Abstract
RNA interference pathways can involve amplification of secondary siRNAs by RNA-dependent RNA polymerases. In plants, RDR6-dependent secondary siRNAs arise from transcripts targeted by some microRNAs (miRNAs). Here, Arabidopsis thaliana secondary siRNAs from mRNA as well as trans-acting siRNAs are shown to be triggered through initial targeting by a 22-nucleotide (nt) miRNA that associates with AGO1. In contrast to canonical 21-nt miRNAs, 22-nt miRNAs primarily arise from foldback precursors containing asymmetric bulges. Using artificial miRNA constructs, conversion of asymmetric foldbacks to symmetric foldbacks resulted in the production of 21-nt forms of miR173, miR472 and miR828. Both 21-and 22-nt forms associated with AGO1 and guided accurate slicer activity, but only 22-nt forms were competent to trigger RDR6-dependent siRNA production from target RNA. These data suggest that AGO1 functions differentially with 21-and 22-nt miRNAs to engage the RDR6-associated amplification apparatus.
Original language | English (US) |
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Pages (from-to) | 997-1003 |
Number of pages | 7 |
Journal | Nature Structural and Molecular Biology |
Volume | 17 |
Issue number | 8 |
DOIs | |
State | Published - Aug 2010 |
Externally published | Yes |
ASJC Scopus subject areas
- Structural Biology
- Molecular Biology