Detection of food and feed plant products obtained by new mutagenesis techniques

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Terminology used in this document 
The term
 conventional GMOs
will be used throughout this report to refer to plant GMOs 
obtained by recombinant DNA technology and characterised by the presence of 
introduced DNA sequences from the same or other species in the final organism. 
Genome editing
, also called gene editing, is a group of new directed mutagenesis 
techniques that facilitate addition, removal, or alteration of DNA sequences at a specific 
location in the genome. This is mostly achieved with the aid of the cell’s natural DNA 
recombination/repair system activated with the use of a site-directed nuclease (SDN), 
creating a double-strand DNA break at a defined location, a repair template sequence 
consisting of an added nucleic acid molecule (
e.g.
an oligonucleotide or longer nucleic 
acid sequence with partial sequence similarity to the target site), or the combination of 
both (modified from 
8
). The techniques require the presence of the SDN in the recipient 
host cell, either following stable integration of recombinant DNA into the plant genome, 
or by transient expression or delivery of a protein/nucleic acid complex into the cell. In 
this document we will refer only to plant cells, but also other organisms could be targets 
of genome editing. When recombinant DNA has been used, it can be segregated away in 
subsequent generations, resulting in genome-edited plants that no longer contain any 
recombinant DNA
16,17
. In the frame of this report, plants obtained with genome editing 
techniques that contain inserted recombinant DNA or unintentionally remaining insertions 
of the transformation vectors are excluded, as these will be similar to the current 
conventional GMOs.
Early but limited success of genome editing was first achieved with protein-directed SDN
s
 
such as meganucleases, zinc finger nucleases (ZFNs) and transcription activator-like 
effector nucleases (TALENs). The techniques of genome editing have advanced rapidly 
following the development of RNA-directed SDNs based on the bacterial CRISPR 
(clustered regularly interspaced short palindromic repeats) system and CRISPR-
associated (Cas) nucleases
8
. Editing of single nucleotides can also be achieved using a 
specific set of enzymes referred to as 'base editors', which aim at modifying DNA at 
specific sites without involving double-strand breaks
18
. 
The DNA sequence alterations introduced through any of the genome editing techniques 
may be single nucleotide variants (SNV), insertions or deletions (called InDels), or, less 
frequently, gene duplications, inversions and translocations
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. 'Short' DNA alterations, as 
mentioned in this report, are referring to changes in one or a few base pairs, while 'large' 
alterations refer to alterations of several dozen base pairs. However, there is a grey zone 
between 'short' and 'large' sequence alterations. When talking about the specificity of 
detection, the criterion to be assessed is not the sequence length itself, but whether or 
not a given DNA alteration is unique or occurs already in any plant species, or potentially 
could occur, and whether or not it can be unequivocally attributed to the application of 
genome editing. This may need to be assessed on a case-by-case basis using approaches 
which should be defined by the ENGL. 
By analogy to the term 'transformation event' used in GMO legislation
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, we propose here 
to use '