The chemical defensome of five model teleost fish

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Eide, M., Zhang, X., Karlsen, O. A., Goldstone, J., Stegeman, J., Jonassen, I., & Goksoyr, A. The chemical defensome of five model teleost fish. Scientific Reports, 11(1), (2021): 10546, https://doi.org/10.1038/s41598-021-89948-0.How an organism copes with chemicals is largely determined by the genes and proteins that collectively function to defend against, detoxify and eliminate chemical stressors. This integrative network includes receptors and transcription factors, biotransformation enzymes, transporters, antioxidants, and metal- and heat-responsive genes, and is collectively known as the chemical defensome. Teleost fish is the largest group of vertebrate species and can provide valuable insights into the evolution and functional diversity of defensome genes. We have previously shown that the xenosensing pregnane x receptor (pxr, nr1i2) is lost in many teleost species, including Atlantic cod (Gadus morhua) and three-spined stickleback (Gasterosteus aculeatus), but it is not known if compensatory mechanisms or signaling pathways have evolved in its absence. In this study, we compared the genes comprising the chemical defensome of five fish species that span the teleosteii evolutionary branch often used as model species in toxicological studies and environmental monitoring programs: zebrafish (Danio rerio), medaka (Oryzias latipes), Atlantic killifish (Fundulus heteroclitus), Atlantic cod, and three-spined stickleback. Genome mining revealed evolved differences in the number and composition of defensome genes that can have implication for how these species sense and respond to environmental pollutants, but we did not observe any candidates of compensatory mechanisms or pathways in cod and stickleback in the absence of pxr. The results indicate that knowledge regarding the diversity and function of the defensome will be important for toxicological testing and risk assessment studies.The work was supported by the Norwegian Research Council as part of the iCOD and iCOD 2.0 projects (Grant Nos. 192441/I30 and 244654/E40), and the dCod 1.0 project (Grant No. 248840) which is part of Centre for Digital Life Norway. The American collaborators were funded by the National Institute of Health (USA) NIH P42ES007381 (Boston University Superfund Center to JJS and JVG), NIH R21HD073805 (JVG) and NHI R01ES029917 (JVG) grants. The Ocean Outlook exchange program funded the trans-Atlantic collaboration