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. Although the types of defensome genes are generally conserved in animals, there are important differences in the complement and function of specific genes between species. Teleost fish is the largest group of vertebrate species and can provide valuable insights into the evolution and functional diversity of defensome genes.
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), Atlantic cod (Gadus morhua), medaka (Oryzias latipes), Atlantic killifish (Fundulus heteroclitus) and three-spined stickleback (Gasterosteus aculeatus). Genome miningrevealed evolved differences in the number and composition of defensome genes that can have implication for how these species sense and respond to environmental pollutants. The results indicate that knowledge regarding the diversity and function of the defensome will be important for toxicological testing and risk assessment studies.