Spectral tuning in vertebrate short wavelength-sensitive 1 (SWS1) visual pigments: Can wavelength sensitivity be inferred from sequence data?

Authors

  • Frances E. Hauser,

    1. Department of Ecology & Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada
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  • Ilke van Hazel,

    1. Department of Ecology & Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada
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  • Belinda S. W. Chang

    Corresponding author
    1. Department of Ecology & Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada
    2. Department of Cell & Systems Biology, University of Toronto, Toronto, Ontario, Canada
    3. Centre for the Analysis of Genome Evolution & Function, University of Toronto, Toronto, Ontario, Canada
    • Correspondence to: Belinda S. W. Chang, Department of Ecology & Evolutionary Biology, University of Toronto, 25 Harbord Street, Toronto, ON M5S 3G5, Canada.

      E-mail: belinda.chang@utoronto.ca

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  • Frances E. Hauser and Ilke van Hazel contributed equally to this study.

ABSTRACT

The molecular mechanisms underlying the enormous diversity of visual pigment wavelength sensitivities found in nature have been the focus of many molecular evolutionary studies, with particular attention to the short wavelength-sensitive 1 (SWS1) visual pigments that mediate vision in the ultraviolet to violet range of the electromagnetic spectrum. Over a decade of study has revealed that the remarkable extension of SWS1 absorption maxima (λmax) into the ultraviolet occurs through a deprotonation of the Schiff base linkage of the retinal chromophore, a mechanism unique to this visual pigment type. In studies of visual ecology, there has been mounting interest in inferring visual sensitivity at short wavelengths, given the importance of UV signaling in courtship displays and other behaviors. Since experimentally determining spectral sensitivities can be both challenging and time-consuming, alternative strategies such as estimating λmax based on amino acids at sites known to affect spectral tuning are becoming increasingly common. However, these estimates should be made with knowledge of the limitations inherent in these approaches. Here, we provide an overview of the current literature on SWS1 site-directed mutagenesis spectral tuning studies, and discuss methodological caveats specific to the SWS1-type pigments. We focus particular attention on contrasting avian and mammalian SWS1 spectral tuning mechanisms, which are the best studied among vertebrates. We find that avian SWS1 visual pigment spectral tuning mechanisms are fairly consistent, and therefore more predictable in terms of wavelength absorption maxima, whereas mammalian pigments are not well suited to predictions of λmax from sequence data alone. J. Exp. Zool. (Mol. Dev. Evol.) 322B: 529–539, 2014. © 2014 Wiley Periodicals, Inc.

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