A route to de novo domestication of wild allotetraploid rice

In this study, traits associated with domestication, such as the shattering and the length of the awns, were changed in a “wild” rice species that has a four-fold set of chromosomes, i.e. a tetraploid rice. Currently widely cultivated rice varieties have only two sets of chromosomes and are therefore diploid. The advantage of an increased set of chromosomes is that if a (negative) mutation occurs, there are still many more gene copies in the genome. In addition, plants with more than two sets of chromosomes can adapt better to changing environmental conditions. The authors of the study used a tetraploid relative of a cultivated rice species as their starting point. This wild rice has traits such as high biomass (so it grows much higher), various stress tolerances and heat tolerance. Many of the genes that were involved in the domestication process of rice are also present in the genome of the wild relatives; these were modified by the scientists with the help of CRISPR/Cas-gene scissors. Among others, this reduced the length of the awns as well as grain loss and the overall height of the plants.

In the course of plant domestication, many positive traits in wild representatives, such as stress tolerances, have been lost in many crop species. CRISPR/Cas gene scissors are therefore used in wild species for targeted domestication (also called de novo domestication). The aim is to change or adapt the genomes of wild species in such a way that they carry certain genetic variants from cultivated plant lines. As a result, such “genome-edited wild species” have traits from wild species that have been “lost” in the course of plant breeding, and combine these traits with “domesticated” traits that are important for cultivation.

The gene scissors were used in this study to simultaneously change several different gene locations in the genome of the wild rice plant to adapt traits important for cultivation. Several small SDN-1 changes were combined, resulting in complex changes in the genome of the plants. Different genes are changed at the same time using multiplexing, or all gene copies are changed. De novo domestication is an ideal example to show how small changes in the genome can induce profound changes in the genome of plants.