title: A duplicated NUCLEOLIN gene with antagonistic activity is required for chromatin organization of silent 45S rDNA in Arabidopsis.
abstract: In plants as well as in animals, hundreds to thousands of 45S rRNA gene copies localize in Nucleolus Organizer Regions (NORs), and the activation or repression of specific sets of rDNA depends on epigenetic mechanisms. Previously, we reported that the Arabidopsis thaliana nucleolin protein NUC1, an abundant and evolutionarily conserved nucleolar protein in eukaryotic organisms, is required for maintaining DNA methylation levels and for controlling the expression of specific rDNA variants in Arabidopsis. Interestingly, in contrast with animal or yeast cells, plants contain a second nucleolin gene. Here, we report that Arabidopsis NUC1 and NUC2 nucleolin genes are both required for plant growth and survival and that NUC2 disruption represses flowering. However, these genes seem to be functionally antagonistic. In contrast with NUC1, disruption of NUC2 induces CG hypermethylation of rDNA and NOR association with the nucleolus. Moreover, NUC2 loss of function triggers major changes in rDNA spatial organization, expression, and transgenerational stability. Our analyses indicate that silencing of specific rRNA genes is mostly determined by the active or repressed state of the NORs and that nucleolin proteins play a key role in the developmental control of this process.
authors.affiliation: CNRS, Laboratoire Génome et Développement des Plantes, Unité Mixte de Recherche 5096, 66860 Perpignan, France.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Durut
authors.forename: Mohamed
authors.initials: M
authors.lastname: Abou-Ellail
authors.forename: Frédéric
authors.initials: F
authors.lastname: Pontvianne
authors.forename: Sadhan
authors.initials: S
authors.lastname: Das
authors.forename: Hisae
authors.initials: H
authors.lastname: Kojima
authors.forename: Seiko
authors.initials: S
authors.lastname: Ukai
authors.forename: Anne
authors.initials: A
authors.lastname: de Bures
authors.forename: Pascale
authors.initials: P
authors.lastname: Comella
authors.forename: Sabine
authors.initials: S
authors.lastname: Nidelet
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Rialle
authors.forename: Remy
authors.initials: R
authors.lastname: Merret
authors.forename: Manuel
authors.initials: M
authors.lastname: Echeverria
authors.forename: Philippe
authors.initials: P
authors.lastname: Bouvet
authors.forename: Kenzo
authors.initials: K
authors.lastname: Nakamura
authors.forename: Julio
authors.initials: J
authors.lastname: Sáez-Vásquez
mesh_terms: D017360:Arabidopsis / Q000235:genetics*; D002843:Chromatin / Q000378:metabolism*; D056915:DNA Copy Number Variations; D019175:DNA Methylation; D004275:DNA, Ribosomal / Q000235:genetics*; D020440:Gene Duplication; D017343:Genes, Plant; D010750:Phosphoproteins / Q000235:genetics*; D011401:Promoter Regions, Genetic; D012335:RNA, Ribosomal / Q000235:genetics*; D016601:RNA-Binding Proteins / Q000235:genetics*; D000097796:Nucleolin
chemical_list: D002843:Chromatin; D004275:DNA, Ribosomal; D010750:Phosphoproteins; D012335:RNA, Ribosomal; D016601:RNA-Binding Proteins; D000097796:Nucleolin; C088179:RNA, ribosomal, 45S