Nitrogen–TOR targets a bivalent chromatin reader to modulate floral transition

Abstract

Nitrogen is an essential nutrient vital for plant health and productivity. How plants integrate nutrient signals and epigenome dynamics to modulate transcription and developmental transition remains largely unknown. Here, we uncover the crucial role of EARLY BOLTING IN SHORT DAYS (EBS) homeostasis in controlling floral transitions in response to nitrogen deficiency. EBS, a bivalent histone reader capable of recognizing both H3K27me3 and H3K4me3 histone marks, can switch its binding preference to regulate the vegetative-to-reproductive transition. We demonstrate that nitrogen and Target of Rapamycin (TOR) signaling regulate EBS protein abundance through a direct TOR–EBS interaction. TOR phosphorylates EBS at the S195 and S196 residues, which promotes EBS stability and represses the transcription of FT and other flowering genes, thereby preventing premature floral transition. Collectively, this study identifies EBS as a direct substrate of TOR and reveals a mechanistic link between nutrient signaling, epigenome dynamics, and plant developmental transition. Our findings provide important insights into complex nutrient–TOR–chromatin interplays and highlight the intricate mechanisms by which plants adapt their growth and developmental processes based on nutrient availability.