High-Resolution Mapping of Crossover Events in the Hexaploid Wheat Genome Suggests a Universal Recombination Mechanism. Issue 3 (1st July 2017)

• Record Type: Journal Article
• Authors: Darrier, Benoit; Rimbert, Hélène; Balfourier, François; Pingault, Lise; Josselin, Ambre-Aurore; Servin, Bertrand; Navarro, Julien; Choulet, Frédéric; Paux, Etienne; Sourdille, Pierre
• Is Part Of: Genetics. Volume 206:Issue 3(2017)
• Page Start: 1373
• Page End: 1388
• Publication Date: 2017-07-01
• Subjects: recombination -- meiosis -- bread wheat -- linkage disequilibrium -- transposon -- hotspot -- sequence motif; Genetics -- Periodicals; 576.5
• DOI: 10.1534/genetics.116.196014
• Languages: English
• ISSNs: 0016-6731

Abstract

Abstract: During meiosis, crossovers (COs) create new allele associations by reciprocal exchange of DNA. In bread wheat ( Triticum aestivum L.), COs are mostly limited to subtelomeric regions of chromosomes, resulting in a substantial loss of breeding efficiency in the proximal regions, though these regions carry ∼60–70% of the genes. Identifying sequence and/or chromosome features affecting recombination occurrence is thus relevant to improve and drive recombination. Using the recent release of a reference sequence of chromosome 3B and of the draft assemblies of the 20 other wheat chromosomes, we performed fine-scale mapping of COs and revealed that 82% of COs located in the distal ends of chromosome 3B representing 19% of the chromosome length. We used 774 SNPs to genotype 180 varieties representative of the Asian and European genetic pools and a segregating population of 1270 F6 lines. We observed a common location for ancestral COs (predicted through linkage disequilibrium) and the COs derived from the segregating population. We delineated 73 small intervals (<26 kb) on chromosome 3B that contained 252 COs. We observed a significant association of COs with genic features (73 and 54% in recombinant and nonrecombinant intervals, respectively) and with those expressed during meiosis (67% in recombinant intervals and 48% in nonrecombinant intervals). Moreover, while the recombinant intervals contained similar amounts of retrotransposons and DNA transposons (42 and 53%), nonrecombinant intervals had a higher level of retrotransposons (63%) and lower levels of DNA transposons (28%). Consistent with this, we observed a higher frequency of a DNA motif specific to the TIR-Mariner DNA transposon in recombinant intervals.