Amplifying recombination genome-wide and reshaping crossover landscapes in Brassicas.

Alexandre Pelé (1) , Matthieu Falque (2) , Gwenn Trotoux (1) , Frederique Eber (1) , Sylvie Negre (1) , Marie Gilet (1) , Virginie Huteau (1) , Maryse Lodé-Taburel (1) , Thibaut Jousseaume (3) , Sylvain Dechaumet (1) , Jérôme Morice (1) , Charles Poncet (4) , Olivier Coriton (1) , Olivier Martin (2) , Mathieu Rousseau-Gueutin (1) , Anne-Marie Chèvre (1)

1 IGEPP - Institut de Génétique, Environnement et Protection des Plantes
2 GQE-Le Moulon - Génétique Quantitative et Evolution - Le Moulon (Génétique Végétale)
3 ESE - Écologie et santé des écosystèmes
4 GDEC - Génétique Diversité et Ecophysiologie des Céréales

Meiotic recombination by crossovers (COs) is tightly regulated, limiting its key role in producing genetic diversity. However, while COs are usually restricted in number and not homogenously distributed along chromosomes, we show here how to disrupt these rules in Brassica species by using allotriploid hybrids (AAC, 2n = 3x = 29), resulting from the cross between the allotetraploid rapeseed (B. napus, AACC, 2n = 4x = 38) and one of its diploid progenitors (B. rapa, AA, 2n = 2x = 20). We produced mapping populations from different genotypes of both diploid AA and triploid AAC hybrids, used as female and/or as male. Each population revealed nearly 3,000 COs that we studied with SNP markers well distributed along the A genome (on average 1 SNP per 1.25 Mbp). Compared to the case of diploids, allotriploid hybrids showed 1.7 to 3.4 times more overall COs depending on the sex of meiosis and the genetic background. Most surprisingly, we found that such a rise was always associated with (i) dramatic changes in the shape of recombination landscapes and (ii) a strong decrease of CO interference. Hybrids carrying an additional C genome exhibited COs all along the A chromosomes, even in the vicinity of centromeres that are deprived of COs in diploids as well as in most studied species. Moreover, in male allotriploid hybrids we found that Class I COs are mostly responsible for the changes of CO rates, landscapes and interference. These results offer the opportunity for geneticists and plant breeders to dramatically enhance the generation of diversity in Brassica species by disrupting the linkage drag coming from limits on number and distribution of COs.

Mots clés: genome; crossing over; genêtic variation; genome

Mots clés: diversité génétique; recombinaison méiotique; diversité génétique; brassica; chromosome

Domaines: Sciences du Vivant [q-bio]

Alexandre Pelé, Matthieu Falque, Gwenn Trotoux, Frederique Eber, Sylvie Negre, et al.. Amplifying recombination genome-wide and reshaping crossover landscapes in Brassicas.. PLoS Genetics, 2017, 13 (5), pp.e1006794. ⟨10.1371/journal.pgen.1006794⟩. ⟨hal-01607280⟩