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Reconstructing de novo silencing of an active plant retrotransposon: dynamics, mechanisms, biological implications

ABSTRACT: In plants, maintenance-methylation mediated by METHYLTRANSFERASE-1 (MET1), siRNA-directed de-novo methylation, and chromatin remodeling by DECREASE IN DNA METHYLATION -1 (DDM1) promote transcriptional gene-silencing of transposable elements (TEs). This process is mostly investigated at steady states reflecting how long-established silent conditions are maintained, faithfully re-iterated or temporarily modified during growth, stress and over generations. How invasive TEs are detected and silenced de novo, however, remains largely unknown. Using inbred lineages of hybrid Arabidopsis epigenomes combining wild-type and met1 or ddm1 chromosomes, we have deciphered the timing, spatial distribution and mechanisms underpinning the proliferation and eventual demise of the endogenous retrotransposon évadé (EVD). Both developmental and molecular features of EVD biology, including a remarkable ability to evade RNA interference, ultimately contribute to its silencing over multiple generations. The underlying processes are accompanied by widespread diversification of the Arabidopsis genome and de-novo epiallelism creating an extensive reservoir of selectable and potentially adaptive traits.

ORGANISM(S): Arabidopsis thaliana

PROVIDER: GSE43412 | GEO | 2013/07/02

SECONDARY ACCESSION(S): PRJNA186008

REPOSITORIES: GEO

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Reconstructing de novo silencing of an active plant retrotransposon: dynamics, mechanisms, biological implications

Project description:In plants, maintenance-methylation mediated by METHYLTRANSFERASE-1 (MET1), siRNA-directed de-novo methylation, and chromatin remodeling by DECREASE IN DNA METHYLATION -1 (DDM1) promote transcriptional gene-silencing of transposable elements (TEs). This process is mostly investigated at steady states reflecting how long-established silent conditions are maintained, faithfully re-iterated or temporarily modified during growth, stress and over generations. How invasive TEs are detected and silenced de novo, however, remains largely unknown. Using inbred lineages of hybrid Arabidopsis epigenomes combining wild-type and met1 or ddm1 chromosomes, we have deciphered the timing, spatial distribution and mechanisms underpinning the proliferation and eventual demise of the endogenous retrotransposon évadé (EVD). Both developmental and molecular features of EVD biology, including a remarkable ability to evade RNA interference, ultimately contribute to its silencing over multiple generations. The underlying processes are accompanied by widespread diversification of the Arabidopsis genome and de-novo epiallelism creating an extensive reservoir of selectable and potentially adaptive traits. Differential expression of EVADE small RNAs between three generations of one specific Col0 met1 derived EpiRIL.

2013-07-02 | E-GEOD-43412 | biostudies-arrayexpress

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2023-02-17 | GSE197718 | GEO

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Project description:Eukaryotic DNA is wrapped around histone octamers to form nucleosomes, which are separated by linker DNA bound by histone H1. In many species, the DNA exhibits methylation of CG dinucleotides, which is epigenetically inherited via a semiconservative mechanism. How methyltransferases access DNA within nucleosomes remains mysterious. Here we show that methylation of nucleosomes requires DDM1/Lsh nucleosome remodelers in Arabidopsis thaliana and mouse. We also show that removal of histone H1, which partially restores methylation in ddm1 mutants, does so primarily in the linker DNA between nucleosomes. In h1ddm1 compound mutants, substantial portions of the genome exhibit dramatically periodic methylation that approaches wild-type levels in linker DNA but is virtually absent in nucleosomes. We also present evidence that de novo methylation supplements semiconservative maintenance of CG methylation across generations. Overall, our results demonstrate that nucleosomes and H1 are barriers to DNA methylation, which are overcome by DDM1/Lsh nucleosome remodelers.

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SPOCD1 is a novel executor of piRNA-directed DNA methylation that links MIWI2 to the de novo DNA methylation machiner

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Project description:The PIWI protein MIWI2 and its associated PIWI-interacting RNAs (piRNAs) instruct DNA methylation of young active transposable elements (TEs) in the male germline. Here we show that MIWI2 associates with TEX15 in foetal gonocytes. TEX15 is predominantly a nuclear protein that is not required for piRNA biogenesis but is essential for piRNA-directed TE de novo methylation and silencing. In summary, TEX15 is an essential executor of mammalian piRNA-directed DNA methylation.

2020-06-18 | PXD019087 | Pride

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Project description:The diversity of small RNA-directed DNA methylation (RdDM) mechanisms have been underestimated due to the nearly complete transcriptional silencing of transposable elements (TEs) in the wild-type reference strains of Arabidopsis thaliana. In plants mutant for the SWI/SNF histone remodeler DDM1, TEs are globally activated due to loss of genome wide heterochromatin condensation. Transcriptionally activated TEs go through additional non-canonical forms of RdDM that are dependent on RNA Polymerase II expression. However, the global targets of the non-canonical RdDM pathway have not been explored. In an attempt to identify and contrast the targets of canonical and expression-dependent non-canonical RdDM, we performed MethylC-seq of genome-wide DNA methylation patterns from several RdDM mutants in either the TE-silent or the TE-active (ddm1) contexts. Arabidopsis wildtype and twenty RdDM pathway mutants

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