Epigenetic Control of Meiotic Recombination in Arabidopsis

Meiotic crossover (CO) frequency varies along chromosomes and is determined by hierarchical mechanisms, including epigenetic organization. For example, the Arabidopsis thaliana pericentromeres are repetitive, densely DNA methylated and suppressed for both RNA polymerase II transcription and recombination. We observe that methyltransferase1 (met1) mutants show extensive remodeling of CO frequency. Elevated centromere-proximal COs in met1 are coincident with pericentromeric decreases and distal increases in CO frequencies. Importantly, the total number of CO events is similar between wild type and met1, suggesting a role for interference and homeostasis in CO remodeling. We have also studied Arabidopsis CO hotspots using pollen-typing and observe that they overlap with intergenic, nucleosome-free regions. We observe that the 3a hotspot shows increased activity in met1, which we hypothesize is caused by CO remodeling driven by elevated centromeric COs. Together these data demonstrate how regional epigenetic organization can pattern recombination frequency along eukaryotic chromosomes at both domain and hotspot scales.