Parallel Evolution in the βA Globin Gene of Black Kite, Bar-Headed Goose and Graylag Goose: Deciphering Hemoglobin Adaptation to High Altitude Hypoxia Using Birds as Models

Parallel evolution involving historically independent amino acid substitutions in hemoglobin (Hb) is expected among closely related lineages; however, such studies in distantly related species are limited especially from the structural point of view. Here we reported structural and phylogenetic based parallel amino acid substitutions in the βA globin gene of the Black kite (BK), Bar-headed goose (BHG), and graylag goose (GLG) to illustrate the adaptation of hemoglobin to high altitude hypoxia and high altitude sickness in humans and animals living at extreme altitudes. Based on our data, there are five to six parallel amino acid substitutions in the βA globin gene of BK, BHG, and GLG. Four of the parallel amino acid substitutions (Asn-βA83-Lys, Gln-βA90-Lys, Asp-βA125-Ala, and Ala-βA128-Ser) are independently evolved only among BK, BHG, and GLG. The individual Ala-βA128-Ser substitution resulted in a significant closeness of the α1 and β1 subunits which probably stabilizes the R state of oxy-Hb at high altitude. Our data contribute to evolutionary biology by providing pieces of evidence into the parallel evolution of BK, BHG, and GLG to high altitude hypoxia and laid a foundation to studying high altitude associated hemoglobinopathies in humans and other animals. Keywords: Parallel evolution; βA globin gene; Black kite; bar-headed goose; graylag goose