A novel rod-like opsin isolated from the extra-retinal photoreceptors of teleost fish

We have isolated a novel opsin from the pineal complex of Atlantic salmon ( Salmo salar) and from the brain of the puffer fish (Figu rubripes). These e xtra-retinal opsins share approximately 74% identity at the nucleotide and amino acid level with rod-opsins from the retina of these species. By PCR, we hare determined that the novel rod-like opsin is not expressed in the sa lmon retina, and the retinal rod-opsin is not expressed in the salmon pinea l, Phylogenetic analysis suggests that the rodlike opsins arose from a gene duplication event approximately 205 million years ago, a time of considera ble adaptive radiation of the bony fish. In,view of the large differences i n the coding sequences of the pineal/brain rod-like opsins, their extra-ret inal sites of expression, and phylogenetic position,ce have termed these no vel opsins 'extra-retinal rod-like opsins' (ERrod-like opsins). We speculat e that the differences between retinal rodopsins and ERrod-like opsins have arisen from their differing photosensory roles and/or genetic drift after the gene duplication event in the Triassic. (C) 2000 Federation of European Biochemical Societies.