Broad non-coding transcription suggests genome surveillance by RNA Polymerase V
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ABSTRACT:
ORGANISM(S): Arabidopsis thaliana
PROVIDER: GSE146913 | GEO | 2020/11/16
REPOSITORIES: GEO
Similar Datasets
Project description:DNA methylation is an important epigenetic mark in many eukaryotic organisms. De novo DNA methylation in plants can be achieved by the RNA-directed DNA methylation (RdDM) pathway, where the plant-specific DNA-dependent RNA polymerase Pol IV transcribes target sequences to initiate 24-nt siRNA production and action. The Arabidopsis DTF1/SHH1 has been shown to associate with Pol IV and is required for 24-nt siRNA accumulation and transcriptional silencing at several RdDM target loci. However, the extent and mechanism of DTF1 function in RdDM is unclear. We show here that DTF1 is necessary for the accumulation of the majority of Pol IV-dependent 24-nt siRNAs. It is also required for a large proportion of Pol IV-dependent de novo DNA methylation. Interestingly, there is a group of RdDM target loci where 24-nt siRNA accumulation but not DNA methylation is dependent on DTF1. Taken together, our results show that DTF1 is a core component of the RdDM pathway. Our results also suggest the involvement of DTF1 in an important negative feedback mechanism for DNA methylation at some RdDM target loci. Examination of whole-genome DNA methylation and small RNA in 12-day-old Col-0, dtf1-2, nrpd1-3 and nrpe1-11 seedlings
2013-06-03 | E-GEOD-44209 | biostudies-arrayexpress
Project description:DNA methylation is an important epigenetic mark in many eukaryotic organisms. De novo DNA methylation in plants can be achieved by the RNA-directed DNA methylation (RdDM) pathway, where the plant-specific DNA-dependent RNA polymerase Pol IV transcribes target sequences to initiate 24-nt siRNA production and action. The Arabidopsis DTF1/SHH1 has been shown to associate with Pol IV and is required for 24-nt siRNA accumulation and transcriptional silencing at several RdDM target loci. However, the extent and mechanism of DTF1 function in RdDM is unclear. We show here that DTF1 is necessary for the accumulation of the majority of Pol IV-dependent 24-nt siRNAs. It is also required for a large proportion of Pol IV-dependent de novo DNA methylation. Interestingly, there is a group of RdDM target loci where 24-nt siRNA accumulation but not DNA methylation is dependent on DTF1. Taken together, our results show that DTF1 is a core component of the RdDM pathway. Our results also suggest the involvement of DTF1 in an important negative feedback mechanism for DNA methylation at some RdDM target loci.
2013-06-03 | GSE44209 | GEO
Project description:Non-coding transcription is an important determinant of heterochromatin formation. In Arabidopsis thaliana a specialized RNA polymerase V (Pol V) transcribes pervasively and produces long non-coding RNA. This facilitates locus-specific establishment of RNA-directed DNA methylation (RdDM). Subsequent maintenance of RdDM is associated with elevated levels of Pol V transcription, which is consistent with a mutual reinforcement of DNA methylation and non-coding transcription. However, the impact of DNA methylation on Pol V transcription remained unresolved. We found that loss of DNA methylation leads to a strong reduction of Pol V transcription. This occurs when DNA methylation is lost in all sequence contexts, which may happen not only in mutants defective in RdDM but also in mutants lacking maintenance DNA methyltransferases. Our results support a model where RdDM is maintained by a mutual reinforcement of DNA methylation and Pol V transcription with a strong crosstalk with other silencing pathways.
2021-08-27 | GSE168869 | GEO
Project description:In plants, heterochromatin is maintained by a small RNA-based gene silencing mechanism known as RNA-directed DNA methylation (RdDM). RdDM requires the non-redundant functions of two plant-specific DNA-dependent RNA polymerases (Pol) Pol IV and Pol V. Pol IV plays a major role in siRNA biogenesis, while Pol V may recruit DNA methylation machinery to target endogenous loci for silencing. Although small RNA-generating regions which are dependent on both Pol IV and Pol V have been identified previously, the genomic loci targeted Pol V for siRNA accumulation and silencing have not been described extensively. To characterize the Pol V-dependent, heterochromatic siRNA-generating regions in the Arabidopsis genome, we deeply sequenced the small RNA populations of wild-type and Pol V mutant plants. Furthermore, we characterized the siRNA-generating regions which were dependent on RdDM effectors and examined their dependency on Pol V. Small RNA libraries were generated and deeply sequenced from mutant alleles dms4-1, drd1-1, dms3-1, and rdm1-4, along with their control library (“Wt(T+S)”) which has been described previously (Kanno et al. 2004 Current Biology). More than 2,000 small RNA-generating loci were identified which were greatly suppressed in Pol V mutants. The Pol V-dependent, heterochromatic siRNA-generating regions were characterized in the Arabidopsis genome by deep sequencing the small RNA populations of wild-type and Pol V mutant plants. Deep SBS sequencing was used for small RNA profiling of immature inflorescence tissues from RNA polymerase V and RdDM mutants.
2012-06-11 | E-GEOD-36424 | biostudies-arrayexpress
Project description:24 nucleotide siRNAs are central players in RNA-directed DNA methylation (RdDM), a process that establishes DNA methylation at transposable elements to ensure genome stability. The plant-specific RNA polymerase IV (Pol IV) is required for siRNA biogenesis and is thought to transcribe RdDM loci to produce primary transcripts that serve as precursors to siRNAs. Yet, no such transcripts have ever been reported. Here, through RNA sequencing and double-stranded RNA sequencing in genotypes that compromise the dicing of siRNA precursors, we were able to identify Pol IV-dependent transcripts from tens of thousands of loci. We show that Pol IV-dependent transcripts correspond to both DNA strands, while the Pol II-dependent transcripts produced upon de-repression of the loci are derived from primarily one strand. We show that Pol IV-dependent transcripts have a 5â monophosphate, lack a polyA tail at the 3â end, and contain no introns; these features distinguish them from Pol II-dependent transcripts. Moreover, RDR2 is shown to play similar roles with Pol IV in both the abundance of siRNA precursors and siRNAs as well as the CHH DNA methylation. The decreased CHH methylation at dcl234 can inhibit the transcription of Pol IV at DRM2-target sites. Finally, the regulations of siRNA biogenesis were explored. To detect siRNA precursors transcribed by RNA polymerase IV, the genome wide profiling of RNA were carried out at dcl234 and dcl234 nrpd1. Different types of RNA (including Total RNA, polyA+ RNA, polyA- RNA, double stranded RNA) libraries were built to detect different transcripts. RDR2 is a RNA-dependent RNA polymerase in Pol IV complex, so the RNA-seq libraries with the mutation of RDR2 were also built. In addition, smRNA libraries with mutations blocking siRNA biogenesis were also built
2014-11-11 | E-GEOD-57215 | biostudies-arrayexpress
Project description:RNA-directed DNA methylation (RdDM) is a small interfering RNA (siRNA)-mediated epigenetic modification that contributes to transposon silencing in plants. RdDM requires a complex transcriptional machinery that includes specialized RNA polymerases, named Pol IV and Pol V, as well as chromatin remodelling proteins, transcription factors, RNA binding proteins, and other plant-specific proteins whose functions are not yet clarified. In Arabidopsis thaliana, DICER-LIKE3 and members of the ARGONAUTE4 group of AROGONAUTE (AGO) proteins are involved, respectively, in generating and using 24-nt siRNAs that trigger methylation and transcriptional gene silencing (TGS) of homologous promoter sequences. AGO proteins act in silencing effector complexes by anchoring the 3â and 5â ends of the guide siRNAs at their N-terminal PAZ domain and MID domain, respectively. In addition, many AGO proteins cleave complementary target RNAs through an endonuclease (âslicerâ) activity in their C-terminal PIWI domain. AGO4 is the main AGO protein implicated in the RdDM pathway. Here we report the identification of the related AGO6 in a forward genetic screen for mutants defective in RdDM and TGS in shoot and root apical meristems in Arabidopsis thaliana. The identification of AGO6, and not AGO4, in our screen is consistent with the primary expression of AGO6 in shoot and root growing points and the preferential association of Pol V with AGO6. Examination of siRNA abundance in the trasngenic wild type plant (contains trigger and silencer transgenes) and the ago6-4 mutant.
2011-12-01 | E-GEOD-28537 | biostudies-arrayexpress
Project description:In plants, RNA polymerase II (Pol II) transcription of inverted DNA repeats produces hairpin RNAs that are processed by several DICER-LIKE enzymes into siRNAs that are 21-24-nt in length. When targeted to transcriptional regulatory regions, the 24-nt size class can induce RNA-directed DNA methylation (RdDM) and transcriptional gene silencing (TGS). In a forward genetic screen to identify mutants defective in RdDM of a target enhancer leading to TGS of a downstream GFP reporter gene in Arabidopsis thaliana, we recovered a structurally mutated silencer locus, named SM-NM-^T35S, in which the 35S promoter driving transcription of an inverted repeat of target enhancer sequences had been specifically deleted. Although Pol II-dependent, hairpin-derived 21-24-nt siRNAs were no longer generated at the newly created SM-NM-^T35S locus, the GFP reporter gene was nevertheless still partially silenced. Silencing was associated with methylation in a short tandem repeat in the upstream target enhancer and with low levels of 24-nt tandem repeat siRNAs. Introducing an nrpd1 mutation into the SM-NM-^T35S line fully released GFP silencing and eliminated both the tandem repeat methylation and associated 24-nt siRNAs, demonstrating their dependence on Pol IV. Deletion of the 35S promoter thus revealed a Pol IV-dependent pathway of 24-nt siRNA biogenesis that was previously inhibited or masked by the Pol II-dependent pathway in wild-type plants. Both Pol II- and Pol IV-dependent siRNAs accrued predominantly from cytosine (C)-containing segments of the tandem repeat monomer, suggesting that the local base composition influenced siRNA accumulation. Preferential accumulation of siRNAs at C-containing sequences was also observed at an endogenous tandem repeat comprising discrete C-rich and AT-rich sections. Our studies illuminate the potential complexity of siRNA generation at repeat-containing loci and show that Pol IV can act in siRNA biogenesis in the absence of a conventional Pol II promoter. Examination of whole-genome DNA methylation status in transgenic T+S Arabidopsis plant
2013-05-30 | E-GEOD-47453 | biostudies-arrayexpress
Project description:In plants, heterochromatin is maintained by a small RNA-based gene silencing mechanism known as RNA-directed DNA methylation (RdDM). RdDM requires the non-redundant functions of two plant-specific DNA-dependent RNA polymerases (Pol) Pol IV and Pol V. Pol IV plays a major role in siRNA biogenesis, while Pol V may recruit DNA methylation machinery to target endogenous loci for silencing. Although small RNA-generating regions which are dependent on both Pol IV and Pol V have been identified previously, the genomic loci targeted Pol V for siRNA accumulation and silencing have not been described extensively. To characterize the Pol V-dependent, heterochromatic siRNA-generating regions in the Arabidopsis genome, we deeply sequenced the small RNA populations of wild-type and Pol V mutant plants. Furthermore, we characterized the siRNA-generating regions which were dependent on RdDM effectors and examined their dependency on Pol V. Small RNA libraries were generated and deeply sequenced from mutant alleles dms4-1, drd1-1, dms3-1, and rdm1-4, along with their control library (“Wt(T+S)”) which has been described previously (Kanno et al. 2004 Current Biology). More than 2,000 small RNA-generating loci were identified which were greatly suppressed in Pol V mutants.
2012-06-11 | GSE36424 | GEO
Project description:The RNA-directed DNA methylation (RdDM) pathway in plants controls gene expression via cytosine DNA methylation. The ability to manipulate RdDM would shed light on the mechanisms and applications of DNA methylation to control gene expression. Here, we identified diverse RdDM proteins that are capable of targeting methylation and silencing in Arabidopsis when tethered to an artificial zinc finger (ZF-RdDM). We studied their order of action within the RdDM pathway by testing their ability to target methylation in different mutants. We also evaluated ectopic siRNA biogenesis, RNA Polymerase V (Pol V) recruitment, targeted DNA methylation, and gene expression changes at thousands of ZF-RdDM targets. We found that co-targeting both arms of the RdDM pathway, siRNA biogenesis and Pol V recruitment, dramatically enhanced targeted methylation. This work defines how RdDM components establish DNA methylation, and enables new strategies for epigenetic gene regulation via targeted DNA methylation.
2019-02-07 | GSE124744 | GEO
Project description:The RNA-directed DNA methylation (RdDM) pathway in plants controls gene expression via cytosine DNA methylation. The ability to manipulate RdDM would shed light on the mechanisms and applications of DNA methylation to control gene expression. Here, we identified diverse RdDM proteins that are capable of targeting methylation and silencing in Arabidopsis when tethered to an artificial zinc finger (ZF-RdDM). We studied their order of action within the RdDM pathway by testing their ability to target methylation in different mutants. We also evaluated ectopic siRNA biogenesis, RNA Polymerase V (Pol V) recruitment, targeted DNA methylation, and gene expression changes at thousands of ZF-RdDM targets. We found that co-targeting both arms of the RdDM pathway, siRNA biogenesis and Pol V recruitment, dramatically enhanced targeted methylation. This work defines how RdDM components establish DNA methylation, and enables new strategies for epigenetic gene regulation via targeted DNA methylation.
2019-02-07 | GSE124546 | GEO