Transcriptional Effects of Dietary Exposure of Oil-Contaminated Calanus finmarchicus in Atlantic Herring (Clupea harengus)

Abstract

Suppression subtractive hybridization (SSH) cDNA library construction and characterization was used to identify differentially regulated transcripts from oil exposure in liver of male Atlantic herring (Clupea harengus) fed a diet containing 900 mg crude oil/kg for 2 mo. In total, 439 expressed sequence tags (EST) were sequenced, 223 from the forward subtracted library (enriched for genes putatively upregulated by oil exposure) and 216 from the reverse subtracted library (enriched for genes putatively downregulated by oil exposure). Follow-up reverse-transcription (RT) quantitative polymerase chain reaction (qPCR) analyses of gene transcription were conducted on additional herring exposed to food containing 9 (low), 90 (medium), and 900 (high) mg crude oil/kg feed for 2 mo. Chronic exposure of Atlantic herring to an oil-contaminated diet mediated upregulation of transcripts encoding antifreeze proteins, proteins in the classical complement pathway (innate immunity), and iron-metabolism proteins. Gene ontology (GO) analysis showed that “cellular response to stress,” “regulation to biological quality,” “response to abiotic stimuli,” and “temperature homeostasis” were the most affected go at the biological processes level, and “carbohydrate binding,” “water binding,” and “ion binding” at the molecular function level. Of the genes examined with RT-qPCR, CYP1A, antifreeze protein, retinol binding protein 1, deleted in malignant brain tumor 1, and ovary-specific C1q-like factor demonstrated a significant upregulation. Myeloid protein 1, microfibrillar-associated protein 4, WAP65, and pentraxin were downregulated in liver of fish from the high exposure group. In conclusion, this study suggests that 2 mo of oil exposure affected genes encoding proteins involved in temperature homeostasis and possible membrane stability in addition to immune-responsive proteins in Atlantic herring.

Acknowledgments

The authors thank EcoArray, Inc., for performing SSH library construction and Sanger sequencing. Statoil-Hydro is thanked for providing the oil from the Åsgard A platform. We thank Tor Andreas Samuelsen, NOFIMA, Bergen, for making the feed used in the experiment and colleagues from IMR, Anders Thorsen, Stian Morken, Ivar Helge Matre, Marita Larsen, Theresa Smith-Jahnsen, Penny Lee Liebig, and Anders Fuglevik, for helping with the sampling of the herring. We also thank Hui-shan Tung, NIFES, for analytical help. This project was funded by the Norwegian Research Council, project 178015.