RESEARCH-PGR: Understanding 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. Thus, meiotic recombination is one of the main forces behind evolution. In addition, it is utilized as an unparalleled instrument of plant and animal breeding. In stark contrast to its importance, surprisingly little is known about mechanisms controlling recombination, particularly in plants. Mechanisms of recombination appear to be different in each major group of eukaryotes and also highly dependent on genome size and complexity. Recombination events are not evenly distributed throughout the genome but predominantly take place at distinct sites called recombination "hotspots". This project seeks to understand why and how specific sites in the genome become recombination hotspots in maize. In addition to contributing significant new insight into an important biological process, the information generated will be useful to breeders who are continuously looking for new ways to increase recombination for more efficient breeding of crop plants. With regard to outreach and training, the project will develop a Science Undergraduate Minority Mentoring Internship and Training (SUMMIT) program which will provide yearly 10-week research training internships for minority undergraduate students. The goal of this project is to illuminate the mechanisms controlling distribution of recombination events in maize. This work capitalizes on the recent success in generating a high-resolution map of double-strand-breaks (DSBs), which initiate meiotic recombination, and a high-resolution map of crossover (COs) in maize. The plan is to elucidate why recombination takes place in specific sites in the genome and understand how the locations of these sites are affected by genetic and epigenetic factors. The molecular mechanisms of hotspot recognition will be unraveled by searching for proteins interacting with the newly discovered DNA sequence motif present at recombination hotspots, examining the role of DNA and histone methylation on hotspot activity, and investigating the link between DSB hotspot presence and chromatin openness. In addition, mechanisms that prevent formation of COs in heterochromatin will be elucidated. This work will further the understanding of how recombination is controlled in plants and how it affects the structure of large and complex plant genomes. All project outcomes will be made accessible to the public. Data generated in this project will be made available to the public through the project website (www.rec-hotspots.org) and through the appropriate long-term repositories such as MaizeGDB and the NCBI's SRA. Genetic resources will be made available through the Maize Genetics Cooperation Stock Center.