DNA-free genome editing with preassembled CRISPR/Cas9 ribonucleoproteins in plants.

Processes of traditional trait development in plants depend on genetic variations derived from spontaneous mutation or artificial random mutagenesis. Limited availability of desired traits in crossable relatives or failure to generate the wanted phenotypes by random mutagenesis led to develop innovative breeding methods that are truly cross-species and precise. To this end, we devised novel methods of precise genome engineering that are characterized to use pre-assembled CRISPR/Cas9 ribonucleoprotein (RNP) complex instead of using nucleic ands or Agrobacterium. We found that our methods successfully engineered plant genomes without leaving any foreign DNA footprint in the genomes. To facilitate introduction of RNP into plant nucleus, we first obtained protoplasts after removing the transfection barrier, cell wall. Whole plants were regenerated from the single cell of protoplasts that has been engineered with the RNP. Pending the improved way of protoplast regeneration technology especially in crop plants, our methods should help develop novel traits in crop plants in relatively short time with safe and precise way.