Arabidopsis SGS2 and SGS3 genes are required for posttranscriptional gene silencing and natural virus resistance

Cell. 2000 May 26;101(5):533-42. doi: 10.1016/s0092-8674(00)80863-6.


Posttranscriptional gene silencing (PTGS) in plants resuits from the degradation of mRNAs and shows phenomenological similarities with quelling in fungi and RNAi in animals. Here, we report the isolation of sgs2 and sgs3 Arabidopsis mutants impaired in PTGS. We establish a mechanistic link between PTGS, quelling, and RNAi since the Arabidopsis SGS2 protein is similar to an RNA-dependent RNA polymerase like N. crassa QDE-1, controlling quelling, and C. elegans EGO-1, controlling RNAi. In contrast, SGS3 shows no significant similarity with any known or putative protein, thus defining a specific step of PTGS in plants. Both sgs2 and sgs3 mutants show enhanced susceptibility to virus, definitively proving that PTGS is an antiviral defense mechanism that can also target transgene RNA for degradation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Arabidopsis / enzymology
  • Arabidopsis / genetics
  • Arabidopsis Proteins*
  • Base Sequence
  • Chromosome Mapping
  • Cloning, Molecular
  • Cucumovirus
  • DNA, Plant
  • Gene Silencing*
  • Genes, Plant*
  • Lycopersicon esculentum / enzymology
  • Molecular Sequence Data
  • Mutagenesis
  • Plant Diseases / virology*
  • Plant Proteins / genetics
  • Plant Proteins / metabolism*
  • Potyvirus
  • RNA Processing, Post-Transcriptional*
  • RNA-Dependent RNA Polymerase / genetics
  • RNA-Dependent RNA Polymerase / metabolism*
  • Tobamovirus


  • Arabidopsis Proteins
  • DNA, Plant
  • Plant Proteins
  • SGS2 protein, Arabidopsis
  • SGS3 protein, Arabidopsis
  • RNA-Dependent RNA Polymerase

Associated data

  • GENBANK/AF239718
  • GENBANK/AF239719