DOI: 10.1101/457200Oct 30, 2018Paper

CCA1 and ATAF2 differentially suppress cytochrome P450-mediated brassinosteroid inactivation in Arabidopsis

BioRxiv : the Preprint Server for Biology
Hao Peng, Michael M Neff


Brassinosteroids (BRs) are a group of steroid hormones regulating plant growth and development. Since BRs do not undergo transport among plant tissues, their metabolism is tightly regulated by transcription factors (TFs) and feedback loops. 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 CCA1-binding sites (CBS) on their promoters. Both EE and CBS are known binding targets of the core circadian clock regulatory protein CCA1. Here, we confirm that CCA1 binds the EE and CBS motifs on BAS1 and SOB7 promoters, respectively. Elevated accumulations of BAS1 and SOB7 transcripts in the CCA1 null mutant cca1-1 indicate that CCA1 is a repressor of their expression. When compared to either cca1-1 or the ATAF2 null mutant ataf2-2 , the cca1-1 ataf2-2 double mutant shows higher SOB7 transcript accumulations and stronger BR-insensitive phenotype of hypocotyl elongation in white light. CCA1 interacts with ATAF2 at both DNA-protein and protein-protein levels. ATAF2 , BAS1 and SOB7 are all circadian-regulated with distinct expression patter...Continue Reading

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