title: microRNA-directed phasing during trans-acting siRNA biogenesis in plants.
abstract: 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.
authors.affiliation: Center for Gene Research and Biotechnology, Oregon State University, Corvallis, Oregon 97331, USA.
authors.forename: Edwards
authors.initials: E
authors.lastname: Allen
authors.forename: Zhixin
authors.initials: Z
authors.lastname: Xie
authors.forename: Adam M
authors.initials: AM
authors.lastname: Gustafson
authors.forename: James C
authors.initials: JC
authors.lastname: Carrington
mesh_terms: D017360:Arabidopsis / Q000235:genetics*; D001483:Base Sequence; D020869:Gene Expression Profiling / Q000379:methods / Q000592:standards; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics; D035683:MicroRNAs / Q000235:genetics*; D008969:Molecular Sequence Data; D034741:RNA, Small Interfering / Q000235:genetics*; D015203:Reproducibility of Results; D014158:Transcription, Genetic / Q000235:genetics
chemical_list: D035683:MicroRNAs; D034741:RNA, Small Interfering