title: The poor lonesome A subgenome of Brassica napus var. Darmor (AACC) may not survive without its mate.
abstract: Constitutive genomes of allopolyploid species evolve throughout their life span. However, the consequences of long-term alterations on the interdependency between each original genome have not been established. Here, we attempted an approach corresponding to subgenome extraction from a previously sequenced natural allotetraploid, offering a unique opportunity to evaluate plant viability and structural evolution of one of its diploid components. We employed two different strategies to extract the diploid AA component of the Brassica napus variety 'Darmor' (AACC, 2n = 4x = 38) and we assessed the genomic structure of the latest AA plants obtained (after four to five rounds of selection), using a 60K single nucleotide polymorphism Illumina array. Only one strategy was successful and the diploid AA plants that were structurally characterized presented a lower proportion of the B. napus A subgenome extracted than expected. In addition, our analyses revealed that some genes lost in a polyploid context appeared to be compensated for plant survival, either by conservation of genomic regions from B. rapa, used in the initial cross, or by some introgressions from the B. napus C subgenome. We conclude that as little as c. 7500 yr of coevolution could lead to subgenome interdependency in the allotetraploid B. napus as a result of structural modifications.
authors: IGEPP, INRA, Agrocampus Ouest, Université de Rennes 1, 35650, Le Rheu, France.
authors: Alexandre
authors: A
authors: Pelé
authors: IGEPP, INRA, Agrocampus Ouest, Université de Rennes 1, 35650, Le Rheu, France.
authors: Gwenn
authors: G
authors: Trotoux
authors: IGEPP, INRA, Agrocampus Ouest, Université de Rennes 1, 35650, Le Rheu, France.
authors: Frédérique
authors: F
authors: Eber
authors: IGEPP, INRA, Agrocampus Ouest, Université de Rennes 1, 35650, Le Rheu, France.
authors: Maryse
authors: M
authors: Lodé
authors: IGEPP, INRA, Agrocampus Ouest, Université de Rennes 1, 35650, Le Rheu, France.
authors: Marie
authors: M
authors: Gilet
authors: IGEPP, INRA, Agrocampus Ouest, Université de Rennes 1, 35650, Le Rheu, France.
authors: Gwenaelle
authors: G
authors: Deniot
authors: IGEPP, INRA, Agrocampus Ouest, Université de Rennes 1, 35650, Le Rheu, France.
authors: Cyril
authors: C
authors: Falentin
authors: IGEPP, INRA, Agrocampus Ouest, Université de Rennes 1, 35650, Le Rheu, France.
authors: Sylvie
authors: S
authors: Nègre
authors: IGEPP, INRA, Agrocampus Ouest, Université de Rennes 1, 35650, Le Rheu, France.
authors: Jérôme
authors: J
authors: Morice
authors: IGEPP, INRA, Agrocampus Ouest, Université de Rennes 1, 35650, Le Rheu, France.
authors: Mathieu
authors: M
authors: Rousseau-Gueutin
authors: IGEPP, INRA, Agrocampus Ouest, Université de Rennes 1, 35650, Le Rheu, France.
authors: Anne-Marie
authors: AM
authors: Chèvre
mesh_terms: D005075:Biological Evolution; D029688:Brassica napus / Q000235:genetics*; D032461:Chromosomes, Plant / Q000235:genetics; D004171:Diploidy; D018745:Genome, Plant; D006824:Hybridization, Genetic; D011058:Pollen / Q000166:cytology; D011123:Polyploidy
keywords: allopolyploidy; evolution; oilseed rape; structural rearrangements; subgenome extraction