Enzyme against alcohol – Too beautiful evolutionary history

Evolution is a well-established fact. How customization works in detail is often unclear. This also applies to the ability of the fruit flies to break down alcohol faster than other fly species. New research has led to the need to rewrite textbooks.

Enzyme against alcohol - Too beautiful evolutionary history
Fruit flies can break down alcohol faster than related fly species. (Imago stock & people / blickwinkel)

Anyone who leaves a banana for a while can be sure to attract fruit flies. For they feed on the agents of decomposition, the yeast fungi and bacteria. They also have hardly any competition, because closely related fly types can simply not handle the high alcohol concentrations in rotting fruit. At the end of the eighties, geneticists discovered that the fruit flies have a particularly laborious version of alcohol dehydrogenase. This variant of the enzyme, which is abbreviated ADH, decomposes the alcohol more quickly, thus making the fruit flies free for their body food.

“This is a textbook example of evolutionary biology for the genetic basis of an adaptation to the environment.”

The theory of the ADH mutation in the fruit flies

And for good reason, says Joe Thornton, Professor of Ecology and Evolution at the University of Chicago. For all experiments available in the eighties support the theory of the ADH mutation as a decisive step in the development of fruitflies. But science has continued to develop since then. And that is why Joe Thornton looked more closely at the textbook of evolution. As a first step he undertook a journey into the genetic past of the fruit flies. He compared all available ADH gene sequences with statistical methods.

“There are so many ADH gene sequences that we can very reliably reconstruct the common ancestors from which today’s fruit trees are derived as well as their relatives who do not cope with the alcohol in rotten fruit.”

This historical gene sequence has then transferred Joe Thornton to fruit flies. Thus, he could almost resurrect the ancestor of today’s fruit flies, at least as far as alcohol dehydrogenase is concerned. Then he presented this historicized and normal fruit flies to rotten fruit.

“It turned out that the flies with the historical gene are as good or badly clear as the modern fruit flies, which contradicts the accepted depiction that they were changes in the ADH that allow the fruit flies to exceed high alcohol concentration. ”

Other genetic changes responsible for alcohol tolerance

Other genetic alterations are probably responsible for their alcohol tolerance. These could, for example, stimulate cells to simply form more ADH or increase the activity of other genes in the pathway of the alcohol. These hypotheses can be tested through the combination of genetic reconstruction of the precursor gene and the production of partially historicized animals. Thanks to the new crispr / Cas9 method, this approach should also be implemented in other animal species. Joe Thornton assumes that some very beautiful stories from molecular evolution will turn out to be fairy tales. The bottom line, however, is that the new experimental approach will strengthen the evolutionary biology. For a single false history does not question the fact of evolution.

“It would be crazy if someone would argue that there is no doubt that the ADH gene has changed, there is no doubt that today’s fruit flyers are more capable of drinking than their ancestors, That species adapt themselves via mutation and selection, we only open the view of the details behind this process. “

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