The hemoglobin oxygen affinity of high-altitude birds in the Qinghai-Tibet Plateau increased compared with their low-altitude proximity species.

The adaptive evolution of vertebrates to extreme environments is the focus of evolutionary biology and physiological ecology.
to compensate for the low oxygen pressure effects of high altitude environment, the animal body through a variety of oxygen transmission channels to ensure the continuous transmission of oxygen to the mitochondria to support the synthesis of aerobic ATP.
in severe low oxygen conditions to maintain arterial oxygen saturation, in the heart and lung function and microcirculation system regulation at the same time, the body needs to increase the hemoglobin oxygen (Hb-O2) affinity to consolidate tissue oxidation levels.
have previously found that the increase in Hb-O2 affinity is caused by different amino acid substitution combinations.
when different species experience similar environmental selection pressures, the evolutionary probability of similarity of adaptive strategies will be decisively influenced by the evolutionary history of populations.
by comparing the hemoglobin functional phenotypes and molecular structures of different high-altitude and low-altitude and long-tailed species, the Institute of Zoology of the Chinese Academy of Sciences found that the hemoglobin oxygen affinity of high-altitude birds in the Qinghai-Tibet Plateau increased compared to their low-altitude proximity species.
increased convergence of these hemoglobin oxygen affinities is mainly dependent on the convergence evolution of potential functional mechanisms, rather than the substitution of the same amino acids in different species.
the parallel amino acid substitution sites that determine the increase of hemoglobin oxygen affinity in high-altitude bird species with ancestral protein remodeling and fixed-point mutagenesis.
the increasein effect of the oxygen affinity of Parus humilis and lophophanes dichrous is determined by the ala of the alpha A34-bit site who replaces it with Thr.
the parallel amino acid substitution is a non-sane substitution result of a double nucleotide CpG site, which means that mutation bias is the possible role in promoting repeat substitution at the same point.
through the simulation of homologous protein structure, it is proved that the amino acid substitution at this site increases the number of hydrogen bonds between alpha and beta sub-bases, thus making the oxidizing conformation of tetrapolymer hemoglobin more stable than deoxidation conformation.
another convergence-increasing oxygen affinity replacement occurred in the black-brow long-tailed and the distant proximity of the spot-head at the site of alpha AP119A, which, unlike alphaA34T, reduced the stability of oxidized hemoglobin.
the study, by comparing the evolution of high-altitude bird species in the Qinghai-Tibet Plateau and the Andes, and the molecular structure that determines the phenotype difference, concludes the regularity of the molecular adaptation mechanism of hemoglobin molecules in high-altitude birds: most of the changes in hemoglobin function associated with altitude in birds are caused by different amino acid substitutions, and very few parallel amino acids derived from similar phetype effects are determined by independent genetic backgrounds. On February 5,
, the results of the study were published online in PNAS by Divergent and parallel routes of the study of the high-altitude passerine birds from Qinghai-Tibet Plateau.
research work has been supported by the Chinese Academy of Sciences' strategic pilot research project and the national natural science foundation's key projects.
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