A Pol V-mediated silencing, independent of RNA-directed DNA methylation, applies to 5S rDNA

PLoS Genet. 2009 Oct;5(10):e1000690. doi: 10.1371/journal.pgen.1000690. Epub 2009 Oct 16.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis / enzymology*
  • Arabidopsis / genetics
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism*
  • Chromosomes, Plant
  • DNA Methylation*
  • DNA, Plant / metabolism*
  • DNA, Ribosomal / metabolism*
  • DNA-Directed RNA Polymerases / genetics
  • DNA-Directed RNA Polymerases / metabolism*
  • RNA, Plant / genetics*
  • RNA, Plant / metabolism
  • RNA, Small Interfering / genetics*
  • Transcription, Genetic

Substances

  • Arabidopsis Proteins
  • DNA, Plant
  • DNA, Ribosomal
  • RNA, Plant
  • RNA, Small Interfering
  • RNA polymerase IV, Arabidopsis
  • RNA polymerase V, Arabidopsis
  • DNA-Directed RNA Polymerases