The trxG family histone methyltransferase SET DOMAIN GROUP 26 promotes flowering via a distinctive genetic pathway

Abstract

SUMMARYHistone methylation is a major component in numerous processes such as determination of flowering time, which is fine-tuned by multiple genetic pathways that integrate both endogenous and environmental signals. Previous studies identified SET DOMAIN GROUP 26 (SDG26) as a histone methyltransferase involved in the activation of flowering, as loss of function of SDG26 caused a late-flowering phenotype in Arabidopsis thaliana. However, the SDG26 function and the underlying molecular mechanism remain largely unknown. In this study, we undertook a genetic analysis by combining the sdg26 mutant with mutants of other histone methylation enzymes, including the methyltransferase mutants Arabidopsis trithorax1 (atx1), sdg25 and curly leaf (clf), as well as the demethylase double mutant lsd1-like1 lsd1-like2 (ldl1 ldl2). We found that the early-flowering mutants sdg25, atx1 and clf interact antagonistically with the late-flowering mutant sdg26, whereas the late-flowering mutant ldl1 ldl2 interacts synergistically with sdg26. Based on microarray analysis, we observed weak overlaps in the genes that were differentially expressed between sdg26 and the other mutants. Our analyses of the chromatin of flowering genes revealed that the SDG26 protein binds at the key flowering integrator SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1/AGAMOUS-LIKE 20 (SOC1/AGL20), and is required for histone H3 lysine 4 trimethylation (H3K4me3) and histone H3 lysine 36 trimethylation (H3K36me3) at this locus. Together, our results indicate that SDG26 promotes flowering time through a distinctive genetic pathway, and that loss of function of SDG26 causes a decrease in H3K4me3 and H3K36me3 at its target gene SOC1, leading to repression of this gene and the late-flowering phenotype.

Transcriptional Dynamics Driving MAMP-Triggered Immunity and Pathogen Effector-Mediated Immunosuppression in Arabidopsis Leaves Following Infection with Pseudomonas syringae pv tomato DC3000

“…Additionally the SET-domain containing genes KRYPTONITE (SDG33) and ASHH1 (SDG26) were induced early in infection. These encode H3K9MTs implicated in crosstalk between DNA and histone methylation (Du et al, 2014) and in transcription regulation and flowering time control (Berr et al, 2015). Thus, the suppression of histone-encoding genes and the selective induction of genes involved in covalent modification of histones evidenced from this study is consistent with an early pathogen strategy to render stretches of DNA more accessible to TFs.…”

Histone H3 lysine 36 methylation affects temperature-induced alternative splicing and flowering in plants

“…In Arabidopsis, the deposition of H3K36me3 is regulated by the histone methyltransferases SDG8 and SDG26 and, accordingly, levels of H3K36me3 are low in sdg8-2 and sdg26-1 mutant plants [44, 45]. We performed an RNA-seq experiment on wild-type (WT) and mutant plants, continuously grown at 16 °C, or one day after a temperature shift to 25 °C.…”

ATX3, ATX4, and ATX5 Encode Putative H3K4 Methyltransferases and Are Critical for Plant Development

“…Prior to this study, nearly all H3K4 methyl transferases characterized in Arabidopsis were those controlling H3K4me3 (Berr et al, 2015;Song et al, 2015). The only enzyme described to catalyze H3K4me2 was E, Boxplot of ChIP-seq peak height of ATX3/4/5-and SDG2-affected H3K4me3 sites.…”