title: Intersection of small RNA pathways in Arabidopsis thaliana sub-nuclear domains.
abstract: In Arabidopsis thaliana, functionally diverse small RNA (smRNA) pathways bring about decreased RNA accumulation of target genes via several different mechanisms. Cytological experiments have suggested that the processing of microRNAs (miRNAs) and heterochromatic small interfering RNAs (hc-siRNAs) occurs within a specific nuclear domain that can present Cajal Body (CB) characteristics. It is unclear whether single or multiple smRNA-related domains are found within the same CB and how specialization of the smRNA pathways is determined within this specific sub-compartment. To ascertain whether nuclear smRNA centers are spatially related, we localized key proteins required for siRNA or miRNA biogenesis by immunofluorescence analysis. The intranuclear distribution of the proteins revealed that hc-siRNA, miRNA and trans-acting siRNA (ta-siRNA) pathway proteins accumulate and colocalize within a sub-nuclear structure in the nucleolar periphery. Furthermore, colocalization of miRNA- and siRNA-pathway members with CB markers, and reduced wild-type localization patterns in CB mutants indicates that proper nuclear localization of these proteins requires CB integrity. We hypothesize that these nuclear domains could be important for RNA silencing and may partially explain the functional redundancies and interactions among components of the same protein family. The CB may be the place in the nucleus where Dicer-generated smRNA precursors are processed and assigned to a specific pathway, and where storage, recycling or assembly of RNA interference components takes place.
authors.affiliation: Department of Biology, University of New Mexico, Albuquerque, New Mexico, United States of America. opontes@unm.edu
authors.forename: Olga
authors.initials: O
authors.lastname: Pontes
authors.forename: Alexa
authors.initials: A
authors.lastname: Vitins
authors.forename: Thomas S
authors.initials: TS
authors.lastname: Ream
authors.forename: Evelyn
authors.initials: E
authors.lastname: Hong
authors.forename: Craig S
authors.initials: CS
authors.lastname: Pikaard
authors.forename: Pedro
authors.initials: P
authors.lastname: Costa-Nunes
mesh_terms: D017360:Arabidopsis / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000378:metabolism; D015153:Blotting, Western; D020541:Coiled Bodies / Q000378:metabolism*; D017931:DNA Primers / Q000235:genetics; D005455:Fluorescent Antibody Technique; D035683:MicroRNAs / Q000096:biosynthesis / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D010940:Plant Proteins / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000235:genetics; D034622:RNA Interference / Q000502:physiology*; D034741:RNA, Small Interfering / Q000096:biosynthesis / Q000378:metabolism*; D043244:Ribonuclease III / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D017931:DNA Primers; C450825:HEN1 protein, Arabidopsis; D035683:MicroRNAs; D010940:Plant Proteins; D034741:RNA, Small Interfering; D043244:Ribonuclease III