DELLA Proteins Interact with HAC1 and Control Plant Growth Via Transcriptional Regulation of the Growth Repressor Gene ERF2

DELLA proteins are negative regulators of gibberellin (GA) signaling. Under GA-deficient conditions, DELLA accumulates in the nucleus and interacts with numerous transcription factors (TFs) via the GRAS domain. Recent studies have shown that DELLA interacts with TFs via the LHR1 subdomain and histone H2A via the PFYRE subdomain, respectively. It is essential for DELLA-mediated global transcription reprograming. DELLA exhibits strong transcriptional activity and acts as a co-activator of GAI-ASSOCIATED FACTOR1 (GAF1)/IDD2. The N-terminus of DELLA is necessary for strong transcriptional activity, but the regulatory activities and mechanisms of DELLA remain unclear. Therefore, we screened DELLA-interacting factors using the proximity biotinylation enzyme AirID and identified HISTONE ACETYLTRANSFERASE OF THE CBP FAMILY1 (HAC1). HAC1-mediated acetylation of histone H3 at the GAF1 target chromatin was necessary for transcriptional activation by the GAF1-DELLA complex. Additionally, the HAC1-mediated transcriptional activity of DELLA was involved in regulating plant growth. Moreover, ETHYLENE RESPONSE FACTOR2 (ERF2) was identified as a growth repressor gene regulated by the GAF1-DELLA-HAC1 complex. Here, we showed that DELLA proteins regulate plant growth via HAC1-mediated transcriptional regulation of ERF2.