The PFYRE Subdomain in Master Growth Repressor DELLA is Essential for Its Association with Target Chromatin via Histone H2A Binding

The DELLA genes encode conserved master growth repressors in plants, and they are also known as ‘Green Revolution’ genes because of their pivotal role in modulating stature of the high-yielding wheat varieties, which were crucial for the success of the ‘Green Revolution’ in the 1960s. At the cellular level, DELLA proteins are nuclear-localized transcription regulators, which play a central role in controlling plant development in response to internal and environmental cues. Recent studies indicate that DELLAs regulate expression of target genes via direct protein-protein interaction of their C-terminal GRAS domain with hundreds of key transcription factors (TFs) and epigenetic regulators. However, the molecular mechanism of DELLA-mediated transcription reprogramming remains unclear. Here, by characterizing missense alleles of an Arabidopsis DELLA, REPRESSOR OF ga1-3 (RGA), we unveil a novel function of the PFYRE subdomain within its GRAS domain for binding to histone H2A via pulldown and co-IP assays. ChIP-Seq analysis further show that this activity is essential for RGA association with its target chromatin globally. Our results indicate that although DELLAs are recruited to target gene promoters by binding to TFs via its LHR1 subdomain, DELLA-H2A interaction via its PFYRE subdomain is necessary to stabilize the TF-DELLA-H2A complex at the target chromatin. This study provides new insight into the two distinct key modular functions in DELLA for its genome-wide transcription regulation in plants. The assay for transposase-accessible chromatin using sequencing (ATAC-seq) for RGA vs rga-11 and RGA treated with GA or mock. Tai-ping Sun