title: Cloning and characterization of aquaglyceroporin genes from rainbow smelt (Osmerus mordax) and transcript expression in response to cold temperature.
abstract: Aquaglyceroporins (GLPs) are integral membrane proteins that facilitate passive movement of water, glycerol and urea across cellular membranes. In this study, GLP-encoding genes were characterized in rainbow smelt (Osmerus mordax mordax), an anadromous teleost that accumulates high glycerol and modest urea levels in plasma and tissues as an adaptive cryoprotectant mechanism in sub-zero temperatures. We report the gene and promoter sequences for two aqp10b paralogs (aqp10ba, aqp10bb) that are 82% identical at the predicted amino acid level, and aqp9b. Aqp10bb and aqp9b have the 6 exon structure common to vertebrate GLPs. Aqp10ba has 8 exons; there are two additional exons at the 5' end, and the promoter sequence is different from aqp10bb. Molecular phylogenetic analysis suggests that the aqp10b paralogs arose from a gene duplication event specific to the smelt lineage. Smelt GLP transcripts are ubiquitously expressed; however, aqp10ba transcripts were highest in kidney, aqp10bb transcripts were highest in kidney, intestine, pyloric caeca and brain, and aqp9b transcripts were highest in spleen, liver, red blood cells and kidney. In cold-temperature challenge experiments, plasma glycerol and urea levels were significantly higher in cold- compared to warm-acclimated smelt; however, GLP transcript levels were generally either significantly lower or remained constant. The exception was significantly higher aqp10ba transcript levels in kidney. High aqp10ba transcripts in smelt kidney that increase significantly in response to cold temperature in congruence with plasma urea suggest that this gene duplicate may have evolved to allow the re-absorption of urea to concomitantly conserve nitrogen and prevent freezing.
authors.affiliation: Department of Ocean Sciences, Memorial University of Newfoundland, St. John's, NL A1C 5S7, Canada. Electronic address: jrhall@mun.ca.
authors.forename: Jennifer R
authors.initials: JR
authors.lastname: Hall
authors.affiliation: Department of Ocean Sciences, Memorial University of Newfoundland, St. John's, NL A1C 5S7, Canada.
authors.forename: Kathy A
authors.initials: KA
authors.lastname: Clow
authors.affiliation: Department of Ocean Sciences, Memorial University of Newfoundland, St. John's, NL A1C 5S7, Canada.
authors.forename: Matthew L
authors.initials: ML
authors.lastname: Rise
authors.affiliation: Department of Ocean Sciences, Memorial University of Newfoundland, St. John's, NL A1C 5S7, Canada.
authors.forename: William R
authors.initials: WR
authors.lastname: Driedzic
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D051397:Aquaglyceroporins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D003001:Cloning, Molecular; D003080:Cold Temperature; D005091:Exons / Q000235:genetics; D029941:Fish Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D005786:Gene Expression Regulation; D005990:Glycerol / Q000097:blood; D007668:Kidney / Q000378:metabolism; D008969:Molecular Sequence Data; D009928:Organ Specificity; D036441:Osmeriformes / Q000097:blood / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012621:Seasons; D014508:Urea / Q000097:blood
chemical_list: D051397:Aquaglyceroporins; D029941:Fish Proteins; D012333:RNA, Messenger; D014508:Urea; D005990:Glycerol
keywords: Aquaglyceroporin; Cold temperature; Glycerol; Rainbow smelt; Urea