Why fruit flies eat just about anything

Say hello to the common fruit fly: a regular guest in most homes, feasting on this banana peel thrown in the trash a few days ago.

Despite their name, these insects feed on various types of plant matter. In an article published in Cell reports Scientists explain that this diversity of diets stems from their flexible response to carbohydrates, which allows us to better understand the changing dietary preferences.

The fruit fly, or Drosophila melanogaster are a frequent subject of research in genetics and have provided answers on the functioning of genes. Like the fruit fly, humans can also eat a wide variety of types of foods and are known as "nutrition generalists". In addition, some genetic cousins ​​of the fruit fly are called "nutrition specialists" and can only feed on very specific plants. Many questions remain about why organisms have such differences in their dietary habits, even within the same genetic family.

"Discovering the differences in molecular mechanisms between generalists and nutrition experts can help us understand how organisms adapt to a variety of nutritional settings," say Kaori Watanabe and Yukako Hattori of the Graduate School of Biostudies. Kyoto University. "In our investigation, we changed the nutrient balance in different foods. Drosophila species and compared their nutritional adaptability as well as their transcriptional and metabolic responses ".

The team began by examining whether the larvae of generalists and specialists could adapt to three experimental diets: high in protein, high in carbohydrates and protein. As expected, generalist flies, including the common fruit fly, grew in all diets. The larvae of specialists, on the other hand, could not survive in conditions rich in carbohydrates.

These specialists are known to eat and reproduce on specific fruits or flowers, and a review of the nutritional profile of their natal diet has shown that they eat low carbohydrates. The team hypothesized that the difference between flies lies in the genetic pathways that control their response to carbohydrates.

"A signaling pathway known as TGF-β / Activin regulates the body's response to carbohydrates.This pathway is flexible enough for GPs and maintains metabolic homeostasis under different regimes.In fact, about 250 Metabolic genes are down-regulated diet is rich in carbohydrates, "they explain.

In contrast, a specialist has expressed these genes at higher levels, where they accumulated metabolites, resulting in reduced adaptation. The same lack of adaptation has also been found when a TGF-β / Activin gene called dawdle is disabled in the common fruit fly.

The findings suggest that generalists have conserved robust carbohydrate-sensitive systems through genome-environment interactions during evolution, while specialists have lost them in consistent low-carb environments. .

The research team concludes, "Since humans and flies share a number of genes and regulatory factors, we can begin to develop an interspecific comparative approach that provides an informative model system to address variability." genetics in humans in response to dietary intakes. "

The document, "Comparative Analyzes Between Species, reveals distinct carbohydrate-sensitive systems among Drosophila Species ", appeared on September 3, 2019 in Cell reports.