(ORDO NEWS) — Scientists at Harvard University have uncovered the genetic cause of the ability to soar in hummingbirds.
Loss of the FBP2 gene resulted in muscle cells being able to quickly absorb fructose from flower nectar.
The geneticists analyzed the genome of the long-tailed hermit hummingbird Phaethornis superciliosus and compared it with the genomes of other hummingbird species and 45 birds, such as the domestic chicken, pigeon and eagle.
This made it possible to determine the genetic differences that allow hummingbirds to obtain a large amount of energy, extracting it from the sugar they consume.
For example, hummingbirds are known to be able to directly metabolize fructose with the same efficiency as glucose.
At the same time, carbohydrates are metabolized within a few minutes after they enter the body. It turned out that all hummingbirds had lost the gene encoding frutose bisphosphatase 2 (FBP2).
This happened between 48 and 30 million years ago, when the common ancestors of all hummingbirds evolved the ability to soar and feed on nectar.
FBP2 is an enzyme involved in the metabolic pathway gluconeogenesis leading to the formation of glucose from pyruvic acid.
Experiments with an avian muscle cell line confirmed that knocking out the FBP2 gene accelerates glycolysis, enhances mitochondrial respiration, and also increases the number of energy-producing mitochondria.
However, in addition to the loss of FBP2, other genetic changes may have occurred in the ancestors of hummingbirds.
Several other proteins that play an important role in sugar metabolism have been found to have amino acid changes, probably due to directional selection.
Further research is needed to assess their role in the evolution of soaring flight in hummingbirds, the scientists say.
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