead, it continues beyond the normal endpoint, producing “readthrough” transcripts that extend into downstream receptor genes. These readthrough RNAs remain in the nucleus, likely because they lack the signals necessary for export and proper processing. Although probably nonfunctional, their production appears to suppress downstream gene activation.
At the same time, the neuron produces antisense RNAs in the opposite direction; transcription running upstream acts as a physical and functional barrier that prevents nearby upstream receptors from being transcribed. Together, readthrough and antisense transcription form a bidirectional shield that protects the chosen receptor’s expression while silencing immediate neighbors.
“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,” explains 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.”
Evidence beyond clonal raider ants
The researchers confirmed the same transcriptional interference mechanism in other social insects, including the Indian jumping ant and the honeybee. This suggests the strategy may be widespread among insects with large odorant receptor repertoires. “This mechanism may be even more broadly distributed than we thought, particularly among insect species with large repertoires of olfactory receptor genes,” Kronauer says. “It’s even possible that fruit flies are the odd ones out.”
Beyond insect olfaction, the study provides a conceptual blueprint for how genomes can regulate tightly clustered gene families. Two-way safeguards—readthrough transcription that silences downstream neighbors and antisense transcription that blocks upstream ones—allow a genome to add new genes without disrupting existing regulation. This may help explain how ants have rapidly diversified their olfactory receptor repertoires over evolutionary time.
“Once you have the system in place like this, you can allow it to become more complex without disrupting anything,” Kronauer notes. “We speculate that this kind of gene regulatory system contributes to allowing the ants to evolve new olfactory receptors so quickly.”
About this olfaction and neuroscience research news
Author: Katherine Fenz
Source: Rockefeller University
Contact: Katherine Fenz – Rockefeller University
Image: The image is credited to Neuroscience News
Original Research: The findings will appear in Current Biology