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First published online October 16, 2003; 10.1104/pp.103.025114 Plant Physiology 133:1565-1577 (2003) © 2003 American Society of Plant Biologists HY5, Circadian Clock-Associated 1, and a cis-Element, DET1 Dark Response Element, Mediate DET1 Regulation of Chlorophyll a/b-Binding Protein 2 Expression1Plant Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, California 92037 (B.B.M., D.S.P., J.C.); Department of Biology, University of California, San Diego, California 92093 (B.B.M., D.S.P.); Department of Cell Biology and Institute for Childhood and Neglected Diseases, The Scripps Research Institute, La Jolla, California 92037 (C.R.A., S.A.K.); and Howard Hughes Medical Institute, The Salk Institute, La Jolla, California 92037 (J.C.)
DET1 is a pleiotropic regulator of Arabidopsis development and controls the expression of many light-regulated genes. To gain a better understanding of the mechanism by which DET1 controls transcription from light-regulated promoters, we identified elements in the chlorophyll a/b-binding protein 2 (CAB2) promoter that are required for DET1-mediated expression. Using a series of reporter constructs in which the luciferase gene is controlled by CAB2 promoter fragments, we defined two DET1-responsive elements in the CAB2 promoter that are essential for proper CAB2 transcription. A 40-bp DET1 dark-response element (DtRE) is required for both dark and root-specific repression of CAB2, whereas the known CAB upstream factor-1 element is required for DET1 activation-associated effects in the light and repression in the roots. HY5, a factor that binds CAB upstream factor-1, is also required for DET1 effects in the light. DtRE binds two distinct activities in Arabidopsis seedling extracts: a novel activity with binding site CAAAACGC that we have named CAB2 DET1-associated factor 1 plus an activity that is likely to be the myb transcription factor Circadian Clock-Associated 1. Both activities are altered in dark-grown det1 extracts as compared with wild type, correlating a change in extractable DNA binding activity with a major change in CAB2 expression. We conclude that DET1 represses the CAB2 promoter in the dark by regulating the binding of two factors, CAB2 DET1-associated factor 1 and Circadian Clock-Associated 1, to the DtRE.
Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/doi/10.1104/pp.103.025114. 1 This work was supported by the National Science Foundation (grant no. MCB96–31390 to J.C.) and by the Howard Hughes Medical Institute. B.B.M. was partially supported by the National Institutes of Health (training grant no. HD 07495). 2 Present address: Department of Biology, CB#3280, Coker Hall, University of North Carolina, Chapel Hill, NC 27599–3280. 3 Present address: Commonwealth Scientific and Industrial Research Organization Plant Industry, G.P.O. Box 1600, Canberra ACT, 2601, Australia. * Corresponding author; e-mail chory{at}salk.edu; fax 858–558–6379. Received April 9, 2003; returned for revision May 23, 2003; accepted July 10, 2003. Related articles in Plant Physiol.:
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