Natural variation and dosage of the HEI10 meiotic E3 ligase control crossover recombination.

During meiosis, homologous chromosomes undergo crossover recombination, which creates genetic diversity and balances homolog segregation. Despite these critical functions, crossover frequency varies extensively within and between species. Although natural crossover recombination modifier loci have been detected in plants, causal genes have remained elusive. Using natural accessions, we identified two major recombination quantitative trait loci (s) that explain 56.9% of crossover variation in Col×Ler F populations. We mapped to semidominant polymorphisms in , which encodes a conserved ubiquitin E3 ligase that regulates crossovers. Null mutants are haploinsufficient, and, using genome-wide mapping and immunocytology, we show that transformation of additional copies is sufficient to more than double euchromatic crossovers. However, heterochromatic centromeres remained recombination-suppressed. The strongest -mediated crossover increases occur in subtelomeric euchromatin, which is reminiscent of sex differences in recombination. Our work reveals that HEI10 naturally limits crossovers and has the potential to influence the response to selection.