The deSUMOylase SPF2 and the cohesin regulators SGO2 and CTF18 suppress crossovers near centromeres.

Crossovers (COs) ensure proper chromosome segregation during meiosis and generate genetic diversity. COs are non-uniformly distributed along chromosomes and almost universally suppressed in centromere-proximal regions, notably creating an important bottleneck for plant breeding. The mechanism of this CO suppression is still not fully understood, but the chromatin state is a contributing factor. Here we identify three factors that actively limit proximal CO in Arabidopsis thaliana: the cohesion establishment factor CTF18, the centromeric cohesin protector SGO2 and the deSUMOylase SPF2. The mutation of these factors allows both the formation of COs in the centromere-proximal region where they were completely absent in the wild type and the enhancement of their frequency where they were rare. COs can be further increased by combining these mutations together or with mutation in the DNA methylase CMT3, suggesting that multiple mechanisms prevent proximal COs in parallel. The identification of the very conserved CTF18, SGO2 and SPF2 as suppressors of centromere-proximal COs highlights the importance of cohesin turnover in this process and opens up new possibilities for plant breeding.