In the last decade, the view of circadian oscillators has expanded from transcriptional feedback to incorporate post-transcriptional, post-translational, metabolic processes and ionic signalling. In plants and animals, there are circadian oscillations in the concentration of cytosolic free Ca2+ ([Ca2+]cyt), though their purpose has not been fully characterized. We investigated whether circadian oscillations of [Ca2+]cyt regulate the circadian oscillator of Arabidopsis thaliana. We report that in Arabidopsis, [Ca2+]cyt circadian oscillations can regulate circadian clock function through the Ca2+-dependent action of CALMODULIN-LIKE24 (CML24). Genetic analyses demonstrate a linkage between CML24 and the circadian oscillator, through pathways involving the circadian oscillator gene TIMING OF CAB2 EXPRESSION1 (TOC1).

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Supported by BBSRC UK research grants BBSRC BB/D010381/1 (A.N.D.), BB/D017904/1 (F.R.) BB/M00113X/1 (H.J.H.) awarded to (A.A.R.W.), Research Studentship (K.H.) and BBSRC Industrial Case (T.H.). A Swiss Science Foundation Award (PBZHP3-123289) and the Isaac Newton Trust Cambridge (M.C.M.R. and S.A.), the National Science Foundation under Grant No. MCB 0817976 (Y-C.T. and J.B.), a Royal Society Grant RG081257 and Corpus Christi College, Cambridge Junior Research Fellowship (M.J.G.), a Cordenadoria de Apoio ao Ensino Superior Brazil studentship (C.T.H.), IEF Marie Curie (Project No. 272186) (M.C.M.R.), a Broodbank Fellowship (M.C.M.R.), a Malaysian Government Studentship (N.I.M-H.). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. The authors are very grateful to the unnamed laboratories who provided (un)published material for the screen.

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Author notes

  1. These authors contributed equally to this work: María Carmen Martí Ruiz, Katharine E. Hubbard, Michael J. Gardner.


  1. Department of Plant Sciences, University of Cambridge, Cambridge, UK

    • María Carmen Martí Ruiz
    • , Katharine E. Hubbard
    • , Michael J. Gardner
    • , Hyun Ju Jung
    • , Sylvain Aubry
    • , Carlos T. Hotta
    • , Nur Izzati Mohd-Noh
    • , Fiona C. Robertson
    • , Timothy J. Hearn
    • , Antony N. Dodd
    • , Julia M. Davies
    •  & Alex A. R. Webb
  2. School of Biological, Biomedical and Environmental Sciences, University of Hull, Hull, UK

    • Katharine E. Hubbard
  3. Department for Plant and Microbial Biology, University of Zürich, Zürich, Switzerland

    • Sylvain Aubry
  4. Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, SP, Brazil

    • Carlos T. Hotta
  5. Department of Bioscience and Health Science, Faculty of Bioscience and Medical Engineering, Universiti Teknologi Malaysia, Skudai, Johor, Malaysia

    • Nur Izzati Mohd-Noh
  6. Department of Biochemistry, University of Zimbabwe, Harare, Zimbabwe

    • Fiona C. Robertson
  7. Biochemistry and Cell Biology, Rice University, Houston, TX, USA

    • Yu-Chang Tsai
    •  & Janet Braam
  8. School of Biological Sciences, Bristol Life Sciences Building, University of Bristol, Bristol, UK

    • Antony N. Dodd
  9. Bayer CropScience NV Innovation Center, Trait Discovery, Gent, Belgium

    • Matthew Hannah
  10. School of Life Sciences, University of Warwick, Coventry, UK

    • Isabelle A. Carré


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M.C.M.R., K.E.H., M.J.G., S.A., C.T.H., N.I.M-N., F.C.R., T.J.H., H.J.J., and A.N.D. performed the experiments and analysed the data. The effects of Ca2+ on circadian gene expression experiments were designed by M.J.G. and M.C.M.R. and performed by them with K.E.H., S.A., C.T.H., F.C.R. and A.N.D. Reverse genetic screening was performed by K.E.H. Analysis of cml23/cml24 mutants was performed by M.C.M.R., K.E.H., N.I.M-N., T.J.H. and H.J.J. Y-C.T. provided lines before publication and advice. M.C.M.R., K.E.H. and A.A.R.W. wrote the manuscript. M.H., I.A.C., J.M.D., J.B. and A.A.R.W. managed the project, advised on interpretation and obtained the funding.

Competing interests

The authors declare no competing interests.

Corresponding author

Correspondence to Alex A. R. Webb.

Supplementary information

  1. Supplementary Information

    Supplementary Table 1, Supplementary Methods, Supplementary Statistical Parameters, Supplementary References and Supplementary Figures 1–6

  2. Reporting Summary

  3. Supplementary Table 2

    Reverse genetic screen of Ca2+ -signalling related mutants.

  4. Supplementary Table 3

    Circadian period estimates of leaf movement for characterization of the genetic relationship between CML23/CML24 and the clock genes. Relative to Figure 5, 6 and Supplementary Figure 4.

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