RerRNA transcripts are detected all through the nucleolus by RNA-FISH (fluorescent in
RerRNA transcripts are detected all through the nucleolus by RNA-FISH (fluorescent in situ hybridization) (Fig. 1C, bottom row). On the other hand, essentially the most prominent 45S rRNA gene DNA-FISH signals are external to the nucleolus (Fig. 1B [red signals], C [top row, green signals]; note that NOR associations can Coccidia Molecular Weight result in fewer than 4 signals). rRNA genes inside the nucleolus are decondensed and more difficult to detect by DNA-FISH, based on the extent of their dispersal (e.g., cf. the two nuclei in Fig. 1B). HISTONE DEACETYLASE six (HDA6) is required for uniparental rRNA gene silencing in hybrid Arabidopsis suecica and for developmentally regulated silencing of variant 1 rRNA genes in nonhybrid A. thaliana (Earley et al. 2006, 2010). HDA6 localizes throughout nuclei, including the nucleolus (Fig. 1C). In hda6 mutants, NORs decondense (Probst et al. 2004; Earley et al. 2006), and rRNA gene FISH signals inside the nucleolus raise (Fig. 1D). In leaves of wild-type plants (ecotype Col-0), variant 2 and three rRNA gene subtypes are expressed,In eukaryotes, 45S ribosomal RNA (rRNA) genes are tandemly arrayed at nucleolus organizer regions (NORs) (see[Keywords: transcription; gene silencing; DNA methylation; histone deacetylation; chromatin assembly; RNA polymerase I; ribosomal RNA gene] eight These authors contributed equally to this function. Present addresses: 9Laboratoire Genome et Developpement des Plantes, UMR 5096 CNRS-University of Perpignan by means of Domitia, Perpignan, France; 10 Department of Plant Biology and Forest Genetics, Swedish University of Agricultural Sciences, Linnean Center for Plant Biology, Uppsala, Sweden; 11 Monsanto Company, St. Louis, MO 63107, USA 12 Corresponding authors E-mail [email protected] E-mail [email protected] Write-up is online at genesdev.org/cgi/doi/10.1101/gad.221648.113. Freely accessible on-line by means of the Genes Development Open Access solution.GENES Development 27:1545550 2013 by Cold Spring Harbor Laboratory Press ISSN 0890-9369/13; genesdev.orgPontvianne et al.Figure 1. Partitioning of active and silent rRNA genes involving the nucleolus and nucleoplasm. (A) Relationships amongst the nucleolus, NORs, and 45S rRNA gene repeats. The drawing in the top rated depicts a metaphase chromosome with the remnants of a nucleolus related together with the secondary constriction, the place of active rRNA genes inside the preceding interphase. The black oval represents a chromomere in which rRNA genes are assembled into dense heterochromatin. In a. thaliana, insertions/deletions in the 39 external transcribed area define rRNA gene variant sorts. (B) Localization of rRNA genes (rDNA) and Pol I. DNA-FISH making use of an rRNA gene probe (red signals) and immunolocalization of Flag-tagged Pol I KDM2 Accession working with an anti-Flag antibody (green signals) have been performed in a. thaliana interphase nuclei. DNA was counterstained with DAPI (gray signals). (C) Subnuclear localization of rRNA genes, pre-rRNA transcripts, and Flag-tagged HDA6. rRNA gene or transcript FISH signals are shown in green, immunolocalized HDA6 is in red, and DAPI-stained DNA is in blue. Merged signals are shown inside the proper column. (D) DNA-FISH detection of rRNA genes in wild-type (Col-0) and hda6 nuclei. rRNA gene FISH signals are shown in red and are merged with all the DAPI (blue) image within the appropriate column. (E) Detection of rRNA gene variant sorts and their transcripts by PCR using genomic DNA or reversetranscribed (RT) cDNA of wild-type (Col-0) or hda6 plants. The amplified region is.
