*4.2.3 Genome editing*

The discovery of genome editing technologies has revolutionized plant and animal research. Through genome editing, researchers can introduce sequencespecific modifications into the genome of different cell types and organisms. The site-specific nucleases (SSNs) have successfully been used in precise gene editing. The SSNs create double-stranded breaks (DSB) in the target DNA. The DSB is repaired through non-homologous end joining (NHEJ) or homologdirected recombination (HDR) pathways resulting in insertion/deletion (INDELS) and substitution mutations in the target region (s), respectively [150, 151]. The technology produces defined mutant; also, the edited crops typically carry the desired trait [152]. Gene editing has been reported in plants including Arabidopsis [153], rice [154], and other crops, The genome editing techniques include meganucleases, zinc finger nucleases (ZFNs), transcription activatorlike effector nucleases (TALENs), clustered regularly interspaced palindromic repeats (CRISPR/Cas9). These techniques have been extensively reviewed [151, 155].
