title: Fertile hypomorphic ARGONAUTE (ago1) mutants impaired in post-transcriptional gene silencing and virus resistance.
abstract: Transgene-induced post-transcriptional gene silencing (PTGS) results from specific degradation of RNAs that are homologous with the transgene transcribed sequence. This phenomenon, also known as cosuppression in plants and quelling in fungi, resembles RNA interference (RNAi) in animals. Indeed, cosuppression/quelling/RNAi require related PAZ/PIWI proteins (AGO1/QDE-2/RDE-1), indicating that these mechanisms are related. Unlike Neurospora crassa qde-2 and Caenorhabditis elegans rde-1 mutants, which are morphologically normal, the 24 known Arabidopsis ago1 mutants display severe developmental abnormalities and are sterile. Here, we report the isolation of hypomorphic ago1 mutants, including fertile ones. We show that these hypomorphic ago1 mutants are defective for PTGS, like null sgs2, sgs3, and ago1 mutants, suggesting that PTGS is more sensitive than development to perturbations in AGO1. Conversely, a mutation in ZWILLE/PINHEAD, another member of the Arabidopsis AGO1 gene family, affects development but not PTGS. Similarly, mutations in ALG-1 and ALG-2, two members of the C. elegans RDE-1 gene family, affect development but not RNAi, indicating that the control of PTGS/RNAi and development by PAZ/PIWI proteins can be uncoupled. Finally, we show that hypomorphic ago1 mutants are hypersensitive to virus infection, confirming the hypothesis that in plants PTGS is a mechanism of defense against viruses.
authors.affiliation: Laboratoire de Biologie Cellulaire, Institut National de la Recherche Agronomique, 78026 Versailles Cedex, France.
authors.forename: Jean-Benoit
authors.initials: JB
authors.lastname: Morel
authors.forename: Christian
authors.initials: C
authors.lastname: Godon
authors.forename: Philippe
authors.initials: P
authors.lastname: Mourrain
authors.forename: Christophe
authors.initials: C
authors.lastname: Béclin
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Boutet
authors.forename: Frank
authors.initials: F
authors.lastname: Feuerbach
authors.forename: Florence
authors.initials: F
authors.lastname: Proux
authors.forename: Hervé
authors.initials: H
authors.lastname: Vaucheret
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development / Q000821:virology; D029681:Arabidopsis Proteins; D060565:Argonaute Proteins; D002874:Chromosome Mapping; D017799:Cucumovirus / Q000254:growth & development; D005298:Fertility / Q000235:genetics; D020868:Gene Silencing; D007113:Immunity, Innate; D008969:Molecular Sequence Data; D009154:Mutation; D010940:Plant Proteins / Q000235:genetics*; D010942:Plant Viruses / Q000254:growth & development*; D012323:RNA Processing, Post-Transcriptional; D018749:RNA, Plant / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic
chemical_list: D029681:Arabidopsis Proteins; D060565:Argonaute Proteins; D010940:Plant Proteins; D018749:RNA, Plant; C117457:AGO1 protein, Arabidopsis; C410506:SGS2 protein, Arabidopsis; C410507:SGS3 protein, Arabidopsis; C529694:AT5G43810 protein, Arabidopsis