Arabidopsis Polycomb Repressive Complex 2 binding sites contain putative GAGA factor binding motifs within coding regions of genes
ABSTRACT: Background. Polycomb Repressive Complex 2 (PRC2) is an essential regulator of gene expression that maintains genes in a repressed state by marking chromatin with trimethylated Histone H3 lysine 27 (H3K27me3). In Arabidopsis, loss of PRC2 function leads to pleiotropic effects on growth and development thought to be due to ectopic expression of seed and embryo-specific genes. While there is some understanding of the mechanisms by which specific genes are targeted by PRC2 in animal systems, it is still not clear how PRC2 is recruited to specific regions of plant genomes.Results. We used ChIP-seq to determine the genome-wide distribution of hemagglutinin (HA)-tagged FERTLIZATION INDEPENDENT ENDOSPERM (FIE-HA), the Extra Sex Combs homolog protein present in all Arabidopsis PRC2 complexes. We found that the FIE-HA binding sites co-locate with a subset of the H3K27me3 sites in the genome and the associated genes were more likely to be de-repressed in mutants of PRC2 components. The FIE-HA binding sites are enriched for three sequence motifs including a putative GAGA factor binding site that is also found in Drosophila Polycomb Response Elements (PREs).Conclusions. Our results suggest that PRC2 binding sites in plant genomes share some sequence features with Drosophila PREs. However, RNA was extracted from intermediate phenotype siFIE plants, clf-7 swn-28 and Col using Qiagen Plant RNeasy mini kit. For each sample, three pools of 10-12 plants were used. The siFIE plants were analysed for FIE mRNA by RT-qPCR; the maximum level of FIE mRNA was found to be 10% of wildtype.
Project description:rs09-08_fie - upregulation of transcripts in the absence of prc2 repressory complex - Role of PRC2 repressory complex for differentiation pathways in Arabidopsis thaliana? - Comparison of transcriptome between two biological replicates of fie mutants in comparison with two biological replicates of Col WT. Keywords: gene knock out 6 dye-swap - CATMA arrays
Project description:EMBRYONIC FLOWER1 (EMF1) is a plant specific gene crucial to Arabidopsis vegetative development. Loss of function mutants in the EMF1 gene mimic the phenotype caused by mutations in Polycomb Group protein (PcG) genes, which encode epigenetic repressors that regulate many aspects of eukaryotic development. In Arabidopsis, Polycomb Repressor Complex 2 (PRC2), made of PcG proteins, catalyzes trimethylation of lysine 27 on histone H3 (H3K27me3) and PRC1-like proteins catalyze H2AK119 ubiquitination. Despite functional similarity to PcG proteins, EMF1 lacks sequence homology with known PcG proteins; thus its role in the PcG mechanism is unclear. To study the EMF1 functions and its mechanism of action, we performed genome-wide mapping of EMF1 binding and H3K27me3 modification sites in Arabidopsis seedlings. The EMF1 binding pattern is similar to that of H3K27me3 modification on the chromosomal and genic level. ChIPOTLe peak finding and clustering analyses both show that the highly trimethylated genes also have high enrichment level of EMF1 binding, termed EMF1_K27 genes. EMF1 interacts with regulatory genes, which are silenced to allow vegetative growth, and with genes specifying differentiated cell fates during vegetative development. H3K27me3 marks not only these genes but also some genes that are involved in endosperm development and maternal effects. Transcriptome analysis, coupled with the H3K27me3 pattern, of EMF1_K27 genes in emf1 and PRC2 mutants showed that EMF1 represses gene activities via diverse mechanisms and plays a novel role in the PcG mechanism. All experiments were done using two channels per chip, comparing DNA associated with immunoprecipitated EMF1 to control genomic DNA, DNA associated with immunoprecipitated histone H3 methylated at lysine 27 to control genomic DNA, or total RNA (converted to cDNA) to control genomic DNA. Two or three replicates per experiment are included.
Project description:In Drosophila, Polycomb Response Elements (PREs) are identified as genomic sequences allowing the maintenance of transcriptional repression in the absence of the initiating signal. Although PREs in Drosophila are well characterized, the existence of mammalian PRE-like elements remains debated. Accumulating evidence supports a model in which CpG islands function to recruit Polycomb-Group complexes (PcG), however, it is not evident which subclasses of CpG islands serve as PREs. Trithorax (Trx), which is required for positive regulation of gene expression in Drosophila, is known to co-bind Drosophila PREs where it is thought to antagonize polycomb-dependent silencing of nearby genes. Here, we demonstrate the existence of Trx-dependent H3K4 dimethylation loci that specifically mark Drosophila PREs and are required for the maintenance of expression of the nearby genes. Similarly, in human cells, we find ~ 3000 MLL1 (human Trx homologue)-dependent H3K4 dimethylation loci, which correlate strongly with CpG island density. In the absence of MLL1 and H3K4 dimethylation at these loci, there is an increase in H3K27 trimethylation levels, suggesting these sites can recruit Polycomb Repressive Complex 2 (PRC2). By inhibiting PRC2-dependent silencing in the absence of MLL1, we establish that a balance exists between MLL1 and PRC2, and their respective capacity to maintain or repress transcription. Thus, by investigating a conserved function between Trx and MLL1, we provide rules for the identification of CpG island subclasses serving as PRE-like sequences within the human genome. To examine changes in histone-modification profiles and gene expression after depletion of Trx in Drosophila S2 cells, and MLL1 in human HCT116 cells. We also treated MLL1-NULL HCT116 cells with GSK126 (5uM) for 4 days and measured changes in gene expression.
Project description:Some flowering plant and vertebrate genes are expressed primarily or exclusively from either the maternal or paternal allele, a phenomenon called genomic imprinting. Flowering plant imprinted gene expression has been described primarily in endosperm, a terminal nutritive tissue consumed by the embryo during seed development or after germination. Imprinted expression in Arabidopsis thaliana endosperm is orchestrated by differences in cytosine DNA methylation between the paternal and maternal genomes, as well as by Polycomb group (PcG) proteins. Currently only eleven imprinted Arabidopsis genes are known. Here we use extensive sequencing of cDNA libraries to identify many new paternally and maternally imprinted genes in A. thaliana endosperm, including transcription factors, proteins involved in hormone signaling, and epigenetic regulators. The imprinted status of many maternally-expressed genes is not altered by mutations in the DNA-demethylating glycosylase DEMETER, the DNA methyltransferase MET1 or the core PcG protein FIE, indicating that these genes are regulated by novel mechanisms or deposited from maternal tissues. We did not find any imprinted genes in the embryo. Our results demonstrate that imprinted gene expression, particularly from the maternal genome, is an extensive, mechanistically complex phenomenon that likely affects multiple aspects of seed development. Epigenetics Examination of genomic imprinting in Arabidopsis endosperm
Project description:CURLY LEAF (CLF), the major histone methyltransferase of Polycomb Repressive Complex 2 (PRC2), modifies trimethylation of histone H3 lysine 27 (H3K27me3) and mediates dynamical chromatin repression in Arabidopsis. Here we used strand specific RNA-sequencing to profile Arabidopsis transcriptomes obtained from roots, shoots, flowers and siliques of Col-0 and clf-28 plants. Our analysis identified a large number of CLF-regulatedd transcripts in Arabidopsis. Transcriptome profiling in roots, shoots, inflorescences and siliques of WT and clf-28 plants with 3 biological replicates.
Project description:CURLY LEAF (CLF), the major histone methyltransferase of Polycomb Repressive Complex 2 (PRC2), modifies trimethylation of histone H3 lysine 27 (H3K27me3) and mediates dynamical chromatin repression in Arabidopsis. Here we profiled Arabidopsis transcriptomes obtained from roots, leaves, flowers and siliques of Col-0 (As described under GEO ID: GSE38612) and clf-28 plants using RNA-seq. Our analysis uncovered 3835 transcription units were up-regulated in clf-28. Compared with ChIP-CHIP data, we found at least 42% of them were associated with H3K27me3. Transcriptom profiling in roots, leaves, flowers and siliques of clf-28 plants.
Project description:rs09-08_fie - upregulation of transcripts in the absence of prc2 repressory complex - Role of PRC2 repressory complex for differentiation pathways in Arabidopsis thaliana? - Comparison of transcriptome between two biological replicates of fie mutants in comparison with two biological replicates of Col WT. Keywords: gene knock out Overall design: 6 dye-swap - CATMA arrays
Project description:The essential histone variant H2A.Z localises to both active and silent chromatin sites. In embryonic stem cells (ESCs), H2A.Z is also reported to co-localise with polycomb repressive complex 2 (PRC2) at developmentally silenced genes. The mechanism of H2A.Z targeting is not clear, but a role for the PRC2 component Suz12 has been suggested. Given this association, we wished to determine if polycomb functionally directs H2A.Z incorporation in ESCs. We demonstrate that the PRC1 component Ring1B interacts with multiple complexes in ESCs. Moreover, we show that although the genomic distribution of H2A.Z co-localises with PRC2, Ring1B and with the presence of CpG islands, H2A.Z still blankets polycomb target loci in the absence of Suz12, Eed (PRC2) or Ring1B (PRC1). Therefore we conclude that H2A.Z accumulates at developmentally silenced genes in ESCs in a polycomb independent manner. Array design includes 2 biological replicates for all samples and technical replication (dye swaps for H3K27me3_WT_ES, EZH2_WT_ES, EZH2_RING1b_KO_ES, H2AZ_WT_ES(2), H2AZ_Eed_KO_ES and H2AZ_Suz12_KO_ES). Ring1B_WT_ES is represented by a single replicate.
Project description:In order to identify candidate target genes of the OBP1 (At3g50410) transcription factor we used dexamethasone inducible system (Lloyd et al, 1994). A single inducible over-expression line was compared to an empty vector control line 10h after DEX induction to identify candidate genes that were confirmed by quantitative RT-PCR.
Project description:Grain yield and protein content were determined for six wheat cultivars grown over three years at multiple sites and at multiple N-fertilizer inputs. Although grain protein was negatively correlated with yield, some grain samples had higher protein contents than expected based on their yields, a trait referred to as grain protein deviation (GPD). We used novel statistical approaches to calculate GPD across environment and to correlate gene expression in the developing caryopsis with this trait. The yield and protein content were initially adjusted for nitrogen fertilizer inputs, and then adjusted for yield (to remove the negative correlation) resulting in environmental corrected GPD. The transcriptome data for all samples were subjected to Principal Component Analysis (PCA) and ANOVA to identify individual Principal Components (PCs) correlating with GPD alone. Scores of the selected PCs significantly related to cultivar differences and GPD but not to the yield or protein content were identified as reflecting a multivariate pattern of gene expression related to genetic variation in GPD. Sets of genes significant for these PCs and hence GPD were identified as candidate genes determining cultivar differences in GPD. Microarray profiling has been used to identify the links between gene expression and grain protein content in 6 different varietes of wheat grown at 2 different sites, 3 N levels and during 3 growth seasons. Six UK cultivars (Istabraq , Hereward, Marksman, Cordiale, Malacca and Xi 19) were grown over three seasons (2008-9, 2009-10 and 2010-11) at Rothamsted . In the present publication, data from two sites are included: Rothamsted and RAGTResearch (Harpenden, UK) and at four other sites in the south-east of the UK (RAGT, Ickleton, Cambridge; Limagrain, Woolpit, Suffolk; Syngenta, Whittlesford, Cambridge; KWS-UK, Thriplow, Hertfordshire) in 2009-10 and 2010-11 only. Three replicate plots were grown at three N levels: 100kg/ha, (N100), 200kg/ha (N200) and 350 kg/ha (N350) (see Barraclough et al., 2010, Chope at al., 2014). Developing heads (10 per plot) were tagged and caryopses were harvested from the Rothamsted (2009, 2010 and 2011) and RAGT (2010 and 2011) sites at 21 days after anthesis (mid-grain filling) to measure gene expression using Affymetrix wheat microarrays giving a total of 161 samples. Six UK cultivars (Istabraq , Hereward, Marksman, Cordiale, Malacca and Xi 19) were grown over three seasons (2008-9, 2009-10 and 2010-11) at Rothamsted Research (Harpenden, UK) and at four other sites in the south-east of the UK (RAGT, Ickleton, Cambridge; Limagrain, Woolpit, Suffolk; Syngenta, Whittlesford, Cambridge; KWS-UK, Thriplow, Hertfordshire) in 2009-10 and 2010-11 only. Three replicate plots were grown at three N levels: 100kg/ha, (N100), 200kg/ha (N200) and 350 kg/ha (N350) (see Barraclough et al., 2010, Chope at al., 2014). Developing heads (10 per plot) were tagged and caryopses were harvested from the Rothamsted (2009, 2010 and 2011) and RAGT (2010 and 2011) sites at 21 days after anthesis (mid-grain filling) to measure gene expression using Affymetrix wheat microarrays giving a total of 161 samples.