Unique functionality of 22-nt miRNAs in triggering RDR6-dependent siRNA biogenesis from target transcripts in Arabidopsis.
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.
Cuperus
Josh T
JT
Molecular and Cellular Biology Program, Department of Botany and Plant Pathology, Oregon State University, Corvallis, Oregon, USA.
Carbonell
Alberto
A
Fahlgren
Noah
N
Garcia-Ruiz
Hernan
H
Burke
Russell T
RT
Takeda
Atsushi
A
Sullivan
Christopher M
CM
Gilbert
Sunny D
SD
Montgomery
Taiowa A
TA
Carrington
James C
JC
D017360:Arabidopsis / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D001483:Base Sequence; D018506:Gene Expression Regulation, Plant; D035683:MicroRNAs / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009711:Nucleotides / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics; D012324:RNA-Dependent RNA Polymerase / Q000378:metabolism*
D029681:Arabidopsis Proteins; D035683:MicroRNAs; D009711:Nucleotides; D012333:RNA, Messenger; D034741:RNA, Small Interfering; C514575:RDR6 protein, Arabidopsis; D012324:RNA-Dependent RNA Polymerase