One missing gene leads to fruitless mating rituals

July 23, 2008

Male fruit flies missing a gene for one particular odor receptor become clueless in matters of love, scientists at Duke University Medical Center have discovered.

Because they lack the ability to read important chemical cues, these flies will indiscriminately attempt to have sex with other males, and with females who have already mated. The signals they're missing are pheromones wafting from mated females and male flies. The work appears online in Nature Neuroscience.

The researchers found that the signals from this pheromone receptor are so important to the flies that they are wired directly into the higher-order processing center of the fly's brain, which governs behavior. This direct connection surprised the scientists, who have studied other fruit fly courtship genes.

"It goes against the dogma that was established for the olfactory and taste systems," said Hubert Amrein, Ph.D., of the Duke Department of Molecular Genetics and Microbiology. "Our finding implies that signals from the outside don't have to go through processing stations in the chemosensory system before being connected to the higher-order brain structures."

Males without a gene called Gr32a, the gustatory receptor gene, showed normal levels of courtship with virgin females. But in competition with normal (or wild-type) male fruit flies, they were outperformed by 4 to 1. In fact, the Gr32a-lacking flies courted the male competitors in addition to the females.

To further investigate the role of the gene, researchers used decapitated, passive flies of both genders, because these do not provide any behavioral feedback that could confound the precise measurement of the sex appeal they held for the male flies being studied. Both types of males courted the decapitated virgin females equally. However, courtship attempts toward decapitated males increased only in the males lacking the Gr32a gene, and these flies attempted copulation, behavior not seen in the wild-type males.

The scientists also found that the males lacking the Gr32a gene courted females who had already mated. Wild-type males, however, were significantly less attracted by mated females, because mated females have received male pheromones during the first mating.

The hapless Gr32a-negative males tried to mate with virgin females even when they had been covered with male pheromones, behavior that the wild-type flies avoided.

"This gene was very powerful for distinguishing between genders and for determining mating status," said co-author Tetsuya Miyamoto, Ph.D., also of the Department of Molecular Genetics and Microbiology. "Male pheromone is so effective that Gr32a mutants court males with almost the same intensity as they do females."

The GR32a gene is not found in humans. "In general, the development of pheromones in human sexual behavior is not as clear-cut as one would hope," Amrein said. "We know that males and females have preferences for certain olfactory cues. The mouse has an olfactory organ, and humans have a remnant of this in the nose, but it doesn't function in people. So I think it is very difficult to make any direct connections between these gene findings in fruit flies and what happens in people."

Source: Duke University

Explore further: How flowers use scent and nectar to manipulate pollinators and herbivores

Related Stories

Why we still collect butterflies

June 11, 2015

Who doesn't love butterflies? While most people won't think twice about destroying a wasp nest on the side of the house, spraying a swarm of ants in the driveway, or zapping pesky flies at an outdoor barbecue, few would intentionally ...

Recommended for you

Magnetism at nanoscale

August 3, 2015

As the demand grows for ever smaller, smarter electronics, so does the demand for understanding materials' behavior at ever smaller scales. Physicists at the U.S. Department of Energy's Ames Laboratory are building a unique ...

How the finch changes its tune

August 3, 2015

Like top musicians, songbirds train from a young age to weed out errors and trim variability from their songs, ultimately becoming consistent and reliable performers. But as with human musicians, even the best are not machines. ...

Study calculates the speed of ice formation

August 3, 2015

Researchers at Princeton University have for the first time directly calculated the rate at which water crystallizes into ice in a realistic computer model of water molecules. The simulations, which were carried out on supercomputers, ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.