title: A Pol V-mediated silencing, independent of RNA-directed DNA methylation, applies to 5S rDNA.
abstract: The plant-specific RNA polymerases Pol IV and Pol V are essential to RNA-directed DNA methylation (RdDM), which also requires activities from RDR2 (RNA-Dependent RNA Polymerase 2), DCL3 (Dicer-Like 3), AGO4 (Argonaute), and DRM2 (Domains Rearranged Methyltransferase 2). RdDM is dedicated to the methylation of target sequences which include transposable elements, regulatory regions of several protein-coding genes, and 5S rRNA-encoding DNA (rDNA) arrays. In this paper, we have studied the expression of the 5S-210 transcript, a marker of silencing release at 5S RNA genes, to show a differential impact of RNA polymerases IV and V on 5S rDNA arrays during early development of the plant. Using a combination of molecular and cytological assays, we show that Pol IV, RDR2, DRM2, and Pol V, actors of the RdDM, are required to maintain a transcriptional silencing of 5S RNA genes at chromosomes 4 and 5. Moreover, we have shown a derepression associated to chromatin decondensation specific to the 5S array from chromosome 4 and restricted to the Pol V-loss of function. In conclusion, our results highlight a new role for Pol V on 5S rDNA, which is RdDM-independent and comes specifically at chromosome 4, in addition to the RdDM pathway.
authors.affiliation: CNRS, UMR 6247 GReD, Clermont Université, INSERM U931, Aubière, France.
authors.forename: Julien
authors.initials: J
authors.lastname: Douet
authors.forename: Sylvie
authors.initials: S
authors.lastname: Tutois
authors.forename: Sylvette
authors.initials: S
authors.lastname: Tourmente
mesh_terms: D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D032461:Chromosomes, Plant; D019175:DNA Methylation; D018744:DNA, Plant / Q000378:metabolism*; D004275:DNA, Ribosomal / Q000378:metabolism*; D012321:DNA-Directed RNA Polymerases / Q000235:genetics / Q000378:metabolism*; D018749:RNA, Plant / Q000235:genetics* / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics*; D014158:Transcription, Genetic
chemical_list: D029681:Arabidopsis Proteins; D018744:DNA, Plant; D004275:DNA, Ribosomal; D018749:RNA, Plant; D034741:RNA, Small Interfering; C499181:RNA polymerase IV, Arabidopsis; C538841:RNA polymerase V, Arabidopsis; D012321:DNA-Directed RNA Polymerases