Regulation of homologous recombination
Context and Issues
Establishment of a novel diversity and stability of a species rely on the ability of plants to have a regular meiosis during which meiotic recombination occurs and generates genetically balanced gametes. For that, at least one crossover must occur within each homologous pair. In the case of polyploid species as bread wheat (Triticum aestivum, AABBDD, 2n=42) originated from hybridization between the tetraploid wheat (Triticum diccocum, AABB, 2n=28) and Ae. tauschii (DD, 2n=14), and oilseed rape (Brassicanapus, AACC, 2n=38 derived from a cross between turnip (B. rapa, AA, 2n=20) and cabbage (B.oleracea, CC, 2n=18), regularity of meiosis depend on the ability of any chromosome to pair with its homologue. For exploiting genetic resources, genomes of progenitors and those of polyploids must pair and recombine.
For optimizing breeding programmes aiming to diversify gene combinations, we try to define more precisely the impact (1) of the genome structure of hybrids on their ability to recombine, (2) genetic systems involved in meiotic recombination.
In oilseed rape and wheat, study of homologous recombination within the different constitutive genomes in different hybrid combinations
In oilseed rape, we have shown that meiosis in F1 plants AAC between B. rapa (AA) and natural or synthetic oilseed rape (AACC) is regular (Leflon et al. 2006) and generates much more recombination events between the A genomes than in hybrids AA or AACC (Leflon et al. 2010; PhD thesis M. Leflon 2007). The level of pairing in hybrids depends also on the oilseed rape genotype (Nicolas et al. 2009). Analysis of derivatives of hybrids with AA + 1 chromosome C or different chromosome C indicates that the specific C09 chromosome plays a key role in the regulation of recombination between A homologous chromosomes (Suay et al. 2014). The impact of this system on distribution of crossovers is in progress (A. Pelé, PhD).
The high rate of homologous recombination in AAC and CCA hybrids between A and C genomes, respectively, is used to introduce a large variability with oilseed rape. Populations of core collections were crossed with the same oilseed rape variety. Large prebreeding populations were generated. This material was sent to the different private partners of Promosol and is used to identify new alleles for disease resistance and nitrogen efficiency.
In wheat: hexaploid wheat synthetics display large differences between them in the level of homologous meiotic pairing. Our objective is now to decipher the genetic determinism involved in chromosome pairing. A F2 population derived from the cross between two contrasted hexaploid synthetics has been evaluated for the level of chromosome pairing. This will allow the detection and mapping of the QTL involved. Another project is to test if wheat pentaploids (AABBD) have the same boosting effect on crossing-over frequencies within A and B genomes as Brassica AAC hybrids.
- UMR IJPB Versailles, France
- UMR GDEC (INRA Clermont-Ferrand)
- UMR Génétique Végétale, Moulon, France
- Wageningen UR, Netherlands
Funding and Support
- Projet ANR, Blanc ANR Blanc COPATH (2008-2010) (Resp : C.Mézard) : Unravelling crossover pathways with Arabidopsis thaliana and crop relatives
- AAP BAP(2014-2015) (PI A.M. Chèvre): Caractérisation et mode d’action d’une machine à recombiner. Modèle Brassica
- Promosol (2011-2014) (PI : A.M. Chèvre) : Exploitation de la biodiversité des progéniteurs pour l’amélioration du colza
- ANR CROC (2015-2018) (PI E. Jenczewski) : Controling Recombination rate in pOlyploid Crops
Leflon M. (2007) Effets de la structure de l’hybride et du fonds génétique sur le taux de recombinaison entre les génomes A de Brassica rapa (AA, 2n=20) et de B.napus (AACC, 2n=38). Application à l’introgression de gènes de résistance à Leptosphaeria maculans dans le colza. Thèse de l’Université de Rennes I - Agrocampus Rennes. Mention : Biologie et Agronomie pp115
Leflon M.*, Grandont L.*, Eber F., Huteau V., Coriton O., Chelysheva L., Jenczewski E., Chèvre A.M. (2010) Crossovers get a boost in Brassica allotriploid and allotetraploid hybrids. The Plant Cell 22: 2253-2264
Leflon M., Eber F., Letanneur J.C., Chelysheva L., Coriton O., Huteau V., Ryder C. D., Barker G., Jenczewski E., Chèvre A.M. (2006) Pairing and recombination at meiosis of Brassica rapa (AA) x Brassica napus (AACC) hybrids. Theor. Appl. Genet. 113 (8): 1467-1480
Nicolas S., Leflon M., Monot H., Eber F., Coriton O., Huteau V., Chèvre A.M., Jenczewski E. (2009) Genetic regulation of meiotic crossovers between related genomes in Brassica napus haploids and hybrids. Plant Cell 21: 373-385.
Suay L., Zhang D., Eber F., Jouy H., Lodé M., Huteau V., Coriton O., Szadkowski E., Leflon M., Martin O.C., Falque M., Jenczewski E., Paillard S. & Chèvre A.M. (2014). Crossover rate between homologous chromosomes and interference are regulated by the addition of specific unpaired chromosomes in Brassica. New phytologist, 201(2): 645-656.