RESEARCH-PGR: Controlling recombination in maize

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Meiotic recombination is a process in which two parental chromosomes, one from the father and the other one from the mother, exchange parts to give rise to the next generation. This process creates new genetic variation in the progeny, which facilitates adaptation to new environments and purges detrimental mutations from genomes. Meiotic recombination is one of the main mechanisms of evolution and is also an unparalleled instrument of plant and animal breeding. However, despite their importance, recombination events are not evenly distributed throughout the genome. Instead, they predominantly take place at distinct sites called recombination hotspots. Compared to other groups of eukaryotes, little is understood about the mechanisms controlling recombination in plants, and particularly little is known about recombination in crops, which tend to have large and complex genomes. The goal of this project is to determine how specific sites in the genome become recombination hotspots in maize, a model species as well as a major crop, how recombination hotspots evolve, and how they can be modified to improve plant breeding methods. A large fraction of maize genes are located in regions that show very limited recombination. Developing ways to increase recombination in these regions will allow more efficient breeding. To further spread the knowledge about meiotic recombination, the laboratories participating in this project will jointly operate a Science Undergraduate Minority Mentoring Internship and Training (SUMMIT) program, which each year will sponsor three 10-week internships for minority undergraduate students. The goal of this project is to elucidate the meiotic recombination landscape in maize and gain the ability to modify it. Meiotic recombination starts with a programmed formation of double-strand breaks (DSBs) in chromosomal DNA. Repair of the DSBs leads to reciprocal exchanges of chromosome arms called crossovers (COs). In most species, including maize, large numbers of meiotic DSBs are generated but very few of them become COs. Furthermore, although DSBs are ubiquitously present throughout the entire maize genome, most COs are near chromosome ends. This project will examine how chromatin as well as DNA sequence affect CO landscape and how the knowledge of recombination mechanisms can be used to alter CO landscape. To understand the role of chromatin and chromosome characteristics in shaping CO distribution, the impact of chromatin state, and the dynamics of homologous chromosome interactions on the progression of CO formation will be investigated. The relationship between genome sequence and CO patterns will also be studied to understand how genetic diversity affects CO landscapes. To test the knowledge on recombination genomics gained from this project, and to apply it for a practical purpose, effectiveness of artificial CO hotspots will be examined. This research will provide a more complete picture of how recombination is controlled in plants and facilitate development of efficient tools to harness it for plant breeding. This award was co-funded by the Plant Genome Research Program in the Division of Integrative Organismal Systems and the Genetic Mechanisms Cluster in the Division of Molecular and Cellular Biosciences.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.