18-BTT EAGER: Controlling meiotic recombination in crops by manipulating DNA methylation

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This consortium plans to develop highly innovative strategies to stimulate recombination in genomic regions that are normally refractory to genetic variation in key crop species. Developing ways to increase recombination rates in genome areas of low recombination will contribute to more efficient breeding. The outcome will allow reducing the time required to develop new elite germplasm and enable rapid introgression of desirable genes from diverse sources to facilitate developing more robust crops that will exhibit superior productivity in sustainable ways and be better suited to deal with the challenges arising from the climate change. The goal of this project is to gain an understanding of how DNA methylation influences the meiotic recombination landscape in plants. Meiotic recombination is initiated by the formation of numerous programmed double-strand breaks in chromosomal DNA, a small proportion of which are processed to form crossovers. Thus, genetic variation generated by a single round of meiotic recombination is limited. Furthermore, the distribution of crossovers in plants with large genomes, which include most crops, is highly biased towards the ends of chromosomes. As a result, extensive interstitial and centromere proximal chromosome regions rarely recombine. Yet, these large genome areas contain roughly one-fifth of the genes in maize and even larger gene fractions in some other crops, which presents a serious impediment to plant breeding. Recent studies indicate that DNA methylation is a critical factor shaping crossover landscapes. However, the exact relationship between recombination and DNA methylation is not understood. This project seeks to elucidate how DNA methylation affects recombination patterns at the mechanistic level and lay foundations for methods to control crossover landscapes in crops by altering DNA methylation. The study will be conducted in maize and Brassica rapa, to explore the behavior of both monocot and dicot genomes. To elucidate the effect of DNA methylation on meiotic recombination, a protocol to transiently alter DNA methylation patterns in meiosis will be developed. The chemically demethylated plants and selected mutants defective in DNA methylation will be used to determine which steps and processes of meiosis are altered by DNA methylation. It will be also established which specific aspect of DNA methylation affects crossover landscape.