Studying The Mechanisms Of Histone Methyltransferase SDG8in Brassinosteroid Regulated Gene Expression

Brassinosteroids (BRs) is a group of polyhydroxylated plant steroid hormones, which is involved in many aspects of plant growth and developmental processes. BRs signal through the receptor BRI1localized to the plasma membrane and other signaling components to regulate the BES1/BZR1family of transcription factors, which modulates the expression of many genes. BES1/BZR1and their interacting proteins regulate the large number of genes. Recent study reported that transcription elongater IWS1interacts with BES1and invloves in BR signal transdcuction. In yeast system, IWS1and histone3lysine36methyltransferase SDG8inform a complax to regulate the transcription of genes. In this study, we investigate the function of Arabidopsis SDG8in BR signaling and the potential mechanisms of its action.First, SDG8T-DNA knockout mutant line was gained, named sdg8. The sdg8plants display reduced-growth dwarf phenotype with compromised BR responses.Then, based on the function analysis of SDG8, we detected the interaction of SDG8between BES1and IWS1. These studies show that SDG8interacts with the transcription factor BES1in vivo and in vitro. In the same way, we found that SDG8interacts with the transcription elongation regulator IWS1.And then, we performed the RNA-seq experiment to study the regulation pattern of SDG8on BR-response genes expression. Global gene expression studies demonstrated that SDG8plays a major role in BR-regulated gene expression. SDG8functions on inducing and repressing the BR-response genes. Gene function analysis results display that SDG8-regulated genes involve in many aspects of cell progresses including BR-involved cell elongation related genes expression.Last, Chromatin Immunoprecipitation (ChIP) experiment showed that H3K36me3is reduced in BR-regulated genes in the sdg8mutant. This study suggests histone lysine methylation can involve in the regulation of BR-responsed gene expression.Based on these results, we propose that SDG8involves BR signal pathway through the interacion with BES1and IWS1; SDG8plays an essential role in mediating BR-regulated gene expression. In this study, a major mechanism by which histone modifications dictate hormonal regulation of gene expression is revealed. It’s important for the exploration of the hormone regulation mechanism.