New York: Refuting a two-decade-old theory, US scientists have claimed that the common fruit fly's impressive tolerance for beer or wine may have nothing to do with the alcohol dehydrogenase (ADH) protein in their body.
Traditionally, it was hypothesised that a molecular change in ADH gene gave the Drosophila melanogaster -- fruit fly species -- its superior ability to metabolise alcohol.
However, the new findings indicate that intuition and signatures of selection in gene sequence may not be enough for scientists to conclusively solve the puzzles of molecular evolution.
"The study doesn't dispute that this species has a high ethanol tolerance. But it suggests that the molecular changes that have led to that high tolerance are not in this protein. They must be in other genes in the genome," explained Kristi L. Montooth, biologist at University of Nebraska-Lincoln in the US.
Using genetic engineering, the scientists resurrected the fruit flies' ADH protein from ancestral species to compare whether the amino acid changes that have occurred in Drosophila melanogaster's ADH enzyme actually improved the fruit flies' ability to tolerate alcohol.
The results showed that the ADH amino acid changes made no discernible difference in the species' ability to survive while being fed increasingly heavy doses of alcohol.
"This paper takes advantage of modern molecular biology and genetic approaches to test some of those hypotheses," Montooth said.
The search for new pathways in fruit flies could offer new clues about alcohol tolerance in humans, the authors added in the paper published in the journal Nature Ecology and Evolution.