Female Flies Act Male After Gene Is Altered

A single genetic change can make female fruit flies act like amorous males -- lusting after other females and wooing them with the species’ elaborate courtship display, according to a report in the current issue of the journal Cell.

Geneticist Barry Dickson and graduate student Ebru Demir made a small change to a gene dubbed fruitless, which got its name because males with a damaged version ignore females and sometimes try to mate with other males.

Although the fruitless gene is present in female and male Drosophila melanogaster flies, it is translated into a slightly different protein in males.

Dickson and Demir, of the Institute of Molecular Biotechnology of the Austrian Academy of Sciences in Vienna, altered the gene so it would always make the male protein, then engineered that gene into female flies.

The engineered females rebuffed males that tried to mate with them. They began to imitate the multi-step male courting dance. Before mating, a male orients his body diagonally to the female, taps her forelegs and chest, sings a high-pitched mating song by rapidly vibrating one wing, licks her genitalia and finally copulates.

The altered females tapped, then sang, but faltered in later steps of courtship.

“It is possible that their song is not perfect,” Dickson said.

Or, he said, they may not have the right pheromones to interest females.

The scientists hypothesize that the fruitless gene acts as a “master switch” that sets in motion a complicated cascade of genetic changes to program flies’ sexual behavior.

They now plan to investigate whether fruitless affects aggressive behavior in flies, which also differs between genders. In Drosophila, females butt heads, whereas fighting male flies get up on their hind legs and box.