Toxicological assessment Chapter III

Genetically modified plants can be altered for agronomic traits, such as virus-, insector herbicide tolerance, and for quality traits, such as enhanced or altered nutritional properties. The genes introduced into the plant may result in the synthesis of new substances that are conventional components of plant foods such as proteins, fats, carbohydrates, or vitamins that are novel in the context of the genetically modified crop. The genetic modification can also result in the synthesis of active substances, which are toxic for adverse exogenous organisms (such as pest organisms). Moreover, as a result from the activity of enzymes generated by the expression of the introduced DNA, new substances may include metabolites of endogenous origin or arising from the use of xenobiotics. Finally, because of technical reasons, the inserted genetic material consists often, in addition to the gene(s)-of-interest, of a molecular marker (in many cases an antibiotic or herbicide resistance marker) and border-DNA (non-coding sequences). At present, transformation methods used result in random integration of the sequences in the genome of the plant, potentially leading to a series of unexpected changes. It is, therefore, clear that requirements for the toxicological assessment of genetically plants may vary from one kind of modification to another. The toxicological evaluation of a genetically modified crop expressing a biological biocide should comply with the requirements for the evaluation of the original organism used as biological biocide, whereas the toxicological evaluation of a well known nutrient may pose much less problems.