Translational research into meiotic recombination: more than mere validations
Résumé
Sustainable crop improvement largely depends on exploiting meiotic crossovers, i.e. the reciprocal exchanges of large DNA fragments between chromosomes. In addition to their mechanistic role in ensuring correct chromosome segregation (essential for fertility), meiotic crossovers are responsible for reshuffling pre-existing patterns of genetic variation between individuals and between species. Great strides have been made in elucidating the basic molecular mechanisms of meiosis and meiotic recombination in model plants over the past 20 years (Mercier et al., 2015). In this talk, we will present the results of our first attempts to translate this improved knowledge into diploid and polyploid Brassica crop species. Our reverse genetics approach has consisted in the functional characterization of meiotic recombination mutants isolated from EMS-mutagenized B. rapa and B. napus populations, that we have evaluated using a combination of cytological and genetic approaches. Our results show that it is possible to increase crossover rate significantly, by knocking-down the activity of an anti-crossover protein, FANCM (Blary et al., 2018). Then, we will demonstrate that regular meiosis is maintained in B. napus even when the number of functional copies of another essential meiotic recombination gene (MSH4) is reduced to a minimum. We have also evaluated the consequences of duplicate MSH4 gene loss on inter-homoeologue crossover and we will discuss implications.
Altogether, our results highlight the benefit of translational research into meiotic recombination, which unravels new properties for already known meiotic actors and opens new avenues to make a wider range of genetic diversity accessible to crop improvement.