9. The need for molecular characterization of GM crops

Guidelines have been set for the molecular characterization of GM crops prior to market and commercial release and these were placed in six categories [53]. These categories are (i) description of the genetic material used for the transformation, including the origin of the donor organism and how the gene was isolated, (ii) description of the transformation method, (iii) description of the transgene loci, (iv) transcript and protein characterization, (v) inheritance and stability of the transgene and (vi) detection and identification of the transgene.

The specified requirements under (i) include information on the plasmid used in the production of the recombinant, detailing genetic elements such as the orientation and position of the transgene expression cassette within the vector, the restriction endonuclease sites of the transformation construct and clearly marked T-DNA borders and promoters. In order to comply, the number of insertion events of the transgene must also be supplied, as well as the transgene insertion site(s). Insertion site detection is expected to be presented as the transgene sequence accompanied by approximately 500 bp of plant DNA in both flanking regions. Possible novel chimeric open reading frames (ORF) should be described and their functionality evaluated. If the flanking sequence contains part of the chimeric ORF, it is expected that more sequencing must be performed beyond the 500 bp radius until a putative ORF is obtained.

Requirements regarding the expression of the transgene entail, among others, details on the translation of the transcript to protein, tissue specificity of the transcript and protein expression, as well as levels of expression. Furthermore, information on the biochemical, molecular and physiological properties of the transgene product is required as well as the stability of the protein(s) in the cell and in the surrounding environment.

It is quite evident that extensive molecular analyses are required for safety assessments, the main objective being the need to demonstrate that GM crops are equivalent to their traditional counterparts, (i.e. substantial equivalence), and that there are no introductions of any additional or new risks to consumer health [32]. These assessments are put in place to quantitatively detect or identify the GM crops, food and feed that are being introduced into the market [54].
