Immediate unidirectional epigenetic reprogramming of NORs occurs independently of rDNA rearrangements in synthetic and natural forms of a polyploid species <Emphasis Type="Italic">Brassica napus</Emphasis> |
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Authors: | Tomasz Ksi??czyk Ales Kovarik Frédérique Eber Virginie Huteau Lucie Khaitova Zuzana Tesarikova Olivier Coriton Anne-Marie Chèvre |
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Institution: | (1) Institut National de la Recherche Agronomique (INRA), UMR118 APBV, BP 35327, 35653 Le Rheu cedex, France;(2) Institute of Biophysics, Academy of Science of the Czech Republic, Brno, Czech Republic;(3) Present address: Laboratory of Cytogenetics and Molecular Biology, Institute of Plant Genetics Polish Academy of Sciences, 60-479 Poznań, Poland; |
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Abstract: | The dynamics of genome modification that occurred from the initial hybridization event to the stabilization of allopolyploid
species remains largely unexplored. Here, we studied inheritance and expression of rDNA loci in the initial generations of
Brassica napus allotetraploids (2n = 38, AACC) resynthesized from Brassica oleracea (2n = 18, CC) and B. rapa (2n = 20, AA) and compared the patterns to natural forms. Starting already from F1 generation, there was a strong uniparental
silencing of B. oleracea genes. The epigenetic reprogramming was accompanied with immediate condensation of C-genome nucleolar organizer region (NOR)
and progressive transgeneration hypermethylation of polymerase I promoters, mainly at CG sites. No such changes were observed
in the A-genome NORs. Locus loss and gains affecting mainly non-NOR loci after the first allotetraploid meiosis did not influence
established functional status of NORs. Collectively, epigenetic and genetic modifications in synthetic lines resemble events
that accompanied formation of natural allopolyploid species. |
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