title: The evolution and functional divergence of the beta-carotene oxygenase gene family in teleost fish--exemplified by Atlantic salmon.
abstract: In mammals, two carotenoid cleaving oxygenases are known; beta-carotene 15,15'-monooxygenase (BCMO1) and beta-carotene 9',10'-oxygenase (BCO2). BCMO1 is a key enzyme in vitamin A synthesis by symmetrically cleaving beta-carotene into 2 molecules of all-trans-retinal, while BCO2 is responsible for asymmetric cleavage of a broader range of carotenoids. Here, we show that the Atlantic salmon beta-carotene oxygenase (bco) gene family contains 5 members, three bco2 and two bcmo1 paralogs. Using public sequence databases, multiple bco genes were also found in several additional teleost species. Phylogenetic analysis indicates that bco2a and bco2b originate from the teleost fish specific genome duplication (FSGD or 3R), while the third and more distant paralog, bco2 like, might stem from a prior duplication event in the teleost lineage. The two bcmo1 paralogs (bcmo1 and bcmo1 like) appear to be the result of an ancient duplication event that took place before the divergence of ray-finned (Actinopterygii) and lobe-finned fish (Sarcopterygii), with subsequent nonfunctionalization and loss of one Sarcopterygii paralog. Gene expression analysis of the bcmo1 and bco2 paralogs in Atlantic salmon reveals regulatory divergence with tissue specific expression profiles, suggesting that the beta-carotene oxygenase subtypes have evolved functional divergences. We suggest that teleost fish have evolved and maintained an extended repertoire of beta-carotene oxygenases compared to the investigated Sarcopterygii species, and hypothesize that the main driver behind this functional divergence is the exposure to a diverse set of carotenoids in the aquatic environment.
authors.affiliation: Centre for Integrative Genetics (CIGENE), Dept. of Animal and Aquacultural Sciences, Norwegian University of Life Sciences (UMB), P.O. Box 5003, N-1432 As, Norway.
authors.forename: Hanna
authors.initials: H
authors.lastname: Helgeland
authors.affiliation: Centre for Integrative Genetics (CIGENE), Dept. of Plant and Environmental Sciences, Norwegian University of Life Sciences (UMB), P.O. Box 5003, N-1432 As, Norway.
authors.forename: Simen Rød
authors.initials: SR
authors.lastname: Sandve
authors.affiliation: Nofima AS, PO Box 5010, N-1432 Ås, Norway.
authors.forename: Jacob Seilø
authors.initials: JS
authors.lastname: Torgersen
authors.affiliation: Centre for Integrative Genetics (CIGENE), Dept. of Animal and Aquacultural Sciences, Norwegian University of Life Sciences (UMB), P.O. Box 5003, N-1432 As, Norway.
authors.forename: Mari Kyllesø
authors.initials: MK
authors.lastname: Halle
authors.affiliation: Centre for Integrative Genetics (CIGENE), Dept. of Animal and Aquacultural Sciences, Norwegian University of Life Sciences (UMB), P.O. Box 5003, N-1432 As, Norway.
authors.forename: Hilde
authors.initials: H
authors.lastname: Sundvold
authors.affiliation: Centre for Integrative Genetics (CIGENE), Dept. of Animal and Aquacultural Sciences, Norwegian University of Life Sciences (UMB), P.O. Box 5003, N-1432 As, Norway.
authors.forename: Stig
authors.initials: S
authors.lastname: Omholt
authors.affiliation: Centre for Integrative Genetics (CIGENE), Dept. of Animal and Aquacultural Sciences, Norwegian University of Life Sciences (UMB), P.O. Box 5003, N-1432 As, Norway.
authors.forename: Dag Inge
authors.initials: DI
authors.lastname: Våge
mesh_terms: D000818:Animals; D019143:Evolution, Molecular; D029941:Fish Proteins / Q000145:classification / Q000235:genetics*; D015971:Gene Expression Regulation, Enzymologic; D006899:Mixed Function Oxygenases / Q000145:classification / Q000235:genetics / Q000502:physiology*; D010802:Phylogeny; D020317:Salmo salar / Q000235:genetics*
chemical_list: D029941:Fish Proteins; D006899:Mixed Function Oxygenases; C079232:beta-carotene hydroxylase
keywords: Beta-carotene oxygenase; Gene family; Genome duplication; Salmon; Teleost fish