Animal nutrition with feeds from genetically modified plants

Plant breeders have made and will continue to make important contributions toward meeting the need for more and better feed and food. The use of new techniques to modify the genetic makeup of plants to improve their properties has led to a new generation of crops, grains and their by-products for feed. The use of ingredients and products from genetically modified plants (GMP) in animal nutrition properly raises many questions and issues, such as the role of a nutritional assessment of the modified feed or feed additive as part of safety assessment, the possible influence of genetically modified (GM) products on animal health and product quality and the persistence of the recombinant DNA and of the 'novel' protein in the digestive tract and tissues of food-producing animals. During the last few years many studies have determined the nutrient value of GM feeds compared to their conventional counterparts and some have additionally followed the fate of DNA and novel protein. The results available to date are reassuring and reveal no significant differences in the safety and nutritional value of feedstuffs containing material derived from the so-called 1st generation of genetically modified plants (those with unchanged gross composition) in comparison with non-GM varieties. In addition, no residues of recombinant DNA or novel proteins have been found in any organ or tissue samples obtained from animals fed with GMP. These results indicate that for compositionally equivalent GMP routine-feeding studies with target species generally add little to nutritional and safety assessment. However, the strategies devised for the nutritional and safety assessment of the 1st generation products will be much more difficult to apply to 2nd generation GMP in which significant changes in constituents have been deliberately introduced (e.g., increased fatty acids or amino acids content or a reduced concentration of undesirable constituents). It is suggested that studies made with animals will play a much more important role in insuring the safety of these 2nd generation constructs.     

Global regulatory burden for field testing of genetically modified trees

Field trials are widely known to be essential for understanding the value and adaptability of trees produced via conventional and transgenic biotechnologies. However, obtaining permission for transgenic field trials is often considered to be very difficult in many countries. To understand the extent of regulatory requirements around the world and the burdens they impose, we surveyed 36 scientists and practitioners from 20 different countries who had experience or direct knowledge of regulatory compliance with field trials of transgenic trees. Results showed that permits and monitoring were universally required, and that public disclosure of field trial locations was required in three quarters of countries. Other major findings were that: separate approvals for different constructs, tree species, and trial locations were required in more than three quarters of the countries; characterization of each transgene insertion event was required as part of the application in four fifths of countries; and the application process itself was perceived as the largest single burden. Regulatory tiers that differentiate different kinds of transgenic trees based on perceived risk were present in only one fifth of countries. The data confirm the widespread perception among scientists that the costs and burdens of conducting field trials with transgenic trees are nearly universal substantial impediments to scientific and breeding progress.     

Novel roles for genetically modified plants in environmental protection

Transgenic plants of environmental benefit typically consist of plants that either reduce the input of agrochemicals into the environment or make the biological remediation of contaminated areas more efficient. Examples include the construction of species that result in reduced pesticide use and of species that contain genes for either the degradation of organics or the increased accumulation of inorganics. Cutting-edge approaches, illustrated by our own work, focus on the applicability of genetically modified (GM) plants that produce insect pheromones or that are specifically tailored to the phytoremediation of cadmium or PCBs. This paper discusses the role that the next generation of GM plants might play in preventing and reducing chemical contamination and in converting contaminated sites into safe agricultural or recreational land.     

Edible genetically modified microorganisms and plants for improved health

The development of new strategies for the delivery of vaccine antigens or immune modulators to the mucosal tissue includes innovative approaches such as the use of genetically modified food microorganisms and plants. Even though the 'proof-of-concept' has recently been established for these two systems, key questions mainly related to efficacy and risk of breaking oral tolerance remain to be critically addressed in the immediate future.     

Quantification of cuticular permeability in genetically modified plants

More and more studies on genetically modified plants are identifying parts of the genetic code with putative involvement in creating the cuticular barrier. Unfortunately, many of these studies suffer from the inadequacy of the chosen methods to quantify, in a reasonably unambiguous way, if and how the efficacy of the cuticular barrier is affected by the genetic change. A short overview of relevant findings is given and a more stringent experimental approach to quantifying effects on cuticular permeability in genetically modified plants proposed.     

Bioavailability of transgenic microRNAs in genetically modified plants

Background

Transgenic expression of small RNAs is a prevalent approach in agrobiotechnology for the global enhancement of plant foods. Meanwhile, emerging studies have, on the one hand, emphasized the potential of transgenic microRNAs (miRNAs) as novel dietary therapeutics and, on the other, suggested potential food safety issues if harmful miRNAs are absorbed and bioactive. For these reasons, it is necessary to evaluate the bioavailability of transgenic miRNAs in genetically modified crops.

Results

As a pilot study, two transgenic Arabidopsis lines ectopically expressing unique miRNAs were compared and contrasted with the plant bioavailable small RNA MIR2911 for digestive stability and serum bioavailability. The expression levels of these transgenic miRNAs in Arabidopsis were found to be comparable to that of MIR2911 in fresh tissues. Assays of digestive stability in vitro and in vivo suggested the transgenic miRNAs and MIR2911 had comparable resistance to degradation. Healthy mice consuming diets rich in Arabidopsis lines expressing these miRNAs displayed MIR2911 in the bloodstream but no detectable levels of the transgenic miRNAs.

Conclusions

These preliminary results imply digestive stability and high expression levels of miRNAs in plants do not readily equate to bioavailability. This initial work suggests novel engineering strategies be employed to enhance miRNA bioavailability when attempting to use transgenic foods as a delivery platform.

     

US regulatory system for genetically modified [genetically modified organism (GMO), rDNA or transgenic] crop cultivars

This paper reviews the history of the federal regulatory oversight of plant agricultural biotechnology in the USA, focusing on the scientific and political forces moulding the continually evolving regulatory structure in place today. Unlike most other jurisdictions, the USA decided to adapt pre-existing legislation to encompass products of biotechnology. In so doing, it established an overarching committee (Office of Science and Technology Policy) to study and distribute various regulatory responsibilities amongst relevant agencies: the Food and Drug Administration, Environmental Protection Agency and US Department of Agriculture. This paper reviews the history and procedures of each agency in the execution of its regulatory duties and investigates the advantages and disadvantages of the US regulatory strategy.     

Risk mitigation of genetically modified bacteria and plants designed for bioremediation

While the possible advantages of bioremediation and phytoremediation, by both recombinant microbes and plants, have been extensively reviewed, the biosafety concerns have been less extensively treated. This article reviews the possible risks associated with the use of recombinant bacteria and plants for bioremediation, with particular emphasis on ways in which molecular genetics could contribute to risk mitigation. For example, genetic techniques exist that permit the site-specific excision of unnecessary DNA, so that only the transgenes of interest remain. Other mechanisms exist whereby the recombinant plants or bacteria contain conditional suicide genes that may be activated under certain conditions. These methods act to prevent the spread and survival of the transgenic bacteria or plants in the environment, and to prevent horizontal gene flow to wild or cultivated relatives. Ways in which these genetic technologies may be applied to risk mitigation in bioremediation and phytoremediation are discussed.

     

Review: genetically modified plants for the promotion of human health

Plants are attractive biological resources because of their ability to produce a huge variety of chemical compounds, and the familiarity of production in even the most rural settings. Genetic engineering gives plants additional characteristics and value for cultivation and post-harvest. Genetically modified (GM) plants of the “first generation” were conferred with traits beneficial to producers, whereas GM plants in subsequent “generations” are intended to provide beneficial traits for consumers. Golden Rice is a promising example of a GM plant in the second generation, and has overcome a number of obstacles for practical use. Furthermore, consumer-acceptable plants with health-promoting properties that are genetically modified using native genes are being developed. The emerging technology of metabolomics will also support the commercial realization of GM plants by providing comprehensive analyzes of plant biochemical components.     

Risk mitigation of genetically modified bacteria and plants designed for bioremediation

While the possible advantages of bioremediation and phytoremediation, by both recombinant microbes and plants, have been extensively reviewed, the biosafety concerns have been less extensively treated. This article reviews the possible risks associated with the use of recombinant bacteria and plants for bioremediation, with particular emphasis on ways in which molecular genetics could contribute to risk mitigation. For example, genetic techniques exist that permit the site-specific excision of unnecessary DNA, so that only the transgenes of interest remain. Other mechanisms exist whereby the recombinant plants or bacteria contain conditional suicide genes that may be activated under certain conditions. These methods act to prevent the spread and survival of the transgenic bacteria or plants in the environment, and to prevent horizontal gene flow to wild or cultivated relatives. Ways in which these genetic technologies may be applied to risk mitigation in bioremediation and phytoremediation are discussed.     

Tolerance to aluminum in genetically modified tobacco plants

Genetically modified tobacco plants tolerant to high aluminum concentrations were developed by integration of constructs containing rhamnolipid genes (rhlA and rhlB). At an aluminum concentration of 200 mM in ionite soil, the control plants perished, whereas the transgenic plants, although they were inhibited, continued to grow and produced seeds.     

The tolerance of tobacco genetically modified plants to aluminium

Introduction of the vector constructions with rhamnolipid genes (rhlA and rhlB) into tobacco plants has resulted in development of genetically modified plants which were tolerant to high concentrations of aluminium. While under aluminium concentration of 200 mM in a soil (ionit resin) all control plants perished, transgenic tobacco plants continued to grow and were fertile.     

Problem formulation in the environmental risk assessment for genetically modified plants

Problem formulation is the first step in environmental risk assessment (ERA) where policy goals, scope, assessment endpoints, and methodology are distilled to an explicitly stated problem and approach for analysis. The consistency and utility of ERAs for genetically modified (GM) plants can be improved through rigorous problem formulation (PF), producing an analysis plan that describes relevant exposure scenarios and the potential consequences of these scenarios. A properly executed PF assures the relevance of ERA outcomes for decision-making. Adopting a harmonized approach to problem formulation should bring about greater uniformity in the ERA process for GM plants among regulatory regimes globally. This paper is the product of an international expert group convened by the International Life Sciences Institute (ILSI) Research Foundation.     

Transgenic,transplastomic and other genetically modified plants: a Canadian perspective

Since the mid 1990s, genetically modified (GM) crops have been grown commercially in Canada on a scale that has increased steadily over the years. An intense debate ensued, as elsewhere, and many fears were expressed regarding not only the technology itself but some of the main GM crops being grown. It would seem appropriate at this time to examine how these novel crops compare to crops bred by more traditional means and what impacts these GM crops have had based on experience and not merely on conjecture. To begin, we will put things in a historical perspective and recall how domestication and conventional plant breeding have shaped the crops of today. Then, we will describe briefly the distinctive features of GM plants (obtained so far mainly by nuclear transgenesis) and how these novel crops are regulated in Canada. We will then give two examples of widely grown GM crops in Canada (insect-resistant corn and herbicide-tolerant canola) and examine the main questions that were raised as well as the actual impacts these crops have had on the farm. These examples will help us outline some of the limitations of the current generation of GM plants and, finally, we will try to get a glimpse of the future by examining some recent technical developments in the field of recombinant DNA technologies applied to plant breeding.     

Opinion building on a socio-scientific issue: the case of genetically modified plants

This paper presents results from a study with the following research questions: (a) are pupils' opinions on genetically modified organisms (GMOs) influenced by biology teaching; and (b) what is important for the opinion pupils hold and how does knowledge work together with other parameters such as values? 64 pupils in an upper secondary school answered questionnaires, in which they expressed opinions and gave arguments on applications of GMOs, before and after biology courses. The pupils' knowledge of genetics and GMOs was also investigated. Eleven pupils were then in-terviewed to examine their reasoning in more depth. More pupils were positive about genetically modified tomatoes after the courses. Males were more positive than females. No correlation was found between knowledge of basic genetics and opinion. Most of the pupils could express arguments for and against the applications but they built their personal opinion on different arguments. An important concern was potential risks. Depending on risk judgement and/or how they trusted scientists, the pupils came to different conclusions. Few had any idea of how the different applications are risk assessed or how scientists work. Other important factors for decision-making were the purpose of the application, the time perspective and feelings.     

Safety assessment of genetically modified plants with deliberately altered composition

The development and marketing of ‘novel’ genetically modified (GM) crops in which composition has been deliberately altered poses a challenge to the European Union (EU)'s risk assessment processes, which are based on the concept of substantial equivalence with a non‐GM comparator. This article gives some examples of these novel GM crops and summarizes the conclusions of a report that was commissioned by the European Food Safety Authority on how the EU's risk assessment processes could be adapted to enable their safety to be assessed.