title: Decondensation of chromosomal 45S rDNA sites in Lolium and Festuca genotypes does not result in karyotype instability.
abstract: Fragile sites (FSs) in plants have been described for species like Lolium and other grasses. Whereas in humans FSs were shown to be involved in genome instabilities; the consequences of FSs expression in plants are not known yet. To evaluate whether FSs cause karyotype instabilities, we assessed the frequency of micronuclei and lagging chromosomes in meristematic cells, the stability of the DNA content, and the occurrence of neocentromeres in the presumed chromosomal fragments of Lolium perenne, Lolium multiflorum, Festuca arrundinacea, and two Festulolium hybrids. The cell cycle analysis along with flow cytometric genome size measurements showed high stability in all genomes evaluated. Neocentromeric activity was neither observed in the presumed fragments nor in any other chromosomal region, then this is not the mechanism responsible by the stability. However, Fluorescence in situ hybridization (FISH) with a 45S ribosomal DNA (rDNA) probe in combination with YOYO staining of metaphasic chromosomes showed that many extended nucleolus organizing region (NOR) form very thin YOYO-positive chromatin fibers connecting the acentric 'fragment' with the centromere-containing chromosome region. The obtained data indicate that the expression of FSs does not result in genome instabilities or neocentromere formation. The FS-containing 45S rDNA carrying chromatin fibers undergo a cell cycle and gene activity-dependent dynamic decondensation process.
authors.affiliation: Department of Biology, Federal University of Lavras-UFLA, Lavras, Minas Gerais State, Brazil.
authors.forename: Laiane Corsini
authors.initials: LC
authors.lastname: Rocha
authors.affiliation: Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), OT Gatersleben, 06466, StadtSeeland, Germany.
authors.forename: Maja
authors.initials: M
authors.lastname: Jankowska
authors.affiliation: Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), OT Gatersleben, 06466, StadtSeeland, Germany.
authors.forename: Joerg
authors.initials: J
authors.lastname: Fuchs
authors.affiliation: Embrapa Dairy Cattle/Embrapa Temperate Agriculture, Pelotas, Rio Grande do Sul State, Brazil.
authors.forename: Andréa
authors.initials: A
authors.lastname: Mittelmann
authors.affiliation: Department of Biology, Federal University of Lavras-UFLA, Lavras, Minas Gerais State, Brazil. vhtechio@gmail.com.
authors.forename: Vânia Helena
authors.initials: VH
authors.lastname: Techio
authors.affiliation: Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), OT Gatersleben, 06466, StadtSeeland, Germany. houben@ipk-gatersleben.de.
authors.forename: Andreas
authors.initials: A
authors.lastname: Houben
mesh_terms: D002452:Cell Count; D043283:Chromosome Fragile Sites / Q000235:genetics; D032461:Chromosomes, Plant / Q000235:genetics*; D031751:Festuca / Q000235:genetics*; D005434:Flow Cytometry; D042822:Genomic Instability; D005838:Genotype; D017404:In Situ Hybridization, Fluorescence; D059785:Karyotype; D008129:Lolium / Q000235:genetics*; D008677:Metaphase / Q000235:genetics; D012335:RNA, Ribosomal / Q000235:genetics*
chemical_list: D012335:RNA, Ribosomal; C088179:RNA, ribosomal, 45S
keywords: Chromatin fiber; DNA content; Forage grass; Fragile sites; Genomic stability; Lolium-Festuca complex