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Characterization of two distinct aryl hydrocarbon receptor (AhR2) genes in Atlantic salmon (Salmo salar) and evidence for multiple AhR2 gene lineages in salmonid fish.
Gene 2003; 303:197-206GENE

Abstract

The aryl hydrocarbon receptor (AhR) mediates the toxicity of several environmental contaminants, e.g. 2,3,7,8-tetrachlorodibenzo-p-dioxin, and other halogenated hydrocarbons in vertebrates. This receptor initiates the transcription of several biotransformation enzymes, which in turn are responsible for causing severe harm to biological tissue. Here we describe the isolation and complete characterization of the first two AhR genes from the teleost fish Atlantic salmon (Salmo salar). The predicted amino acid sequences contain regions characteristic of other vertebrate AhRs including basic helix-loop-helix (bHLH) and PER-ARNT-SIM (PAS) domains but show little similarity to other vertebrate AhRs across the C-terminal half. Furthermore, they do not contain distinct Q-rich domains as found in the mammalian AhR, which is in line with previously described fish AhR genes. The salmon cDNAs encode 1106 and 1107 putative residues, respectively, approximately 50 amino acids longer than previously characterized AhR genes. Phylogenetic analyses demonstrated that the two salmon AhR sequences cluster within the AhR subfamily of the bHLH-PAS family, in a clade containing fish AhR2 genes. Although the two AhR2 forms are 92% identical at the amino acid level, the distribution of sequence differences and the presence of both forms in 30 tested individuals suggest that they are not allelic but derived from separate loci. Interestingly, they are not orthologs of the rainbow trout (Oncorhynchus mykiss) AhR2 alpha and beta genes and the new salmon loci are therefore here designated AhR2 gamma and AhR2 delta. In line with this, PCR with DNA from rainbow trout revealed a new trout AhR locus that was more similar to the two salmon genes than to the trout AhR2 alpha and beta genes, suggesting that the rainbow trout possesses at least three distinct AhR2 genes. The presence of multiple AhR genes in these species is probably a consequence of the genome duplications that occurred in the early evolution of fish and later also specifically in the salmonid lineage. Reverse transcription-PCR analyses revealed that both AhR2 gamma and AhR2 delta are transcribed in the liver, spleen and muscles of adult salmon.

Authors+Show Affiliations

Department of Animal Ecology, Lund University, Ecology Building, Sölvegatan 37, Sweden. maria.hansson@zooekol.lu.seNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Comparative Study
Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

12559581

Citation

Hansson, Maria C., et al. "Characterization of Two Distinct Aryl Hydrocarbon Receptor (AhR2) Genes in Atlantic Salmon (Salmo Salar) and Evidence for Multiple AhR2 Gene Lineages in Salmonid Fish." Gene, vol. 303, 2003, pp. 197-206.
Hansson MC, Wittzell H, Persson K, et al. Characterization of two distinct aryl hydrocarbon receptor (AhR2) genes in Atlantic salmon (Salmo salar) and evidence for multiple AhR2 gene lineages in salmonid fish. Gene. 2003;303:197-206.
Hansson, M. C., Wittzell, H., Persson, K., & von Schantz, T. (2003). Characterization of two distinct aryl hydrocarbon receptor (AhR2) genes in Atlantic salmon (Salmo salar) and evidence for multiple AhR2 gene lineages in salmonid fish. Gene, 303, pp. 197-206.
Hansson MC, et al. Characterization of Two Distinct Aryl Hydrocarbon Receptor (AhR2) Genes in Atlantic Salmon (Salmo Salar) and Evidence for Multiple AhR2 Gene Lineages in Salmonid Fish. Gene. 2003 Jan 16;303:197-206. PubMed PMID: 12559581.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Characterization of two distinct aryl hydrocarbon receptor (AhR2) genes in Atlantic salmon (Salmo salar) and evidence for multiple AhR2 gene lineages in salmonid fish. AU - Hansson,Maria C, AU - Wittzell,Håkan, AU - Persson,Kerstin, AU - von Schantz,Torbjörn, PY - 2003/2/1/pubmed PY - 2003/3/26/medline PY - 2003/2/1/entrez SP - 197 EP - 206 JF - Gene JO - Gene VL - 303 N2 - The aryl hydrocarbon receptor (AhR) mediates the toxicity of several environmental contaminants, e.g. 2,3,7,8-tetrachlorodibenzo-p-dioxin, and other halogenated hydrocarbons in vertebrates. This receptor initiates the transcription of several biotransformation enzymes, which in turn are responsible for causing severe harm to biological tissue. Here we describe the isolation and complete characterization of the first two AhR genes from the teleost fish Atlantic salmon (Salmo salar). The predicted amino acid sequences contain regions characteristic of other vertebrate AhRs including basic helix-loop-helix (bHLH) and PER-ARNT-SIM (PAS) domains but show little similarity to other vertebrate AhRs across the C-terminal half. Furthermore, they do not contain distinct Q-rich domains as found in the mammalian AhR, which is in line with previously described fish AhR genes. The salmon cDNAs encode 1106 and 1107 putative residues, respectively, approximately 50 amino acids longer than previously characterized AhR genes. Phylogenetic analyses demonstrated that the two salmon AhR sequences cluster within the AhR subfamily of the bHLH-PAS family, in a clade containing fish AhR2 genes. Although the two AhR2 forms are 92% identical at the amino acid level, the distribution of sequence differences and the presence of both forms in 30 tested individuals suggest that they are not allelic but derived from separate loci. Interestingly, they are not orthologs of the rainbow trout (Oncorhynchus mykiss) AhR2 alpha and beta genes and the new salmon loci are therefore here designated AhR2 gamma and AhR2 delta. In line with this, PCR with DNA from rainbow trout revealed a new trout AhR locus that was more similar to the two salmon genes than to the trout AhR2 alpha and beta genes, suggesting that the rainbow trout possesses at least three distinct AhR2 genes. The presence of multiple AhR genes in these species is probably a consequence of the genome duplications that occurred in the early evolution of fish and later also specifically in the salmonid lineage. Reverse transcription-PCR analyses revealed that both AhR2 gamma and AhR2 delta are transcribed in the liver, spleen and muscles of adult salmon. SN - 0378-1119 UR - https://www.unboundmedicine.com/medline/citation/12559581/Characterization_of_two_distinct_aryl_hydrocarbon_receptor__AhR2__genes_in_Atlantic_salmon__Salmo_salar__and_evidence_for_multiple_AhR2_gene_lineages_in_salmonid_fish_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0378111902011782 DB - PRIME DP - Unbound Medicine ER -