In my last post I argued that the current system for regulating genetically engineered (GE) crops for commercialization in the United States is inadequate because it is possible to design GE plants in such a way that USDA, EPA or FDA regulation of them–and therefore any regulation of them in the U.S.–is not required. But I only briefly mentioned one reason why GE crops need to be regulated in the first place: the technologies used to create them are highly mutagenic.
Proponents of agricultural genetic engineering tout the “precision” of the technology and, compared to traditional plant breeders, genetic engineers do have very precise knowledge of the genes they select for insertion into crop plants; they know those genes right down to their exact DNA sequences. But, what proponents of the technology may neglect to mention is that genetic engineers don’t have any control at all over where in a recipient plant those selected DNA sequences will land. And they often–estimates indicate 27-63% of the time in plants like rice and Arabidopsis (a “model” plant often used for research) –land right smack dab in the middle of some random gene in the recipient plant, disrupting its function and thereby mutating it. Published reports (see Latham et al., 2006 and references therein) also indicate that engineering genes into a recipient plant’s DNA is nearly always accompanied by small or substantial deletions or rearrangements of recipient plant DNA, insertions of DNA sequences not intended for insertion (usually of bacterial origin), and “somaclonal” variation (heritable changes associated with the process of regenerating into whole, fertile plants the individual plant cells that have had foreign genes inserted into them). These are all highly probable and randomly occurring consequences associated with crop genetic engineering as it is currently practiced. So in fact, there is actually a great deal of imprecision associated with inserting a gene or genes into crop plants via genetic engineering.
Depending on the functions of the gene(s) affected, unintended mutations could result in altered levels of things normally found in the recipient plants like pigments, nutrients or even toxins like the glycoalkaloids found in green potatoes. Mutations that result in visible changes, like yellow plants as a result of reduced levels of the green pigment chlorophyll, are easy enough to winnow out. But GE plants that contain unintended mutations that don’t result in changes in their outward appearance are harder to eliminate. And it is possible that unintended mutations resulting from the process(es) of genetic engineering itself, as opposed to the products of the particular foreign gene(s) genetically engineered into a crop plant, could negatively impact GE food and feed products. For example, the possibility that negative impacts reported in laboratory animals fed GE corn or GE potatoes might be related to unintended mutations in those GE products has not, to my knowledge, been ruled out.
The value of utilizing animal feeding studies to determine the safety of GE foods is debatable. The FDA has stated that “feeding studies on whole foods have limited sensitivity because of the inability to administer exaggerated doses” (as opposed to feeding studies carried out with individual chemicals). But molecular genetic methods for identifying many unintended changes in GE plants are available and FDA should require developers to use them prior to approving any GE food crop for commercialization. Instead, as noted in a previous post (12/7/11), FDA doesn’t require any regulation of most GE food or feed products at all.
Many developers of GE crops are already testing their potential products for unintended changes that might have occurred during the genetic engineering process and discarding any mutant plants they may have identified. We did at Calgene prior to commercializing the Flavr Savr™ tomato. But the testing process should be made mandatory for commercialization. U.S. regulatory policies regarding GE foods should be changed accordingly.