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Arabidopsis small RNAs associated with RDR6-dependent RNA-directed DNA Methylation

ABSTRACT: Background: The majority of plant transposable elements (TEs) are found in a silenced state that is epigenetically propagated by the maintenance of symmetrical DNA methylation. TE methylation is established and reinforced by a mechanism of RNA-dependent DNA methylation, which is dependent on transcription of the PolIV RNA polymerase. Recently, a pathway has been described that initiates de novo DNA methylation dependent on components of the RNAi post-transcriptional silencing pathway, independent of PolIV. To define the function of this new pathway, we have focused on the RDR6 protein, which plays a central role in the pathway we refer to as RDR6-dependent RNA-directed DNA Methylation (RDR6-RdDM). Methods: We have sequenced total small RNAs from wild-type and three mutant genotypes: ddm1, ddm1/rdr6, and rdr6. Conclusions: We demonstrate that RDR6-RdDM utilizes 21 and 22 nucleotide siRNAs to de novo methylate actively transcribing TEs. In addition, we find that the RDR6-RdDM pathway functions in the efficient initiation and re-establishment of TE transcriptional silencing, while it is not necessary to maintain trans-generational epigenetic silencing.

ORGANISM(S): Arabidopsis thaliana

PROVIDER: GSE41755 | GEO | 2013/04/11

SECONDARY ACCESSION(S): PRJNA178113

REPOSITORIES: GEO

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Arabidopsis small RNAs associated with RDR6-dependent RNA-directed DNA Methylation

Project description:Background: The majority of plant transposable elements (TEs) are found in a silenced state that is epigenetically propagated by the maintenance of symmetrical DNA methylation. TE methylation is established and reinforced by a mechanism of RNA-dependent DNA methylation, which is dependent on transcription of the PolIV RNA polymerase. Recently, a pathway has been described that initiates de novo DNA methylation dependent on components of the RNAi post-transcriptional silencing pathway, independent of PolIV. To define the function of this new pathway, we have focused on the RDR6 protein, which plays a central role in the pathway we refer to as RDR6-dependent RNA-directed DNA Methylation (RDR6-RdDM). Methods: We have sequenced total small RNAs from wild-type and three mutant genotypes: ddm1, ddm1/rdr6, and rdr6. Conclusions: We demonstrate that RDR6-RdDM utilizes 21 and 22 nucleotide siRNAs to de novo methylate actively transcribing TEs. In addition, we find that the RDR6-RdDM pathway functions in the efficient initiation and re-establishment of TE transcriptional silencing, while it is not necessary to maintain trans-generational epigenetic silencing. Examination of flower bud small RNAs from wild-type and 3 mutant genotypes

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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 wt Col ecotype of Arabidopsis thaliana. In plants mutant for the SWI/SNF2 histone remodeler DDM1, TEs are globally activated due to loss of genome wide heterochromatin condensation. Activated TEs go through additional non-canonical forms of RdDM. However, the global targets of the non-canonical RdDM pathway are unidentified. In an attempt to identify and contrast the targets of canonical and non-canonical RdDM, we sequenced small RNAs from several RdDM mutants in either the TE-silent or the TE-active (ddm1) contexts. Examination of unopened flower bud small RNAs from wild type and various single or double mutant combinations, many of which have biological replicates. Small RNA sequences from wt Col, controls and other mutants shown in the study are available at GSE41755 and GSE57191.

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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 wt Col ecotype of Arabidopsis thaliana. In plants mutant for the SWI/SNF2 histone remodeler DDM1, TEs are globally activated due to loss of genome wide heterochromatin condensation. Activated TEs go through additional non-canonical forms of RdDM. However, the global targets of the non-canonical RdDM pathway are unidentified. In an attempt to identify and contrast the targets of canonical and non-canonical RdDM, we sequenced small RNAs from several RdDM mutants in either the TE-silent or the TE-active (ddm1) contexts.

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Arabidopsis MORC proteins function in the efficient establishment of RNA directed DNA methylation

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