Genetic and Epigenetic Control of Arabidopsis Meiotic Recombination Hotspots

Meiotic crossover creates genetic diversity and underpins genetic analysis and crop breeding. It has long been appreciated that crossover frequency is non-random in genomes with the presence of hotspots and coldspots. Using population genetic approaches we have generated maps of historical crossover frequency in the Arabidopsis genome. This revealed that crossovers are concentrated at gene transcriptional start and termination sites, consistent with correlations between gene density and recombination observed in other plants. Hotspot gene promoters associate with epigenetic marks enriched on transcriptionally active genes and using experimental genetics we have demonstrated that H2A.Z is required for normal crossover frequency. More recently we have used RNA-directed DNA methylation to silence crossover hotspots, further demonstrating the importance of chromatin for recombination. I will present new data on our use of genome-wide approaches to map meiotic recombination proteins, including the SPO11 endonuclease, and what this is revealing about control of crossover locations and frequency. A greater understanding of how DNA sequence and epigenetic information modulate meiotic recombination will find useful applications during crop breeding.