Scientists Identify Gene That Controls Sex Drive In Male Flies

Many of the sex-specific features that distinguish males and females of any species are genetically predetermined. Using the Drosophila fruit fly as a model organism, Dr. Mattox and Dauwalder are interested in elucidating the genetic components of sexually dimorphic morphology, physiology, and even, to some extent, behavior.

Over the years, many of the major steps in the Drosophila sex determination pathway have been identified, including the activation of sex-specific forms of the master gene regulators Doublesex (DSX) and Fruitless (FRU). The male and female forms of DSX and FRU regulate the expression of a host of largely undefined target genes, which, in turn, direct the development of sexually dimorphic traits.

In their most recent report, Mattox and Dauwalder identify takeout as one such target gene, and reveal a previously unidentified role for it in male fly courtship behavior. The research team discovered that takeout gene expression is regulated in a sex-specific manner by DSX and FRU: only in males is takeout expressed in the head (more specifically, in brain-associated clusters of fat cells).

The researchers showed that mutations affecting the male-specific expression of takeout in the head result in decreased male courtship behavior. Adult male fruit flies exhibit a series of well-characterized courtship behaviors, which include the persistent following of the female and the vibration of one wing to generate a mating song. Dr. Mattox and colleagues observed that adult male flies in which takeout is mutated maintained the ability to perform these behaviors, but did so less often – apparently suffering from a decreased motivation to mate.

"The new work shows that in well-fed flies the takeout gene is active almost exclusively in males and motivates them to court females… It is interesting and unexpected that products synthesized from male fat cells influence sexual behavior in the fruitfly," explains Dr. Mattox.

In addition to identifying a gene that directly mediates sexual behavior, this discovery that the male-specific expression of takeout in the adult fly head is required for normal courtship behavior is also prompting some researchers to consider that perhaps takeout plays a broader biological role balancing the appetite for food and sex.