Loss of a gluconeogenic muscle enzyme contributed to adaptive metabolic traits in hummingbirds
Ekaterina Osipova, Rico Barsacchi, Tom Brown, Keren R. Sadanandan, Andrea H. Gaede, Amanda Monte, Julia Jarrells, Claudia Moebius, Martin Pippel, Douglas L. Altshuler, Sylke Winkler, Marc Bickle, Maude W. Baldwin, Michael Hiller
Abstract
Hummingbirds possess distinct metabolic adaptations to fuel their energy-demanding hovering flight, but the underlying genomic changes are largely unknown. Here, we generated a chromosome-level genome assembly of the long-tailed hermit and screened for genes that have been specifically inactivated in the ancestral hummingbird lineage. We discovered that FBP2 (fructose-bisphosphatase 2), which encodes a gluconeogenic muscle enzyme, was lost during a time period when hovering flight evolved. We show that FBP2 knockdown in an avian muscle cell line up-regulates glycolysis and enhances mitochondrial respiration, coincident with an increased mitochondria number. Furthermore, genes involved in mitochondrial respiration and organization have up-regulated expression in hummingbird flight muscle. Together, these results suggest that FBP2 loss was likely a key step in the evolution of metabolic muscle adaptations required for true hovering flight.