Alternative silencing states of Transposable Elements in Arabidopsis
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PROVIDER: PRJEB83093 | ENA |
REPOSITORIES: ENA
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Project description:The propagation of epigenetic marks has received a great deal of attention, yet the initiation of epigenetic silencing on a new transgene, virus, or transposable element remains incompletely characterized. The overlapping function of multiple silencing mechanisms has obscured this area of investigation. Here, we have revealed two broad mechanisms that are both able to initiate silencing independently: homology-based silencing and expression-dependent silencing. By transforming exogenous transposable elements into Arabidopsis, we circumvented homology-based silencing allowing us to isolate and investigate the molecular mechanism of expression-dependent silencing. We found that several small RNA-generating mechanisms all trigger de novo expression-dependent RNA-directed DNA methylation (RdDM) through RNA Polymerase V. In addition, the silencing of transposable elements fragments stalls at the RdDM phase, while full-length elements quickly progress through RdDM to maintenance methylation and heterochromatin formation. We found that there is a narrow window of time for the transition to a fully silenced state. Transformation into a mutant genotype followed by introgression into wild-type does not result in the same level of silencing as direct transformation into wild-type. This demonstrates that the genotype of transposable element insertion or transgene transformation is key for establishing the transgenerational extent of epigenetic silencing.
2017-08-25 | GSE86787 | GEO
Project description:The mutagenic activity of transposable elements (TEs) is suppressed by epigenetic silencing and small interfering RNAs (siRNAs), especially in gametes that would transmit transposed elements to the next generation. In pollen from the model plant Arabidopsis, we show that TEs are unexpectedly reactivated and transpose, but only in the pollen vegetative nucleus, which accompanies the sperm cells but does not provide DNA to the fertilized zygote. TE expression coincides with down-regulation of the heterochromatin remodeler DECREASE IN DNA METHYLATION 1 and of most TE siRNAs. However, 21 nucleotide siRNA from Athila retrotransposons is generated in pollen and accumulates in sperm, indicating that siRNA from TEs activated in the vegetative nucleus can target silencing in gametes. We propose a conserved role for reprogramming in germline companion cells, such as nurse cells in insects and vegetative nuclei in plants, to reveal intact TEs in the genome and regulate their activity in gametes. Mature pollen was collected from Columbia reference strain plants by vacuum filtration (Johnson-Brousseau and McCormick, 2004). DNA and RNA were isolated from a ddm1-2 plant in the Columbia reference background. Small RNAs of 19–28 nt were size selected by denaturing 15% PAGE, and cloned as in Brennecke et al. (2007). Additional details regarding the cloning of small RNAs are found in the Supplemental Data. The small RNA libraries were sequenced on Illumina 1G sequencer. The total number of sequences perfectly matching the Arabidopsis genome were as follows: WT inflorescence, 4,158,848 (2,286,133 unique); WT pollen, 1,034,665 (437,984 unique); ddm1 inflorescence, 4,098,772 (1,637,771 unique); and WT sperm, 760,651 (429,972 unique).
2014-09-04 | E-GEOD-61028 | biostudies-arrayexpress
Project description:The mutagenic activity of transposable elements (TEs) is suppressed by epigenetic silencing and small interfering RNAs (siRNAs), especially in gametes that would transmit transposed elements to the next generation. In pollen from the model plant Arabidopsis, we show that TEs are unexpectedly reactivated and transpose, but only in the pollen vegetative nucleus, which accompanies the sperm cells but does not provide DNA to the fertilized zygote. TE expression coincides with down-regulation of the heterochromatin remodeler DECREASE IN DNA METHYLATION 1 and of most TE siRNAs. However, 21 nucleotide siRNA from Athila retrotransposons is generated in pollen and accumulates in sperm, indicating that siRNA from TEs activated in the vegetative nucleus can target silencing in gametes. We propose a conserved role for reprogramming in germline companion cells, such as nurse cells in insects and vegetative nuclei in plants, to reveal intact TEs in the genome and regulate their activity in gametes.
2014-09-04 | GSE61028 | GEO
Project description:MBD2 couples DNA methylation to Transposable Elements silencing during male gametogenesis
| PRJNA989636 | ENA
Project description:TNRC18 recognizes H3K9me3 to mediate transposable elements silencing at ERV regions
| PRJNA826890 | ENA
Project description:DNA methylation is an essential component of transposable element (TE) silencing, yet the mechanism by which methylation causes transcriptional repression remains poorly understood. Here we study the Arabidopsis thaliana Methyl-CpG Binding Domain (MBD) proteins MBD1, MBD2, and MBD4, and show that MBD2 acts as a transposable element (TE) repressor during male gametogenesis. MBD2 bound chromatin regions containing high levels of CG methylation, and MBD2 was capable of silencing the FWA gene when tethered to its promoter. MBD2 loss caused TE activation in the vegetative cell (VC) of mature pollen without affecting DNA methylation levels, demonstrating that MBD2-mediated silencing acts strictly downstream of DNA methylation. Loss of silencing in mbd2 became more significant in the mbd5 mbd6 or adcp1 mutant backgrounds, as well as in plants with chemically induced genome-wide DNA demethylation, suggesting that MBD2 acts redundantly with other silencing pathways to safeguard TEs from activation. Overall, our study identifies MBD2 as a novel methyl reader that acts downstream of DNA methylation to silence TEs during male gametogenesis.
2024-01-12 | GSE236290 | GEO
Project description:DNA methylation and histone H1 mediate transcriptional silencing of genes and transposable elements, but how they interact is unclear. In plants and animals with mosaic genomic methylation, functionally mysterious methylation is also common within constitutively active housekeeping genes. Here we show that H1 is enriched in methylated sequences, including genes, of Arabidopsis thaliana, yet this enrichment is independent of DNA methylation. Loss of H1 disperses heterochromatin, globally alters nucleosome organization, and activates H1-bound genes, but only weakly de-represses transposable elements. However, H1 loss strongly activates transposable elements hypomethylated through mutation of DNA methyltransferase MET1. Hypomethylation of genes also activates antisense transcription, which is enhanced by H1 loss. Our results demonstrate that H1 and DNA methylation jointly maintain transcriptional homeostasis by silencing transposable elements and aberrant intragenic transcripts. Such functionality plausibly explains why DNA methylation, a well-known mutagen, has been maintained within coding sequences of crucial plant and animal genes.
2019-11-20 | GSE122394 | GEO
Project description:TNRC18 recognizes H3K9me3 to mediate transposable elements silencing at ERV regions [WGBS]
| PRJNA978064 | ENA
Project description:This SuperSeries is composed of the following subset Series: GSE24571: Transposable elements and small RNAs contribute to gene expression divergence between Arabidopsis thaliana and Arabidopsis lyrata [RNA-Seq] GSE38109: Natural variation in Arabidopsis thaliana transcriptomes Refer to individual Series
2012-05-21 | E-GEOD-38113 | biostudies-arrayexpress
Project description:TNRC18 recognizes H3K9me3 to mediate transposable elements silencing at ERV regions [CUT&RUN]
| PRJNA826894 | ENA