Single cis‐elements in brassinosteroid‐induced upregulated genes are insufficient to recruit both redox states of the BIL1/BZR1 DNA‐binding domain

The plant‐specific transcription factor BRZ‐INSENSITIVE‐LONG 1 (BIL1)/BRASSINAZOLE‐RESISTANT 1 (BZR1) regulates the growth of Arabidopsis thaliana via brassinosteroid signaling, acting as both a gene repressor and activator. Its upregulation requires environmental cues mediated by PHYTOCHROME INTERACTING FACTOR 4 (PIF4), with oxidative modifications via H 2 O 2 enhancing their interaction. However, the nature of the tripartite complex of cis ‐elements, BIL1/BZR1, and PIF4 under redox changes remains unclear. Here, we demonstrate that oxidation of the DNA‐binding domain (DBD) of BIL1/BZR1 alters its DNA‐binding ability. However, single cis ‐elements enriched in brassinosteroid‐induced genes do not support binding of either redox form, nor does BIL1/BZR1 DBD heterodimerize with PIF4 DBD on these elements. These findings highlight the complexity of brassinosteroid transcriptional regulation beyond DNA‐binding specificity and redox modifications.