Massive crossover elevation via combination of <i>HEI10</i> and <i>recq4a recq4b</i> during <i>Arabidopsis</i> meiosis.

Abstract

During meiosis, homologous chromosomes undergo reciprocal crossovers, which generate genetic diversity and underpin classical crop improvement. Meiotic recombination initiates from DNA double-strand breaks (DSBs), which are processed into single-stranded DNA that can invade a homologous chromosome. The resulting joint molecules can ultimately be resolved as crossovers. In <i>Arabidopsis</i>, competing pathways balance the repair of ∼100-200 meiotic DSBs into ∼10 crossovers per meiosis, with the excess DSBs repaired as noncrossovers. To bias DSB repair toward crossovers, we simultaneously increased dosage of the procrossover E3 ligase gene <i>HEI10</i> and introduced mutations in the anticrossovers helicase genes <i>RECQ4A</i> and <i>RECQ4B</i> As <i>HEI10</i> and <i>recq4a recq4b</i> increase interfering and noninterfering crossover pathways, respectively, they combine additively to yield a massive meiotic recombination increase. Interestingly, we also show that increased <i>HEI10</i> dosage increases crossover coincidence, which indicates an effect on interference. We also show that patterns of interhomolog polymorphism and heterochromatin drive recombination increases distally towards the subtelomeres in both <i>HEI10</i> and <i>recq4a recq4b</i> backgrounds, while the centromeres remain crossover suppressed. These results provide a genetic framework for engineering meiotic recombination landscapes in plant genomes.