Inspecting the chemical compounds concerned in insect mating

Examining the chemicals involved in insect mating

This imaginary perfume bottle illustrates the role pheromones play in Drosophila courtship decisions by showing the silhouettes of a male chasing a courted female. The naming of this fictional eau de pheromone “dew lover” was inspired by the etymological origin of the genus Drosophila, which is based on the modern scientific Latin adaptation of the Greek words drósos (“dew”) and phílos (“loving”). Vernier et al. show that the coupling of cognition and production of some mating pheromones is regulated by the action of a pleiotropic pheromone receptor. Photo Credit: Digital Art by Yehuda Ben-Shahar, Washington University in St. Louis

It’s almost Valentine’s Day and love is in the air. Or in the waxy layer on your skin if you’re a vinegar fly. There, flies encounter pheromones, which play an important role in regulating sexual attraction.

Flies use pheromones to ensure they are courting and mating with fellow flies. As new fly species split from a common ancestor but continue to share the same environment, they need a way to quickly diversify their pheromones to suppress interspecies mating. When members of two related species no longer find each other attractive, this helps prevent interbreeding.

But it’s more complicated than “she loves me, she loves me not.”

Since the perception and production of pheromones is mediated by different tissues and cell pathways, the development of new mating pheromones requires coordinated evolution of both the genes responsible for the perception of the pheromones and the genes that produce them.

A new iScience study led by Yehuda Ben-Shahar of Washington University in St. Louis identifies a link between the genetic instructions for sex pheromone production and perception. The research was conducted in collaboration with Jocelyn Millar of the University of California, Riverside.

Researchers reported that a single protein called Gr8a is expressed in different organs in male and female flies and appears to play an inhibitory role in mating decisions. The results point to one of the ways flies might erect behavioral barriers to protect themselves from mating with the wrong partner.

“Mating pheromones often show rapid evolution,” said Ben-Shahar, professor of biology in Arts & Sciences. “Because pheromone communication requires a very robust and specific structural recognition of chemicals used as pheromones by the proteins that bind them in sensory neurons (chemoreceptors), this means that major molecular changes in either the receptor or the pheromone can cause the.” sexual attraction between males and males would decrease females.”

Ben-Shahar and his team found that Gr8a is expressed in tissues in fly mouthparts, including the proboscis, and in taste neurons in the forelimbs of both males and females. They also found Gr8a in cells in the abdomen of men. This was important because it gave Ben-Shahar and his team the first hint that a gene previously identified as a sensory chemoreceptor must also have non-neuronal functions.

“Our results provide a relatively simple molecular explanation for how signal production and perception are linked in vinegar flies,” said Ben-Shahar. “A single pleiotropic protein may both act as a receptor for pheromones in sensory neurons and, via a less understood process, contribute to their production in the pheromone-producing cells (oenocytes) of men.”

In one of the experiments Ben-Shahar and his team conducted, the scientists took flies mutated for the Gr8a receptor and reconstituted them with input from another species of vinegar fly. This experiment demonstrated that the introduction of Gr8a from a different species was sufficient to alter the animal’s overall pheromone profile.

The scientists haven’t figured out exactly how the chemoreceptor affects the way the signal is generated, but they do know that it causes quantitative and qualitative differences in the pheromones. And even small changes in pheromones could be enough to discourage closely related flies from finding each other attractive — and alter their mate-selection behaviors.

The question of how closely related species develop and maintain mating barriers is a question that has implications for different areas of basic and applied biological research.

“Based on our observations, mutations in a single gene could provide a molecular pathway for the evolution of a pheromone communication system while preserving functional coupling between a pheromone and its receptor,” said Ben-Shahar. “Our research uncovers a potential way for pheromone systems to evolve rapidly as new species emerge.”

More information:
Cassondra L. Vernier et al., A pleiotropic chemoreceptor facilitates mating pheromone production and cognition, iScience (2022). DOI: 10.1016/j.isci.2022.105882

Provided by Washington University in St. Louis

Citation: Investigating the Chemicals Involved in Insect Mating (2023 January 31) Retrieved January 31, 2023 from

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