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ENVIRONMENTAL STRESS AND ADAPTATION TO STRESS

SENSITIVE TO FREEZING6 Integrates Cellular and Environmental Inputs to the Plant Circadian Clock^1,[W],[OA]

School of Biological and Biomedical Sciences, Durham University, Durham DH1 3LE, United Kingdom (H.K.); Institute of Molecular Plant Sciences, University of Edinburgh, Edinburgh EH9 3JH, United Kingdom (A.J.W.T); and Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, United Kingdom (H.G.M.)

The sensitive to freezing6 (sfr6) mutant of Arabidopsis (Arabidopsis thaliana) is late flowering in long days due to reduced expression of components in the photoperiodic flowering pathway in long-day photoperiods. Microarray analysis of gene expression showed that a circadian clock-associated motif, the evening element, was overrepresented in promoters of genes down-regulated in sfr6 plants. Analysis of leaf movement rhythms found sfr6 plants showed a sucrose (Suc)-dependent long period phenotype; unlike wild-type Arabidopsis, the clock in sfr6 plants did not have a shorter rhythm in the presence of Suc. Other developmental responses to Suc were unaltered in sfr6 plants, suggesting insensitivity to Suc is restricted to the clock. We investigated the effect of sfr6 and Suc upon clock gene expression over 24 h. The sfr6 mutation resulted in reduced expression of the clock components CIRCADIAN CLOCK ASSOCIATED1, GIGANTEA, and TIMING OF CAB1. These changes occurred independently of Suc supplementation. Wild-type plants showed small increases in clock gene expression in the presence of Suc; this response to Suc was reduced in sfr6 plants. This study shows that large changes in level and timing of clock gene expression may have little effect upon clock outputs. Moreover, although Suc influences the period and accuracy of the Arabidopsis clock, it results in relatively minor changes in clock gene expression.

The authors 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) are: Harriet G. McWatters (harriet.mcwatters{at}plants.ox.ac.uk) and Heather Knight (p.h.knight{at}durham.ac.uk).

^[W] The online version of this article contains Web-only data.

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www.plantphysiol.org/cgi/doi/10.1104/pp.108.123901

^* Corresponding author; e-mail harriet.mcwatters{at}plants.ox.ac.uk.

Received June 3, 2008; accepted June 30, 2008; published July 9, 2008.

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				Compiled by, F. Tooke, T. Chiurugwi, and N. Battey Flowering Newsletter bibliography for 2008 J. Exp. Bot., June 23, 2009; (2009) erp154v1. [Full Text] [PDF]