CRISPR-Cas–mediated heritable chromosome fusions in Arabidopsis.

The genome of Arabidopsis thaliana consists of 10 chromosomes. By inducing CRISPR-Cas–mediated breaks at subcentromeric and subtelomeric sequences, we fused entire chromosome arms, obtaining two eight-chromosome lines. In one line, both arms of chromosome 3 were fused to chromosome 1. In another line, the arms were transferred to chromosomes 1 and 5. Both chromosome number–reduced lines were fertile. Phenotypic and transcriptional analyses revealed no differences compared with wild-type plants. After crossing with the wild type, the progeny showed reduced fertility. The meiotic recombination patterns of the transferred chromosome arms were substantially changed. Directed chromosome number changes in plants may enable new breeding strategies, redefining linkage groups and establishing genetic barriers. Moreover, our data indicate that plants are highly robust to engineered karyotype changes. Editor's summary: Restructuring chromosomes alters inheritance patterns of genetic information. In plants, chromosomal rearrangements can reproductively isolate engineered plants from wild relatives or can change the inheritance of desirable agronomic traits. Rönspies et al. used the model plant Arabidopsis thaliana as a testbed to implement CRISPR-Cas technology to fuse chromosomes together (see the Perspective by Zhang and Dawe). The researchers generated plants with eight chromosomes instead of 10, which appeared to be phenotypically normal and were self-fertile. Altered recombination patterns illustrated the changes to genetic inheritance rules. This work opens avenues for large-scale chromosomal changes in plants and provides insights into the plasticity of plant genomes. —Madeleine Seale [ABSTRACT FROM AUTHOR]