Phylogenetic origins and adaptive evolution of avian and mammalian haemoglobin genes

Abstract

Recent years have seen rapid growth in amino acid sequence data on globins and nucleotide sequence data on haemoglobin genes and pseudogenes, and cladistic analysis of these data continues to reveal new facets of globin evolution. Our present findings demonstrate: (1) avian and mammalian embryonic alpha genes (pi and xi, respectively) had a monophyletic origin involving an alpha locus duplication about 400 Myr ago soon after the duplication which separated alpha and beta genes; (2) much later in phylogeny, independent beta-gene duplications produced the embryonic rho locus of birds and embryonic epsilon and fetal gamma loci of mammals. This parallels the earlier finding that myoglobins evolved more than once from generalized globin ancestors. Here we support the view that such globin evolution resulted from natural selection acting on mutations in duplicated genes. Thus, our evidence contradicts the neutralist view in which almost all amino acid substitutions in descent to extant globins evaded positive selection.

Phylogenetic relationships of the Cobitoidea (Teleostei: Cypriniformes) inferred from mitochondrial and nuclear genes with analyses of gene evolution

“…Therefore, variation in evolutionary rates (e.g. dN/dS ratio), especially those between taxa sufficiently closely related (for example within mammals), is considered a strong indicator of anagenesis driven by selection pressure over time (Czelusniak et al, 1982;Kawahara and Imanishi, 2007;Lynch and Conery, 2000;Toll-Riera et al, 2011). This variation of possible factors is hypothesized to have contributed greatly to the function differentiation we observe today in the genes and diversification of organisms (Wang et al, 2009).…”

Genomic evidence for independent origins of β-like globin genes in monotremes and therian mammals

“…The progenitors of the ␣-and ␤-globin gene families originated via tandem duplication of an ancestral, single-copy globin gene Ϸ450-500 Mya in the common ancestor of gnathostome vertebrates (1)(2)(3). The ancestral gene arrangement, consisting of a linked set of ␣-and ␤-like globin genes on the same chromosome, has been retained in teleosts such as the zebra fish (Danio rerio; ref.…”

Globin-intron Sequences Imply Molecular Relationships Between the Galapagos Giant Tortoise and the Aldabra Giant Tortoise

“…3 shows a genetic relationship of only introns of the three Geochelone species tested and constructed by the ML statistical method 17) whose accuracy of both the topology and branch length were tested and confirmed by several statistical methods as stored in MEGA such as Maximum-Evolutionary, Neighbor-Joining, UPGMA, and Maximum Parsimony 17) . Goodman et al 10) and Czelusniak et al 11) measured the separation time of β−α globin lineages of gnathostome and amniote (reptile-bird-mammal) ancestors to be about 300-425 mya (average time: 362.5 mya). They also estimated teleost-tetrapod to amniote α globin ancestor and tetrapod to aminote β ancestor to be 300-400 mya and 300-340 mya, respectively.…”

“…During the early Cretaceous, Madagascar separated from Africa 26) , and the South Atlantic widened rapidly into a major ocean of approximately 1,000 km wide (about one-third of its present width), while Antarctica was still attached to South America and moved south-westward continually at a slow speed 9) . If the divergence time scaled according to hemoglobin genealogy, as reported in the literature [10][11][12]27) , is correct, then where is the origin of G. nigra and G. gigantea?…”

“…Globin genes consist of three exons and two introns, and exon nucleotide sequences (or primary structures) were widely used for construction of molecular relationships among living organisms [10][11][12][13] . On the contrary, very little is known about intron nucleotide sequences of reptilian globin 6) .…”