The molecular evolution of avian ultraviolet- and violet-sensitive visual pigments

Mol Biol Evol. 2007 Aug;24(8):1843-52. doi: 10.1093/molbev/msm109. Epub 2007 Jun 7.

Abstract

The shortwave-sensitive SWS1 class of vertebrate visual pigments range in lambda(max) from the violet (385-445 nm) to the ultraviolet (UV) (365-355 nm), with UV-sensitivity almost certainly ancestral. In birds, however, the UV-sensitive pigments present in a number of species have evolved secondarily from an avian violet-sensitive (VS) pigment. All avian VS pigments expressed in vitro to date encode Ser86 whereas Phe86 is present in all non-avian ultraviolet sensitive (UVS) pigments. In this paper, we show by site directed mutagenesis of avian VS pigments that Ser86 is required in an avian VS pigment to maintain violet-sensitivity and therefore underlies the evolution of avian VS pigments. The major mechanism for the evolution of avian UVS pigments from an ancestral avian VS pigment is undoubtedly a Ser90Cys substitution. However, Phe86, as found in the Blue-crowned trogon, will also short-wave shift the pigeon VS pigment into the UV whereas Ala86 and Cys86 which are also found in natural avian pigments do not generate short-wave shifts when substituted into the pigeon pigment. From available data on avian SWS1 pigments, it would appear that UVS pigments have evolved on at least 5 separate occasions and utilize 2 different mechanisms for the short-wave shift.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Substitution
  • Animals
  • Birds / genetics*
  • Color
  • Color Perception
  • DNA, Complementary / genetics
  • Evolution, Molecular*
  • Models, Molecular
  • Mutagenesis, Site-Directed
  • Phylogeny
  • Retinal Pigments / genetics*
  • Retinal Pigments / metabolism
  • Rod Opsins / chemistry*
  • Ultraviolet Rays*

Substances

  • DNA, Complementary
  • Retinal Pigments
  • Rod Opsins