microRNA-directed phasing during trans-acting siRNA biogenesis in plants

Edwards Allen, Zhixin Xie, Adam M. Gustafson, James C. Carrington

Research output: Contribution to journalArticlepeer-review

1633 Scopus citations


Plants and animals use small RNAs (microRNAs [miRNAs] and siRNAs) as guides for posttranscriptional and epigenetic regulation. In plants, miRNAs and trans-acting (ta) siRNAs form through distinct biogenesis pathways, although they both interact with target transcripts and guide cleavage. An integrated approach to identify targets of Arabidopsis thaliana miRNAs and ta-siRNAs revealed several new classes of small RNA-regulated genes, including conventional genes such as Argonaute2 and an E2-ubiquitin conjugating enzyme. Surprisingly, five ta-siRNA-generating transcripts were identified as targets of miR173 or miR390. Rather than functioning as negative regulators, miR173- and miR390-guided cleavage was shown to set the 21-nucleotide phase for ta-siRNA precursor processing. These data support a model in which miRNA-guided formation of a 5′ or 3′ terminus within pre-ta-siRNA transcripts, followed by RDR6-dependent formation of dsRNA and Dicer-like processing, yields phased ta-siRNAs that negatively regulate other genes.

Original languageEnglish
Pages (from-to)207-221
Number of pages15
Issue number2
StatePublished - Apr 22 2005


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