Project description:Polycomb Group Proteins (PcGs) is critical in defining the epigenetic blueprint for animal and plant development. In plants, loss of different PcGs display both common and unique phenotypic defects, yet little is known about how these are established. Here, based on quantitative comparison of epigenomics data from mutants of key PcG components in Arabidopsis seedlings, we found that the PcG partners of CURLY LEAF (CLF), one of the major plant H3K27 trimethyltransferases, determines its selectivity in repressing gene loci involved in distinct developmental programs. The non-redundant role of CLF in determining flower development is specifically associated with HETEROCHROMATIN PROTEIN1 (LHP1). This context dependent effect of CLF corresponds well with tissue-biased target gene expression, and importantly, to differential co-occupancy of transcription factors, such as MADS box and B3-domain transcription factors. These results provide valuable insight as to the dynamic interplay between different PcGs and their collaborative control of plant development. To compare the effect of different PcGs on epigenetic structure from the genome-wide scale, we used chromatin immunoprecipitation followed by high-throughtput sequencing (ChIP-seq) to characterize the genome-wide binding profile of H3K27me3 in Col, clf-29, tfl2-2, atbmi1a/b and atring1a/b ; To investigate the functional consequence of the distinct H3K27me3 profile controlled by different combinations of PcGs, we characterized the transcriptome change in PcG mutants, including Col, clf-29, tfl2-2, lhp1-6, atbmi1a/b, atring1a/b, and clf29swn21.
Project description:The Polycomb Group (PcG) proteins form two protein complexes, PcG Repressive Complex 1 (PRC1) and PRC2, which are key epigenetic regulators in eukaryotes. PRC2 represses gene expression by catalyzing the trimethylation of histone H3 lysine 27 (H3K27me3). In Arabidopsis (Arabidopsis thaliana), CURLY LEAF (CLF) and SWINGER (SWN) are two major H3K27 methyltransferases and core components of PRC2, playing essential roles in plant growth and development. Despite their importance, genome-wide binding profiles of CLF and SWN have not been determined and compared yet. In this study, we generated transgenic lines expressing GFP-tagged CLF/SWN under their respective native promoters and used them for ChIP-seq analyses to profile the genome-wide distributions of CLF and SWN in Arabidopsis seedlings. We also profiled and compared the global H3K27me3 levels in wild-type (WT) and PcG mutants (clf, swn, and clf swn). Our data show that CLF and SWN bind to almost the same set of genes, except that SWN has a few hundred more targets. Two short DNA sequences, the GAGA-like and Telo-box-like motifs, were found enriched in the CLF and SWN binding regions. The H3K27me3 levels in clf, but not in swn, were markedly reduced compared with WT; and the mark was undetectable in the clf swn double mutant. Further, we profiled the transcriptomes in clf, swn, and clf swn, and compared with that in WT. Thus this work provides a useful resource for the plant epigenetics community for dissecting the functions of PRC2 in plant growth and development.
Project description:Plant BBR/BPC transcription factors contain the conserved Basic-Pentacystein (BPC) DNA-binding domain. Arabidopsis group II BBR/BPC proteins interact with PRC1 component LHP1 in vivo. Microarray experiments with Arabidopsis bpc4 bpc6, lhp1-4 and lhp1-4 bpc4 bpc6 suggest an importance of this interaction in the concerted repression of homeotic genes. In this study, we used the ATH1 GeneChip microarray to investigate transcript abundance in different Arabidopsis thaliana genotypes.
Project description:Chromatin remodeling factors of the Imitation Switch (ISWI) family play important roles in epigenetic regulations of gene expression in yeast and animals, whereas their function in plants remains elusive. Here we report characterization of the Arabidopsis ISWI genes CHR11 and CHR17. Double mutant chr11 chr17 displayed a dramatically reduced plant size with early flowering. In addition, epidermis of the double mutant leaves showed cell characteristics seen only in floral organs. These phenotypes resemble, at least partially, those of the Polycomb mutants curly leaf (clf) and like heterochromatin protein1 (lhp1). Microarray analysis revealed that a number of targets of the Polycomb pathway were derepressed in chr11 chr17 leaves. Furthermore, triple mutants combining chr11 chr17 with clf-29 or lhp1-6 both greatly enhanced clf-29 and lhp1-6 phenotypes, respectively. All these results strongly suggest that the ISWI family genes in Arabidopsis may function in gene silencing via the Polycomb pathway
Project description:Chromatin remodeling factors of the Imitation Switch (ISWI) family play important roles in epigenetic regulations of gene expression in yeast and animals, whereas their function in plants remains elusive. Here we report characterization of the Arabidopsis ISWI genes CHR11 and CHR17. Double mutant chr11 chr17 displayed a dramatically reduced plant size with early flowering. In addition, epidermis of the double mutant leaves showed cell characteristics seen only in floral organs. These phenotypes resemble, at least partially, those of the Polycomb mutants curly leaf (clf) and like heterochromatin protein1 (lhp1). Microarray analysis revealed that a number of targets of the Polycomb pathway were derepressed in chr11 chr17 leaves. Furthermore, triple mutants combining chr11 chr17 with clf-29 or lhp1-6 both greatly enhanced clf-29 and lhp1-6 phenotypes, respectively. All these results strongly suggest that the ISWI family genes in Arabidopsis may function in gene silencing via the Polycomb pathway Leaves from 15-day-old seedlings of wild-type Col-0 and chr11-1 chr17-1 were used for RNA preparation.In the experiment data,A refers to Col-0, and B refers to chr11-1 chr17-1.
Project description:BACKGROUND: Polycomb group complexes PRC1 and PRC2 repress gene expression at the chromatin level in eukaryotes. The classic recruitment model of Polycomb group complexes in which PRC2-mediated H3K27 trimethylation recruits PRC1 for H2A monoubiquitination was recently challenged by data showing that PRC1 activity can also recruit PRC2. However, the prevalence of these two mechanisms is unknown, especially in plants as H2AK121ub marks were examined at only a handful of Polycomb group targets. RESULTS: By using genome-wide analyses, we show that H2AK121ub marks are surprisingly widespread in Arabidopsis thaliana, often co-localizing with H3K27me3 but also occupying a set of transcriptionally active genes devoid of H3K27me3. Furthermore, by profiling H2AK121ub and H3K27me3 marks in atbmi1a/b/c, clf/swn, and lhp1 mutants we found that PRC2 activity is not required for H2AK121ub marking at most genes. In contrast, loss of AtBMI1 function impacts the incorporation of H3K27me3 marks at most Polycomb group targets. CONCLUSIONS: Our findings show the relationship between H2AK121ub and H3K27me3 marks across the A. thaliana genome and unveil that ubiquitination by PRC1 is largely independent of PRC2 activity in plants, while the inverse is true for H3K27 trimethylation.
Project description:BACKGROUND: Polycomb group complexes PRC1 and PRC2 repress gene expression at the chromatin level in eukaryotes. The classic recruitment model of Polycomb group complexes in which PRC2-mediated H3K27 trimethylation recruits PRC1 for H2A monoubiquitination was recently challenged by data showing that PRC1 activity can also recruit PRC2. However, the prevalence of these two mechanisms is unknown, especially in plants as H2AK121ub marks were examined at only a handful of Polycomb group targets. RESULTS: By using genome-wide analyses, we show that H2AK121ub marks are surprisingly widespread in Arabidopsis thaliana, often co-localizing with H3K27me3 but also occupying a set of transcriptionally active genes devoid of H3K27me3. Furthermore, by profiling H2AK121ub and H3K27me3 marks in atbmi1a/b/c, clf/swn, and lhp1 mutants we found that PRC2 activity is not required for H2AK121ub marking at most genes. In contrast, loss of AtBMI1 function impacts the incorporation of H3K27me3 marks at most Polycomb group targets. CONCLUSIONS: Our findings show the relationship between H2AK121ub and H3K27me3 marks across the A. thaliana genome and unveil that ubiquitination by PRC1 is largely independent of PRC2 activity in plants, while the inverse is true for H3K27 trimethylation.