How annotations on genes control fly behavior

In fruit flies, the “for” gene determines whether a fly becomes a rover or a sitter. Rover flies travel long distances for food while sitter flies don’t, yet scientists have been puzzled by how the gene itself translates into the two different behaviors. (James Niland/Flickr Creative Commons)

Research on fruit flies shows that some behaviors may be determined by molecules that act like annotators – highlighting genes to turn on and crossing out others to turn off. A recent study in the Proceedings of the National Academy of Sciences showed this is happening in a gene common to a variety of animals, including humans.

In fruit flies, the “for” gene determines whether a fly becomes a rover or a sitter. Rover flies travel long distances for food while sitter flies don’t, yet scientists have been puzzled by how the gene itself translates into the two different behaviors.

They found that different versions of the “for” gene will recruit different amounts of annotators that suppress or encourage the gene’s function.

Scientists often talk about the central dogma – DNA provides the code that is eventually converted into proteins via messengers – but reality proves much more complicated.

Beyond the genetic blueprint, there is an additional blueprint that determines whether a gene is turned off and how much it produces when it’s turned on. That additional blueprint is sketched by annotators that package entire regions of genetic material or latch onto the specific genes themselves.

One such annotator is the critical link between rover and sitter behaviors in fruit flies, researchers showed. When they genetically engineered flies without the ability to produce the annotator, they found no differences between the behaviors of the rover and sitter flies. In fact, both flies were able to visit the same number of sugar droplets in a foraging arena.

With their annotator working, the sitter flies weren’t able to visit much more than half of the sugar sources as their rover companions.    

Surprisingly, both rover and sitter flies were able to live much longer without food when they didn’t have the ability to produce the annotator. Sitter flies were able to live the longest compared to how long they would have lived if they still had it.

Both rover and sitter flies have their own unique “for” gene that makes them rover or sitter flies, but these recent findings show that those unique “for” genes don’t actually determine behavior on their own. Depending on the version of the gene a fly possesses, different amounts of annotators will be recruited to turn the gene off or on.

These annotator effects in the genomes of nearly all organisms are part of a rapidly developing field of research called epigenetics. Scientists are discovering that genetic differences beyond the protein-coding parts of the genome have huge effects especially in predispositions to disease.

Studies show that the environment, including early-childhood exposures, can play transformative roles in which genes are actually turned on later in life.  


Diler Haji is a campus correspondent for The Daily Campus. He can be reached via email at diler.haji@uconn.edu.