Metazoan opsin evolution reveals a simple route to animal vision

Feuda, Roberto and Hamilton, Sinead C. and McInerney, James O. and Pisani, Davide (2012) Metazoan opsin evolution reveals a simple route to animal vision. Proceedings of the National Academy of Sciences . ISSN 1091-6490

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All known visual pigments in Neuralia (Cnidaria, Ctenophora, and Bilateria) are composed of an opsin (a seven-transmembrane G protein-coupled receptor), and a light-sensitive chromophore, generally retinal. Accordingly, opsins play a key role in vision. There is no agreement on the relationships of the neuralian opsin subfamilies, and clarifying their phylogeny is key to elucidating the origin of this protein family and of vision. We used improved methods and data to resolve the opsin phylogeny and explain the evolution of animal vision. We found that the Placozoa have opsins, and that the opsins share a common ancestor with the melatonin receptors. Further to this, we found that all known neuralian opsins can be classified into the same three subfamilies into which the bilaterian opsins are classified: the ciliary (C), rhabdomeric (R), and go-coupled plus retinochrome, retinal G protein-coupled receptor (Go/RGR) opsins. Our results entail a simple scenario of opsin evolution. The first opsin originated from the duplication of the common ancestor of the melatonin and opsin genes in a eumetazoan (Placozoa plus Neuralia) ancestor, and an inference of its amino acid sequence suggests that this protein might not have been light-sensitive. Two more gene duplications in the ancestral neuralian lineage resulted in the origin of the R, C, and Go/RGR opsins. Accordingly, the first animal with at least a C, an R, and a Go/RGR opsin was a neuralian progenitor.

Item Type: Article
Keywords: ancestral character state reconstruction; Metazoa; protein evolution;
Academic Unit: Faculty of Science and Engineering > Biology
Item ID: 4519
Depositing User: Dr. James McInerney
Date Deposited: 30 Sep 2013 13:46
Journal or Publication Title: Proceedings of the National Academy of Sciences
Publisher: National Academy of Sciences
Refereed: Yes

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