title: Conserved structure and expression of hsp70 paralogs in teleost fishes.
abstract: The cytosolic 70KDa heat shock proteins (Hsp70s) are widely used as biomarkers of environmental stress in ecological and toxicological studies in fish. Here we analyze teleost genome sequences to show that two genes encoding inducible hsp70s (hsp70-1 and hsp70-2) are likely present in all teleost fish. Phylogenetic and synteny analyses indicate that hsp70-1 and hsp70-2 are distinct paralogs that originated prior to the diversification of the teleosts. The promoters of both genes contain a TATA box and conserved heat shock elements (HSEs), but unlike mammalian HSP70s, both genes contain an intron in the 5' UTR. The hsp70-2 gene has undergone tandem duplication in several species. In addition, many other teleost genome assemblies have multiple copies of hsp70-2 present on separate, small, genomic scaffolds. To verify that these represent poorly assembled tandem duplicates, we cloned the genomic region surrounding hsp70-2 in Fundulus heteroclitus and showed that the hsp70-2 gene copies that are on separate scaffolds in the genome assembly are arranged as tandem duplicates. Real-time quantitative PCR of F. heteroclitus genomic DNA indicates that four copies of the hsp70-2 gene are likely present in the F. heteroclitus genome. Comparison of expression patterns in F. heteroclitus and Gasterosteus aculeatus demonstrates that hsp70-2 has a higher fold increase than hsp70-1 following heat shock in gill but not in muscle tissue, revealing a conserved difference in expression patterns between isoforms and tissues. These data indicate that ecological and toxicological studies using hsp70 as a biomarker in teleosts should take this complexity into account.
authors.affiliation: Department of Zoology, 6270 University Blvd., University of British Columbia, Vancouver, BC V6T 1Z4, Canada.
authors.forename: David C H
authors.initials: DC
authors.lastname: Metzger
authors.affiliation: Section for Marine Living Resources, National Institute of Aquatic Resources, Technical University of Denmark, Vejlsøvej 39, 8600 Silkeborg, Denmark.
authors.forename: Jakob
authors.initials: J
authors.lastname: Hemmer-Hansen
authors.affiliation: Department of Zoology, 6270 University Blvd., University of British Columbia, Vancouver, BC V6T 1Z4, Canada. Electronic address: pschulte@zoology.ubc.ca.
authors.forename: Patricia M
authors.initials: PM
authors.lastname: Schulte
mesh_terms: D000818:Animals; D005399:Fishes; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D023281:Genomics / Q000379:methods; D018840:HSP70 Heat-Shock Proteins / Q000737:chemistry* / Q000145:classification / Q000235:genetics*; D018869:Heat-Shock Response / Q000235:genetics*; D010802:Phylogeny; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D018840:HSP70 Heat-Shock Proteins; D012333:RNA, Messenger; C081884:heat-shock protein 70.1
keywords: Fish; Gene duplication; HSP70; Heat shock proteins; Intron; Paralog; Synteny; Tandem duplication