Humans have been selectively modifying plants and animals for many millennia. For much of this time, they had little or no knowledge of what they were doing at the gene or molecular level. Over the last century, and before the introduction of modern recombinant DNA technology, several breeding methods were developed that resulted in gross changes at the molecular level, but, again, these were not characterized or often well understood. In the case of plants, these tools include modifying the chromosome number (bananas, melons, wheat), rescuing interspecific embryos that would not occur in nature (broccoflowers), fusing cells from different species (radish cauliflower), culturing only the male anther and using the chemical colchicine to create a fertile plant (super male asparagus) and mutation breeding through either radiation or chemicals (over 2,000 crop varieties including Asian pears, grapefruits and pasta wheat, are products of such mutation breeding). These techniques do not allow any control at the genome level; rather, multiple genes are transferred together or mutated, and unwanted traits are eliminated through subsequent selection and backcrossing. Using modern analytical tools we can now demonstrate that all these forms of plant breeding introduce a variety of changes in DNA, ranging from point mutations and single base pair deletions and insertions, to loss or acquisition of genes, to, as mentioned, changes in numbers of whole chromosomes. Far and away, the greatest changes at the molecular level are introduced by the various forms of mutation breeding.
The 4-stranded DNA to which you allude has always existed in organisms, and given that these G-quadruplex structures are mostly present in telomeres where they serve to stabilize the chromosome, they are far more likely to be affected by mutagenesis breeding than by any of the other methods of modification. But this is not an issue, as it is important to remember that in all plant breeding programs, successive rounds of planting and selection are used to cull out events with obvious and/or undesirable phenotypes and select for plants with unchanged/superior agronomic and phenotypic traits. Regardless of the method of breeding applied to select for genetic changes, the candidate plants that are advanced for potential distribution and planting will closely resemble their elite parental lines, with the obvious exception of the intended modification.
Likewise, your concern about the anticipation of the development of pest resistance is not novel. Integrated pest management is an important cornerstone of any cropping system. Biotech provides a much broader, more effective set of tools that can be used with existing systems and has the potential to be rapidly deployed in anticipation of emerging diseases and altered pest pressure. In addition, gene stacking and gene rotation means that there is a potential for multiple layers of protection, which should reduce pressure and ensure greater robustness and longevity in pest-/disease-resistance management. There are also lesser negative effects, such as diminished impact on non-target insects, with the non-target effects of insecticides being much greater than in, for example, Bt crops.
The increasing power of analytical techniques, and the massive accumulation of omics data and the informatics tools to which you allude, are providing novel insights into the molecular dynamics of the plant cell. One interesting outcome from this increasing knowledge is that it shows extensive genetic similarity among genomes of diverse organisms that are only remotely related. For example, parts of the nucleic acid sequence of a common bacterium present in our guts, E. coli, have been found in the DNA of organisms such as canola, grasses, amphibians, birds and mammals—including humans. Such findings cast doubt on the value of assigning genes to a particular species and the validity of using terms such as “species-specific DNA." Likewise, it is becoming increasingly apparent that a significant proportion of plant genomes are made up of retrotransposons (jumping genes) (Hull, 2002). Retroelements have been found in all plants investigated and are very heterogeneous, suggesting that they are an ancient component of genomes, and as they insert themselves into the genome, retroelements act as mutagenic agents. Insertion of retrotransposon elements can inactivate or alter gene function. Such elements make up 50 to 75 percent of the genome in some cereals, such as corn, and some of this may be due to specific breeding by native American “biotechnologists” who selected for the tremendous morphological variety these jumping genes provided. (Given such instability and uncertainty, perhaps we should have a moratorium on eating plants.)
When compared with classical plant breeding methods, modern genetic engineering techniques have been observed to produce less unintended DNA modification. Studies have also shown that GM crops are often more closely related to the parental strain used in their development than to other members of the same genus and species with respect to their transcriptomic, proteomic and metabolomics profiles (Ricroch et al., 2011; Baker et al., 2006; Catchpole et al., 2005). For example, metabolomic studies on potatoes have shown that conventional plant breeding produces both intended and unintended effects and that insertion of transgenes can occur with little apparent effect on composition, even when the GM variety produces significant quantities of a new metabolite (e.g., fructans) Indeed, when the introduced gene product was removed from the analysis parameters, analysis showed no significant variation in the metabolic phenotype, including harmful glycoalkaloids, between the GM crop and the progenitor lines, whereas other, conventionally bred cultivars, showed much greater variation in metabolic phenotypes (Chassy et al., 2008). Similar results have been observed at the proteome level for other plant species. It also appears that environmental and cultural conditions have more impact on plant composition than do breeding and selection programs (Ricroch et al., 2012).
While biotech crops undergo extensive regulatory evaluation before commercialization, plants created by conventional techniques undergo no formal food or environmental safety evaluation, as they are generally regarded as safe (classified as GRAS). Despite the extensive genetic manipulation of crop plants by older methods, cases of novel or completely unexpected adverse consequences for commercialized varieties of these crops are extremely rare. Thus, from a scientific perspective, the term “genetically modified organism” is not an accurate descriptor of the products solely of modern biotechnology, since, as noted, virtually all domesticated crops and animals have been subjected to varying degrees of genetic modification.
The consensus of scientific opinion and evidence from over 600 studies worldwide is that biotechnology-derived foods and feeds present no new or unusual dangers to the environment or human health (American Medical Association, World Health Organization, OECD, Seven Academies Report, Royal Society of London, National Research Council, Society of Toxicology). In 2001 and 2011, the European Commission released two reports that cover 25 years of research on GM crops or food on human health or the environment: “A Decade of EU-Funded GMO Research (2001—2010)” and “EC-Sponsored Research on the Safety of Genetically Modified Organisms (1985—2000).” Both concluded that the use of a more precise technology and greater regulatory scrutiny probably makes biotech crops even safer than conventional plants and foods.
The most that can be expected of any oversight regimen is that foods developed using all methods should receive the same level of evaluation, with regard to both impact on the environment and safety to the consumer. Millions of people have already eaten the products of genetic engineering, and no adverse effects have been demonstrated. Both current science and long-term experience support the repeated conclusions of learned bodies that the product, not the process by which it is developed, is what should be evaluated for both risk and benefit. Scientists are confident that if we abandon the scientific method in judging the safety of the food supply and the impact on the environment, we will slow or destroy the advances that will reduce the use of unsafe chemicals and less safe agricultural practices in this country, and we will limit the potential of better nutrition that promises to improve the quality of life for everyone.
Baker JM, Hawkins ND, Ward JL, Lovegrove A, Napier JA, Shewry PR, Beale MH. 2006. A metabolomic study of substantial equivalence of field-grown genetically modified wheat. Plant Biotechnol J 4:381–392.
Burge, G.N. Parkinson, Hazel, P. Todd, A.K. Neidle, S. 2006. Quadruplex DNA: sequence, topology and structure. Nucleic Acids Res., 34 (2006), pp. 5402–5415.
Catchpole GS, Beckmann M, Enot DP, Mondhe M, Zywicki B, Taylor J, Hardy N, Smith A, King RD, Kell DB, Fiehn O, Draper J. 2005. Hierarchical metabolomics demonstrates substantial compositional similarity between genetically modified and conventional potato crops. Proc Natl Acad Sci USA 102:14458–14462.
Chassy, B.; Egnin, M; Gao, Y.; Glenn, K.; Kleter, G.A.; Nestel, P.; Newell-McGloughlin, M.; Phipps, R.H.; Shillito, R. 2008 Nutritional and Safety Assessments of Foods and Feeds Nutritionally Improved through Biotechnology: Case Studies Comprehensive reviews in food science and food safety 7 . - p. 50 - 99.
EU Commission Report. 2001. EC-sponsored research into the safety of Genetically Modified Organisms. Fifth Framework Programme - External Advisory Groups “GMO research in perspective.” Report of a workshop held by External Advisory Groups of the "Quality of Life and Management of Living Resources" Programme. http://europa.eu.int/comm/research/quality-of-life/gmo/index.html and http://europa.eu.int/comm/research/fp5/eag-gmo.html.
EU Commission Report. 2011. A decade of EU-funded GMO research (2001-2010) Reference: IP/10/1688 Event Date: 09/12/2010 http://europa.eu/rapid/press-release_IP-10-1688_en.htm.
Hull R, Lockhart B, Olszewski N. 2002. Viral sequences integrated into plant genomes. Ann Rev Phytopathol 40:119–136.
Ricroch AE, Bergé JB, & Kuntz M. 2011. Evaluation of genetically engineered crops using transcriptomic, proteomic and metabolomic profiling techniques. Plant physiology PMID: 21350035.