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Journal of Experimental Biology partnership with Dryad

SUMMARY

A long-standing concept in vision science has held that a single photoreceptor expresses a single type of opsin, the protein component of visual pigment. However, the number of examples in the literature of photoreceptors from vertebrates and invertebrates that break this rule is increasing. Here, we describe a newly discovered Limulus opsin, Limulus opsin5, which is significantly different from previously characterized Limulus opsins, opsins1 and 2. We show that opsin5 is co-expressed with opsins1 and 2 in Limulus lateral and ventral eye photoreceptors and provide the first evidence that the expression of co-expressed opsins can be differentially regulated. We show that the relative levels of opsin5 and opsin1 and 2 in the rhabdom change with a diurnal rhythm and that their relative levels are also influenced by the animal's central circadian clock. An analysis of the sequence of opsin5 suggests it is sensitive to visible light (400–700 nm) but that its spectral properties may be different from that of opsins1 and 2. Changes in the relative levels of these opsins may underlie some of the dramatic day–night changes in Limulus photoreceptor function and may produce a diurnal change in their spectral sensitivity.

FOOTNOTES

  • * Present address: Nuffield Laboratory of Ophthalmology, Oxford University, Levels 5 and 6, West Wing, John Radcliffe Hospital, Headington, OX3 9DU, UK

  • This work was supported by the following grants: the NSF – IOS-0517272 to B.-A. Battelle, REU-0648969 to the Whitney Laboratory, and IOS-0721608 to T. W. Cronin; the NIH – EY08571 to the Department of Ophthalmology, University of Florida School of Medicine, and S10RR14638 to the Whitney Laboratory; Research to Prevent Blindness Inc. – to the Department of Ophthalmology, University of Florida School of Medicine; and the Air Force Office of Scientific Research – FA9550-09-1-0149 to T. W. Cronin. A.L., R.G. and E.G. were REU research trainees. Deposited in PMC for release after 12 months.

  • Supplementary material available online at http://jeb.biologists.org/lookup/suppl/doi:10.1242/jeb.043869/-/DC1

  • LIST OF ABBREVIATIONS

    bp
    base pair
    BP
    bootstrap proportion
    CNS
    central nervous system
    EST
    expressed sequence tag
    ir
    immunoreactivity
    LDS
    light-driven shedding
    LE
    lateral eye
    mAbOps5
    mouse monoclonal antibody directed against the C-terminus of opsin5
    ME
    median eye
    Ops
    opsin
    OCM
    organ culture medium
    pAbOps1
    rabbit polyclonal antibody directed against the C-terminus of opsin1
    PAGE
    polyacrylamide gel electrophoresis
    PCR
    polymerase chain reaction
    RACE
    rapid amplification of cDNA ends
    ROI
    region of interest
    TRS
    transient rhabdom shedding
    VE
    ventral eye
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