title: Unstable Inheritance of 45S rRNA Genes inArabidopsis thaliana.
abstract: The considerable genome size variation inArabidopsis thalianahas been shown largely to be due to copy number variation (CNV) in 45S ribosomal RNA (rRNA) genes. Surprisingly, attempts to map this variation by means of genome-wide association studies (GWAS) failed to identify either of the two likely sources, namely the nucleolus organizer regions (NORs). Instead, GWAS implicated atrans-acting locus, as if rRNA gene CNV was a phenotype rather than a genotype. To explain these results, we investigated the inheritance and stability of rRNA gene copy number using the variety of genetic resources available inA. thaliana- F2 crosses, recombinant inbred lines, the multiparent advanced-generation inter-cross population, and mutation accumulation lines. Our results clearly show that rRNA gene CNV can be mapped to the NORs themselves, with both loci contributing equally to the variation. However, NOR size is unstably inherited, and dramatic copy number changes are visible already within tens of generations, which explains why it is not possible to map the NORs using GWAS. We did not find any evidence oftrans-acting loci in crosses, which is also expected since changes due to such loci would take very many generations to manifest themselves. rRNA gene copy number is thus an interesting example of "missing heritability"-a trait that is heritable in pedigrees, but not in the general population.
authors.affiliation: Gregor Mendel Institute, Austrian Academy of Sciences, Vienna Biocenter (VBC), 1030, Austria.
authors.forename: Fernando A
authors.identifier: 0000-0003-1538-9752
authors.initials: FA
authors.lastname: Rabanal
authors.affiliation: Gregor Mendel Institute, Austrian Academy of Sciences, Vienna Biocenter (VBC), 1030, Austria.
authors.forename: Viktoria
authors.initials: V
authors.lastname: Nizhynska
authors.affiliation: Central European Institute of Technology, Masaryk University, 625 00 Brno, Czech Republic.
authors.forename: Terezie
authors.initials: T
authors.lastname: Mandáková
authors.affiliation: Gregor Mendel Institute, Austrian Academy of Sciences, Vienna Biocenter (VBC), 1030, Austria.
authors.forename: Polina Yu
authors.initials: PY
authors.lastname: Novikova
authors.affiliation: Central European Institute of Technology, Masaryk University, 625 00 Brno, Czech Republic.
authors.forename: Martin A
authors.initials: MA
authors.lastname: Lysak
authors.affiliation: University College London Genetics Institute, WC1E 6BT, UK.
authors.forename: Richard
authors.initials: R
authors.lastname: Mott
authors.affiliation: Gregor Mendel Institute, Austrian Academy of Sciences, Vienna Biocenter (VBC), 1030, Austria magnus.nordborg@gmi.oeaw.ac.at.
authors.forename: Magnus
authors.identifier: 0000-0001-7178-9748
authors.initials: M
authors.lastname: Nordborg
mesh_terms: D017360:Arabidopsis / Q000235:genetics*; D003433:Crosses, Genetic; D056915:DNA Copy Number Variations / Q000235:genetics; D018628:Gene Dosage; D017343:Genes, Plant; D056426:Genetic Loci; D007178:Inbreeding; D040582:Inheritance Patterns / Q000235:genetics*; D009697:Nucleolus Organizer Region / Q000235:genetics; D012335:RNA, Ribosomal / Q000235:genetics*; D011995:Recombination, Genetic / Q000235:genetics; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics
chemical_list: D012335:RNA, Ribosomal; C088179:RNA, ribosomal, 45S
keywords: 45S rRNA genes; Arabidopsis thaliana; natural variation; ribosomes