Maximizing meiotic crossover rates reveals the map of Crossover Potential

Abstract

Sexual dysmorphism in the number and distribution of meiotic crossovers is seen across species but is poorly understood. Here, we disrupt multiple anti-crossover pathways in hermaphrodite Arabidopsis and analyze thousands of female and male progeny genomes. The greatest crossover increase is seen in zyp1 recq4 mutants, with a 12-fold rise in females and 4.5-fold in males. Additional manipulation of crossover regulators does not further increase crossovers but shifts the balance between crossover pathways, suggesting competition for a shared, limited precursor pool. While wild-type crossover patterns differ between sexes, mutant crossover landscapes converge on a unique distinct profile, which we term Crossover Potential (CO_P). CO_P can be accurately predicted using only sequence and chromatin features. We propose that CO_P reflects the density of eligible recombination precursors, which is determined by genomic features and is thus identical across sexes, with sexual dimorphism resulting solely from differential regulation of their maturation into crossovers.