Over the last few years, we have heard a lot about New Genomic Techniques, with both favorable and critical views. To help generate an informed discussion, we have developed this guide to help you understand the basics of genome editing and what the law is like in different countries around the world.
By Paulo Peralta, Technical Expert of CIOPORA
Conventional plant breeding generally relies on techniques which results are difficult to predict. Depending on the species, it might require a long time to complete the selection process, to generate the desired characteristics, and introduce traits into stable and uniform new plant varieties. Thus, plant breeding is continuously evolving, and breeders are searching for new alternatives to accelerate the creation of novel varieties. As a result, New Plant Breeding Techniques (NPBTs) have arisen as a tool enabling breeders to achieve their goals faster.
Among the most prevailing NPBTs, are mutagenesis mediated by site-directed nucleases (SDNs) and cisgenesis; both bearing a risk of expression of unknown traits as low as those products obtained by natural crossing or conventional breeding. In this sense, cisgenesis is described as a technique aimed to promote genetic exchange only between sexual compatible species. For instance, one rose variety could be improved with disease resistance genes from another rose variety by genetic engineering, but the new variety would be a cisgenic and not a transgenic or genetically modified organism (GMO).
Some of the most common mutagenesis mediated by SDNs are Zinc Finger Nucleases (ZFN), TAL Effector Nuclease (TALEN), and the so called CRISPR/Cas9. All these techniques use site directed nucleases to introduce a DNA double strand break at specific sites. While ZFN and TALEN required creating a gene-editing protein (nuclease) from scratch for each specific DNA modification, with CRISPR the same Cas9 molecule can be directed to any sequence to be modified. For this reason, CRISPR/Cas9 can be implemented faster at lower cost and comparatively it is a more precise method. All these advantages have made CRISPR/Cas9 a widely popular gene editing technique.
For regulation purposes, special attention is given to the type of mutagenesis mediated by SDNs. Genome editing of SDN-1 type produces a double-stranded break, that activates the DNA repair system of the cell by introducing a short and random sequence or even point mutations at targeted genomic locations. Due to the characteristics of the changes introduced by SDN-1 applications, they are compared with plants carrying spontaneous mutations or plants produced by classical mutagenesis. SDN-2 also produces the double-stranded break, and while the break is repaired by the cell, a small nucleotide template (complementary to the area of the break) is provided to the system. The template induces a change in one or a few nucleotides resulting in a mutation of the target gene. Likewise, SDN-3 induces a double-stranded break in the DNA, but the supplied template contains a larger nucleotide sequence. The natural repair process of the cell then utilizes this template to repair the break, resulting in the introduction of new genetic material.
Many authors also use the term new genomic techniques (NGTs) exchangeable for NPBTs. However, NGT is a term referred to those techniques targeting genomic changes such as epigenetic induction; double or single strand breaks in the DNA or acting specifically on RNA. While NPBT is a more general definition, encompassing not only genetic changes but also selection techniques such marker-assisted selection (MAS), and supporting breeding (reverse breeding or accelerating breeding).
Map of regulation on Genome Editing worldwide:
Check the Guide of regulatory Approaches for Genome Edited in several countries: