HCR2 limits crossovers by repressing HEI10 transcription in Arabidopsis

Meiotic crossover creates new genetic variations and is produced by the repair of programmed DSBs (DNA double strand break sites). Despite excessive meiotic DSBs, crossover number is limited along each pair of homologous chromosomes. The majority of crossovers are interfering and formed by crossover-promoting ZMM proteins including HEI10, a dosage dependent E3 ligase. However, molecular mechanisms restricting number of interfering crossovers remain unexplored. We here identified HCR2 (HIGH CROSSOVER RATE 2) via a forward genetic screen using fluorescent reporter in Arabidopsis. Using genome wide crossover mapping and fluorescent reporter systems we found that the hcr2 and meiosis specific HCR2 knockdown plants display elevated crossover frequency in chromosome arms, with reduced crossover interference. The hcr2 mutation lead to increase the transcript level of HEI10, thereby elevating crossover number. Our data reveal a novel mechanism of limiting crossovers by which HCR2 transcription regulator represses HEI10 transcription.1