Meeting Abstract
Four families of oxygen-binding proteins are found in animals, which are divided into two major groups: proteins that use iron to bind oxygen (hemoglobins and hemerythrins) and two non-homologous families of hemocyanins that use copper. Hemerythrins (Hr) genes are present in the three domains of life, Archaea, Bacteria, and Eukaryota; however, within Animalia, Hrs have been reported only in marine species in six phyla (Annelida, Brachiopoda, Priapulida, Bryozoa, Cnidaria, and Arthropoda). Hemocyanins, found in arthropods and molluscs, bind oxygen in the same manner, but they are distinct in their molecular structure – often designated HcA and HcM, respectively. We investigated the diversity and evolution of Hr, HcA and HcM in metazoans, by employing in silico approaches to survey >100 metazoan transcriptomes and genomes. We found 58 candidate Hr genes actively transcribed in 36 species distributed in 11 animal phyla, with new records in Echinodermata, Hemichordata, Mollusca, Nemertea, Phoronida, and Platyhelminthes. Moreover, we found that “Hrs” reported from Cnidaria and Arthropoda were not consistent with that of other metazoan. Five putative novel HcM genes were retained from taxa examined in this study, including two annelid species from the same family, Chaetopteridae. Concerning HcA, 18 putative novel genes presenting at least two of the three domains were retained, representing 18 metazoan species distributed across six phyla. The presence of HcA in Annelida, Cycliophora, and Echinodermata represent novel observations. Work presented here contradicts the canonical view that 1) Hemerythrins are absent in deuterostomes and 2) hemocyanins are restricted to molluscs and arthropods. The occurrence of blood pigments in metazoans is underestimated.
