Ethics and transgenic crops: a review

Ethics and Transgenic Crops: a Review

Genetic engineering of crop plants with enhanced disease resistance has offered considerable promise and experimental power, however, with varying degrees of success. Traditional breeding has been very successful, though not in all cases. While the technology for gene manipulation in virtually any crop plant has been available for several years, field success has been hampered by our overall lack of understanding of the essential determinants mediating disease. Two key questions regarding molecular breeding will be addressed: (i) what genes or conceptual approaches can be used that have a realistic chance to be effective? and (ii) can we extrapolate useful information from model plants? Arabidopsis has served as an invaluable model system in many aspects of plant biology, including plant pathology and plant stress physiology, with many insights viewed to be directly applicable to crop plants. In addition, Arabidopsis has several experimental advantages: the genome has been sequenced, microarray chips are available, and there are a multitude of well characterised mutants. In addition, reverse genetics will continue as a powerful tool to examine gene function in Arabidopsis. The pros and cons of Arabidopsis application will be discussed. Sclerotinia sclerotiorum will serve as an example for approaches to disease control for soilborne fungal pathogens. The idea of interfering with fungal compatibility determinants coupled with biotechnology approaches will be described. S. sclerotiorum is an extremely broad host range, economically important, necrotrophic fungal plant pathogen. Diseases caused in economically important plants by S. sclerotiorum occur worldwide, cause considerable damage, have proven difficult to control (culturally or chemically) and host resistance to this fungus has been inadequate. A primary determinant contributing to the pathogenic success of this fungus is the ability to form sclerotia. The sclerotium of S. sclerotiorum is a multicellular, highly pigmented, rigid, asexual, resting or overwintering structure composed of condensed vegetative hyphal cells, which become interwoven and aggregate together, and it is capable of surviving years in soil. The importance of sclerotia for the pathogenic success of this fungus is underscored by the fact that sclerotia are the primary survival structures of this fungus upon which all other developmental phases of the fungus depend. Thus, sclerotia are an attractive target for intervention with the persistence of this pathogen. Effective pathogenesis by this fungus requires the secretion of oxalic acid, a primary pathogenicity determinant. Since this necrotrophic fungus requires host cell death for pathogenic success, we examined whether or not modulation of programmed cell death would impact the plant response to this aggressive pathogen. In animals, programmed cell death or its morphological equivalent, apoptosis, is genetically controlled cellular suicide. Multicellular organisms eliminate redundant, damaged or aged cells by this gene-directed cell death process. It is a complex process that is essential for development, maintenance of cellular homeostasis and for defence against environmental insults such as pathogen attack. Taking a trans-kingdom approach, transgenic crop plants that express animal anti-apoptotic genes have been generated. These genes all suppress apoptotic death in animal cells. We have shown that expression of these genes in tobacco and tomato abrogate disease development in plants infected with S. sclerotiorum. Plants with null mutations in these transgenes did not protect against pathogens. These data suggest that disease development requires host cell death pathways, thus differing from traditional concepts associated with necrotrophy. Transgenic plants also displayed tolerance or resistance to several abiotic stresses (heat, cold, salt and drought). Functional plant homologues of these mammalian genes are being identified. Taken together, our data suggest that modulation of host cell death is crucial in dictating the outcome of several fungal-plant interactions. The complete genome of S. sclerotiorum has been sequenced. The assembled sequence encodes a 39Mb genome size with >8 fold coverage. The generation of an optical map and our collaboration with the ‘Botrytis community’ is expected to yield new insight into fungal biology via comparative genomics.

The quest for patent rights has seen bioprospecting as a scientific and commercial research paradigm in which bioprospectors explore secluded locations around Cameroon in order to find ‘new drugs from exotic plants’. Bioprospectors derive genetic and biochemical materials that are both scientifically and commercially valuable, and they subsequently patent these materials abroad away from the original source to justify legal ownership through intellectual property law. An almost unprecedented amount of discussion has been stimulated on the merits and demerits of genetic engineering of crop plants and biodiversity exploitation and has divided both the public and scientific communities. The arguments for and against genetic engineering are invariably based on visions or missions of the new technology from widely different ethical perspectives. Fundamental issues of man's relationship with nature and theological matters are issues of concern. The genetic engineering of living cells, plants, animals and human beings has brought ethical concerns and issues to the conservation of biodiversity. Agricultural productivity depends in part on the availability of biodiversity for the development of improved cultivars. Until the 1970s, biodiversity was considered to be part of the ‘common heritage of humanity’. Under the regime of patent rights, biological resources are treated as belonging to the ‘public domain’ and are not owned by any individual, group, or state. From a common heritage of mankind, biodiversity is evolving into a resource under the sovereignty of nation states and is subject to intellectual property rights (IPRs). The new technology has witnessed a lot of illegal exploitation and commercialisation of these biological resources which is considered as biopiracy.

Genetically modified (GM) crops are now being grown extensively in North and South America and China, although not in Europe. Food produced from these crops has become a part of the normal diet in North and South America and in China, but not in Europe, where contention continues despite the fact that millions of US citizens eat GM soya without any ill effects in a very litigious society, and many Europeans have eaten GM soya while in the US without any adverse consequences. > Why has the British public, who normally so pragmatically welcome scientific advances, resisted the introduction of genetically modified crops? European consumers' continuous and ardent opposition to GM crops and foods has had serious repercussions for plant research, for the commercial development of new crops and, most importantly, for developing countries that could benefit most from GM crops. Several countries in Africa and elsewhere have resisted growing such crops, mainly for fear of being unable to export them to the European market ( The Economist , 2002). It is therefore worthwhile to investigate what actually went wrong in the debate about GM food and crops in Europe and how these foods have earned such a bad name. Such an analysis could not only help to overcome public fears of this technology, but also help scientists and policy makers to address similar concerns in the future, such as the growing debate over nanotechnology. The concerns of European consumers about the potential health and environmental threats of GM crops have resulted in an unprecedented effort to investigate those anxieties and communicate with the wider public, particularly in the UK, where the use of public consultation has been extensively developed. The first of these initiatives was the extensive Farm Scale Evaluations of three GM crops (herbicide‐resistant beet, oil seed rape and maize), whose …

The history of transgenic crops at present can be divided in two parts. The first era deals with the development of Genetically Modified (GM) crops. As the time went on, various social, political, environmental and technical issues related to transgenic crops took their birth. The development of transgenic crops has raised some issues more especially the problem of food and environmental safety, some technical impacts like effect on non target organisms, development of cross pest resistance, use of selectable marker genes, etc. There exists a thought that the pace of research in genetic engineering of crop plants may some day lead to the development of variations that will not ensure the survival of living creatures including human beings. Most of such concerns are just psychological and are often based on fear of negative political fall out or media coverage. The genetic engineering of crop plants is now moving towards the course of correction. It is the responsibility of concerned researchers to interpret such hazards and their solutions on technical basis and, therefore, establish a based line of acceptance for transgenic crops to the consumers.

Fungal diseases damage crop plants and affect agricultural production. Transgenic plants have been produced by inserting antifungal genes to confer resistance against fungal pathogens. Genes of fungal cell wall-degrading enzymes, such as chitinase and glucanase, are frequently used to produce fungal-resistant transgenic crop plants. In this review, we summarize the details of various transformation studies to develop fungal resistance in crop plants.

World poverty and hunger are closely related toenvironmental degradation, caused by increasingpopulation pressure and urban expansions, soilerosion, limitation of water resources, gaseouspollution, and massive industrialization.Furthermore, climate changes and extreme weatherpatterns pose new challenges for crop productionand food security. Sustainable agriculture for theproduction of food and fiber, usingenvironmentally-conscious farming practices basedon understanding plant ecological interactions, iscrucial for the preservation of natural resources forfuture generations.This special issue focuses on recent researchprogress on understanding plant interaction withabiotic and biotic stress factors for sustainableagriculture. Plant stresses inflected by salinity,drought, floods, temperature extremes, radiation,and toxic substances deposited in the soil togetherwith diseases and insects attacks, are the majorlimitations of crop cultivation incurring substantialreduction in yield and hence elevate economiclosses to the farmers.Sustainable agriculture is challenged by thelosses in crop genetic diversity. Conservation ofavailable germplasm and the efficient utilization ofgenetic resources are important aspects of currentresearch. In this special issue, Yumurtaci (2015)reviewed the utilization of wild relatives for thedevelopment of abiotic and biotic stress tolerantnew varieties of four major food crops includingwheat, barley, maize and oat.Modern advances in biotechnology offerinnovative approaches for understanding thefundamental mechanisms of abiotic and bioticstress and the development of stress tolerant crops.On this topic, Bakhsh (2015) reviewed currentresearch achievements towards the development ofabiotic stress tolerant crops through geneticengineering. In addition, Ram and Sharma (2015)studied the molecular characterization of TaPase inwheat, a gene known to be involved in plantresponse to stress.Plant diseases represent another major challengefor sustainable agriculture. To illustrate theimportance of integrating genetic engineering in thestrategies to combat plant diseases, Elayabalan etal. (2015) reviewed relevant advances in thedevelopment of banana plants resistant to thebanana bunchy top disease.Moreover, crop plants must adapt to adverseclimatic conditions, particularly those associatedwith the global climatic changes. Stresses due toabiotic stress factors like drought, extremetemperature and salinity and heavy metal toxicityinflect tremendous losses in crop productivity andare considered as major challenging factors forfuture agriculture sustainability. This topic wasaddressed in this special issue in several papers.Ud-Din et al. (2015) addressed drought effect onrice yield in relation to hormonal application.Siddika et al. (2015) studied the response to hightemperature stress of Basella alba, a leaf vegetablecommonly names as vine spinach.On the topic of heavy metal toxicity, Fasahat(2015) reviewed progress made in understandingcadmium toxicity and tolerance in rice. The specialissue also include studies on nutrient uptake fromunder saline conditions in potato (Oustani et al.,2015) and ion content in wild sage (Lantanacamara) treated with mepiquat chloride applicationunder shading (Matsoukis et al., 2015). In additionAjambang et al. (2015) examined the response ofoil palm to defoliation stress. Obviously,understanding abiotic and biotic stress mechanismsis essential for the development of tolerant cropcultivars under the global climate change.ReferencesAjambang, W., S. W. Ardie, H. Volkaert, M.Galdima and S. Sudarsono. 2015. Hugecarbohydrate assimilates delay response tocomplete defoliation stress in oil palm (Elaeisguineensis Jacq.). Emir. J. Food Agric.27(1):126-137.Bakhsh, A. 2015. Genetic engineering of cropplants against abiotic stress: Current

Exacerbation of plant growth and productivity due to a wide range of stresses has significantly affected global food security, agricultural productivity, and quality worldwide. In order to bridge the gap between the supply and demand of the ever-increasing global population, it is indispensable to foster a new breed of stress-tolerant crops with refined traits and higher yields against several abiotic and biotic stresses. The transgenic approach of conventional breeding, owing to the limited and time-consuming success due to the complex nature of genes involved in stress tolerance, is now being widely adopted to breed crop plants with enhanced stress tolerance. Thus, identification and characterization of critical genes involved in abiotic and biotic stress tolerance are an important requisite to develop stress-tolerant crops. Genetic engineering of crop plants employs two strategies (i) either manipulating single functional gene or (ii) by editing those regulatory genes which modulate the expression of other stress-responsive genes. Genome editing using artificial nucleases such as zinc finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENS), and Clustered Regulatory Interspaced Short Palindromic Repeat (CRISPR), CRISPR-associated protein 9 (Cas9), has significantly impacted basic as well as applied research including plant breeding by accelerating the editing of target genome in precise and predictable manner. Here, in this chapter, we are not going to discuss the past transgenic development approaches; mostly we will review some of the recent advancement made in the field of transgenic plants and the potential exploitation of genome-editing tools such as in conferring environmental stress tolerance in crops under field condition.

Principles and practices of plant genomics. Volume 2: Molecular breeding

Genetic Engineering of Crop Plants

The world today is faced with great challenges to produce adequate food, fibre, feed, industrial products and ecosystem services. Under the influence of global climate changes, the situation is getting worse by the destabilization of our ecosystem. With the increasing population, the challenge to develop ecosystem goods and services to meet human needs in the future is very important. Water scarcity, drought conditions and global climate change are major constraints in crop production worldwide. Uncertain rainfall is making conditions worse for farmers. Water stress along with other abiotic stresses is very complex in nature and is a serious challenge that needs to be met urgently in order to sustain and enhance productivity. Agriculture in India and other developing countries is a system which gambles with the monsoon and where irrigation is limited in major parts of the crop cultivation area. Genetic engineering techniques hold great promise for developing crop cultivars with high tolerance to drought. Biotechnological approaches can be utilized; drought and high salinity-tolerant genes can be discovered efficiently and subsequently cloned. Transgenic breeding is a new technology for the development of stress tolerance in crop plants. Drought stress is controlled by multiple polygenes, including signal transduction genes, transcriptional regulation genes and a series of genes for protection, defence and stress tolerance. It is very important to improve the drought tolerance of crops and to evolve plants with various mechanisms for adapting to adverse climatic environments. The introduction of transgenic technology to breeding crops has provided significant benefits to the industry; the first transgenic traits developed and commercialized were designed for insect and herbicide resistance in existing varieties. Eventually, by genetically enhanced technologies, current varieties must be improved or new varieties should be developed that adapt to environmental stresses and have the genetic potential to improve yield factors. This will lead to new levels of sustainable agriculture, with stable yield improvement.

Strigolactones (SLs) represent an important new plant hormone class marked by their multifunctional roles in plants and rhizosphere interactions, which stimulate hyphal branching in arbuscular mycorrhizal fungi (AMF) and seed germination of root parasitic plants. SLs have been broadly implicated in regulating root growth, shoot architecture, leaf senescence, nodulation, and legume–symbionts interaction, as well as a response to various external stimuli, such as abiotic and biotic stresses. These functional properties of SLs enable the genetic engineering of crop plants to improve crop yield and productivity. In this review, the conservation and divergence of SL pathways and its biological processes in multiple plant species have been extensively discussed with a particular emphasis on its interactions with other different phytohormones. These interactions may shed further light on the regulatory networks underlying plant growth, development, and stress responses, ultimately providing certain strategies for promoting crop yield and productivity with the challenges of global climate and environmental changes.

Genetic engineering of crop plants has been in progress since the dawn of agriculture, about 10 000 years ago. For millennia the genetic make-up of our crop plants has been changed by mankind's selection of naturally occurring variants. As the trade routes were developed, novel plant types were introduced into new environments and provided more variation from which to choose. At the end of the nineteenth century an understanding of the laws of heredity was gained and plant breeding protocols were devised whereby selection became accompanied by deliberate crossing. As the knowledge of the genetic structure of crop plants improved, new ways of manipulation were invented and exploited. Indeed plant breeding became a testing bed for new ideas in genetics. For the plant breeder the techniques which were most widely employed in the past were those which aided breeding, for example techniques which speeded up the production of new varieties, but still used traditional routes of crossing and selection. This was a transitional phase between plant breeding as an art and plant breeding as a science.

Genetic Engineering of Crop Plants: Colombia as a Case Study

The production of wheat is severely affected by abiotic stresses such as cold, drought, salinity, and high temperature. Although constitutive promoters are frequently used to regulate the expression of alien genes, these may lead to undesirable side-effects in transgenic plants. Therefore, identification and characterization of an inducible promoter that can express transgene only when exposed to stresses are of great importance in the genetic engineering of crop plants. Previous studies have indicated the abiotic stress-responsive behavior of myo-inositol oxygenase (MIOX) gene in different plants. Here, we isolated the MIOX gene promoter from wheat (TaMIOX). The in-silico analysis revealed the presence of various abiotic stress-responsive cis-elements in the promoter region. The TaMIOX promoter was fused with the UidA reporter gene and transformed into Arabidopsis thaliana. The T3 single-copy homozygous lines were analyzed for GUS activity using histochemical and fluorometric assays. Transcript expression of TaMIOX::UidA was significantly up-regulated by heat (fivefold), cold (sevenfold), and drought (fivefold) stresses as compared to transgenic plants grown without stress-induced conditions. The CaMV35S::UidA plants showed very high GUS activity even in normal conditions. In contrast, the TaMIOX::UidA plants showed prominent GUS activity only in stress treatments (cold, heat, and drought), which suggests the inducible behavior of the TaMIOX promoter. The substrate myo-inositol feeding assay of TaMIOX::UidA plants showed lesser GUS activity as compared to plants treated in abiotic stress conditions. Results support that the TaMIOX promoter could be used as a potential candidate for conditional expression of the transgene in abiotic stress conditions.