title: RDR2 partially antagonizes the production of RDR6-dependent siRNA in sense transgene-mediated PTGS.
abstract: BACKGROUND
  RNA-DEPENDENT RNA POLYMERASE6 (RDR6) and SUPPRESSOR of GENE SILENCING 3 (SGS3) are required for DNA methylation and post-transcriptional gene silencing (PTGS) mediated by 21-nt siRNAs produced by sense transgenes (S-PTGS). In contrast, RDR2, but not RDR6, is required for DNA methylation and TGS mediated by 24-nt siRNAs, and for cell-to-cell spreading of IR-PTGS mediated by 21-nt siRNAs produced by inverted repeat transgenes under the control of a phloem-specific promoter.
  
  
  RESULTS
  In this study, we examined the role of RDR2 and RDR6 in S-PTGS. Unlike RDR6, RDR2 is not required for DNA methylation of transgenes subjected to S-PTGS. RDR6 is essential for the production of siRNAs by transgenes subjected to S-PTGS, but RDR2 also contributes to the production of transgene siRNAs when RDR6 is present because rdr2 mutations reduce transgene siRNA accumulation. However, the siRNAs produced via RDR2 likely are counteractive in wildtype plants because impairement of RDR2 increases S-PTGS efficiency at a transgenic locus that triggers limited silencing, and accelerates S-PTGS at a transgenic locus that triggers efficient silencing.
  
  
  CONCLUSIONS
  These results suggest that RDR2 and RDR6 compete for RNA substrates produced by transgenes subjected to S-PTGS. RDR2 partially antagonizes RDR6 because RDR2 action likely results in the production of counteractive siRNA. As a result, S-PTGS efficiency is increased in rdr2 mutants.
authors.affiliation: Institut Jean-Pierre Bourgin, INRA, Versailles, France.
authors.forename: Vincent
authors.initials: V
authors.lastname: Jauvion
authors.forename: Maud
authors.initials: M
authors.lastname: Rivard
authors.forename: Nathalie
authors.initials: N
authors.lastname: Bouteiller
authors.forename: Taline
authors.initials: T
authors.lastname: Elmayan
authors.forename: Hervé
authors.initials: H
authors.lastname: Vaucheret
mesh_terms: D019175:DNA Methylation / Q000235:genetics; D018744:DNA, Plant / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism*; D034622:RNA Interference; D018749:RNA, Plant / Q000378:metabolism; D034741:RNA, Small Interfering / Q000096:biosynthesis*; D019076:Transgenes / Q000235:genetics*
chemical_list: D018744:DNA, Plant; D010940:Plant Proteins; D018749:RNA, Plant; D034741:RNA, Small Interfering