Genome editing techniques and their applications in developing disease resistance in plants

Abstract

Plant breeding aims at improving the yield and quality of crops using various tools and techniques. Presently, molecular breeding is one of the most widely used practices for crop improvement but is limited by the available gene pool and crossing barriers. Genome editing is the recent alternative technique which is largely used for crop improvement. The field of genome editing was mainly flourished since the development of Zinc Finger Nucleases. Later, TALENs became more popular in plants but soon CRISPR/Cas9 dominated these techniques. Focused research on the CRISPR system in prokaryotes revealed more enzymes that can target not only DNA but RNA also, e.g. Cas13 and Cas12. These enzymes have been successfully used for RNA knockdown or RNA editing and nucleic acid detection which is of utmost importance in disease diagnosis. Further modifications in the system by fusion of deaminase enzymes developed base editors. Targeted conversion of a DNA base into a desirable single nucleotide polymorphism (SNP) is enabled by base editing. The technique has been advanced to a level where one can target multiple genes in a plant at a time. Among the several applications, the improvement of different traits like biotic stress, abiotic stress, quality and yield are primary applications in the field of plant science. The development of disease resistance, particularly virus resistance in plants was one of the initial applications of CRISPR/Cas9. The purpose was to replicate the defense system of prokaryotes against viruses in plants. Resistance against RNA viruses has been developed by targeting eIF4E gene. It has been also used for developing resistance against fungal and bacterial diseases by mainly targeting the negative regulators of disease resistance in plants. The targeted genes are MLO locus for powdery mildew resistance in wheat and tomato and ERF922 for blast resistance in rice. Similarly, for bacterial resistance, different susceptibility genes have been targeted. Considering the potential and diverse applications, CRISPR/Cas-based genome editing is undoubtedly one of the most efficient and effective techniques for developing disease resistance in plants