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First published online March 23, 2007; 10.1104/pp.107.096206 Plant Physiology 144:391-401 (2007) © 2007 American Society of Plant Biologists ELF4 Is Required for Oscillatory Properties of the Circadian Clock1,[W]Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, United Kingdom (H.G.M.); Max Planck Institute for Plant Breeding Research, D–50829 Cologne, Germany (E.K., S.J.D.); School of Biological Sciences, University of Liverpool, Liverpool L69 7ZB, United Kingdom (A.H.); Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706 (M.R.D., R.M.A.); Institute of Plant Biology, Biological Research Centre of the Hungarian Academy of Sciences, H–6726 Szeged, Hungary (P.G., F.N.); and Institute of Molecular Plant Sciences, University of Edinburgh, Edinburgh EH9 3JH, United Kingdom (A.J.M.)
Circadian clocks are required to coordinate metabolism and physiology with daily changes in the environment. Such clocks have several distinctive features, including a free-running rhythm of approximately 24 h and the ability to entrain to both light or temperature cycles (zeitgebers). We have previously characterized the EARLY FLOWERING4 (ELF4) locus of Arabidopsis (Arabidopsis thaliana) as being important for robust rhythms. Here, it is shown that ELF4 is necessary for at least two core clock functions: entrainment to an environmental cycle and rhythm sustainability under constant conditions. We show that elf4 demonstrates clock input defects in light responsiveness and in circadian gating. Rhythmicity in elf4 could be driven by an environmental cycle, but an increased sensitivity to light means the circadian system of elf4 plants does not entrain normally. Expression of putative core clock genes and outputs were characterized in various ELF4 backgrounds to establish the molecular network of action. ELF4 was found to be intimately associated with the CIRCADIAN CLOCK-ASSOCIATED1 (CCA1)/LONG ELONGATED HYPOCOTYL (LHY)-TIMING OF CAB EXPRESSION1 (TOC1) feedback loop because, under free run, ELF4 is required to regulate the expression of CCA1 and TOC1 and, further, elf4 is locked in the evening phase of this feedback loop. ELF4, therefore, can be considered a component of the central CCA1/LHY-TOC1 feedback loop in the plant circadian clock.
1 This work was supported by the Max Planck Society and the Life Sciences Research Foundation (S.J.D. group) and by the Biotechnology and Biological Sciences Research Council (A.J.M. group; award no. G10325) and the Human Frontier Science Program Organization (award no. RG0299/1999–M). E.K. was supported by a Max-Planck-Gesellschaft fellowship within the International Max Planck Research School program. Work in R.M.A.'s laboratory was supported by the College of Agricultural and Life Sciences and the Graduate School of the University of Wisconsin and by the National Science Foundation (grant no. 0209786). H.M.W. is a Royal Society University Research Fellow. 2 These authors contributed equally to the article. The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Seth J. Davis (davis{at}mpiz-koeln.mpg.de). [W] The online version of this article contains Web-only data. www.plantphysiol.org/cgi/doi/10.1104/pp.107.096206 * Corresponding author; e-mail davis{at}mpiz-koeln.mpg.de; fax 49–(0)221–5062267. Received January 19, 2007; accepted March 16, 2007; published March 23, 2007. This article has been cited by other articles:
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