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Title

Structural and functional divergence of two fish aquaporin-1 water channels following teleost-specific gene duplication

AuthorsTingaud-Sequeira, Angèle; Chauvigné, François ; Fabra, Mercedes; Lozano, Juan José; Raldúa, Demetrio; Cerdà, Joan
KeywordsTeleost
Physiological adaptations
Genomic analyses
Issue Date23-Sep-2008
PublisherBioMed Central
CitationBMC Evolutionary Biology 8: 259 (2008)
AbstractBackground Teleost radiation in the oceans required specific physiological adaptations in eggs and early embryos to survive in the hyper-osmotic seawater. Investigating the evolution of aquaporins (AQPs) in these vertebrates should help to elucidate how mechanisms for water homeostasis evolved. The marine teleost gilthead sea bream (Sparus aurata) has a mammalian aquaporin-1 (AQP1)-related channel, termed AQP1o, with a specialized physiological role in mediating egg hydration. However, teleosts have an additional AQP isoform structurally more similar to AQP1, though its relationship with AQP1o is unclear. Results By using phylogenetic and genomic analyses we show here that teleosts, unlike tetrapods, have two closely linked AQP1 paralogous genes, termed aqp1a and aqp1b (formerly AQP1o). In marine teleosts that produce hydrated eggs, aqp1b is highly expressed in the ovary, whereas in freshwater species that produce non-hydrated eggs, aqp1b has a completely different expression pattern or is not found in the genome. Both Aqp1a and Aqp1b are functional water-selective channels when expressed in Xenopus laevis oocytes. However, expression of chimeric and mutated proteins in oocytes revealed that the sea bream Aqp1b C-terminus, unlike that of Aqp1a, contains specific residues involved in the control of Aqp1b intracellular trafficking through phosphorylation-independent and -dependent mechanisms. Conclusion We propose that 1) Aqp1a and Aqp1b are encoded by distinct genes that probably originated specifically in the teleost lineage by duplication of a common ancestor soon after divergence from tetrapods, 2) Aqp1b possibly represents a neofunctionalized AQP adapted to oocytes of marine and catadromous teleosts, thereby contributing to a water reservoir in eggs and early embryos that increases their survival in the ocean, and 3) Aqp1b independently acquired regulatory domains in the cytoplasmatic C-terminal tail for the specific control of Aqp1b expression in the plasma membrane
DescriptionAdditional files: Alignment of the amino acid sequences of vertebrate AQP1 and teleost Aqp1a and Aqp1b.--Water permeability of X. laevis oocytes expressing sea bream wild-type (WT) or mutant Aqp1b.--Degenerate and gene- or cDNA-specific oligonucleotide primers used for cloning and RT-PCR analysis.--Forward and reverse primers employed to introduce mutations into the sea bream Aqp1b cDNA
Publisher version (URL)http://dx.doi.org/10.1186/1471-2148-8-259
URIhttp://hdl.handle.net/10261/8265
DOI10.1186/1471-2148-8-259
ISSN1471-2148
Appears in Collections:(ICM) Artículos
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