Analysis of the function of two circadian-regulated CONSTANS-LIKE genes

Authors

  • Susan Ledger,

    1. School of Biological Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand, and
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    • These authors contributed equally to the work.

  • Carl Strayer,

    1. NSF Center for Biological Timing, Department of Cell Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
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    • Present address: Department of Biology, University of Virginia, Gilmer Hall, Charlottesville, VA 22903, USA.

    • These authors contributed equally to the work.

  • Fern Ashton,

    1. School of Biological Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand, and
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  • Steve A. Kay,

    1. NSF Center for Biological Timing, Department of Cell Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
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  • Jo Putterill

    Corresponding author
    1. School of Biological Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand, and
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For correspondence (fax +64 9 373 7416; e-mail J.Putterill@auckland.ac.nz).

Summary

The Arabidopsis genes CONSTANS-LIKE 1 (COL1) and CONSTANS-LIKE 2 (COL2) are predicted to encode zinc finger proteins with ∼67% amino acid identity to the protein encoded by the flowering-time gene CONSTANS (CO). We show that the circadian clock regulates expression of COL1 and COL2 with a peak in transcript levels around dawn. We analyzed transgenic plants misexpressing COL1, COL2 and CO. Unlike CO, altered expression of COL1 and COL2 in transgenic plants had little effect on flowering time. However, analysis of circadian phenotypes in the transgenic plants showed that over-expression of COL1 can shorten the period of two distinct circadian rhythms. Experiments with the highest COL1 over-expressing line indicate that its circadian defects are fluence rate-dependent, suggesting an effect on a light input pathway(s).

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