The molecular basis for UV vision in birds: spectral characteristics, cDNA sequence and retinal localization of the UV-sensitive visual pigment of the budgerigar (Melopsittacus undulatus)

Biochem J. 1998 Feb 15;330 ( Pt 1)(Pt 1):541-7. doi: 10.1042/bj3300541.


Microspectrophotometric (msp) studies have shown that the colour-vision system of many bird species is based on four pigments with absorption peaks in the red, green, blue and UV regions of the spectrum. The existence of a fourth pigment (UV) is the major difference between the trichromacy of humans and the tetrachromacy of such birds, and recent studies have shown that it may play a determining role in such diverse aspects of behaviour as mate selection and detection of food. Avian visual pigments are composed of an opsin protein covalently bound via a Schiff-base linkage to the chromophore 11-cis-retinal. Here we report the cDNA sequence of a UV opsin isolated from an avian species, Melopsittacus undulatus (budgerigar or small parakeet). This sequence has been expressed using the recombinant baculovirus system; the pigment generated from the expressed protein on addition of 11-cis-retinal yielded an absorption spectrum typical of a UV photopigment, with lambdamax 365+/-3 nm. This is the first UV opsin from an avian species to be sequenced and expressed in a heterologous system. In situ hybridization of this sequence to budgerigar retinas selectively labelled a sub-set of UV cones, representing approx. 9% of the total cone population, that are distributed in a semi-regular pattern across the entire retina.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Cloning, Molecular
  • DNA, Complementary / genetics
  • Genes
  • In Situ Hybridization
  • Membrane Proteins / chemistry
  • Molecular Sequence Data
  • Parakeets / physiology*
  • Phylogeny
  • Recombinant Proteins
  • Retinal Cone Photoreceptor Cells / physiology*
  • Rod Opsins / physiology*
  • Spectrum Analysis
  • Ultraviolet Rays
  • Vision, Ocular / physiology*


  • DNA, Complementary
  • Membrane Proteins
  • Recombinant Proteins
  • Rod Opsins

Associated data

  • GENBANK/Y11787