Mechanisms of BES1-regulated gene expression downstream of brassinosteroid signaling in Arabidopsis thaliana

Brassinosteroids (BRs), the plant steroid hormones, play an important role in mediating plant responses to developmental and environmental cues. BRs signal through a membrane receptor BRI1 and a GSK3 kinase BIN2 to control the activity of BES1/BZR1 family transcription factors. To understand how BES1 regulates gene expression, I looked into both trans-acting protein factors and cis-acting DNA elements that affect BES1 functions, by yeast genetic screen and chromatin immunoprecipitation coupled with DNA microarray (ChIP-chip), respectively. We identified 1609 BES1 direct target genes and discovered conserved DNA motifs in BES1 binding regions. We also showed that BES1 target genes were largely devoid of H3K27me3. In contrast, 35% of BES1 target genes were associated with H3K9me3 and two putative H3K9me3 demethylases, ELF6 and REF6, were recruited to target gene promoters by interacting with BES1, loss-of-function of which caused BR-related phenotypes. Therefore, we provided significant insights into mechanisms of BES1-regulated gene expression