Genome Editing: New Approaches to Create Disease- Resistant Crops

Genome editing achieves a greater precision in genetic modification of living organisms while minimizing the unintended consequences and opposition to products developed through Genetically Modified Organism (GMO) technologies [1]. These technologies are powerful and versatile tools and have revolutionized methods of modifying living organisms for many intended purposes. Targeted genome editing using specialized nucleases offers methods with increased accuracy by introducing deletions, insertions, and replacement to site-specific genomic locations. Examples include the use of Zinc Finger Nuleases, CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats), Oligonucleotide-directed mutagenesis, RNA-dependent DNA methylation, and precision breeding for crop plant improvement [2,3]. The CRISPR/Cas9 was first discovered in the mid-1980s, in bacteria as a part of their immune system against viruses. The Cas9 nuclease target specific genomic sites with the help of a single guide RNA (sgRNA). Each sgRNA (targeting molecule) is composed of a 20-nucleotide spacer immediately upstream of a Proto-spacer Adjacent Motif (PAMs). The sequence of spacer and PAM must be complementary to a specific genomic location, allowing targeted mutagenesis of genes.