Summary: The protein Orco is essential for the survival of olfactory neurons in ants. Mutation of the orco gene in Harpegnathos saltator ants drastically reduced their number of olfactory neurons, disrupting their social interactions.
This study highlights the importance of Orco in 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 protein Orco is vital for the development and survival of olfactory neurons in ants.
- Mutant ants lacking Orco experienced 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
While smell plays a significant role in human social interactions—for example, signaling fear or establishing proximity—for ants, it is vitally important.
Researchers from New York University and the University of Florida have discovered that a key protein called Orco, essential for the function of olfactory cells, is also essential for cell survival in ants.
Their study showed that the mutation orc gene v Harpegnathos saltator jumping ants dramatically reduced the number of olfactory neurons, suggesting that Orco is essential for the development and life of these cells.
Findings published in Scientific advancesoffers insight into the cellular and molecular basis of how animals socialize.
“Understanding how the nervous system develops is one of the most pressing challenges of modern neuroscience,” said Bogdan Sieriebriennikov, a postdoctoral fellow in NYU’s Department of Biology and first author of the study.
He can smell and mutant ants
Using pheromone communication, ants have evolved approximately 400 olfactory receptors—a number closer to humans than most other insects.
“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’ together in a large society of hundreds, thousands or even a million individuals.”
Even for people who rely on other senses to communicate, smell is essential.
“Loss of olfactory 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,” Yan added.
To better understand how ants’ sense of smell affects their social interactions, NYU scientists previously created the first genetically engineered ants using CRISPR to edit orc gene. These “mutant” ants, which lacked the Orco protein, experienced changes in their olfactory organs and had difficulty interacting.
“We found that the antennae – which are the ant’s ‘noses’ – have very few cells. They were almost empty, indicating that the cells that sense odor were missing in the mutant ants,” Yan said.
Neuronal survival depends on Orco
In their new study in Scientific advances, the researchers used single-nucleus gene expression profiling of ant antennae and fluorescence microscopy to analyze the development of olfactory cells. Mutant insects lacking Orco have been shown to lose most of their olfactory neurons before adulthood.
“Cells appear to be formed normally and begin to develop – grow, change shape and turn on certain genes that they will need later, such as receptors for smell,” Sieriebriennikov noted.
“Once the developing cells turn on the odor receptors, very soon they start to die in large numbers.”
This death of neurons can be caused by stress. Since the odorant receptors in the mutant ants cannot form a complex with Orco to reach 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 of the evolution of neural development to accommodate the expansion of odorant receptor genes,” said Kayli Sieber, a doctoral student at the University of Florida and co. -first author of the study.
Interestingly, some odorant receptors survived without Orco. The cells in which they were present also expressed other types of receptors, suggesting that the activity they facilitate is necessary for neuronal development.
“Some neurons need to ‘fire’ regularly to develop properly.” Without Orca, the olfactory cells did not ‘fire’ and complete their development, leading to their death,” said Sieriebriennikov.
The researchers also found that some odor 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 that causes odorant receptors to be randomly activated by nearby genomic regions that normally regulate other genes in other cells. Alternatively, the receptors in these cells may have a novel function, such as the odorant receptors found in glia C. elegans worms or human sperm.
“Turning on odorant receptor genes in cells that don’t smell 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’s some exciting new role. odor receptors in non-smelling cells that we will discover in the future,” noted Sieriebriennikov.
“Our findings improve our understanding of the sensory systems of social insects, including the olfactory neural development that provides the framework for social communication,” Yan said.
Funding: Other authors of the study include Olena Kolumba, Jakub Mlejnek and Shadi Jafari. This research was supported by the National Institutes of Health (R01-DC020203, T32-DC015994), the National Science Foundation Industry-University Research Center for Arthropod Management Technologies (#IIP1821914), and the Human Frontier Science Program (LT000010/2020-L).
About these new developments in neuroscience and genetics
Author: Rachel Harrison
Source: NYU
Contact: Rachel Harrison – NYU
Picture: Image is credited to Neuroscience News
Original Research: Open access.
“Orco-dependent survival of odorant receptor neurons in ants” by Bogdan Sieriebriennikov et al. Scientific advances
Abstract
Orco-dependent survival of odorant receptor neurons in ants
Olfaction is essential for the complex social behavior of insects. In order to distinguish complex social cues, ants have evolved an extended number odorant receptor (Or) genes.
Mutations in the obligate odorant co-receptor gene orc lead to loss of ~80% of antennal lobe glomeruli in jumping ants Harpegnathos saltator. However, the cellular mechanism remains unclear.
Here, we demonstrate massive apoptosis of odorant receptor neurons (ORNs) at mid- to late stages of pupal development, likely due to ER stress in the absence of Orco.
Further bulk and single-nuclear transcriptome analysis shows that although the majority orc-expressing ORN dies orc mutants, a small fraction of them survive: They express ionotropic receptor (Ir) genes that form IR complexes.
Moreover, we found that some Or genes are expressed in mechanosensory neurons and non-neuronal cells, likely due to leaky regulation from nearbyOr genes.
Our findings provide a comprehensive overview of ORN development and Or expression in H. saltator.