Brassinosteroids (BRs) are a group of steroid hormones regulating plant growth and development. BAS1 (CYP734A1, formerly CYP72B1) and SOB7 (CYP72C1) are two BR-inactivating cytochrome P450s identified in Arabidopsis thaliana. We previously found that a TF ATAF2 (ANAC081) suppresses BAS1 and SOB7 expression by binding to the Evening Element (EE) and CIRCADIAN CLOCK ASSOCIATED 1 (CCA1)-binding site (CBS) on their promoters. Both the EE and CBS are known binding targets of the circadian regulatory protein CCA1. Here, we confirm that as a transcriptional repressor, CCA1 binds the EE and CBS motifs on BAS1 and SOB7 promoters, respectively. CCA1 interacts with ATAF2 at both DNA–protein and protein–protein levels. ATAF2, BAS1, and SOB7 are all circadian regulated with distinct expression patterns.
CCA1 and ATAF2 differentially suppress BAS1- and SOB7-mediated BR inactivation.
This research establishes the connection between circadian clock and BR homeostasis.Dr. Hao Peng, PhD
J Exp Bot 2020 Jan;71(3):970-985
Department of Crop and Soil Sciences, Washington State University, Pullman, WA, USA.
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