The Full Globin Repertoire of Turtles Provides Insights into Vertebrate Globin Evolution and Functions.
Bottom Line: The globin E gene was selectively lost in the green anole, and the genes coding for globin X and globin Y were deleted in chicken.Histochemical analyses showed high levels of globin E in the pigment epithelium of the eye.Globin E probably has a myoglobin-like role in transporting O2 across the pigment epithelium to supply in the metabolically highly active retina.
Affiliation: Institute of Zoology, Department of Biology, University of Hamburg, Germany.Show MeSH
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Mentions: The three Hbα genes of the painted turtle reside on a single contig (JH584800) in head-to-tail orientation (fig. 2C and supplementary table S3, Supplementary Material online). When compared with the putative orthologs in the softshell turtle, HbZ was found to be the highest conserved Hbα (91.5% identity) (supplementary table S4, Supplementary Material online). The HbAd and HbAa of the two turtles share 89.4% and 86.6%, respectively, of the amino acids. All analyzed Hbα have 1:1 orthologs in the chicken genome, which display between 82.4% and 90.1% identity (supplementary table S4, Supplementary Material online). In contrast to the softshell turtle, the painted turtle possesses three Hbβ genes. Phylogenetic analysis and sequence comparison revealed that HbB1 and HbB2 have orthologs in both turtle species, but the softshell turtle lost the ortholog of HbG (or it is not represented in the current assembly). Although the HbB1 and HbB2 genes have orthologs in chicken, HbG is duplicated in chicken and, therefore, there is no 1:1 ortholog to the turtle HbG (figs. 2D and 3). The turtle and chicken Hbβ genes have no 1:1 orthologs in the human genome (Hoffmann et al. 2010) (fig. 3). The Hb genes of the turtle are separated on two different clusters (fig. 2C and D). Gene synteny analyses of the Hbα region identified MPG-NPRL3 and (GbY)-TMEM8a-MPRL28 as the neighboring genes. The gene order is highly conserved among vertebrates (fig. 2C). The numbers of Hb genes may differ between closely related species, which is due to a high rate of lineage-specific gene duplication (Hoffmann et al. 2008) (fig. 3). The Hbβ genes are embedded in a cluster of olfactory receptor genes (OR) (fig. 2D).Fig. 3.—
Affiliation: Institute of Zoology, Department of Biology, University of Hamburg, Germany.