Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
2036487 | Cell | 2010 | 12 Pages |
SummaryMicroRNAs (miRNAs) control gene expression in animals and plants. Like another class of small RNAs, siRNAs, they affect gene expression posttranscriptionally. While siRNAs in addition act in transcriptional gene silencing, a role of miRNAs in transcriptional regulation has been less clear. We show here that in moss Physcomitrella patens mutants without a DICER-LIKE1b gene, maturation of miRNAs is normal but cleavage of target RNAs is abolished and levels of these transcripts are drastically reduced. These mutants accumulate miRNA:target-RNA duplexes and show hypermethylation of the genes encoding target RNAs, leading to gene silencing. This pathway occurs also in the wild-type upon hormone treatment. We propose that initiation of epigenetic silencing by DNA methylation depends on the ratio of the miRNA and its target RNA.
Graphical SummaryFigure optionsDownload full-size imageDownload high-quality image (212 K)Download as PowerPoint slideHighlights► The moss DICER-LIKE1a (PpDCL1a) protein is required for miRNA biogenesis ► The related PpDCL1b protein is required for target cleavage but not miRNA biogenesis ► In PpDCL1b mutants, genes encoding miRNA targets are silenced by DNA methylation ► This epigenetic gene silencing is initiated by high miRNA to target RNA ratios