title: The Evolutionary History of Daphniid α-Carbonic Anhydrase within Animalia.
abstract: Understanding the mechanisms that drive acid-base regulation in organisms is important, especially for organisms in aquatic habitats that experience rapidly fluctuating pH conditions. Previous studies have shown that carbonic anhydrases (CAs), a family of zinc metalloenzymes, are responsible for acid-base regulation in many organisms. Through the use of phylogenetic tools, this present study attempts to elucidate the evolutionary history of the α-CA superfamily, with particular interest in the emerging model aquatic organism Daphnia pulex. We provide one of the most extensive phylogenies of the evolution of α-CAs, with the inclusion of 261 amino acid sequences across taxa ranging from Cnidarians to Homo sapiens. While the phylogeny supports most of our previous understanding on the relationship of how α-CAs have evolved, we find that, contrary to expectations, amino acid conservation with bacterial α-CAs supports the supposition that extracellular α-CAs are the ancestral state of animal α-CAs. Furthermore, we show that two cytosolic and one GPI-anchored α-CA in Daphnia genus have homologs in sister taxa that are possible candidate genes to study for acid-base regulation. In addition, we provide further support for previous findings of a high rate of gene duplication within Daphnia genus, as compared with other organisms.
authors.affiliation: Program in Ecology & Evolutionary Biology, Department of Biology, University of Oklahoma, 730 Van Vleet Oval, Norman, OK 73019, USA ; University of Oklahoma Biological Station, 15389 Station Road, Kingston, OK 73439, USA.
authors.forename: Billy W
authors.initials: BW
authors.lastname: Culver
authors.affiliation: University of Oklahoma Biological Station, 15389 Station Road, Kingston, OK 73439, USA ; Murray State College, One Murray Campus, Tishomingo, OK 73460, USA.
authors.forename: Philip K
authors.initials: PK
authors.lastname: Morton