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Light inputs shape the Arabidopsis circadian system

Wenden, Bénédicte and Kozma-Bognár, László and Edwards, Kieron D. and Hall, Anthony J. W. and Locke, James C. W. and Millar, Andrew J. (2011) Light inputs shape the Arabidopsis circadian system. Plant Journal, 66 (3). pp. 480-491. ISSN 0960-7412.

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The circadian clock is a fundamental feature of eukaryotic gene regulation that is emerging as an exemplar genetic sub-network for systems biology. The circadian system in Arabidopsis plants is complex, in part due to its phototransduction pathways, which are themselves under circadian control. We therefore analysed two simpler experimental systems. Etiolated seedlings entrained by temperature cycles showed circadian rhythms in the expression of genes that are important for the clock mechanism, but only a restricted set of downstream target genes were rhythmic in microarray assays. Clock control of phototransduction pathways remained robust across a range of light inputs, despite the arrhythmic transcription of light-signalling genes. Circadian interactions with light signalling were then analysed using a single active photoreceptor. Phytochrome A (phyA) is expected to be the only active photoreceptor that can mediate far-red (FR) light input to the circadian clock. Surprisingly, rhythmic gene expression was profoundly altered under constant FR light, in a phyA-dependent manner, resulting in high expression of evening genes and low expression of morning genes. Dark intervals were required to allow high-amplitude rhythms across the transcriptome. Clock genes involved in this response were identified by mutant analysis, showing that the EARLY FLOWERING 4 gene is a likely target and mediator of the FR effects. Both experimental systems illustrate how profoundly the light input pathways affect the plant circadian clock, and provide strong experimental manipulations to understand critical steps in the plant clock mechanism.

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Additional Information:© 2011 The Authors. The Plant Journal © 2011 Blackwell Publishing Ltd. Received 1 October 2010; revised 22 December 2010; accepted 17 January 2011; published online 4 March 2011. We are grateful to Sarah Hodge and Adrian Thomson for expert technical assistance and to Qian Xing for preliminary data under FR. BW was supported by INRA. LKB’s work was supported by the Hungarian Scientific Research Fund (grant no.OTKA-73362) and by the János Bólyai Research Scholarship from the Hungarian Academy of Sciences. Work in the Millar lab was supported by Biotechnology and Biological Sciences Research Council (BBSRC) awards G19886 and E015263 to AJM. The Centre for Systems Biology at Edinburgh is a Centre for Integrative Systems Biology supported by BBSRC and Engineering and Physical Sciences Research Council (EPSRC) award D019621.
Funding AgencyGrant Number
Hungarian Scientific Research FundOTKA-73362
Hungarian Academy of SciencesUNSPECIFIED
Biotechnology and Biological Sciences Research Council (BBSRC)G19886
Biotechnology and Biological Sciences Research Council (BBSRC)E015263
Engineering and Physical Sciences Research Council (EPSRC)D019621
Subject Keywords:circadian rhythms; biological clocks; Arabidopsis thaliana; temperature; far red light; phytochrome; gene circuit
Issue or Number:3
Record Number:CaltechAUTHORS:20110523-102712393
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Official Citation:Wenden, B., Kozma-Bognár, L., Edwards, K. D., Hall, A. J., Locke, J. C. and Millar, A. J. (2011), Light inputs shape the Arabidopsis circadian system. The Plant Journal, 66: 480–491. doi: 10.1111/j.1365-313X.2011.04505.x
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:23763
Deposited By: Jason Perez
Deposited On:24 May 2011 15:24
Last Modified:03 Oct 2019 02:49

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