Brassinosteroid mutant (bzr1-1D and det2) analysis

Brassinosteroid (BR) homeostasis and signaling are crucial for normal growth and development of plants. BR signaling through cell-surface receptor kinases and intracellular components leads to dephosphorylation and accumulation of the nuclear protein BZR1. How BR signaling regulates gene expression, however, remains unknown. Here we show that BZR1 is a transcriptional repressor that has a previously unknown DNA binding domain and binds directly to the promoters of feedback-regulated BR biosynthetic genes. To identify additional BZR1-regulated genes and to understand the BR-regulated transcriptional pathways, we examined the effects of bzr1-1D and det2 mutations on the expression of BR-regulated genes by using the Arabidopsis full-genome oligo microarray (Affymetrix). Microarray analyses identified additional potential targets of BZR1 and illustrated, together with physiological studies, that BZR1 coordinates BR homeostasis and signaling by playing dual roles in regulating BR biosynthesis and downstream growth responses. Keywords: other