Molecular cloning of fresh water and deep‐sea rod opsin genes from Japanese eel Anguilla japonica and expressional analyses during sexual maturation¹

Abstract

We have determined the complete cDNA sequences of fresh water rod opsin gene (fwo) and deep-sea rod opsin gene (dso) from Japanese eel Anguilla japonica. The cDNA clones of fwo and dso consisted of 1437 and 1497 nucleotides, respectively. The predicted opsins of both genes consisted of 352 amino acid residues. Southern blot and PCR analyses of genomic DNA indicated that the Japanese eel genome contains only one fwo and one dso and they are intronless. Quantitative RT-PCR analyses revealed that the expression of fwo decreases with sexual maturation while that of dso increases.z 2000 Federation of European Biochemical Societies.

Temporal and spatial changes in the expression pattern of multiple red and green subtype opsin genes during zebrafish development

“…Besides primate M/LWS opsin genes, occurrence of opsin subtypes is characteristic of fish, and the resulting variations of opsin repertoire among species should be intricately involved in the evolutionary adaptations of fish to diverse M. Takechi and S. Kawamura Red and green opsins in zebrafish retina aquatic photo-environments. To date, however, the only known example of differential usage of opsin subtypes in a given fish species has been the ontogenic shift of rod opsin expression between fresh-water and deep-sea subtypes in eels (Archer et al, 1995;Zhang et al, 2000). The present study provides the first evidence that subtype differentiation of cone opsins in fish contributes not only to temporal but also to regional differentiation of the retina with distinct spectral sensitivities.…”

“…However, documented variations of spectral sensitivities of visual pigments among fish species are mostly attributed to chromophore type A1 or A2 (Bowmaker, 1995), evolutionary changes of opsin amino acid sequences (Yokoyama, 2000), opsin types expressed in the retina (Carleton and Kocher, 2001), or developmental changes of expressed opsin types in a photoreceptor cell (Cheng and Novales Flamarique, 2004). Only two cases of differential usage of opsin subtypes have been reported; RH1 opsins of eels at different ontogenic stages (fresh-water and deep-sea types; Archer et al, 1995;Zhang et al, 2000) and SWS2 opsins of cichlids where different species inhabiting different niches expressed different subtypes (SWS2-A and SWS2-B; Carleton and Kocher, 2001). Little is known how opsin subtypes are distributed phylogenetically and ecologically among fish species and how differently they are expressed in the retina spatially and temporally in a given species.…”

A second visual rhodopsin gene,rh1-2, is expressed in zebrafish photoreceptors and found in other ray-finned fishes

“…The first example is from eels, which express the rh1fwo gene with the 11-cis 3,4-dehydroretinal (A2) chromophore in the early stages of life, where a red-shifted rhodopsin is thought to provide an advantage in the more long wavelength-shifted spectral environment of freshwater (Bridges, 1972;Loew, 1995). During maturation, eels migrate to a marine environment, with a more restricted and blue-shifted light spectrum, coupled with expression of a blue-shifted rh1dso gene, regenerated with 11-cis retinal (A1) chromophore (Hope et al, 1998;Zhang et al, 2000). This switch of both opsin and chromophore is a clear example of an adjustment of the visual system as a result of a change in photic environment.…”

“…Several eel species have two rhodopsins, one freshwater (rh1fwo) and one marine (rh1dso), and expression shifts from the former to the latter following migration during maturation (Beatty, 1975;Hope et al, 1998;Zhang et al, 2000;Zhang et al, 2002). The short-fin pearleye (Scopelarchus analis), a deep-sea teleost, also expresses an additional rh1 gene, rh1b, in the accessory retina of adult fish after descending to greater ocean depths (Pointer et al, 2007).…”

Remodeling of the Cone Photoreceptor Mosaic during Metamorphosis of Flounder <i>(Pseudopleuronectes americanus)</i>

“…Because vision can be affected by photoreceptor arrangement and spectral sensitivities, remodeling these features might improve the match between visual function and habitat, as described extensively in a variety of teleost fish species. Teleost retinal remodeling includes several possible developmental changes: (1) new photoreceptor classes may be added by new cell addition or by changes in existing cone morphology, opsin chromophore, or opsin subtype Archer et al, 1995;Hope et al, 1998;Shand et al, 1999Shand et al, , 2002Novales Flamarique, 2000;Zhang et al, 2000;Haacke et al, 2001;Chinen et al, 2003;Cheng and Novales Flamarique, 2004;Mader and Cameron, 2004;Takechi and Kawamura, 2005]; (2) cell classes may be lost by cell death [Bowmaker and Kunz, 1987;Beaudet et al, 1993;Novales Flamarique and Hawryshyn, 1996;Novales Flamarique, 2000;Deutschlander et al, 2001;Allison et al, 2003], or (3) cells might move in relation to one another to form different arrangements Shand et al, 1999;Haacke et al, 2001;Helvik et al, 2001]. In the winter flounder, Pseudopleuronectes americanus , photoreceptors change the peak wavelength sensitivity and physical arrangement when larvae settle into deeper water, providing an excellent model for examining the relationship between photoreceptor cell birth, opsin expression, and physical position.…”