Fertile hypomorphic ARGONAUTE (ago1) mutants impaired in post-transcriptional gene silencing and virus resistance.
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.
Morel
Jean-Benoit
JB
Laboratoire de Biologie Cellulaire, Institut National de la Recherche Agronomique, 78026 Versailles Cedex, France.
Godon
Christian
C
Mourrain
Philippe
P
Béclin
Christophe
C
Boutet
Stéphanie
S
Feuerbach
Frank
F
Proux
Florence
F
Vaucheret
Hervé
H
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
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