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First published online October 29, 2004; 10.1104/pp.104.042523 Plant Physiology 136:3751-3761 (2004) © 2004 American Society of Plant Biologists Circadian Rhythms of Ethylene Emission in Arabidopsis1,[w]Unit Plant Hormone Signaling and Bio-Imaging, Department of Molecular Genetics, University of Ghent, Belgium (F.V., D.V.D.S.); Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, England, United Kingdom (S.C.T., M.J.D.D., A.J.M.); Life Science Trace Gas Facility, Department of Molecular and Laser Physics, University of Nijmegen, The Netherlands (L.J.J.L., F.J.M.H.); and Department of Molecular, Cell and Developmental Biology, University of California, Los Angeles, California 90095–1606 (Z.-Y.W., E.M.T.)
Ethylene controls multiple physiological processes in plants, including cell elongation. Consequently, ethylene synthesis is regulated by internal and external signals. We show that a light-entrained circadian clock regulates ethylene release from unstressed, wild-type Arabidopsis (Arabidopsis thaliana) seedlings, with a peak in the mid-subjective day. The circadian clock drives the expression of multiple ACC SYNTHASE genes, resulting in peak RNA levels at the phase of maximal ethylene synthesis. Ethylene production levels are tightly correlated with ACC SYNTHASE 8 steady-state transcript levels. The expression of this gene is controlled by light, by the circadian clock, and by negative feedback regulation through ethylene signaling. In addition, ethylene production is controlled by the TIMING OF CAB EXPRESSION 1 and CIRCADIAN CLOCK ASSOCIATED 1 genes, which are critical for all circadian rhythms yet tested in Arabidopsis. Mutation of ethylene signaling pathways did not alter the phase or period of circadian rhythms. Mutants with altered ethylene production or signaling also retained normal rhythmicity of leaf movement. We conclude that circadian rhythms of ethylene production are not critical for rhythmic growth.
1 This work was supported by a Biotechnology and Biological Science Research Council (graduate studentship to S.C.T.), by the Fund for Scientific Research (Flanders; grant nos. G.0281.98, WO.004.99, and G.0345.02 to D.V.D.S.), by the European Community Training and Mobility of Researchers Programme, and by the Gatsby Charitable Foundation, the Royal Society, and the Biotechnology and Biological Science Research Council (grants to A.J.M.). 2 These authors contributed equally to the paper. 3 Present address: Institute of Grassland and Environmental Research, Aberystwyth, Ceredigion, SY23 3EB, UK. 4 Present address: Carnegie Institution, Department of Plant Biology, 260 Panama Street, Stanford, CA 94305. [w] The online version of this article contains Web-only data. Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/doi/10.1104/pp.104.042523. * Corresponding author; e-mail Dominique.VanDerStraeten{at}ugent.be; fax 32–9–264–5333. Received March 18, 2004; returned for revision July 29, 2004; accepted August 13, 2004. This article has been cited by other articles:
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