Unique Functionality of 22 nt miRNAs in Triggering RDR6-Dependent siRNA Biogenesis from Target Transcripts in Arabidopsis

Authors

Josh T. Cuperus, Oregon State University
Alberto Carbonell, Oregon State University
Noah Fahlgren, Oregon State UniversityFollow
Hernan Garcia-Ruiz, Oregon State UniversityFollow
Russell T. Burke, Oregon State University
Atsushi Takeda, Oregon State University
Christopher M. Sullivan, Oregon State University
Sunny D. Gilbert, Oregon State University
Taiowa A. Montgomery, Oregon State University
James C. Carrington, Oregon State UniversityFollow

Date of this Version

8-2010

Citation

Nat Struct Mol Biol. 2010 August ; 17(8): 997–1003. doi:10.1038/nsmb.1866.

Comments

Copyright 2010. Used by permission.

Abstract

RNA interference pathways may involve amplification of secondary siRNAs by RNA-dependent RNA polymerases. In plants, RDR6-dependent secondary siRNAs arise from transcripts targeted by some microRNA (miRNA). Here, Arabidopsis thaliana secondary siRNA from mRNA, and trans-acting siRNA, are shown to be triggered through initial targeting by 22 nt miRNA that associate with AGO1. In contrast to canonical 21 nt miRNA, 22 nt miRNA primarily arise from foldback precursors containing asymmetric bulges. Using artificial miRNA constructs, conversion of asymmetric foldbacks to symmetric foldbacks resulted in 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 miRNA were competent to trigger RDR6-dependent siRNA from target RNA. These data suggest that AGO1 functions differentially with 21 and 22 nt miRNA to engage the RDR6-associated amplification apparatus.