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Science 19 December 2008:
Vol. 322. no. 5909, pp. 1832 - 1835
DOI: 10.1126/science.1161403

Reports

The Circadian Clock in Arabidopsis Roots Is a Simplified Slave Version of the Clock in Shoots

Allan B. James,1 José A. Monreal,1 Gillian A. Nimmo,1 Ciarán L. Kelly,1 Pawel Herzyk,2,3 Gareth I. Jenkins,1 Hugh G. Nimmo1*

The circadian oscillator in eukaryotes consists of several interlocking feedback loops through which the expression of clock genes is controlled. It is generally assumed that all plant cells contain essentially identical and cell-autonomous multiloop clocks. Here, we show that the circadian clock in the roots of mature Arabidopsis plants differs markedly from that in the shoots and that the root clock is synchronized by a photosynthesis-related signal from the shoot. Two of the feedback loops of the plant circadian clock are disengaged in roots, because two key clock components, the transcription factors CCA1 and LHY, are able to inhibit gene expression in shoots but not in roots. Thus, the plant clock is organ-specific but not organ-autonomous.

1 Division of Molecular and Cellular Biology, Faculty of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK.
2 Division of Integrated Biology, Faculty of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK.
3 The Sir Henry Wellcome Functional Genomics Facility, Faculty of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK.

* To whom correspondence should be addressed. E-mail: h.g.nimmo{at}bio.gla.ac.uk

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Posttranslational Regulation of CIRCADIAN CLOCK ASSOCIATED1 in the Circadian Oscillator of Arabidopsis.
E. Yakir, D. Hilman, I. Kron, M. Hassidim, N. Melamed-Book, and R. M. Green (2009)
Plant Physiology 150, 844-857
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Science. ISSN 0036-8075 (print), 1095-9203 (online)