An RNA-dependent RNA polymerase gene in Arabidopsis is required for posttranscriptional gene silencing mediated by a transgene but not by a virus.
Posttranscriptional gene silencing is a defense mechanism in plants that is similar to quelling in fungi and RNA interference in animals. Here, we describe four genetic loci that are required for posttranscriptional gene silencing in Arabidopsis. One of these, SDE1, is a plant homolog of QDE-1 in Neurospora crassa that encodes an RNA-dependent RNA polymerase. The sde1 mutation was specific for posttranscriptional gene silencing induced by transgenes rather than by viruses. We propose that the role of SDE1 is to synthesize a double-stranded RNA initiator of posttranscriptional gene silencing. According to this idea, when a virus induces posttranscriptional gene silencing, the virus-encoded RNA polymerase would produce the double-stranded RNA and SDE1 would be redundant.
Dalmay
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T
The Sainsbury Laboratory, John Innes Centre, Norwich, United Kingdom.
Hamilton
A
A
Rudd
S
S
Angell
S
S
Baulcombe
D C
DC
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics; D001483:Base Sequence; D019175:DNA Methylation; D005656:Fungal Proteins; D020868:Gene Silencing; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009492:Neurospora crassa / Q000201:enzymology; D030821:Plants, Genetically Modified; D012323:RNA Processing, Post-Transcriptional; D012324:RNA-Dependent RNA Polymerase / Q000235:genetics*; D017386:Sequence Homology, Amino Acid; D014027:Tobacco Mosaic Virus / Q000235:genetics; D019076:Transgenes
D005656:Fungal Proteins; C119303:QDE1 protein, Neurospora crassa; D012324:RNA-Dependent RNA Polymerase