Cytoskeletal signaling as a shared pathway for convergent genetic mechanisms underlying loss of flight in birds

Loss of flight in birds is an adaptive feature of evolutionary processes. Morphological and physiological differences are known among flightless bird species; however, the genetic mechanisms behind them are largely unexplored. Notably, wild birds and poultry that have lost flight owing to evolution and domestication, respectively, show phenotypic convergence, suggesting that different selective pressures through the same genetic pathways may cause loss of flight in birds; however, little is known about the genetic basis of this potential commonality. In this study, we obtained genomes of 28 wild bird and 15 duck species, and conducted comparative genomics and whole-genome resequencing analyses, respectively, to investigate the genetic basis underlying loss of flight in birds. The results of positive selection analysis using the genomic data of wild birds showed that 70 genes enriched in the cytoskeleton in muscle cells signaling pathway experienced strong positive selection, suggesting that this may be a key pathway leading to the loss of flight. Using the genomic data of domestic ducks for selective sweep analysis, we identified 139 candidate genes, among which FN1 and ANKRD1 were involved in the cytoskeleton in muscle cells signaling pathway; moreover, we detected strong positive selection signals in wild birds, suggesting that both wild birds and poultry may mediate flight loss through this pathway. Overall, this study deepens the understanding the evolution of flight in birds and provides novel insights and basis for future studies on flight in birds.