From: University of Nebraska - Lincoln
Published January 16, 2017 10:08 AM

Study refutes how fruit flies developed alcohol tolerance

The common fruit fly, the tiny insect drawn to your beer or wine, has evolved to have an impressive tolerance for alcohol.

More than two decades ago, in one of the first papers using gene sequences to find signatures of natural selection, scientists hypothesized that a molecular change in an enzyme gave the Drosophila melanogaster fruit fly species its superior ability to metabolize alcohol. Scientists concluded that the change they found in the Alcohol dehydrogenase (ADH) protein could be the adaptation that allowed D. melanogaster to colonize ethanol-rich habitats in rotting fruit better than its nearly identical relative, Drosophila simulans.

It seemed a logical conclusion that the gene sequence changes that altered amino acids in an enzyme that breaks down alcohol would be the mechanism of natural selection.

However, the authors of a new paper published online Jan. 13 by Nature Ecology & Evolution say they have now refuted that hypothesis.

Their 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. Tests also are needed to check how the changes function in organisms.

Using genetic engineering, scientists resurrected the fruit flies' ADH protein from ancestral species to compare whether the amino acid changes that have occurred in D. melanogaster’s ADH enzyme actually improved the fruit flies' ability to tolerate alcohol. The answer, conclusively, was “no.”

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