Evaluation of CRISPR/Cas9 Constructs in Wheat Cell Suspension Cultures

Despite intensive optimization efforts, developing an efficient sequence-specific CRISPR/Cas-mediated genome editing method remains a challenge, especially in polyploid cereal species such as wheat. Validating the efficacy of nuclease constructs prior to using them in planta is, thus, a major step of every editing experiment. Several construct evaluation strategies were proposed, with PEG-mediated plasmid transfection of seedling-derived protoplasts becoming the most popular. However, the usefulness of this approach is affected by associated construct copy number bias and chromatin relaxation, both influencing the outcome. Therefore, to achieve a reliable evaluation of CRISPR/Cas9 constructs, we proposed a system based on an Agrobacterium-mediated transformation of established wheat cell suspension cultures. This system was used for the evaluation of a CRISPR/Cas9 construct designed to target the ABA 8′-hydroxylase 1 gene. The efficiency of editing was verified by cost-effective means of Sanger sequencing and bioinformatic analysis. We discuss advantages and potential future developments of this method in contrast to other in vitro approaches.