Journal of Plant Biotechnology : eISSN 2384-1397 / pISSN 1229-2818

Fig. 1.

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Fig. 1.

The presumed regulatory relevance of crop mutants generated with genome editing technology. This analysis assumed that genome editing enzymes are introduced in the form of protein or RNA, and not in form of DNA. Initially, the genome-editing pathways were categorized as non-homologous end-joining (NHEJ) and homology-directed repair (HDR) because HDR requires exogenous DNA that may potentially increase the regulatory relevance in light of the definition of a ‘living modified organism’ in the Cartagena Protocol on Biosafety. HDR was further segmented into three pathways according to the length of exogenous DNA. Although NHEJ can also cause gene modification as HDR with a short DNA sequence, such pathways are treated differently from a regulatory viewpoint. Therefore, NHEJ-mediated indel generation was further subdivided into deletion and insertion. Secondly, genome-editing crops were subdivided based on the type of mutation to map these mutations according to their regulatory relevance. NHEJ-mediated deletion and insertion were categorized into gain-of-function and leaky or null mutations. HDR with a gene element was categorized into transgenesis and cisgenesis. Cisgenesis is considered to be less relevant to the regulations than transgenesis because a cisgene is derived from a cross-compatible species. Similarly, HDR with a short sequence was considered to be less relevant to the regulations than HDR using a full gene element because the short sequence is only a portion of the gene element. HDR with a short sequence was subdivided into gain-of-function mutations and loss-of-function mutations because crops generated via HDR with a short sequence are more likely to resemble crops generated via NHEJ on a product-basis. Crops generated via HDR with a short sequence were considered to be more relevant to the regulations than crops produced via NHEJ owing to the use of exogenous DNA. Four potential regulatory lines are vertically indicated from the most stringent (line 4) to the least stringent (line 1). Mutants which are mapped beyond the regulatory line are significantly relevant to the regulations. Leaky mutations denote a type of mutation that may leave some function, but not at the level of the wild type allele (Araki et al., 2015)

J Plant Biotechnol 2018;45:299-305
© 2018 J Plant Biotechnol