In a new study, researchers have discovered that locusts may have taken a creative approach to perceiving odors and pheromones. They largely avoid the classical G protein-coupled receptor (GPCR) pathway. This major discovery sheds light on the ultimate mechanisms contributing to the way honey bees – and in return, many other insects – encode odorous stimuli. It allows new discoveries into their behavioral reactions to distinct scents.
Prof. Kang Le, principal investigator, conducts the research at the Institute of Zoology, Chinese Academy of Sciences (CAS). They reported their findings in the journal Science Advances on September 10. Insect ORs had been a subject of controversy for years, with contentious arguments over whether they achieved olfactory reception through GPCR-like methods or used entirely different pathways. According to the researchers, this study provides insight into the inner workings of locusts. It indicates that they employ inositol 1,4,5-trisphosphate (IP3) as a central second messenger in their olfaction.
The Role of OBP10 and OBP13
To understand how these changes occur, the researchers honed in on two major odorant-binding proteins, OBP10 and OBP13. These proteins are absolutely essential for recognizing pheromones. These proteins specifically bind the pheromone 4-vinylanisole (4VA). They subsequently carry it over to the target olfactory receptor OR35, as well as its common co-receptor Orco. This mechanism is a major shift from canonical pathways and suggests a unique pathway evolved for a specialist like the locust.
Through their initial work, the researchers selected 4VA as a good model compound. This decision ultimately set them on a path to discover the complex underpinnings of locust olfactory signaling. They studied the binding mechanisms of the interactions between OBP10, OBP13, and OR35. To do so, they mapped a complex pathway in fruit flies that links odor detection to behavioral responses. This finding might have wider implications for understanding how insects communicate and adapt to their surroundings.
A Universal Second Messenger
The data further implicate IP3 as a ponto-genicular pathway generalized second messenger of olfactory signal transduction in locusts. Most remarkably, this mechanism is used to process not just pheromones, but to process plant volatiles and alarm signals. Such extensive versatility provides an exciting glimpse into the evolutionary importance of this signaling pathway in allowing locusts to efficiently modulate their environment.
By going around the GPCR pathway, locusts have possibly evolved a leaner mechanism to make sense of a cocktail of confusing chemical cues. Prof. Kang Le and his colleagues think this adaptation can increase insects’ chances of survival to new heights. Most importantly, it boosts their likelihood of outpacing predators and having more fruitful encounters with mates.
Implications for Future Research
The study’s findings should motivate further research comparing the olfactory systems of other insects. This has the potential to identify critical insights that could drive the development of sophisticated and effective pest control strategies. Researching how locusts and other insects detect smell has the potential to transform agricultural practices. It can help them better coordinate efforts to combat locust swarms that decimate farmland.