title: Production of aberrant promoter transcripts contributes to methylation and silencing of unlinked homologous promoters in trans.
abstract: Previous work has suggested that de novo methylation of plant nuclear genes can be triggered by an RNA-DNA interaction. To test whether transcription of a promoter would induce de novo methylation and silencing of unlinked genes driven by the same promoter, a chimeric 'gene' consisting of a nopaline synthase promoter (NOSpro) positioned downstream of the cauliflower mosaic virus 35S promoter (35Spro) and flanked at the 3' end by a NOS terminator (NOSter) was constructed and introduced into the genome of a plant that normally expresses an unmethylated NOSpro-neomycinphosphotransferase (nptII) gene. Transformants were tested for kanamycin resistance and NOSpro RNA synthesis. Most produced a full-length polyadenylated NOSpro RNA, which did not induce silencing or methylation at the NOSpro-nptII target gene. One, however, contained truncated non-polyadenylated NOSpro RNA; in this plant, the NOSpro-nptII gene became silenced and methylated in the NOSpro region. Molecular analysis of the NOSpro silencing locus revealed two incomplete copies of the 35Spro-NOSpro gene arranged as an inverted repeat with NOSpro sequences at the center. Reducing NOSpro transcription by crossing a 35Spro-silencing locus partially reactivated nptII gene expression and decreased NOSpro methylation at the target locus, thus implicating aberrant NOSpro RNA in this trans-silencing phenomenon.
authors.affiliation: Institute of Molecular Biology, Austrian Academy of Sciences, Billrothstrasse 11, A-5020 Salzburg, Austria.
authors.forename: M F
authors.initials: MF
authors.lastname: Mette
authors.forename: J
authors.initials: J
authors.lastname: van der Winden
authors.forename: M A
authors.initials: MA
authors.lastname: Matzke
authors.forename: A J
authors.initials: AJ
authors.lastname: Matzke
mesh_terms: D000594:Amino Acid Oxidoreductases / Q000235:genetics; D002678:Chimera / Q000235:genetics; D019175:DNA Methylation; D018744:DNA, Plant / Q000235:genetics* / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D007613:Kanamycin Resistance / Q000235:genetics; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D018744:DNA, Plant; D018749:RNA, Plant; D000594:Amino Acid Oxidoreductases; C021883:nopaline synthase