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Structure and evolution of the Teleost extraretinal rod‐like opsin ( errlo ) and ocular rod opsin ( rho ) genes: Is teleost rho a retrogene?
Author(s) -
Bellingham James,
Tarttelin Emma E.,
Foster Russell G.,
Wells Dominic J.
Publication year - 2003
Publication title -
journal of experimental zoology part b: molecular and developmental evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.823
H-Index - 63
eISSN - 1552-5015
pISSN - 1552-5007
DOI - 10.1002/jez.b.18
Subject(s) - opsin , biology , intron , exon , rhodopsin , gene , synteny , gene duplication , takifugu rubripes , lamprey , genetics , actinopterygii , anatomy , genome , fish <actinopterygii> , retinal , biochemistry , fishery
In Teleost fish examined to date the ocular rod opsin gene, rho , is intronless, unlike the rod opsin genes of other vertebrate classes which possess a five exon/four intron structure. We have examined in silico the structure of rho (which is expressed uniquely in the retina) and the closely related extraretinal rod‐like opsin (exo‐rhodopsin) gene, errlo (which is expressed uniquely in the pineal), in the puffer‐fish, Fugu rubripes (Takifugu rubripes) . Whilst the ocular rho is intronless in common with other Teleosts, the pineal errlo has the five exon/four intron structure common to the rod opsin gene of other vertebrates. A comparison of the sequence surrounding the errlo and rho loci indicates that the errlo locus is syntenic with RHO , the human rod opsin gene, rather than rho . We suggest that the intronless rho may have arisen through an ancient retrotransposition of a mature mRNA originating from errlo . This duplication event has occurred early in the evolution of the Actinopterygii (ray‐finned fish) since the rho of the primitive Actinopterygians such as sturgeon, bowfin, and gar is also intronless. Since it appears that the intron containing errlo is the ancestral opsin gene that gave rise to the intronless rho in the Teleostei, errlo is therefore the true orthologue of the rod opsin gene in other vertebrate classes. We suggest that loss of expression of errlo in the retina could be related to the metabolic and physiological advantages, such as a reduction in splicing events during RNA processing, that may be conferred through possession of an additional, intronless rod opsin gene in the form of rho. J. Exp. Zool. (Mol. Dev. Evol.) 297B: 1–10, 2003. © 2003 Wiley‐Liss, Inc.