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Evolution of visual pigments and related molecules
F Tokunaga1, O Hisatomi, T Satoh
1Department of Earth and Space Science, Graduate School of Science, Osaka University, Japan.
Novartis Foundation Symposium
|December 30, 1999
Summary
Vertebrate visual pigments, including rhodopsin (Rh), evolved along five gene lines. Rods and cones possess homologous phototransduction molecules, differing in amino acid sequences for distinct light responses.
Area of Science:
- Molecular Biology
- Evolutionary Biology
- Vision Science
Background:
- Vertebrate visual pigments are crucial for light detection.
- Phylogenetic analysis reveals evolutionary relationships among visual pigment genes.
Purpose of the Study:
- To classify vertebrate visual pigments based on molecular phylogeny.
- To investigate the evolution of phototransduction molecules in rods and cones.
Main Methods:
- Constructed molecular phylogenetic trees using amino acid sequence identity of visual pigments.
- Cloned cDNAs for phototransduction system molecules (phosphodiesterase, opsin kinase, arrestin).
- Generated phylogenetic trees for these molecules.
Main Results:
- Visual pigments classified into five groups (L, ML, MS, S, Rh) with distinct evolutionary lines.
- Identified specific pigment groups in goldfish, medaka, and frogs.
- Phototransduction molecules segregated into rod- and cone-specific groups.
- Homologous molecules in rods and cones exhibit different amino acid sequences.
Conclusions:
- Phylogenetic analysis provides a framework for understanding visual pigment evolution.
- Distinct molecular compositions in rods and cones underlie their differential light responses.