We all know that Drosophila are the gayest bunch of gays that ever gayed up genetics. This is especially true when you create mutations in fruitless (nee fruity), “the gay gene”. Male flies with mutations in fruitless will try to get it on with other males (e.g., doi:10.1016/S0092-8674(00)81802-4). That’s gay!
But fruitless is an old school gene that needs to be fucked up to turn the flies gay (doi:10.1093/molbev/msj070; the first author on that paper is, I shit you not, named Gailey). Drosophila really aren’t as gay as they are made to appear in the articles describing fruitless mutants. But the males are still kind of in to dudes, as is shown by a new paper from Manyuan Long’s group (doi:10.1073/pnas.0800693105).
Long’s group previously described an RNA gene that is unique to D. melanogaster, and not found in any of its sibling species (doi:10.1073/pnas.072066399). The gene, named sphinx, arose when the transcript of its parent gene was reverse transcribed and inserted back into the genome (in a process known as retroposition). It has also evolved quite rapidly, suggesting it was acted on by natural selection. Additionally, there are male-specific and a female-specific transcripts of sphinx.
So, there is probably some evolution story to unravel about the sphinx gene. In the new paper by Dai et al., Long and colleagues have performed a functional analysis of sphinx, and what they found was quite interesting. Via an analysis of flies carrying mutant forms of sphinx, they were able to show that the gene plays a role in preventing males from courting other males. Males carrying two mutant copies of sphinx spend more time courting other males than flies with a good copy of sphinx.
Here’s where you ask: but sphinx is a new gene — what about the close relatives who don’t have any copies of sphinx? Well, they’re gayer than D. melanogaster. When wild type flies are compared, males from the other species all spend more time courting other males than do D. melanogaster males, suggesting that the sphinx gene keeps D. melanogaster males from being as gay as their close relatives.
This would be a great opportunity to test genetic engineering for the “correction” of teh gay. You see, if you were to insert sphinx into the other species, they should be less gay. Unfortunately, Dai et al. don’t do that experiment, so we’re left to wonder with gayness can be cured by transgenics.
Dai et al. 2008. The evolution of courtship behaviors through the origination of a new gene in Drosophila. PNAS 105: 7478-7483 doi:10.1073/pnas.0800693105
Gailey et al. 2006. Functional Conservation of the fruitless Male Sex-Determination Gene Across 250 Myr of Insect Evolution. MBE 23: 633-643 doi:10.1093/molbev/msj070
Ryner et al. 1996. Control of Male Sexual Behavior and Sexual Orientation in Drosophila by the fruitless Gene. Cell 87: 1079-1089 doi:10.1016/S0092-8674(00)81802-4
Wang et al. 2002. Origin of sphinx, a young chimeric RNA gene in Drosophila melanogaster. PNAS 99: 4448-4453 doi:10.1073/pnas.072066399