How the fly flies
1 Dec 2011 by Evoluted New Media
The key to keeping a fly flying – and its distinctive buzzing sound – is a gene called Spalt, which German researchers say is essential for superfast muscles and could have important medical implications for humans. Flies have tiny wings compared to their bodies, and in order to fly efficiently have to flap their wings very fast. A Drosophila melanogaster moves her wings at a frequency of 200 Hz – meaning her flight muscles contract and relax 200 times per second.
“In contrast, a hundred meters sprinter who moves his legs only a few times per second moves like a snail,” said Frank Schnorrer, who led the research at the Max Planck Institute of Biochemistry.
Muscles used in flight are unique – their contractions are regulated by nerve impulses as usual, but are also triggered by tension. Each fly has two types of flight muscle which enable wing oscillations – one to move the wings down, while at the same time stretching the other type to induce a contraction to pull the wings up again.
By targeted gene silencing, Schnorrer’s research group – Muscle Dynamics – were able to identify the switch essential for the formation of flight muscles: the transcription factor Spalt. It exists only in flight muscles and is responsible for the specific architecture of their microfibrils which enable the contraction of muscles in response to applied tension. It also plays an important role in the transcription of the genetic information into RNA and proteins necessary in the respective cell type.
“The gene Spalt is essential for the generation of the ultrafast super muscles,” said Schnorrer. “Without Spalt, the fly builds only normal leg muscles instead of flight muscles.”
The flight muscles no longer responded to tension, and behave like normal leg muscles. The scientists also succeeded in creating flight muscle-like muscles in the fly’s legs by only inserting spalt.
Schnorrer said these results could be medically important. “Human body muscles do not have Spalt and are hardly regulated by tension,” he said. “But the human cardiac muscle builds Spalt and the tension inside the ventricle influences the heartbeat intensity. Whether Spalt plays a role in heartbeat regulation is not yet known and remains to be investigated.”
Spalt mediates an evolutionarily conserved switch to fibrillar muscle fate in insects
