Dataset Information

Domestication and growth hormone transgenesis cause similar changes in gene expression in coho salmon (Oncorhynchus kisutch).

ABSTRACT: Domestication has been extensively used in agricultural animals to modify phenotypes such as growth rate. More recently, transgenesis of growth factor genes [primarily growth hormone (GH)] has also been explored as a rapid approach to accelerating performance of agricultural species. Growth rates of many fishes respond dramatically to GH gene transgenesis, whereas genetic engineering of domestic mammalian livestock has resulted in relatively modest gains. The most dramatic effects of GH transgenesis in fish have been seen in relatively wild strains that have undergone little or no selection for enhanced growth, whereas genetic modification of livestock necessarily has been performed in highly domesticated strains that already possess very rapid growth. Such fast-growing domesticates may be refractory to further stimulation if the same regulatory pathways are being exploited by both genetic approaches. By directly comparing gene expression in wild-type, domestic, and GH transgenic strains of coho salmon, we have found that domestication and GH transgenesis are modifying similar genetic pathways. Genes in many different physiological pathways show modified expression in domestic and GH transgenic strains relative to wild-type, but effects are strongly correlated. Genes specifically involved in growth regulation (IGF1, GHR, IGF-II, THR) are also concordantly regulated in domestic and transgenic fish, and both strains show elevated levels of circulating IGF1. Muscle expression of GH in nontransgenic strains was found to be elevated in domesticated fish relative to wild type, providing a possible mechanism for growth enhancement. These data have implications for genetic improvement of existing domesticated species and risk assessment and regulation of emerging transgenic strains.

SUBMITTER: Devlin RH

PROVIDER: S-EPMC2651260 | biostudies-literature | 2009 Mar

REPOSITORIES: biostudies-literature

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Domestication and growth hormone transgenesis cause similar changes in gene expression in coho salmon (Oncorhynchus kisutch).

Devlin Robert H RH Sakhrani Dionne D Tymchuk Wendy E WE Rise Matthew L ML Goh Benjamin B

Proceedings of the National Academy of Sciences of the United States of America 20090217 9

Domestication has been extensively used in agricultural animals to modify phenotypes such as growth rate. More recently, transgenesis of growth factor genes [primarily growth hormone (GH)] has also been explored as a rapid approach to accelerating performance of agricultural species. Growth rates of many fishes respond dramatically to GH gene transgenesis, whereas genetic engineering of domestic mammalian livestock has resulted in relatively modest gains. The most dramatic effects of GH transgen ...[more]

PMID: 19223591

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Project description:The glutathione S-transferases (GSTs) are a family of phase II detoxification enzymes which protect against chemical injury. In contrast to mammals, GST expression in fish has not been extensively characterized, especially in the context of detoxifying waterborne pollutants. In the Northwestern United States, coho salmon (Oncorhynchus kisutch) are an important species of Pacific salmon with complex life histories that can include exposure to a variety of compounds including GST substrates. In the present study we characterized the expression of coho hepatic GST to better understand the ability of coho to detoxify chemicals of environmental relevance. Western blotting of coho hepatic GST revealed the presence of multiple GST-like proteins of approximately 24-26kDa. Reverse phase HPLC subunit analysis of GSH affinity-purified hepatic GST demonstrated six major and at least two minor potential GST isoforms which were characterized by liquid chromatography electrospray ionization tandem mass spectrometry (LC/ESI MS-MS) and Fourier transform-ion cyclotron resonance (FT-ICR) MS analyses. The major hepatic coho GST isoforms consisted of a pi and a rho-class GST, whereas GSTs representing the alpha and mu classes constituted minor isoforms. Catalytic studies demonstrated that coho cytosolic GSTs were active towards the prototypical GST substrate 1-chloro-2,4-dinitrobenzene, as well as towards ethacrynic acid and nitrobutyl chloride. However, there was no observable cytosolic GST activity towards the pesticides methyl parathion or atrazine, or products of oxidative stress, such as cumene hydroperoxide and 4-hydroxynonenal. Interestingly, coho hepatic cytosolic fractions had a limited ability to bind bilirubin, reflecting a potential role in the sequestering of metabolic by-products. In summary, coho salmon exhibit a complex hepatic GST isoform expression profile consisting of several GST classes, but may have a limited a capacity to conjugate substrates of toxicological significance such as pesticides and endogenous compounds associated with cellular oxidative stress.

Project description:Wild stocks of Pacific salmon in the Northwestern United States have declined in recent years, and the major factors contributing to these losses include water pollution and loss of habitat. In salmon, sublethal chemical exposures may impact critical behaviors (such as homing, feeding, predator-avoidance) that are important for species survival. Therefore, understanding the potential for these species to biotransform organic compounds within sensitive target tissues such as liver, gills and olfactory region can help estimate or predict their susceptibility to pollutants. In this study, we used real-time quantitative polymerase chain reaction (Q-PCR), Western blotting, and catalytic assays to characterize the expression of Phase I biotransformation enzymes in coho salmon (Oncorhynchus kisutch), a sensitive species in the Pacific Northwest. Gene expression analysis using Q-PCR assays developed for coho genes revealed the presence of the predominant cytochrome P450 mRNAs (CYP1A, CYP2K1, CYP2M1, CYP3A27) in the olfactory rosettes and provided quantitative mRNA expression levels in coho liver and gills. Q-PCR analysis revealed relatively high expression of the major CYP isoforms in the liver and olfactory rosettes, which was generally confirmed by Western blotting. Extrahepatic CYP expression was generally higher in the olfactory rosettes as compared to the gills. Catalytic studies demonstrated functional CYP1A-dependent ethoxyresorufin-O-deethylase, CYP2-dependent pentoxyresorufin-O-dealkylase, CYP2K1-dependent testosterone 16beta-hydroxylase, and CYP3A27-dependent testosterone 6beta-hydroxylase activities in liver, but not at detectable levels in gills. In contrast, flavin-containing monooxygenase (FMO)-dependent thiourea S-oxidase activity was readily observed in the gills and was substantially higher than that observed in liver. Collectively, the results of this study suggest that the olfactory rosettes are important sites of extrahepatic biotransformation in coho salmon, and that tissue specific-differences in Phase I metabolism may lead to contrasting tissue-specific biotransformation capabilities in this species.

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Project description:Conservation units (CUs) are important tools for supporting the implementation of standardized management practices for exploited species. Following the adoption of the Wild Salmon Policy in Canada, CUs were defined for Pacific salmon based on characteristics related to ecotype, life history and genetic variation using microsatellite markers as indirect measures of local adaptation. Genomic data sets have the potential to improve the definition of CUs by reducing variance around estimates of population genetic parameters, thereby increasing the power to detect more subtle patterns of population genetic structure and by providing an opportunity to incorporate adaptive information more directly with the identification of variants putatively under selection. We used one of the largest genomic data sets recently published for a nonmodel species, comprising 5662 individual Coho salmon (Oncorhynchus kisutch) from 149 sampling locations and a total of 24,542 high-quality SNPs obtained using genotyping-by-sequencing and mapped to the Coho salmon reference genome to (1) evaluate the current delineation of CUs for Coho in Canada and (2) compare patterns of population structure observed using neutral and outlier loci from genotype-environment association analyses to determine whether separate CUs that capture adaptive diversity are needed. Our results reflected CU boundaries on the whole, with the majority of sampling locations managed in the same CU clustering together within genetic groups. However, additional groups that are not currently represented by CUs were also uncovered. We observed considerable overlap in the genetic clusters identified using neutral or candidate loci, indicating a general congruence in patterns of genetic variation driven by local adaptation and gene flow in this species. Consequently, we suggest that the current CU boundaries for Coho salmon are largely well-suited for meeting the Canadian Wild Salmon Policy's objective of defining biologically distinct groups, but we highlight specific areas where CU boundaries may be refined.

Dataset Information

Domestication and growth hormone transgenesis cause similar changes in gene expression in coho salmon (Oncorhynchus kisutch).

Publications

Domestication and growth hormone transgenesis cause similar changes in gene expression in coho salmon (Oncorhynchus kisutch).

Similar Datasets

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