Natural variation identifies SNI1, the SMC5/6 component, as a modifier of meiotic crossover in <i>Arabidopsis</i>.

Abstract

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 <i>Arabidopsis thaliana</i> accessions, Col and L<i>er</i>, we mapped a crossover modifier locus to semidominant polymorphisms in <i>SUPPRESSOR OF NPR1-1 INDUCIBLE 1</i> (<i>SNI1</i>), which encodes a component of the SMC5/6 complex. The <i>sni1</i> mutant exhibits a modified pattern of recombination across the genome with crossovers elevated in chromosome distal regions but reduced in pericentromeres. Mutations in <i>SNI1</i> result in reduced crossover interference and can partially 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 <i>sni1</i> mutant are FANCM independent. Furthermore, genetic analysis of other SMC5/6 mutants confirms the observations of crossover redistribution made for <i>SNI1</i> The study reveals the importance of the SMC5/6 complex in ensuring the proper progress of meiotic recombination in plants.