Dynamic of DNA methylation during Arabidopsis reproduction
Ontology highlight
ABSTRACT: Cytosine methylation is a key epigenetic mark in many organisms, important for both transcriptional control and genome integrity. While relatively stable during somatic growth, DNA methylation is reprogrammed genome-wide during mammalian reproduction. Reprogramming is essential for zygotic totipotency, and to prevent transgenerational inheritance of epimutations. The extent of DNA methylation reprogramming in plants however remains unclear. Here, we developed sensors reporting with single-cell resolution CG and non-CG methylation in Arabidopsis. Live imaging during reproduction revealed distinct and sex-specific dynamics for both contexts. We found that CHH methylation in the egg cell depends on DRM2 and Pol V, two main actors of RNA-directed DNA methylation, but does not depend on Pol IV. Our sensors provide insight into global DNA methylation dynamics at the single cell level with high temporal resolution, and offer a powerful tool to track CG and non-CG methylation both during development and in response to environmental cues in all organisms with methylated DNA.
Project description:DNA methylation is a mechanism of epigenetic gene regulation and genome defense conserved in many eukaryotic organisms. In Arabidopsis, the DNA methyltransferase DRM2 controls RNA-directed DNA methylation in a pathway that also involves the plant specific RNA Polymerase V (Pol V). The Arabidopsis genome also encodes an evolutionarily conserved but catalytically inactive DNA methyltransferase DRM3. Here, we show that DRM3 has moderate effects on global RNA-directed DNA methylation and small RNA abundance throughout the genome, and DRM3 protein physically interacts with Pol V. In drm3 mutants, we observe a lower level of Pol V-dependent transcripts, even though Pol V chromatin occupancy is increased at many sites in the genome. These findings suggest that DRM3 acts to promote Pol V transcriptional elongation or assist in the stabilization of Pol V transcripts, and shed further light on the mechanism of RNA-directed DNA methylation. For wildtype plants as well as drm3, drm2, and nrpe1 mutants ChIP-seq was carried out using an endogenous NRPE1 antibody given to us by the Craig Pikaard lab. Two biological replicates of ChIP-seq were also carried out using anti-Flag resin on wildtype and drm3 plants carrying a Flag epitope tagged version of NRPE1. Small RNA sequencing was carried out on Col, drm3, drm2, and nrpe1 plants. Finally, whole-genome bisulfite sequencing analysis was carried out on previously published datasets (as detailed below) which were realigned using a newer genome version and mapping protocol. As such the updated processed files are part of this submission. Please note that the drm2, drm3, and nrpe1 mutant libraries used in this study were previously published (GSE39901), as were the 2 other Col replicates used (GSE36129) as below and thus duplicated sample records were created for the convenient retrieval of the complete raw data from SRA; Bisulfite_seq-Col_1 - GSM881756 Bisulfite_seq-Col_2 - GSM1193638 Bisulfite_seq-drm3 - GSM981017 Bisulfite_seq-drm2 - GSM981015 Bisulfite_seq-nrpe1- GSM981040
Project description:DNA methylation is a mechanism of epigenetic gene regulation and genome defense conserved in many eukaryotic organisms. In Arabidopsis, the DNA methyltransferase DRM2 controls RNA-directed DNA methylation in a pathway that also involves the plant specific RNA Polymerase V (Pol V). The Arabidopsis genome also encodes an evolutionarily conserved but catalytically inactive DNA methyltransferase DRM3. Here, we show that DRM3 has moderate effects on global RNA-directed DNA methylation and small RNA abundance throughout the genome, and DRM3 protein physically interacts with Pol V. In drm3 mutants, we observe a lower level of Pol V-dependent transcripts, even though Pol V chromatin occupancy is increased at many sites in the genome. These findings suggest that DRM3 acts to promote Pol V transcriptional elongation or assist in the stabilization of Pol V transcripts, and shed further light on the mechanism of RNA-directed DNA methylation.
Project description:The role of on-CG methylation in seed development and dormancy remains unknown. There are four genes in charge of non-CG methylation in Arabidopsis: drm1, drm2, cmt2 and cmt3. The majority of non-CG methylation in vegetative tissues, leaf, is gone in homozygous ddcc mutant line (Hume et al., 2014). To uncover the possible role of non-CG DNA methylation in seed development and dormancy, we characterized the transcriptome of ddcc mutant in Arabidopsis post-mature green seeds using Illumina sequencing. Meanwhile, post-mature green seeds from wild type were used as control.
Project description:The role of on-CG methylation in seed development and dormancy remains unknown. There are four genes in charge of non-CG methylation in Arabidopsis: drm1, drm2, cmt2 and cmt3. The majority of non-CG methylation in vegetative tissues, leaf, is gone in homozygous ddcc mutant line (Hume et al., 2014). To uncover the possible role of non-CG DNA methylation in seed development and dormancy, we characterized the methylome of ddcc mutant in Arabidopsis dry seed using Illumina sequencing. Meanwhile, vegetative tissue, leaves from 3 week plant with ddcc mutant and from wild type, and dry seed from wild type plant were used as control. Illumina sequencing of bisulfite-converted genomic DNA from dry seed and 3-week-plant leaves of ddcc mutant and wild type.
Project description:The role of on-CG methylation in seed development and dormancy remains unknown. There are four genes in charge of non-CG methylation in Arabidopsis: drm1, drm2, cmt2 and cmt3. The majority of non-CG methylation in vegetative tissues, leaf, is gone in homozygous ddcc mutant line (Hume et al., 2014). To uncover the possible role of non-CG DNA methylation in seed development and dormancy, we characterized the transcriptome of ddcc mutant in Arabidopsis post-mature green seeds using Illumina sequencing. Meanwhile, post-mature green seeds from wild type were used as control. Illumina sequencing of transcripts from post-mature green seeds of ddcc mutant and wild type. Two biological replicates were collected.
Project description:The role of non-CG methylation in seed development and dormancy remains unknown. There are four genes in charge of non-CG methylation in Arabidopsis: drm1, drm2, cmt2 and cmt3. The majority of non-CG methylation in vegetative tissues, leaf, is gone in homozygous ddcc mutant line (Hume et al., 2014). To uncover the possible role of non-CG DNA methylation in seed development and dormancy, we characterized the methylome of ddcc mutant in Arabidopsis postmature-green-stage seed and dry seed using Illumina sequencing. Meanwhile, vegetative tissue, leaves from 3 week plant with ddcc mutant and from wild-type, and postmature-green-stage seed and dry seed from wild-type plant were used as control.
Project description:In plants, transposons and non-protein-coding repeats are epigenetically silenced by CG and non-CG methylation. This pattern of methylation is mediated in part by small RNAs and two specialized RNA polymerases, Pol IV and Pol V, in a process called RNA-directed DNA methylation. By contrast, many protein-coding genes transcribed by Pol II contain in their gene bodies exclusively CG methylation that is independent of small RNAs and Pol IV/Pol V activities. It is unclear how the different methylation machineries distinguish between transposons and genes. Here we report on a group of atypical genes that display in their coding region a transposon-like methylation pattern, which is associated with gene silencing in sporophytic tissues. We performed a methylation-sensitive amplification polymorphism analysis to search for targets of RNA-directed DNA methylation in Arabidopsis thaliana and identified several members of a gene family encoding cysteine-rich peptides (CRPs). We also examined small RNA abundance at individual CRP genes in the wild type plant, nrpd1, and rdr2 mutant plants.
Project description:In plants, transposons and non-protein-coding repeats are epigenetically silenced by CG and non-CG methylation. This pattern of methylation is mediated in part by small RNAs and two specialized RNA polymerases, Pol IV and Pol V, in a process called RNA-directed DNA methylation. By contrast, many protein-coding genes transcribed by Pol II contain in their gene bodies exclusively CG methylation that is independent of small RNAs and Pol IV/Pol V activities. It is unclear how the different methylation machineries distinguish between transposons and genes. Here we report on a group of atypical genes that display in their coding region a transposon-like methylation pattern, which is associated with gene silencing in sporophytic tissues.
Project description:Cytosine DNA methylation is a heritable epigenetic mark present in many eukaryotic organisms. While DNA methylation likely has a conserved role in gene silencing, the levels and patterns of DNA methylation appear to vary drastically among different organisms. Here, we used shotgun genomic bisulfite sequencing (BS-Seq) to compare DNA methylation in eight diverse plant and animal genomes. We found that patterns of methylation are very similar in flowering plants with methylated cytosines detected in all sequence contexts, whereas CG methylation predominates in animals. Vertebrates have methylation throughout the genome except for CpG islands. Gene body methylation is conserved with clear preference for exons in most of the organisms. Furthermore, genes appear to be the major target of methylation in Ciona and honeybee. Among the eight organisms, the green alga Chlamydomonas has the most unusual pattern of methylation, having non-CG methylation enriched in exons of genes rather than in repeats and transposons. In addition, we demonstrate that the Dnmt1 cofactor Uhrf1 has a conserved function in maintaining CG methylation in both transposons and gene bodies in the mouse, Arabidopsis, and zebrafish genomes. Comparison of methylation across eight eukaryotic organisms
Project description:RNA-directed DNA methylation (RdDM) functions in de novo methylation in CG, CHG, and CHH contexts. Here, we performed map-based cloning of OsNRPE1, which encodes the largest subunit of Pol V, a key regulator of gene silencing and reproductive development in rice. We found that rice Pol V is required for CHH methylation on RdDM loci by transcribing long non-coding RNAs. Pol V influences the accumulation of 24-nt siRNAs in a locus-specific manner. Biosynthesis of 24-nt siRNAs on loci with high CHH methylation levels and low CG and CHG methylation levels tends to depend on Pol V. In contrast, low methylation levels in the CHH context and high methylation levels in CG and CHG contexts predisposes 24-nt siRNA accumulation to be independent of Pol V. H3K9me1 and H3K9me2 tend to be enriched on Pol V-independent 24-nt siRNA loci, whereas various active histone modifications are enriched on Pol V-dependent 24-nt siRNA loci. DNA methylation is required for 24-nt siRNAs biosynthesis on Pol V-dependent loci but not on Pol V-independent loci. Our results reveal the function of rice Pol V for long non-coding RNA production, DNA methylation, 24-nt siRNA accumulation, and reproductive development. This SuperSeries is composed of the SubSeries listed below.