DELLA-mediated gene repression is maintained by chromatin modification in rice.

DELLA proteins are master regulators of gibberellic acid (GA) signaling through their effects on gene expression. Enhanced DELLA accumulation in rice and wheat varieties has greatly contributed to grain yield increases during the green revolution. However, the molecular basis of DELLA-mediated gene repression remains elusive. In this work, we show that the rice DELLA protein SLENDER RICE1 (SLR1) forms a tripartite complex with Polycomb-repressive complex 2 (PRC2) and the histone deacetylase HDA702 to repress downstream genes by establishing a silent chromatin state. The slr1 mutation and GA signaling resulted in dissociation of PRC2 and HDA702 from GA-inducible genes. Loss-of-function or downregulation of the chromatin regulators impaired SLR1-dependent histone modification and gene repression. Time-resolved analysis of GA signaling revealed that GA-induced transcriptional activation was associated with a rapid increase of H3K9ac followed by H3K27me3 removal. Collectively, these results establish a general epigenetic mechanism for DELLA-mediated gene repression and reveal details of the chromatin dynamics during transcriptional activation stimulated by GA signaling.