title: A T7-driven silencing system in transgenic plants expressing T7 RNA polymerase is a nuclear process.
abstract: We previously demonstrated a case of silencing in transgenic plants expressing T7 RNA polymerase in which expression of a reporter gene placed under the control of the T7 promoter was silenced. Here we demonstrate that endogenous genes can be silenced by the same system. The T7-driven silencing system does not conform to several aspects characteristic of post-transcriptional RNA silencing in plants, and this prompted an investigation into the mechanisms underlying this type of silencing. The present paper demonstrates that T7-driven silencing is a post-transcriptional process that is restricted to the nucleus. Nuclear run-on assays indicated the presence of silenced gene transcripts in both orientations. SiRNA corresponding to the silenced gene could not be traced in the cytoplasm but was found in nuclei. The silenced gene was hypermethylated. We present evidence that a tobacco RNA-dependent RNA polymerase (RdRP) is not involved in T7-mediated silencing, but indicate the involvement of a nuclear RdRP in this type of silencing.
authors.affiliation: Robert H. Smith Institute for Plant Sciences and Genetics in Agriculture, The Hebrew University of Jerusalem, Faculty of Agricultural, Food and Environmental Quality Sciences, Rehovot, Israel.
authors.forename: Yuval
authors.initials: Y
authors.lastname: Peretz
authors.forename: Michal
authors.initials: M
authors.lastname: Levy
authors.forename: Eva
authors.initials: E
authors.lastname: Avisar
authors.forename: Orit
authors.initials: O
authors.lastname: Edelbaum
authors.forename: Haim
authors.initials: H
authors.lastname: Rabinowitch
authors.forename: Ilan
authors.initials: I
authors.lastname: Sela
mesh_terms: D017123:Bacteriophage T7 / Q000235:genetics* / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism*; D012321:DNA-Directed RNA Polymerases / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D018506:Gene Expression Regulation, Plant; D030821:Plants, Genetically Modified / Q000201:enzymology* / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D034622:RNA Interference; D012323:RNA Processing, Post-Transcriptional; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D012324:RNA-Dependent RNA Polymerase / Q000235:genetics / Q000378:metabolism; D014026:Nicotiana / Q000201:enzymology* / Q000235:genetics; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D018749:RNA, Plant; D034741:RNA, Small Interfering; D014764:Viral Proteins; C062210:bacteriophage T7 RNA polymerase; D012324:RNA-Dependent RNA Polymerase; D012321:DNA-Directed RNA Polymerases