A Pol V-Mediated Silencing, Independent of RNA-Directed DNA Methylation, Applies to 5S rDNA

Julien Douet (1) , Sylvie Tutois (1) , Sylvette Tourmente (1)

1 GReD - Génétique, Reproduction et Développement

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. Citation: Douet J, Tutois S, Tourmente S (2009) A Pol V-Mediated Silencing, Independent of RNA-Directed DNA Methylation, Applies to 5S rDNA. PLoS Genet 5(10): e1000690.

Domaines: Génétique des plantes

Julien Douet, Sylvie Tutois, Sylvette Tourmente. A Pol V-Mediated Silencing, Independent of RNA-Directed DNA Methylation, Applies to 5S rDNA. PLoS Genetics, 2009, 5 (10), pp.e1000690. ⟨10.1371/journal.pgen.1000690⟩. ⟨hal-01920591⟩