HY5, Circadian Clock-Associated 1, and a cis-Element, DET1 Dark Response Element, Mediate DET1 Regulation of Chlorophyll alb-Binding Protein 2 Expression

• Published in: Plant physiology (Bethesda) Vol. 133; no. 4; pp. 1565 - 1577
• Main Authors: Maxwell, Bridey B., Andersson, Carol R., Poole, Daniel S., Kay, Steve A., Chory, Joanne
• Format: Journal Article
• Language: English
• Published: American Society of Plant Biologists 01.12.2003
• Subjects: Binding sites; Chlorophylls; Focus Issue on Light Signaling; Gene expression regulation; Genes; Genetic mutation; Hypocotyls; Phenotypes; Plant cells; Plants; Seedlings
• ISSN: 0032-0889; 1532-2548

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.