title: Double-stranded RNA binding proteins DRB2 and DRB4 have an antagonistic impact on polymerase IV-dependent siRNA levels in Arabidopsis.
abstract: Biogenesis of the vast majority of plant siRNAs depends on the activity of the plant-specific RNA polymerase IV (PolIV) enzyme. As part of the RNA-dependent DNA methylation (RdDM) process, PolIV-dependent siRNAs (p4-siRNAs) are loaded onto an ARGONAUTE4-containing complex and guide de novo DNA methyltransferases to target loci. Here we show that the double-stranded RNA binding proteins DRB2 and DRB4 are required for proper accumulation of p4-siRNAs. In flowers, loss of DRB2 results in increased accumulation of p4-siRNAs but not ta-siRNAs, inverted repeat (IR)-derived siRNAs, or miRNA. Loss of DRB2 does not impair uniparental expression of p4-dependent siRNAs in developing endosperm, indicating that p4-siRNA increased accumulation is not the result of the activation of the polIV pathway in the male gametophyte. In contrast to drb2, drb4 mutants exhibit reduced p4-siRNA levels, but the extent of this reduction is variable, according to the nature and size of the p4-siRNAs. Loss of DRB4 also leads to a spectacular increase of p4-independent IR-derived 24-nt siRNAs, suggesting a reallocation of factors from p4-dependent to p4-independent siRNA pathways in drb4. Opposite effects of drb2 and drb4 mutations on the accumulation of p4-siRNAs were also observed in vegetative tissues. Moreover, transgenic plants overexpressing DRB2 mimicked drb4 mutants at the morphological and molecular levels, confirming the antagonistic roles of DRB2 and DRB4.
authors.affiliation: Université de Perpignan Via Domitia, CNRS UMR5096 LGDP, 66860 Perpignan Cedex, France.
authors.forename: Thierry
authors.initials: T
authors.lastname: Pélissier
authors.forename: Marion
authors.initials: M
authors.lastname: Clavel
authors.forename: Cristian
authors.initials: C
authors.lastname: Chaparro
authors.forename: Marie-Noëlle
authors.initials: MN
authors.lastname: Pouch-Pélissier
authors.forename: Hervé
authors.initials: H
authors.lastname: Vaucheret
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Deragon
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D019951:DNA Polymerase beta / Q000037:antagonists & inhibitors*; D009154:Mutation; D034741:RNA, Small Interfering / Q000096:biosynthesis* / Q000235:genetics; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; C561224:DRB2 protein, Arabidopsis; C511456:DRB4 protein, Arabidopsis; D034741:RNA, Small Interfering; D016601:RNA-Binding Proteins; D019951:DNA Polymerase beta