Arabidopsis mutants impaired in cosuppression

• Published in: The Plant cell Vol. 10; no. 10; pp. 1747 - 1757
• Main Authors: Elmayan, T. (INRA, Versailles, France.), Balzergue, S, Beon, F, Bourdon, V, Daubremet, J, Guenet, Y, Mourrain, P, Palauqui, J.C, Vernhettes, S, Vialle, T
• Format: Journal Article
• Language: English
• Published: United States American Society of Plant Physiologists 01-10-1998; American Society of Plant Biologists (ASPB)
• Subjects: ACTIVIDAD ENZIMATICA; ACTIVITE ENZYMATIQUE; ADN; Alleles; Arabidopsis - genetics; Arabidopsis - metabolism; ARABIDOPSIS THALIANA; ARN MENSAJERO; ARN MESSAGER; BETA-GLUCURONIDASE; DEGRADACION; DEGRADATION; DNA; DNA METHYLATION; DNA, Bacterial - genetics; DNA, Bacterial - metabolism; DNA, Recombinant - genetics; DNA, Recombinant - metabolism; ENZYMIC ACTIVITY; EXPRESION GENICA; EXPRESSION DES GENES; GENE; GENE EXPRESSION; GENE RECESSIF; GENES; GENES RECESIVOS; Genes, Plant; Genetic loci; Genetic mutation; GENETIC REGULATION; GENETICA; GENETICS; GENETIQUE; GLICOSIDASAS; Glucuronidase - genetics; GLYCOSIDASE; GLYCOSIDASES; INDUCED MUTATION; Life Sciences; LOCI; LOCUS; MESSENGER RNA; Methylation; Models, Genetic; MUTACION INDUCIDA; MUTANT; MUTANTES; MUTANTS; Mutation; MUTATION PROVOQUEE; NIA2 GENE; NITRATE REDUCTASE; NITRATO REDUCTASA; Plant cells; PLANTAS TRANSGENICAS; PLANTE TRANSGENIQUE; Plants; Plants genetics; Plants, Genetically Modified; POST-TRANSCRIPTIONAL GENE SILENSING; RECESSIVE GENES; REPORTER GENES; RNA; RNA, Messenger - genetics; RNA, Messenger - metabolism; RNA, Plant - genetics; RNA, Plant - metabolism; SGS 1 LOCUS; SGS 2 LOCUS; Suppression, Genetic; TRANSCRIPCION; TRANSCRIPTION; Transgenes; TRANSGENIC PLANTS; BETA GLUCURONIDASE
• ISSN: 1040-4651; 1532-298X
• DOI: 10.1105/tpc.10.10.1747

Post-transcriptional gene silencing (cosuppression) results in the degradation of RNA after transcription. A transgenic Arabidopsis line showing post-transcriptional silencing of a 35S-uidA transgene and uidA-specific methylation was mutagenized using ethyl methanesulfonate. Six independent plants were isolated in which uidA mRNA accumulation and beta-glucuronidase activity were increased up to 3500-fold, whereas the transcription rate of the 35S-uidA transgene was increased only up to threefold. These plants each carried a recessive monogenic mutation that is responsible for the release of silencing. These mutations defined two genetic loci, called sgs1 and sgs2 (for suppressor of gene silencing). Transgene methylation was distinctly modified in sgs1 and sgs2 mutants. However, methylation of centromeric repeats was not affected, indicating that sgs mutants differ from ddm (for decrease in DNA methylation) and som (for somniferous) mutants. Indeed, unlike ddm and som mutations, sgs mutations were not able to release transcriptional silencing of a 35S-hpt transgene. Conversely, both sgs1 and sgs2 mutations were able to release cosuppression of host Nia genes and 35S-Nia2 transgenes. These results therefore indicate that sgs mutations act in trans to impede specifically transgene-induced post-transcriptional gene silencing