Massive Crossover Suppression by CRISPR-Cas-mediated Plant Chromosome Engineering

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Abstract
Recent studies have demonstrated that not only genes, but also entire chromosomes can be engineered using CRISPR-Cas9 1–5. A major objective of applying chromosome restructuring (CR) in plant breeding is the manipulation of genetic exchange 6. Here we show that meiotic recombination can be suppressed in nearly the entire chromosome using CR. We were able to induce a heritable inversion of a more than 17 Mb-long chromosome fragment, which contained the centromere and covered most of chromosome 2 of the Arabidopsis ecotype Col-0. Only the 2 and 0.5 Mb-long telomeric ends remained in their original orientation. In SNP marker analysis with the offspring of crosses with the ecotype Ler-1, we detected a massive reduction of crossovers (CO) within the inverted chromosome region, coupled with a shift of CO to the telomeric ends. Interestingly, the few genetic exchanges detected within the inversion all originated from double CO. This not only indicates that heritable genetic exchange can occur by interstitial chromosome pairing, but also that it is restricted to the production of viable progeny.