MUSEO ARGENTINO DE CIENCIAS NATURALES "BERNARDINO RIVADAVIA"
Unidad Ejecutora - UE
Convergent evolution of hemoglobin function in high-altitude andean waterfowl involves limited parallelism at the molecular sequence level
NATARAJAN, C.; PROJETO-GARCIA, J.; MORIYAMA, H.; WEBER, R. E.; MUÑOZ-FUENTES, V.; GREEN, A. J.; KOPUCHIAN, C.; TUBARO, P. L.; ALZA, L.; BULGARELLA, M.; SMITH, M. M.; WILSON, R. E.; FAGO, A.; MCCRACKEN, K. G.; STORZ, J. F.
PUBLIC LIBRARY SCIENCE
Lugar: San Francisco; Año: 2015 p. 1 - 1
A fundamental question in evolutionarygenetics concerns the extent to which adaptive phenotypicconvergence is attributable toconvergent or parallel changes at the molecular sequence level. Here we reporta comparative analysis of hemoglobin (Hb) function in eight phylogeneticallyreplicated pairs of high- and low-altitude waterfowl taxa to test forconvergence in the oxygenation properties of Hb, and to assess the extent towhich convergence in biochemical phenotype is attributable to repeated aminoacid replacements. Functional experiments on native Hb variants and proteinengineering experiments based on sitedirected mutagenesis revealed thephenotypic effects of specific amino acid replacements that were responsiblefor convergent increases in Hb-O2 affinity in multiple high-altitude taxa. In six of theeight taxon pairs, high-altitude taxa evolved derived increases in Hb-O2 affinity that werecaused by a combination of unique replacements, parallel replacements (involvingidentical-by-state variants with independent mutational origins in differentlineages), and collateral replacements (involving shared, identical-by-descentvariants derived via introgressive hybridization). In genome scans ofnucleotide differentiation involving high- and low-altitude populations ofthree separate species, function-altering amino acid polymorphisms in theglobin genes emerged as highly significant outliers, providing independent evidencefor adaptive divergence in Hb function. The experimental results demonstratethat convergent changes in proteinfunction can occur through multiple historical paths, and can involve multiplepossible mutations. Most cases of convergence in Hb function did not involveparallel substitutions and most parallel substitutions did not affect Hb-O2 affinity,indicating that the repeatability of phenotypic evolution does not requireparallelism at the molecular level.