DESIGN OF GUIDE RNA FOR CRISPR/Cas PLANT GENOMES EDITING
CRISPR/Cas technology of genome editing is a powerful tool for making targeted changes in DNA of various organisms, including plants. The choice of the precise nucleotide sequence (protospacer) in the gene be edited is important for the design of guide RNA, which can be carried out by specialized software. We review and compare all known on-line and off-line resources for guide RNA design, with special attention paid to the tools capable of searching for the off-target edits sites in plant genomes. Use of Cas12a may be preferable to Cas9. Techniques allowing C→T and G→A base editing without DNA cleavage are discussed along with most basic requirements for the design of effective and highly specific guide RNAs. Ways for improving guide RNA design software are presented. We also discuss lesser risks of off-target editing in plant genomes as opposed to genomes of animals. Examples of edited plant genomes including those that do not lead to the creation of transgenic plants are reviewed.