Natural variation identifies SNI1, the SMC5/6 component, as a modifier of meiotic crossover

The frequency and distribution of meiotic crossovers are tightly controlled; however, variation in this process can be observed both within and between species. Using crosses of two natural Arabidopsis thaliana accessions, Col and Ler, we mapped a cross -over modifier locus to semidominant polymorphisms in SUPPRES-SOR OF NPR1-1 INDUCIBLE 1 (SNI1), which encodes a component of the SMC5/6 complex. The sni1 mutant exhibits a modified pattern of recombination across the genome with crossovers elevated in chromosome distal regions but reduced in pericentromeres. Muta-tions in SNI1 result in reduced crossover interference and can par-tially restore the fertility of a Class I crossover pathway mutant, which suggests that the protein affects noninterfering crossover repair. Therefore, we tested genetic interactions between SNI1 and both RECQ4 and FANCM DNA helicases, which showed that additional Class II crossovers observed in the sni1 mutant are FANCM independent. Furthermore, genetic analysis of other SMC5/6 mutants confirms the observations of crossover redistri-bution made for SNI1. The study reveals the importance of the SMC5/6 complex in ensuring the proper progress of meiotic recom-bination in plants.

Automated summary

This study reveals the importance of the SMC5/6 complex in ensuring the proper progress of meiotic recombination in plants, showing the impact of SNI1 mutations and interactions with other genes on crossover distribution.