- Crop genetics: Reducing transgene escape routes
Gray, AJ; Raybound, AF
Nature, vol. 392, no. 6677, pp. 653-654, 16 Apr 1998
Genetically modified crops and the food derived from them have had a bad press, but a rare piece of good news is provided by Daniell et al. in this month's Nature Biotechnology. They report a development that has profound implications for the risk assessment of genetically modified crops. Most crops are modified by inserting genes into the nucleus, and the genes can therefore spread to other crops or wild relatives by movement of pollen. By engineering tolerance to the herbicide glyphosate into the tobacco chloroplast genome, however, the authors have not only obtained high levels of transgene expression, but, because chloroplasts are inherited maternally in many species, they have also prevented transmission of the gene by pollen--closing a potential escape route for transgenes into the environment.
- A transgene-centered approach to the biosafety of transgenic phosphinothricin-tolerant plants
Metz, PLJ; Stiekema, WJ; Nap, J-P*
Molecular Breeding [Mol. Breed.], vol. 4, no. 4, pp. 335-341, 1998
The microbial bar and pat genes confer tolerance to the non-selective herbicide phosphinothricin (PPT; sold as Basta or Finale). This tolerance in plants could provide an environmental gain compared to current-day herbicide cocktails, but the safety of such a transgene approach is questioned by many. The biosafety of the presence of these herbicide tolerance genes in plants is evaluated in a 'transgene-centered approach'. Potentially, the introduction of transgenic PPT-tolerant crops could result in acquired PPT tolerance in weedy relatives of these crops. Assuming responsible use of this trait in agronomy, the ecological consequences with respect to weediness or spread of the transgenic PPT tolerance are concluded to be negligible. The key issue for the toxicological evaluation is whether or not the plant has actually been sprayed with PPT. Consumption of the gene and/or gene product from unsprayed transgenic plant material will not have adverse effects. In case of PPT-sprayed material, PPT or its derivatives could be present in food and feed and crop-specific metabolites might be formed. To date, the toxicological impact of such a putative exposure is not sufficiently clear, and further premarket testing is recommended.
- Public Concerns Over Transgenic Crops
Genome Research [Genome Res.], vol. 9, no. 12, pp. 1159-1162, Dec 1999
Over the past 16 years it has become possible to isolate genes from any class of living organism and introduce them into most of our crop plants. This provides a wider choice of genes for crop improvement than is available by conventional plant breeding. International studies worldwide on genome organization, genetic mapping, and the isolation of genes are providing many new opportunities to modify crops. In 1999, there were almost 40 million hectares of transgenic crops grown across the world (James 1999). Although there is considerable optimism about the future prospects for transgenic crops among the scientific and plant breeding community, public concerns are being expressed in some countries. The assessment and potential impact of transgenic crops has been discussed in scientific publications and at conferences for over a decade, but now the subject is a major focus of presure groups, with vandalism of transgenic field plots in some countries and substantial amounts of money being spent internationally on opposition. The aim of this paper is to give a perspective on current concerns.
- Quantitation of genetically modified organisms in food
Huebner, P; Studer, E; Luethy, J
Nature Biotechnology [Nat. Biotechnol.], vol. 17, no. 11, pp. 1137-1138, Nov 1999
Although the debate surrounding food containing genetically modified organisms (GMOs) is still far from a consensus in Europe, a decision to label GM foods to allow consumers an informed choice has been made by some countries and governments. The enforcement of the Swiss Food Regulation and of the EU Novel Food Regulation is based on a PCR detection system specific for the 35S promoter originating from cauliflower mosaic virus. This 35S promoter element is often used in GM plants, including those currently approved in Switzerland (Roundup Ready soybean (RRS), Bt-176, and Bt-11 corn). The qualitative 35S-PCR detection system has been thoroughly tested in collaborative studies; however, its detection limit was found to vary up to a factor of 20 (from 100 pg to 2 ng RRS-DNA) between different analytical laboratories. Additionally, due to its high sensitivity, the 35S-PCR detection system is not suited to distinguish between intended GMO mixtures and GMO comingling due to unseparated channels for conventional and GMO raw materials during harvest, transport, and stocking. In practice, the 35S-PCR test allows the detection of GMO contents of foods and raw materials in the range of 0.01-0.1%. Attempts have been made to diminish the interlaboratory variations by the standardization of the PCR protocol, by the use of certified external reference material with well-defined amounts of GMOs, and by the development of quantitative PCR detection systems. Recently, the Swiss government revised its food regulations, introducing a threshold value of 1% GMO content as the basis for food labeling. The enforcement of such threshold values clearly requires quantitative detection systems such as quantitative competitive PCR (QC-PCR), real-time PCR, or immunochemical detection of modified proteins using ELISA system. Whereas ELISA is widely acknowledged to be of practical use at the earliest stages of manufacture, there is the disadvantage of protein denaturation as a consequence of processing. Thus, the detection of DNA by quantitative PCR techniques has a number of advantages, including the survival of DNA in many, albeit not all manufacturing processes.
- Tandem constructs: preventing the rise of superweeds
Trends in Biotechnology [Trends Biotechnol.], vol. 17, no. 9, pp. 361-366, Sep 1999
Transgenic crops may interbreed with nearby weeds, increasing their competitiveness, and may themselves become a `volunteer' weed in the following crop. The desired transgene can be coupled in tandem with genes that would render hybrid offspring or volunteer weeds less able to compete with crops, weeds and wild species. Genes that prevent seed shatter or secondary dormancy, or that dwarf the recipient could all be useful for mitigation and may have value to the crop. Many such genes have been isolated in the past few years.
- A rational approach to labeling biotech-derived foods
Science (Washington) [Science (Wash.)], vol. 284, no. 5419, pp. 1471-1472, 28 May 1999
Scientists around the world are using recombinant DNA techniques to improve plants. These transgenic plants can have enhanced resistance to pests, disease, drought, salinity, frost, and herbicides, as well as enhanced nutritional value, improved processing characteristics, and better teste. In 1998, they were cultivated on about 69.5 million acres. In the United States, the Food and Drug Administration (FDA) is responsible for ensuring the safety and wholesomeness of the nation's food supply (except poultry and most meats). Most biotechnology-derived products are regulated under the agency's official policy on foods derived from new plant varieties, which applies irrespective of whether the plant arose by molecular or conventional methods. The policy elaborates a scientific and "transparent" (that is, clear and predictable) regulatory approach, mandating when consultations with the FDA are necessary, when labeling is required, and what information should be conveyed in labels. At a time when there are international debates regarding food labeling, it is useful to review the rationale behind the FDA approach.
- Transgenic plants for tropical regions: Some considerations about their development and their transfer to the small farmer
Proceedings of the National Academy of Sciences, USA [Proc. Natl. Acad. Sci. USA], vol. 96, no. 11, pp. 5978-5981, 25 May 1999
Biotechnological applications, especially transgenic plants probably hold the most promise in augmenting agricultural production in the first decades of the next millennium. However, the application of these technologies to the agriculture of tropical regions where the largest areas of low productivity are located, and where they are most needed, remains a major challenge. In this paper, some of the important issues that need to be considered to ensure that plant biotechnology is effectively transferred to the developing world are discussed.
- Public reactions and scientific responses to transgenic crops
Current Opinion in Biotechnology [Curr. Opin. Biotechnol.], vol. 10, no. 2, pp. 203-208, Apr 1999
There is currently intense debate in parts of Europe about the commercial production of transgenic food crops. Information from the press and lobbying groups has not encouraged an informed and balanced consideration of the issues. In marked contrast, there is widespread acceptance of transgenic food crops in North America.
- Transgene escape and transplastomics
Chamberlain, D; Stewart, CN Jr*
Nature Biotechnology [Nat. Biotechnol.], vol. 17, no. 4, pp. 330-331, Apr 1999
Genetically modified (GM) food is big news at the moment, particularly in Europe. Hysteria seems to have gripped the British press (from the lowbrow tabloids to the highbrow broadsheets) in a furor of at least the magnitude of Salmonella in eggs and BSE in beef (food scares seem to be a special favorite of Fleet Street). Press releases appear weekly with descriptions of the latest anti-GM crop activities of groups like Greenpeace, who have, for instance, deposited 4 tons of GM soybeans on Tony Blair's doorstep, and filed a lawsuit against the EPA for approving transgenic plants carrying the Bacillus thuringiensis toxin (see http://www.greenpeace.org for details). The UK government is reappraising its stance on commercial growing of GM crops, and Monsanto was fined in Lincolnshire, England for failing to conduct proper field trials. Clearly, the use of transgenic technology - and the perceived threat of uncontrolled transgene spread - is a hot, organically produced, nontransgenic potato. In this issue, Scott and Wilkinson assess the probability of pollen-mediated movement of transgenes from transplastomic (rather than nuclear transgenic) Brassica napus to its wild relative Brassica rapa.
- The real curse of Frankenfood
Nature Biotechnology [Nat. Biotechnol.], vol. 17, no. 2, 113, Feb 1999
Antibiotechnology Jeremiahs have long predicted that the industry would create something it couldn't control. Now it seems they were right. After insisting for years that their own recombinant DNA-manipulated crop and garden plants merited extraordinary government regulation, agricultural biotechnology companies are now having trouble persuading consumers that foods from these plants are safe and not fundamentally different from other foods.
- Horizontal gene transfer as a biosafety issue: A natural phenomenon of public concern
Droege, M; Puehler, A*; Selbitschka, W
Journal of Biotechnology [J. Biotechnol.], vol. 64, no. 1, pp. 75-90, 17 Sep 1998
The transfer of genetic information between distantly or even unrelated organisms during evolution had been inferred from nucleotide sequence comparisons. These studies provided circumstantial evidence that in rare cases genes had been laterally transmitted amongst organisms of the domains bacteria, archaea and eukarya. Laboratory-based studies confirmed that the gene pools of the various domains of organisms are linked. Amongst the bacterial gene exchange mechanisms transduction, transformation and conjugation, the latter was identified as the mechanism with potentially the broadest host range of transfer. Previously, the issue of horizontal gene transfer has become important in the context of biosafety. Gene transfer studies carried out under more natural conditions such as in model ecosystems or in the environment established that all gene transfer mechanisms worked under these conditions. Moreover, environmental hot-spots were identified where favourable conditions such as nutrient enrichment increased the probability of genetic exchange among bacteria. In particular, the phytosphere was shown to provide conducive conditions for conjugative gene exchange. Concern has been expressed that transfer of recombinant DNA (e.g. antibiotic resistance genes) from genetically modified organisms (GMOs) such as transgenic plants to phytosphere bacteria may occur and thus contribute to the undesirable spread of antibiotic resistance determinants. Studies which were performed to address this issue clearly showed that such a transfer occurs, if at all, at extremely low frequency.
- Novel and transgenic food crops: Overview of scientific versus public perception
Ruibal-Mendieta, NL; Lints, FA
Transgenic Research [Transgen. Res.], vol. 7, no. 5, pp. 379-386, Sep 1998
Recombinant DNA technology offers opportunities to develop new products in many different fields, including agriculture and the agro-food area. Transgenic plants with improved agronomic traits currently grow in field trials and a few varieties have already reached the European market. By and large, new technologies raise both concerns and expectations and modern biotechnology is no exception. Indeed, a voluntary moratorium on experiments involving recombinant DNA molecules was called for in 1974. At the present time, although a majority of academic and industrial scientists agree that transgenic food crops pose no risk for the environment or human health, some others believe that certain applications of modern plant biotechnology are hazardous. In particular, deliberate releases of genetically modified plants are regarded as risky. There is also a disparity between expert and lay perception of r-DNA technology applications to food crops, which makes public information a difficult task. This paper aims at exposing these conflicting points of view on the agricultural applications of modern biotechnology. We also propose some recommendations pertaining to public information in Europe. It appears that consensus conferences might be a good approach to stimulate public information and public debate in Europe, although this approach has to be adapted to the cultural context of each country.
- Containment of herbicide resistance through genetic engineering of the chloroplast genome
Daniell, H; Datta, R; Varma, S; Gray, S; Lee, Seung-Bum
Nature Biotechnology [Nat. Biotechnol.], vol. 16, no. 4, pp. 345-348, Apr 1998
Glyphosate is a potent herbicide. It works by competitive inhibition of the enzyme 5-enol-pyruvyl shikimate-3-phosphate synthase (EPSPS), which catalyzes an essential step in the aromatic amino acid biosynthetic pathway. We report the genetic engineering of herbicide resistance by stable integration of the petunia EPSPS gene into the tobacco chloroplast genome using the tobacco or universal vector. Southern blot analysis confirms stable integration of the EPSPS gene into all of the chloroplast genomes (5000-10,000 copies per cell) of transgenic plants. Seeds obtained after the first self-cross of transgenic plants germinated and grew normally in the presence of the selectable marker, whereas the control seedlings were bleached. While control plants were extremely sensitive to glyphosate, transgenic plants survived sprays of high concentrations of glyphosate. Chloroplast transformation provides containment of foreign genes because plastid transgenes are not transmitted by pollen. The escape of foreign genes via pollen is a serious environmental concern in nuclear transgenic plants because of the high rates of gene flow from crops to wild weedy relatives.
- Containing excitement over transplastomic plants
Bilang, R; Potrykus, I
Nature Biotechnology [Nat. Biotechnol.], vol. 16, no. 4, pp. 333-334, Apr 1998
Several traits engineered into agricultural crops require high-level expression of the newly introduced gene(s). Many transgenic plants never even reach the farmer because expression of the new trait is either not strong enough or insufficiently reliable. Plants with new genetic information inserted into every plastid instead of the nuclear genome - so-called transplastomic plants - promise to overcome this limitation because up to 10,000 copies of the transgene are present in each cell, leading to extraordinarily high levels of transgene products. In this issue, Daniell et al. demonstrate another advantage of transplastomic plants in agrobiotechnology - the biocontainment of newly introduced genes based on the lack of gene-flow through pollen.
- Chemical fingerprinting for the evaluation of unintended secondary metabolic changes in transgenic food crops
Noteborn, H.P.J.M. ; Lommen, A.; Van Der Jagt, R.C.; Weseman, J.M.
Journal of Biotechnology (J. Biotechnol.), vol. 77, no. 1, pp. 103-114,Jan 2000
A common element in designed guidelines for assessment of the food safety of transgenic crops is centred on a comparative analytical analysis with conventionally bred crop plants, assuming that these products have a long history of safe use (i.e. OECD-principle of substantial equivalence). In this study we examine the utility of an off-line combination of 400 MHz proton (@u1H)-NMR spectroscopy and liquid chromatography (LC) for the multi-component comparison of low-molecular weight compounds (i.e. chemical fingerprinting) in complex plant matrices. The developed NMR-methodology can contribute to the demonstration of substantial equivalence by its ability to compare possible compositional alterations in a novel food crop with respect to related non-transgenic reference lines. In this respect a hierarchical approach is proposed by comparing the chemical fingerprints of the transgenic crop plant to those of: (1) isogenic parental or closely related lines bred at identical and multiple sites; (2) extended ranges of commercial varieties of that plant; and (3) downstream processing effects. This is of importance to assess the likelihood that some of the statistical differences in a transgenic crop plant may be false positives due to chance alone or arose from natural genetic and/or physiologic variations.