Project description:The 5-methylcytosine DNA glycosylase/lyase REPRESSOR OF SILENCING 1 (ROS1)-mediated active DNA demethylation is critical for shaping the genomic DNA methylation landscape in Arabidopsis. Whether and how the stability of ROS1 may be regulated by post-translational modifications is unknown. Using a methylation-sensitive PCR (CHOP-PCR)-based forward genetic screen for Arabidopsis DNA hypermethylation mutants, we identified the SUMO E3 ligase SIZ1 as a critical regulator of active DNA demethylation. Dysfunction of SIZ1 leads to hyper-methylation at approximately one thousand genomic regions. SIZ1 physically interacts with ROS1 and mediates the SUMOylation of ROS1. The SUMOylation of ROS1 is reduced in siz1 mutant plants. Compared to that in wild type plants, the protein level of ROS1 is significantly decreased, even though there is an increased level of ROS1 transcripts in siz1 mutant plants. Our results suggest that SIZ1 positively regulates active DNA demethylation by promoting the stability of ROS1 protein through SUMOylation.
Project description:Arabidopsis ROS1 is the first genetically characterized DNA demethylase in eukaryotes. Dysfunction of ROS1 leads to increase in DNA methylation level at thousands of genomic loci. However, the features of ROS1 targets are not well understood. In this study, we identified and characterized ROS1 target loci in Arabidopsis Col-0 and C24 ecotypes. Most ROS1 targets are transposable elements (TEs) and intergenic regions. Compared to other TEs, ROS1-targeted TEs are closer to protein coding genes, suggesting a role for ROS1 in preventing the spreading of DNA methylation from highly methylated TEs to nearby genes. Interestingly, we found that unlike general TEs, ROS1 targets are associated with an enrichment of H3K18ac and H3K27me3, and depletion of H3K27me and H3K9me2. We investigated the antagonism between ROS1 and RNA-directed DNA methylation (RdDM) by identifying and characterizing thousands of genomic regions regulated by both ROS1 and RdDM. Unexpectedly, we uncovered thousands of previously unidentified RdDM targets by analyzing the DNA methylome of ros1/nrpd1 double mutant plants. In addition, we show that ROS1 also antagonizes RdDM-independent DNA methylation at more than a thousand genomic loci. Our results provide significant insights into the genome-wide effects of both ROS1-mediated active DNA demethylation and RNA-directed DNA methylation as well as their interaction in plants. Using small RNA-Seq(sRNA-Seq) to get small RNA profiling of WT, ros1-4, nrpd1 single mutants and ros1-4/nrpd1doubble mutant
Project description:To survey transcriptome changes by the mutations of a DNA demethylase ROS1 responding to a phytohormone abscisic acid, we performed the Next-gen sequencing (NGS) associated RNA-seq analysis. Two ROS1 knockout lines (ros1-3, ros1-4; Penterman et al. 2007 [PMID: 17409185]) with the wild-type Col line (wt) were subjected. Three samples (ros1-3, ros1-4 and wt), biological triplicates, ABA or mock treatment, using Illumina HiSeq 2500 system
Project description:Active DNA demethylation is an important epigenetic phenomenon in many eukaryotes. In Arabidopsis thaliana, ROS1, a 5-methylcytosine DNA glycosylase, is responsible for active DNA demethylation via a base excision repair process. Here, we found that Bromodomain and ATPase domain-containing protein 1 (BRAT1) associates with BRP1 (BRAT1 Partner 1) and forms a tight BRAT1–BRP1 complex required for DNA demethylation. To identify hypermethylated loci at the whole-genome level in brat1, brp1, and ros1, we performed whole-genome bisulfite sequencing. Compare the DNA methylation profiles of 10-day old seedlings materials of mutants (brat1, brp1, and ros1) to wild type by whole-genome bisulfite sequencing.
Project description:To servey the methylome changes by mutation of a DNA demethylase ROS1, we performed the Next-gen sequencing (NGS) associated whole genome bisulfite sequencing (BS-seq) analysis. Two ROS1 knockout lines (ros1-3 and ros1-4; Penterman et al. 2007 [PMID: 17409185]) were subjected in this study.
Project description:DNA cytosine methylation is a hallmark of epigenetic gene silencing. DNA demethylation requires ROS1, a bifunctional DNA glycosylase/lyases and open chromatin status mediated by IDM1. HDA6 is a RDP3-like histone deacetylase and was confirmed to mediate DNA methylation. In previous screening for ros1 suppressor, we identified two hda6 mutants reverting ros1-caused hypermethylation at RD29A and 35S promoters respectively, indicating the antagonization of DNA methylation between HDA6 and ROS1. To learn antagonized effects between HDA6 and ROS1 at DNA cytosine methylation genome-wide, we performed whole genome bisulfite sequencing to search antagonized targets of HDA6 and ROS1 and their specific targets to evaluate their roles on DNA methylation. To evaluate HDA6’s roles in sRNA biogenesis and nucleosome positioning, we also performed small RNA sequencing and genome-wide mapping of nucleosome positioning of C24, ros1, hda6-9 and hda6-10. Our results indicate that around 43% ros1-caused CG hypermethylation, 74.5% and 84.5% ros1-caused CHG and CHH hypermethylation were reverted by the two hda6 alleles in the ros1 background respectively. These results indicate that most of ROS1-demethylated targets are also HDA6-mediated DNA methylated targets. In addition, we observed that HDA6-affected DNA methylation targets are far more than ROS1-demethylation targets at CHG and CHH context, but not at CG context. sRNA analysis showed that HDA6 inhibits LTR/Gypsy and TE gene 24nt siRNA accumulation, while promotes RC/Helitron 24nt siRNA accumulation. Our Mono-nucleosome positioning data further showed that the two hda6 alleles have striking difference on nucleosome positioning, hda6-10 obviously have different nucleosome positioning patterns with hda6-9. Our results indicate HDA6 not only mediates overall DNA methylation at CG, CHG and CHH context, and antagonizes with ROS1 mediated DNA demethylation, but also regulates nucleosome positioning and small RNA accumulation at some genome specific regions.
Project description:To survey transcriptome changes by the mutations of a DNA demethylase ROS1 responding to a phytohormone abscisic acid, we performed the Next-gen sequencing (NGS) associated RNA-seq analysis. Two ROS1 knockout lines (ros1-3, ros1-4; Penterman et al. 2007 [PMID: 17409185]) with the wild-type Col line (wt) were subjected.
Project description:We examined spontaneously occurring variation in DNA methylation in wild type Col-0 plants, together with nrpd1 and ros1 mutants that are all propagated from single-seed descent for 10 generations.
Project description:SUMOylation, a post-translational protein modification, is dramatically upregulated and critically involved in heat stress response conservatively among species. Previous studies in Arabidopsis indicated that numerous chromatin associated proteins are SUMOylation substrates and most of heat-enhancing SUMOylation reactions occur in nucleus. However, the global functional connection between gene expression regulation and SUMOylation on chromatin is completely unknown in plant cells. Here we show a genome-wide relationship of chromatin-associated SUMOylation and transcription switches under room temperature, heat stress, and recovering conditions in Arabidopsis. The SUMO-associated chromatin sites, characterized via whole-genome ChIP-seq assays, are generally correlated with active chromatin markers. In response to heat stress, we found chromatin-associated SUMO signals increased at promoter-transcriptional start site regions and decreased in the gene bodies. Further RNA-seq analysis supported the role of chromatin-associated SUMOylation in activation of transcription during rapid responses to high temperature. Changing of SUMO signals on chromatin is correlated with upregulation of heat-responsive genes and downregulation of growth-related genes. Disruption of the SUMO ligase gene SIZ1 abolishes SUMO signals on chromatin and attenuates the rapid transcriptional responses to heat stress. Interestingly, the SUMO signal peaks are enriched in DNA elements recognized by distinguished groups of transcription factors under different temperature conditions. Collectively, our data provide evidence that SUMOylation on chromatin regulates transcription switches during development and heat stress response, improving our understanding on the precise roles of SUMOylation in plant cells.
Project description:SUMOylation, a post-translational protein modification, is dramatically upregulated and critically involved in heat stress response conservatively among species. Previous studies in Arabidopsis indicated that numerous chromatin associated proteins are SUMOylation substrates and most of heat-enhancing SUMOylation reactions occur in nucleus. However, the global functional connection between gene expression regulation and SUMOylation on chromatin is completely unknown in plant cells. Here we show a genome-wide relationship of chromatin-associated SUMOylation and transcription switches under room temperature, heat stress, and recovering conditions in Arabidopsis. The SUMO-associated chromatin sites, characterized via whole-genome ChIP-seq assays, are generally correlated with active chromatin markers. In response to heat stress, we found chromatin-associated SUMO signals increased at promoter-transcriptional start site regions and decreased in the gene bodies. Further RNA-seq analysis supported the role of chromatin-associated SUMOylation in activation of transcription during rapid responses to high temperature. Changing of SUMO signals on chromatin is correlated with upregulation of heat-responsive genes and downregulation of growth-related genes. Disruption of the SUMO ligase gene SIZ1 abolishes SUMO signals on chromatin and attenuates the rapid transcriptional responses to heat stress. Interestingly, the SUMO signal peaks are enriched in DNA elements recognized by distinguished groups of transcription factors under different temperature conditions. Collectively, our data provide evidence that SUMOylation on chromatin regulates transcription switches during development and heat stress response, improving our understanding on the precise roles of SUMOylation in plant cells.