A molecular module in gibberellin signaling-mediated flowering

Zhang and Jian et al. reveal an epigenetic regulatory mechanism underlying gibberellin signaling-mediated flowering.

By Chunyu Zhang and Xingliang Hou; South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China

Background: The timing of floral induction is tightly controlled by environmental cues and intrinsic signals. The critical role of gibberellin (GA) in this process has been extensively studied in the past decades. DELLA proteins serve as the central regulatory hubs of GA signaling. The mechanism of GA-dependent transcription involves the recruitment of DELLA proteins to transcription factors. In general, epigenetic modifiers are believed to cooperate with transcription factors to regulate gene expression, but how epigenetic regulation participates in GA-dependent transcription of the floral integrator genes in plants remains unclear.

Question: Which epigenetic modifiers participate in GA-dependent transcription of the floral integrator genes? What is the detailed molecular mechanism involved in this process?

Findings: BRAHMA (BRM), a core catalytic subunit of the SWI/SNF-type chromatin remodeling complex, is involved in GA signaling-mediated flowering via the formation of the DELLA-BRM-NF-YC module in Arabidopsis. DELLA proteins promote the interaction of BRM with the transcription factor NUCLEAR FACTOR Y-C (NF-YC), impairing the binding of NF-YC to the floral integrator gene SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 (SOC1), resulting in late flowering. Meanwhile, DELLA proteins accelerate the binding of BRM to SOC1. In the presence of GA, GA-triggered DELLA degradation disturbs the DELLA-BRM-NF-YC module and the H3K4me3 level at SOC1 chromatin increases, resulting in higher gene expression and early flowering.

Next steps: We will investigate whether the BRM-NF-Y module is also responsive to other phytohormone signals and how BRM integrates different phytohormone signals during plant development.