1 missing gene leads to fruitless mati...( DURHAM N.C. Male fruit flies missin...)

DURHAM, N.C. 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 copulati
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