MRG1/2 histone methylation readers and HD2C histone deacetylase associate in repression of the florigen gene FT to set a proper flowering time in response to day‐length changes

Abstract

Summary Day‐length changes represent an important cue for modulating flowering time. In Arabidopsis, the expression of the florigen gene FLOWERING LOCUS T (FT) exhibits a 24‐h circadian rhythm under long‐day (LD) conditions. Here we focus on the chromatin‐based mechanism regarding the control of FT expression. We conducted co‐immunoprecipitation assays along with LC‐MS/MS analysis and identified HD2C histone deacetylase as the binding protein of the H3K4/H3K36 methylation reader MRG2. HD2C and MRG1/2 regulate flowering time under LD conditions, but not under short‐day conditions. Moreover, HD2C functions as an effective deacetylase in planta, mainly targeting H3K9ac, H3K23ac and H3K27ac. At dusk, HD2C is recruited to FT to deacetylate histones and repress transcription in an MRG1/2‐dependent manner. More importantly, HD2C competes with CO for the binding of MRG2, and the accumulation of HD2C at the FT locus occurs at the end of the day. Our findings not only reveal a histone deacetylation mechanism contributing to prevent FT overexpression and precocious flowering, but also support the model in which the histone methylation readers MRG1/2 provide a platform on chromatin for connecting regulatory factors involved in activating FT expression in response to daylight and decreasing FT expression around dusk under long days.

Histone Methylation Related Therapeutic Challenge in Cardiovascular Diseases

“…Generally, histones are featured by their large quantity and various modification residues ( 46 , 58 ). At least eight modifications have been identified in histones, and these modifications are catalyzed by distinct enzymes ( 59 , 60 ).…”

HD2-type histone deacetylases: unique regulators of plant development and stress responses

“…FLOWERING LOCUS T (FT) is a origen gene that promotes owering in Arabidopsis under long-day conditions. Guo, et al (2020) studied the epigenetic regulation mechanism of the FT gene in Arabidopsis and reported that HD2C is recruited to the locus of FT at dusk via an MRG1/2 dependent pathway to regulate owering time under long-day conditions. HD2C binds with histone methylation readers MRG1/2 and deacetylates lysine 9, 23, 27 of histone H3 to repress FT gene expression and early owering.…”

The Crosstalk Between Epigenetic Mechanisms and Alternative RNA Processing Regulation

“…In plants, Arabidopsis encodes two homologs of human MRG15, MRG1 and MRG2, which bind to H3K4me3/H3K36m3modifying histone marks and trigger temperature-induced flowering via the florigen gene FT (Bu et al, 2014). However, it seems like that MRG1/2 have diversified from their animal homologs during evolution, yet they still maintain their conserved H3K36me3-binding molecular function (Xu et al, 2014;An et al, 2020;Guo et al, 2020). Recently, a protein complex in Arabidopsis, called anti-silencing 1 (ASI1)-ASI1 immunoprecipitated protein 1 (AIPP1)-enhanced downy mildew 2 (EDM2) (AAE) complex, was identified targeting genic heterochromatic elements to regulate APA (Duan et al, 2017).…”