HY5, Circadian Clock-Associated 1, and a cis-element, DET1 dark response element, mediate DET1 regulation of chlorophyll a/b-binding protein 2 expression.
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.
Maxwell
Bridey B
BB
Plant Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, California 92037, USA.
Andersson
Carol R
CR
Poole
Daniel S
DS
Kay
Steve A
SA
Chory
Joanne
J
D000818:Animals; D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000235:genetics*; D001483:Base Sequence; D050976:Basic-Leucine Zipper Transcription Factors; D001665:Binding Sites; D002940:Circadian Rhythm / Q000235:genetics*; D001517:Coleoptera; D003624:Darkness; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects*; D017930:Genes, Reporter; D047908:Intracellular Signaling Peptides and Proteins; D008027:Light; D008156:Luciferases / Q000235:genetics; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000254:growth & development / Q000528:radiation effects; D016415:Sequence Alignment; D014157:Transcription Factors / Q000235:genetics*
D029681:Arabidopsis Proteins; D050976:Basic-Leucine Zipper Transcription Factors; C114425:CCA1 protein, Arabidopsis; C088435:DET1 protein, Arabidopsis; C109254:HY5 protein, Arabidopsis; D047908:Intracellular Signaling Peptides and Proteins; D009687:Nuclear Proteins; D014157:Transcription Factors; D008156:Luciferases