Summary: The protein Orco is critical for the survival of olfactory neurons in ants. Mutating the orco gene in Harpegnathos saltator ants dramatically reduced the number of their olfactory neurons, disrupting their social interactions.
This study highlights the importance of Orco for neural development and social communication in ants. Understanding these mechanisms can provide insight into sensory-mediated social behavior in both animals and humans.
Key facts:
- The Orco protein is vital for the development and survival of olfactory neurons in ants.
- Mutant ants lacking Orco suffered significant neuronal death and impaired social interactions.
- The study offers new insights into how sensory systems and social behavior are linked in animals.
source: NYU
Although smell plays a significant role in human social interactions—for example, signaling fear or generating proximity—for ants, it is vital.
Researchers at New York University and the University of Florida have found that a key protein called Orco, essential for the function of olfactory cells, is also critical for cell survival in ants.
Their study showed that mutating the orc gene c Harpegnathos saltator jumping ants dramatically reduced the number of olfactory neurons, suggesting that Orco is required for the development and life of these cells.
The findings, published in Scientific progressoffer insights into the cellular and molecular basis of how animals socialize.
“Understanding how the nervous system develops is among the most pressing challenges in modern neuroscience,” said Bogdan Sieribriennikov, a postdoctoral fellow in NYU’s Department of Biology and first author of the study.
Sense of smell and mutant ants
Ants have evolved approximately 400 odor receptors—a number closer to humans than most other insects—thanks to their use of pheromone communication.
“Ants, like humans, are highly social and exhibit cooperative social behavior, and thus provide an ideal system for studying sensory-mediated social behavior,” explained Hua Yan, assistant professor of biology at the University of Florida and lead author of the study.
“Extended odorant receptor genes allow ants to ‘talk’ to each other in a large society of hundreds, thousands or up to a million individuals.”
Even for people who rely on other senses for communication, smell is essential.
“Loss of odorant receptor neuron function leads to deficits in olfactory perception and is often associated with social isolation, neurological disorders such as schizophrenia, and social disorders such as autism,” Yang added.
To better understand how ants’ sense of smell affects their social interactions, researchers at New York University previously created the first genetically modified ants by using CRISPR to edit orc gen. These “mutant” ants, lacking the Orco protein, underwent changes in their olfactory organs and had difficulty interacting.
“We found that the antennae – which are the ‘nose’ of the ant – have very few cells. They were almost empty, suggesting that the smell-sensing cells are missing in the mutant ants,” Yang said.
Neuronal survival depends on Orco
In their new study in Scientific progress, the researchers used single-nuclear gene expression profiling of ant antennae and fluorescence microscopy to analyze the development of olfactory cells. Mutant insects lacking Orco were found to lose most of their olfactory neurons before adulthood.
“The cells appear to have been created normally and begin to develop — to grow, change shape, and turn on certain genes that they will need later, such as odorant receptors,” noted Sieribriennikov.
“Once the developing cells turn on the odorant receptors, very soon they begin to die in huge numbers.”
This neuronal death can be due to stress. Because the odorant receptors in the mutant ants cannot form a complex with Orco to travel to the cell membrane, the newly formed receptors clog the organelles, leading to stress and death.
Such neuronal death may also show patterns specific to social insects. “Until now, these unique processes have not been found in solitary insects and may provide important evidence for the evolution of neural development to adapt to the expansion of odorant receptor genes,” said Kylie Sieber, a doctoral student at the University of Florida et al. – first author of the study.
Interestingly, some odorant receptors survived even without Orco. The cells in which they are present also express other types of receptors, suggesting that the activity they facilitate is essential for neuronal development.
“Some neurons need to periodically ‘fire’ to develop properly. Without Orco, the olfactory cells did not ‘fire’ and did not complete their development, leading to their death,” said Sieriebriennikov.
The researchers also discovered that some odorant receptors are present in non-odor cells, such as mechanosensory neurons that detect movement and glia that wrap around neurons and help them function.
This may be due to imperfect gene regulation, which causes random activation of odorant receptors from nearby genomic regions that normally regulate other genes in other cells. Alternatively, the receptors may have a novel function in these cells, such as the odorant receptors found in the glia of C. elegans worms or human sperm.
“Incorporating odor receptor genes into non-smelling cells could be completely useless to the organism, but then again, evolution tends to use such mistakes to give existing genes a new function, so maybe “There is some exciting new role for odorant receptors in non-olfactory cells that we will discover in the future,” noted Sieribriennikov.
“Our findings improve our understanding of the sensory systems of social insects, including the olfactory neural development that provides a framework for social communication,” Yang said.
Financing: Other study authors include Olena Columba, Jakub Mleinek and Shadi Jafari. This research was supported by the National Institutes of Health (R01-DC020203, T32-DC015994), the National Science Foundation Industry-University Cooperative Research Center for Arthropod Management Technologies (#IIP1821914), and the Human Frontiers Science Program (LT000010/2020- L).
About this news about neurological and genetic research
Author: Rachel Harrison
source: NYU
Contact: Rachel Harrison – New York University
Image: Image credited to Neuroscience News
Original research: Free access.
“Orco-dependent survival of odorant receptor neurons in ants” by Bogdan Sieriebriennikov et al. Scientific progress
Summary
Orco-dependent survival of odorant receptor neurons in ants
Olfaction is essential for complex social behavior in insects. To distinguish complex social signals, ants have evolved a large number odorant receptor (Or) genes.
Mutations in the obligate odorant co-receptor gene orc lead to loss of ~80% of antennal lobe glomeruli in the jumping ant Harpegnathos saltator. However, the cellular mechanism remains unclear.
Here, we demonstrate massive apoptosis of odorant receptor neurons (ORNs) in mid- to late-stage pupal development, possibly due to ER stress in the absence of Orco.
Additional mass and single-core transcriptome analysis indicated that although most orc-expressing ORNs die orc mutants, a small fraction of them survive: They express ionotropic receptor (Ir) genes that form IR complexes.
We also found that some Or genes are expressed in mechanosensory neurons and non-neuronal cells, possibly due to leaky regulation by nearby non-Or genes.
Our findings provide a comprehensive overview of ORN development and Or expression in H. saltator.
