Genome Editing Technologies
Genome editing does not require the introduction of new gene sequences, separating it decisively from transgenic plants. Rather, it may direct only one or a few nucleotide changes within a plant genome (Rani et al., 2016, Mao et al., 2016). This fact changes the regulatory playing field that governs genetically modified organisms (GMOs) that involve introduction of genes from other species. As a result, genome editing can offer advantages to, or even be used to complement, other forms of biotechnology. For example, genome editing can offer a more facile and versatile replacement for gene silencing, but can also be used in concert with this technology in certain instances that require more sophistication than either technology is capable of on its own, such as functional genomics studies. Moreover, since genome-editing technologies can offer improvements to practically any organism, not only plants can be altered. Genome editing has found a place in livestock development, veterinary science and – perhaps most importantly for normalization of the technology – human health and medicine.
In general, genome editing utilizes various defense strategies developed by bacteria to target specific sequences of DNA and cleave those sequences at targeted sites with nucleases — enzymes that cut DNA. The technology is then able to make use of DNA repair mechanisms found already in the cells of all organisms, and, by repairing the sites of cleavage, establish specialized changes that will be carried through the genome of the ‘edited’ organism to subsequent generations.
Although genome editing technology is in the spotlight today, its emergence has been a long time coming, as new editing systems have been discovered over the past decade and the ability to apply this technology has become increasingly facile (Stella and Montoya , 2016). Originating with the identification of mega-nucleases, the field underwent a rapid revolution through the characterization of the clustered regularly interspaced short palindromic repeats (CRISPR)-associated protein (Cas) system, which is easy to use, low in cost, and robust in application. CRISPR-Cas9 as a technology resulted in a quantum leap of progress in the plant sciences; applications are only now becoming realized both in research laboratories as well as in the field. Various technologies which fall under the umbrella of genome editing are presented in Appendix 1).