title: Post-transcriptional gene silencing triggered by sense transgenes involves uncapped antisense RNA and differs from silencing intentionally triggered by antisense transgenes.
abstract: Although post-transcriptional gene silencing (PTGS) has been studied for more than a decade, there is still a gap in our understanding of how de novo silencing is initiated against genetic elements that are not supposed to produce double-stranded (ds)RNA. Given the pervasive transcription occurring throughout eukaryote genomes, we tested the hypothesis that unintended transcription could produce antisense (as)RNA molecules that participate to the initiation of PTGS triggered by sense transgenes (S-PTGS). Our results reveal a higher level of asRNA in Arabidopsis thaliana lines that spontaneously trigger S-PTGS than in lines that do not. However, PTGS triggered by antisense transgenes (AS-PTGS) differs from S-PTGS. In particular, a hypomorphic ago1 mutation that suppresses S-PTGS prevents the degradation of asRNA but not sense RNA during AS-PTGS, suggesting a different treatment of coding and non-coding RNA by AGO1, likely because of AGO1 association to polysomes. Moreover, the intended asRNA produced during AS-PTGS is capped whereas the asRNA produced during S-PTGS derives from 3' maturation of a read-through transcript and is uncapped. Thus, we propose that uncapped asRNA corresponds to the aberrant RNA molecule that is converted to dsRNA by RNA-DEPENDENT RNA POLYMERASE 6 in siRNA-bodies to initiate S-PTGS, whereas capped asRNA must anneal with sense RNA to produce dsRNA that initiate AS-PTGS.
authors.affiliation: Institut Jean-Pierre Bourgin, UMR1318, INRA, 78000 Versailles, France.
authors.forename: Jean-Sébastien
authors.initials: JS
authors.lastname: Parent
authors.affiliation: Institut Jean-Pierre Bourgin, UMR1318, INRA, 78000 Versailles, France.
authors.forename: Vincent
authors.initials: V
authors.lastname: Jauvion
authors.affiliation: Institut Jean-Pierre Bourgin, UMR1318, INRA, 78000 Versailles, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Bouché
authors.affiliation: Institut Jean-Pierre Bourgin, UMR1318, INRA, 78000 Versailles, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Béclin
authors.affiliation: URGI, INRA, 78000 Versailles, France.
authors.forename: Mélanie
authors.initials: M
authors.lastname: Hachet
authors.affiliation: URGI, INRA, 78000 Versailles, France.
authors.forename: Matthias
authors.initials: M
authors.lastname: Zytnicki
authors.affiliation: Institut Jean-Pierre Bourgin, UMR1318, INRA, 78000 Versailles, France herve.vaucheret@versailles.inra.fr.
authors.forename: Hervé
authors.initials: H
authors.lastname: Vaucheret
mesh_terms: D017360:Arabidopsis / Q000235:genetics; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D060565:Argonaute Proteins / Q000235:genetics; D009154:Mutation; D034622:RNA Interference; D020871:RNA Stability; D016372:RNA, Antisense / Q000096:biosynthesis / Q000378:metabolism*; D012330:RNA, Double-Stranded / Q000378:metabolism; D034741:RNA, Small Interfering / Q000096:biosynthesis; D012324:RNA-Dependent RNA Polymerase / Q000378:metabolism; D019076:Transgenes
chemical_list: C117457:AGO1 protein, Arabidopsis; D029681:Arabidopsis Proteins; D060565:Argonaute Proteins; D016372:RNA, Antisense; D012330:RNA, Double-Stranded; D034741:RNA, Small Interfering; C514575:RDR6 protein, Arabidopsis; D012324:RNA-Dependent RNA Polymerase