Investigation of Recombination Differences Between Sexes Using High-Resolution Physical Mapping in Maize

Humans depend on meiotic recombination to generate genetic variation for the development of food and fiber products necessary to our survival. However, the process of recombination and the resulting crossovers (COs) during meiosis is not completely understood. In Arabidopsis and maize, CO’s are associated with gene promoters and genes at a greater frequency (Choi et al. 2013; Wijnker et al. 2013; Li et al. 2015; Rodgers-Melnick et al. 2015; Shilo et al. 2015). The reported underlying chromatin structure of these regions have a variety of active chromatin modifications including decreased nucleosome occupancy, changes in DNA and histone methylation. Though there is an understanding of the basic patterning of CO events in the maize genome, there are unexplained differences in CO rates between male and female (Rhoades, 1941). Using the completed B73, and extension genome sequence of Mo17 inbred genomes, it was possible to begin investigating these differences. This research examines the previously identified CO control mechanisms using a high-resolution physical map in maize to discover if the CO control mechanisms used in male and the female are the same. We confirm the effects of DNA methylation, and histone modification are important to enabling a CO event are the same between the sexes. However, significant differences between the male and female were found for the overall CO rates, and in nearly a dozen 1 Mb regions, as well as changes in the placement of the CO in relationship to the transcription start sequence (TSS) of the gene. These results are beginning to unravel the differences between CO behavior in the male and female within the maize species.