Nigel G. Halford-Genetically Modified Crops

Download Nigel G. Halford-Genetically Modified Crops

Post on 23-Oct-2015




5 download

Embed Size (px)


Plant molecular biology came to the fore in the early 1980s and there has been tremendous growth in the subject since then. The study of plant genes and genomes and the development of techniques for the incorporation of novel or modified genes into plants eventually led to the commercialisation of genetically modified (GM) crops in the mid-1990s. This was seen as the start of a biotechnological revolution in plant breeding. However, plant biotechnology has become one of the hottest debates of the age and, in Europe at least, one of the greatest challenges that plant scientists have ever faced.


<ul><li><p>2nd Edition</p><p>P824.9781848168381-tp .indd 1 8/2/11 10:08 AM</p></li><li><p>This page intentionally left blankThis page intentionally left blank</p></li><li><p>Imperial College PressICP</p><p>Rothamsted Research, UK</p><p>Nigel G Halford</p><p>2nd Edition</p><p>P824.9781848168381-tp .indd 2 8/2/11 10:08 AM</p></li><li><p>British Library Cataloguing-in-Publication Data</p><p>A catalogue record for this book is available from the British Library.</p><p>Published by</p><p>Imperial College Press</p><p>57 Shelton Street</p><p>Covent Garden</p><p>London WC2H 9HE</p><p>Distributed by</p><p>World Scientific Publishing Co. Pte. Ltd.</p><p>5 Toh Tuck Link, Singapore 596224</p><p>USA office: 27 Warren Street, Suite 401-402, Hackensack, NJ 07601</p><p>UK office: 57 Shelton Street, Covent Garden, London WC2H 9HE</p><p>Printed in Singapore.</p><p>For photocopying of material in this volume, please pay a copying fee through the Copyright</p><p>Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, USA. In this case permission to</p><p>photocopy is not required from the publisher.</p><p>ISBN-13 978-1-84816-838-1</p><p>ISBN-10 1-84816-838-1</p><p>Typeset by Stallion Press</p><p>Email:</p><p>All rights reserved. This book, or parts thereof, may not be reproduced in any form or by any means,</p><p>electronic or mechanical, including photocopying, recording or any information storage and retrieval</p><p>system now known or to be invented, without written permission from the Publisher.</p><p>Copyright 2012 by Imperial College Press</p><p>GENETICALLY MODIFIED CROPS</p><p>2nd Edition</p><p>Catherine - Genetically modified crops.pmd 10/21/2011, 10:51 AM1</p></li><li><p>b1219 Genetically Modified Crops</p><p>CONTENTS</p><p>Preface ix</p><p>1. DNA, Genes, Genomes and Plant Breeding 1</p><p>1.1 A Brief History of Genetics 11.2 Deoxyribonucleic Acid (DNA) 41.3 Genes 81.4 Gene Expression 91.5 Genomes 101.6 Genetic Change 111.7 Plant Breeding 111.8 Modern Plant Breeding 151.9 Wide and Forced Crossing and Embryo 18</p><p>Rescue1.10 Radiation and Chemical Mutagenesis 191.11 The Advent of Genetic Modification 20</p><p>2. The Techniques of Plant Genetic Modification 23</p><p>2.1 A Brief History of the Development 23of Recombinant DNA Technology</p><p>2.2 Agrobacterium tumefaciens 262.3 Use of Agrobacterium tumefaciens in Plant 27</p><p>Genetic Modification2.4 Transformation of Protoplasts 302.5 Particle Gun 31</p><p>v</p><p>b1219_FM.qxd 9/15/2011 3:26 PM Page v</p></li><li><p>2.6 Other Direct Gene Transfer Methods 322.7 Agrobacterium-mediated Transformation 34</p><p>Without Tissue Culture2.8 Selectable Marker Genes 342.9 Visual/Scoreable Marker Genes 382.10 Design and Construction of Genes for 40</p><p>Introduction into Plants2.11 Promoter Types 432.12 The Use of GM to Characterise Gene 45</p><p>Promoters2.13 Gene Over-Expression and Silencing 47</p><p>3. The Use of GM Crops in Agriculture 51</p><p>3.1 Why Use Genetic Modification (GM) in Plant 51Breeding?</p><p>3.2 Slow-ripening Fruit 553.3 Herbicide Tolerance 573.4 Insect Resistance 643.5 Virus Resistance 683.6 Modified Oil Content 703.7 Modified Starch for Industrial and Biofuel Uses 803.8 High Lysine Corn 833.9 Vitamin Content: Golden Rice 843.10 Fungal Resistance 883.11 Drought, Heat and Cold Tolerance; Climate 90</p><p>Change3.12 Salt Tolerance 943.13 Biopharming 973.14 Removal of Allergens 1033.15 Conclusions 105</p><p>4. Legislation Covering GM Crops and Foods 107</p><p>4.1 Safety of GM Plants Grown in Containment 1074.2 Safety of Field Releases of GM Plants 111</p><p>vi Contents</p><p>b1219 Genetically Modified Crops</p><p>b1219_FM.qxd 9/15/2011 3:26 PM Page vi</p></li><li><p>4.3 Safety of GM Foods 1154.4 European Union Regulations 1184.5 Labelling and Traceability Regulations 1204.6 Safety Assessment and Labelling Requirements 124</p><p>in the USA</p><p>5. Issues that have Arisen in the GM Crop 127and Food Debate</p><p>5.1 Are GM Foods Safe? 1335.2 Will Genetic Modification Produce New Food 134</p><p>Allergens?5.3 Is it Ethical to Transfer Genes Between Different 136</p><p>Species?5.4 Animal Studies 1375.5 GM Crops Do Not Work 1385.6 Did Tryptophan Produced by Genetic 139</p><p>Modification Kill People?5.7 The Monarch Butterfly 1415.8 The Pusztai Affair 1425.9 Alarm Caused by Contradictory Results of 144</p><p>Biosafety Studies5.10 Superweeds 1465.11 Insect Resistance to Bt Crops 1475.12 Segregation of GM and non-GM Crops: 148</p><p>Co-existence of GM and Organic Farming5.13 Antibiotic Resistance Marker Genes 1505.14 Patenting 1525.15 Loss of Genetic Diversity 1535.16 The Dominance of Multinational Companies 1545.17 The StarLink and ProdiGene Affairs 1555.18 The Cauliflower mosaic virus 35S RNA Gene 157</p><p>Promoter5.19 Implications for Developing Countries 1585.20 Terminator Technology 1605.21 Unintentional Releases 161</p><p>Contents vii</p><p>b1219 Genetically Modified Crops</p><p>b1219_FM.qxd 9/15/2011 3:26 PM Page vii</p></li><li><p>5.22 Asynchronous Approvals 1635.23 The United Kingdom Farm-Scale Evaluations 1635.24 Conclusions 165</p><p>Index 169</p><p>viii Contents</p><p>b1219 Genetically Modified Crops</p><p>b1219_FM.qxd 9/15/2011 3:26 PM Page viii</p></li><li><p>b1219 Genetically Modified Crops</p><p>PREFACE</p><p>It is fifteen years since the first large-scale cultivation of geneticallymodified (GM) crops and eight years since the first edition of thisbook was published. Since then, the use of GM crops has continuedto rise around the world, with 134 million hectares being grown in2009. The number of traits that have been introduced by geneticmodification remains limited and there is still no established mar-ket for GM varieties of some of the worlds major crops, namelyrice, wheat and potato. GM rice looks set to take off but GM wheatremains some way off and GM potato, after some false starts in the1990s, is currently limited to the early stages of development of avariety designed to produce industrial starch. Nevertheless, pre-dictions that the technology would be lost in the face of fierceopposition from pressure groups and consumer hostility in someparts of the world have proved incorrect and GM crop varietiescontinue to be popular with farmers wherever they have beenmade available.</p><p>For plant scientists in the United Kingdom and the rest ofEurope the situation remains a frustrating one. The GM cropdebate of the late 1990s and early 2000s was lost and great damagewas done to the European plant biotechnology industry as a result.The European regulatory system is now so difficult to negotiatethat biotechnology companies are focused on obtaining approvalfor their products to be imported into Europe so that they can begrown elsewhere rather than approval for their varieties to becultivated in Europe. European farmers are therefore becoming</p><p>ix</p><p>b1219_FM.qxd 9/15/2011 3:26 PM Page ix</p></li><li><p>increasingly disadvantaged as they have to compete with GM cropvarieties that they are not allowed to grow. As non-GM crop prod-ucts become more difficult to source it is recognised that thesituation cannot continue as it is, but efforts to re-start the debateare greeted with the same shrill predictions of disaster and thesame headlines as before. Meanwhile, the USA, Argentina, Brazil,India, Canada, China, Paraguay, South Africa and 17 other coun-tries all extend their lead in developing what will be a keytwenty-first century technology. </p><p>In this edition, the chapter on the use of GM crops in agricul-ture is expanded while those covering techniques, legislation andthe GM crop debate are updated. The reason for writing the firstedition was that people in the United Kingdom and the rest ofEurope had been bombarded with scare stories, misinformationand half truths and found it difficult to obtain answers to theirlegitimate questions about genetic modification: what is it, how isit done, how does it differ from what has been done before, is itsafe, how is it regulated and what implications does it have forplant breeding, agriculture and the environment? People are stillasking those questions and the aim of this edition of the book, aswith the first, is to provide the answers.</p><p>x Preface</p><p>b1219 Genetically Modified Crops</p><p>b1219_FM.qxd 9/15/2011 3:26 PM Page x</p></li><li><p>b1219 Genetically Modified Crops</p><p>DNA, GENES, GENOMES ANDPLANT BREEDING</p><p>1.1 A Brief History of GeneticsTo many people the beginnings of genetics can be traced back tothe publication in 1859 of Charles Darwins book On the Origin ofSpecies by Means of Natural Selection. This established the theory ofevolution based on the principle of natural selection, discoveredindependently at the same time by Alfred Russell Wallace, andwas the culmination of decades spent collecting and examiningevidence.</p><p>Darwin argued that species and individuals within speciescompete with each other. Furthermore, individuals within aspecies are not all the same; they differ, or show variation. Thosethat are best fitted for their environment are the most likely tosurvive, reproduce and pass on their characteristics to the nextgeneration. If the environment changes or a species colonises a newenvironment, different characteristics may be selected for, leadingto change, or evolution. The diversity of life on Earth could there-fore be explained by the adaptation of species and groups ofindividuals within species to different and changing environments,leading to the extinction of some species and the appearance ofothers. Species that were similar had arisen from a recent commonancestor. Most controversially, humans were similar to other apesnot because God had made it so but because humans and otherapes had a relatively recent common ancestor.</p><p>1</p><p>1</p><p>b1219_Chapter-01.qxd 9/15/2011 3:28 PM Page 1</p></li><li><p>Darwin and Wallace were not the only scientists whose think-ing was challenging the notion of lifes diversity arising fromsupernatural creation. Georges Cuvier, in Paris, had noted that fos-sils in deep rock strata were less like living animals than those inshallow strata. In 1796 he published a paper on living and fossilelephants, arguing that the fossils were clear evidence of extinction.He developed his ideas further and wrote extensively on them in aseries of papers, Recherches sur les ossements fossiles de quadrupdes,in 1812. About the same time, studies were revealing that theanatomies of different animals were based on the same internalpatterns and another French scientist, Jean-Baptiste Lamarck, hadalready put forward his theory that animals could transform intoone another. Lamarck proposed that animals changed in responseto their environment and passed these changes on to their off-spring. He published his ideas in Recherches sur lorganisation descorps vivants in 1802, Philosophie Zoologique in 1809 and a series ofvolumes entitled Histoire naturelle des animaux sans vertbresbetween 1815 and 1822. Although his evidence for extinction wasinconsistent with creationism, Cuvier strongly opposed the notionof evolution and was a fierce critic of Lamarck. His influence prob-ably stymied the development of evolutionary theory until thepublication of On the Origin of Species by Means of Natural Selectionhalf a century later.</p><p>There was a problem with the theory of evolution by naturalselection and Darwin was well aware of it. At that time, the traitsof parents were believed to be mixed in their offspring so that thecharacteristics of the offspring would always be intermediatebetween those of the parents. If this were true, natural selection asDarwin proposed it could not work because the process requiresthere to be variation within a population so that differences can beselected for. Blending traits would have the effect of reducing vari-ation with every successive generation. Darwin even consideredvariations on Lamarcks theory that changes acquired during anorganisms lifetime could be passed on to its offspring.</p><p>The solution of the problem was found by Gregor Mendel but,ironically, Darwin was never aware of Mendels work. In 1857,</p><p>2 Genetically Modified Crops</p><p>b1219 Genetically Modified Crops</p><p>b1219_Chapter-01.qxd 9/15/2011 3:28 PM Page 2</p></li><li><p>Mendel performed some experiments with pea plants in the gar-den of the Austrian monastery where he was a monk. Mendelrecorded the different characteristics of the plants, such as height,seed colour, seed coat colour and pod shape, and observed thatoffspring sometimes, but not always, showed these same charac-teristics. In his first experiments, he self-pollinated short and tallplants and found that they bred true, the short having short off-spring and the tall having tall offspring. However, when he crossedshort and tall plants he found that all of the offspring (the F1 gen-eration) were tall. He crossed the offspring again and the shortcharacteristic reappeared in about a quarter of the next generation(the F2 generation).</p><p>Many years and experiments later, Mendel concluded thatcharacteristics were passed from one generation to the next inpairs, one from each parent, and that some characteristics weredominant over others. His most famous experiments concerningthe inheritance of a trait in which the seeds were wrinkled are stilltaught in schools today. His findings were published but ignoredfor decades as the work of an amateur. Later, they became knownas the Mendelian laws and the foundation of modern genetics andplant breeding.</p><p>The significance of Mendels work was that it showed that,whether or not the offspring of two parents resemble one parent orare an intermediate between the two, they inherit a single unit ofinheritance from each parent. These units are reshuffled in everygeneration and traits can reappear, so variation is not lost. Units ofinheritance subsequently became known as genes.</p><p>The next big advance came in 1902, when a British doctor,Sir Archibald Garrod, studied an inherited human disease,Alkaptonuria. Alkaptonuria sufferers excrete dark red urine becausethey lack an enzyme that breaks down the reddening agent, alkap-ton. Garrod noted that Alkaptonuria recurred in families and thatparents of sufferers were often closely related to each other. In otherwords, it was an inherited condition. In 1902 he published The inci-dence of Alkaptonuria: a study in chemical individuality, in TheLancet. He continued to develop his ideas and published his most</p><p>DNA, Genes, Genomes and Plant Breeding 3</p><p>b1219 Genetically Modified Crops</p><p>b1219_Chapter-01.qxd 9/15/2011 3:28 PM Page 3</p></li><li><p>famous work, Inborn Errors of Metabolism, in 1909. The significanceof Garrods work was that it made the link between the inheritanceof one particular gene and the activity of a single protein.</p><p>Like Mendel, Garrod was ahead of his time and his work wasforgotten until the link between genes and proteins was madeagain in the 1930s by American geneticists George Beadle andEdward Tatum. Beadle and Tatum showed that a mutation in thefungus Neurospora crassa affected the synthesis of a single enzymerequired to make an essential nutrient, and that the mutation wasinherited through successive generations. This led to Beadle andTatum publishing the one gene, one enzyme hypothesis in 1941.The hypothesis still stands today, although it has been modifiedslightly to account for the fact that some proteins are made upof more than one subunit and the subunits may be encoded bydifferent genes.</p><p>1.2 Deoxyribonucleic Acid (DNA)With the principles of inheritance established, the search was on forthe substance through which the instructions for life were passedfrom one generation...</p></li></ul>