Số hóa bởi Trung tâm Học liệu – ĐHTN · application of plant genetic manipulation to agronomic traits (herbicide, pest, and disease resistance), which can be considered

Số hóa bởi Trung tâm Học liệu – ĐHTN http://www.lrc-tnu.edu.vn

P l a n t B i o t e c h n o l o g y :

t h e g e n e t i c m a n i p u l a t i o n o f p l a n t s

Second edition

Adrian Slater

N i g e l W . S c o t t

M a r k R . F o w l e r

De Montfort University

DAI HOC THAI NGUYEN

TRUNGTAM HOC LIEU

OXFORD UNIVERSITY PRESS


O X F O R D UNIVERSITY PRESS

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by Oxford University Press Inc., New York © Adrian Slater, Nigel W. Scott, and Mark R. Fowler 2008

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Data available Library of Congress Cataloging in Publication Data

Slater, Adrian. Plant biotechnology: the genetic manipulation of plants / Adrian Slater,

Nigel W. Scott, Mark R. Fowler. — 2nd ed. p.; cm.

Includes bibliographical references and index. ISBN 978-0-19-928261-6 falk. paper)

1. Plant biotechnology. 2. Plant genetic engineering. I. Scott, Nigel W. II. Fowler, Mark R. III. Title.

[DNLM: 1. Plants, Genetically Modified—genetics. 2. Crops, Agricultural—genetics. SB 123.57 S631p 2008] TP248.27.P55S59 2008 631.3*23—dc22 2008003362 Typeset by Graphicraft Limited, Hong Kong Printed in Great Britain by Ashford Colour Press Ltd., Gosport, Hants. ISBN 978-0-19-928261-6

3 3 7 9 10 8 6 4 2


Foreword

The Green Revolution, led by Norman Borlaug, Monkombu Swaminathan, and Gurdev Khush, enabled the world's food supply to be tripled during the last three decades of the 20th century. The extraordinary increase in agricultural productivity was made possible by the adoption of genetically improved varieties coupled with advances in crop management. In many countries food supply increased faster than demand and the technological progress contributed to a decrease in the unit cost of production so that farmers were able to share the benefits of the advances with consumers, by offering food to them at lower prices. Intensive (high-input/high-yield) agriculture has served the populations of the developed countries well but two problems have come to occupy these people. First, the full-scale exploitation of intensive agriculture protocols does deliver high yields of high-quality produce, but the environmental impact of the processes is often high. Second, the farmers have, in fact, the need to dispose of surplus food so that there is a downward pressure on prices in the world market that undermines farmers' incentives.

The position of the people in the low-income countries contrasts starkly with that in the developed countries. The world's population has increased from 2.5 billion to 6.1 billion in the last 50 years and it is unlikely to stabilize before 2100 by which time another 3 billion people will inhabit the planet. Most of the increase will occur in the low-income countries where poverty and hunger are already widespread. Each night 800 million people go to bed hungry and suffer from malnutrition, and one-fifth of humankind (about 1.2 billion people) lives on earnings of less than a dollar per day. We must satisfy the need for more food in an environmentally friendly way but we are confronted by major challenges. Prime agricultural land is being diverted to non-agricultural uses to meet the growing demand from housing, urbanization, and industrialization. Countries inhabited by half the world's population are already experiencing water crises, while the high agrochemical inputs that maximize yields exert a high environmental impact, which is not acceptable. There is a desperate need to produce more food from less land with less water and reduced agrochemical inputs.

The majority of agricultural scientists, led by Borlaug, Swaminathan, and Khush, are convinced that the required crops of high yield, high quality, low cost, and low environmental impact can be delivered by the exploitation of the techniques for plant biotechnology in molecular breeding strategies. The commercial adoption of transgenic crops by farmers has been one of the most rapid cases of technology diffusion in the history of agriculture. Between 1996 and 2002, the area planted commercially Số hóa bởi Trung tâm Học liệu – ĐHTN http://www.lrc-tnu.edu.vn

Foreword

with transgenic crops increased from 1.7 million to 58.7 million ha. Some 6 million farmers in 16 countries grow transgenic crops and more than a quarter of such crops are grown in developing countries.

The Norman Borlaug Institute was established to provide an international framework for co-operation in development of molecular breeding strategies. The core research activities provide a perfect environment for training students and research scientists who will respond to the challenges and opportunities outlined above. This book is based upon courses taught by the authors in The Norman Borlaug Institute.

The text defines the concepts and describes the technologies that enable the genetic manipulation of crop plants. It describes in detail the development of the two traits (herbicide and pest resistance) that are most prevalent in commercial genetically modified (GM) crops and examines the reasons for their success. The potential for developments in other crop traits such as disease resistance, abiotic stress tolerance, and improvements of yield and quality are considered and the possibility of using plants as factories for molecular farming is also explored.

The book is strengthened by confronting the wider social aspects of GM crops, and several of the controversies surrounding this new technology are thoroughly aired. The eco-terrorist fringe has constrained the development and exploitation of crop biotechnology but the measured discussion in this book will enable readers to deal with the self-serving campaigners whose actions undermine the undernourished, while they themselves benefit from three full meals each day. Meanwhile someone dies of starvation every 2.1 seconds.

Norman Borlaug himself is convinced that the world has the technology to permit a population of 10 billion people to be sustained but he is concerned that farmers may be prevented from exploiting the new technology by small, vociferous, well-financed groups of anti-science zealots. These affluent campaigners can afford to pay high prices for poorly regulated 'organic' food production. On the other hand the billion chronically poor and hungry people already in the world cannot do so and the crisis seems likely to grow as the population increases. The new technology described in this text will be the salvation of the undernourished, freeing them from obsolete, low-yielding, and more costly production technology. Professor M.C. Elliott Director The Norman Borlaug Institute for Plant Science Research


Preface t o the f i r s t ed i t ion

Plant biotechnology has made tremendous progress in recent years and has enjoyed a previously unknown level of public awareness. Unfortunately, much of this awareness has arisen from the negative publicity that surrounds genetically modified (GM) crops. One only has to think of the media coverage of food safety issues (so-called frankenfoods) or environmental concerns (the Monarch butterfly affair) to gain some appreciation of the public antipathy to this technology. As a result, the GM debate has been fuelled largely by misinformation, and has generated much more heat than light. It is surprising that in the course of this debate, there has not been an accessible textbook available to which serious students of the subject could turn for information and understanding.

The aim of this book is to provide enough information and examples to give the reader a sound knowledge of plant biotechnology in all its various guises, but particularly those related to the genetic manipulation of crop plants. It is not intended to provide an encyclopaedic coverage of the subject; such a task would require a volume far larger than this. As such, this is a textbook, and therefore a learning and teaching aid, rather than an academic treatise. Hopefully, the book also encourages a critical appraisal of plant biotechnology: not just the scientific aspects, but also the economic, social, moral, and ethical issues that surround and, some would say, plague the subject. Although this book is aimed at undergraduate and postgraduate students, we do not assume a huge amount of prior knowledge, and hope that other people will find the book to be accessible, informative, and enjoyable. We hope that this book will make a contribution to the GM crop debate, facilitating a rational exchange of views between informed people.

The first four chapters of the book are designed to provide a more technical introduction to subjects such as gene expression, tissue culture, and plant transformation that enables the remainder of the book to be fully appreciated. They can, of course, be read in their own right and contain information relevant to other areas of biology. The rest of the book looks in detail at various aspects of plant genetic manipulation applied to crop improvement. There are four chapters which deal in depth with the application of plant genetic manipulation to agronomic traits (herbicide, pest, and disease resistance), which can be considered as first-generation plant biotechnology. Three of the remaining chapters deal with more challenging and diverse advances in the areas of stress resistance, crop yield and quality, and molecular farming. It is in these areas that GM crops have the potential to produce real, widespread social and economic benefits, particularly for developing countries. Chapter 12 attempts to give Số hóa bởi Trung tâm Học liệu – ĐHTN http://www.lrc-tnu.edu.vn

Preface to the first edition

an overview of plant biotechnology, past, present, and future, with reference to the legislative framework and economic, social, moral, and ethical issues.

Throughout the book, case studies are used as extended illustrative examples of particular points that have been made in the main text. These are meant to be read as part of the body of each chapter. However, background information for clarification of advanced concepts, or more advanced information itself, is clearly presented in boxes that can be read as and when required. There is, at the end of each chapter, a Further reading section, which is not intended to be an exhaustive reference section, but gives enough pointers to allow and encourage further investigation. Various web-links to informative websites are also included in the further reading section. The World Wide Web provides an invaluable resource for investigating plant biotechnology, but care should be exercised when accessing information of dubious provenance. We would, however, encourage the use of the excellent online-journal sites to enable, in many cases freely, an interchange of knowledge and ideas, one of the cornerstones of science.

There is a website associated with this book, which will contain hyperlinked chapter web-links, further references, downloadable figures from the book, and update sections. We hope that this website will help to keep the reader of this book fully informed and up to date with developments in plant biotechnology.

We would like to thank all those who have contributed to the making of this book, not least the people whose original investigations are the basis of this book. We apologize unreservedly for any mistakes, all of which are ours, omissions or failure to acknowledge fully. Finally we would like to thank our friends and families, in particular Arlene, lane, and Hilary, for their continued support and encouragement throughout the writing of this book. February 2003


Preface t o the second ed i t ion

When we were invited by Oxford University Press to prepare this second edition, we must admit to approaching the task with mixed feelings.

On the one hand, we have been gratified by the success of the first edition and the complimentary reviews it has received. This confirmed our perception that there had been a conspicuous lack of an accessible textbook on plant biotechnology at a time when the field had reached a level of maturity that demanded one. It has been particularly pleasing to note that the book has been popular not only in the USA (the home of commercial genetically modified (GM) crops) and in Europe (where there is so much antipathy to them), but also in the developing economies where the potential value of this technology is widely appreciated.

On the other hand, the fact that we ourselves have been unable to exploit this book fully in our own teaching has been a source of great regret. Shortly after publication of the first edition, De Montfort University was one of a number of UK universities that was compelled to close its Departments of Biological Sciences and Chemistry, due in part to a lack of demand from UK school leavers to study science. This means that we no longer have the opportunity to fully 'road test' the textbook by teaching an entire module on plant biotechnology, although it is still of value in other areas of our teaching.

De Montfort University also closed the Norman Borlaug Institute for Plant Science Research in which we were based, and which Professor Elliott writes about so passionately in the Foreword. The Institute was an ambitious venture to develop high-yield/high-quality/low-cost/low-environmental-impact crops to address the desperate need to increase world food production. The Institute faced insuperable odds in trying to sustain its funding stream in a post-1992 UK university during the era of public backlash against GM crops. One of the knock-on effects of the rejection of GM food by the UK public described in Chapter 12 was the drying up of public and industrial funding for research directly focused on crop improvement. For good or ill, competitive plant science funding in the UK has been focused on the genomics of model systems such as Arabidopsis (see Chapters 1 and 13). At the same time, the distribution of central research funds to UK universities via the Research Assessment Exercise meant that the dice was always loaded against an institute whose primary mission was crop improvement for the benefit of mankind, rather than research publications as ends in themselves. As a result, our teaching and research in plant biotechnology now overlaps with other groups and departments in the university, including forensic science, biomedical science, pharmacy, and textiles, in areas such Số hóa bởi Trung tâm Học liệu – ĐHTN http://www.lrc-tnu.edu.vn

Preface to the second edition

as food and medicinal plant authentication and the genetic modification of non-food crops for pharmaceutical and fibre production.

One of the unforeseen consequences for us of no longer being directly involved in GM food crop research is that we have been able to cast a more dispassionate eye over progress in the past few years. It is striking, for example, that the rapid rate of adoption of GM crops worldwide (a 60-fold increase in area grown in the first 11 vears of commercialization) has not been matched by an increase in the number of GM traits. The 'big two' traits - herbicide tolerance and pest resistance - still predominate, with the most rapid advance being the development of stacked herbicide-/pest-resistant crops. The predominant GM crop species also remain the major US commercial crops (soybean, maize, cotton, and oilseed rape), rather than the most important world food crops (rice and wheat). Of particular note is the fact that several of the important agronomic traits such as disease and stress resistance that we discussed at length in the first edition appear to have foundered at the pre-commercialization stage. Some of the more novel 'molecular farming' traits about which there was considerable excitement a few years ago have also still to make a commercial impact.

So what is new in the field of plant biotechnology that justifies a second edition? There have been some important technological advances in the rationalization of transformation vectors around the Gateway platform, and the clarification of the miRNA mechanisms underpinning sense and antisense transgene silencing. However, the major developments on the horizon are those that encompass 'post-genomics' in their deeper understanding of biological systems and the effect of genetic modification upon them. Indeed, some of the advances such as TILLING could be described as 'post-GMics' in the sense that they point the way forward to selecting mutants in targeted genes without GM technology. For this reason, we have written a new chapter that reviews the current status of plant genomics and its potential impact on crop improvement.

We have also taken this opportunity to improve the format and presentation of the book. The use of colour has emphasized the structural components of chapters such as boxes and case studies. It has also allowed us to show important features in the figures and to highlight ke\vvords in the text. The wider margins also permit kev concepts to be drawn out. We trust that these improvements will help to make the text more attractive and accessible.

We would like to dedicate this second edition to all of our colleagues over the vears who shared the Norman Borlaug Institute vision of harnessing plant biotechnologv for humanitarian goals. lanuary 2008


Contents

List of abbreviations xix

1 Plant genomes: the organization and expression of plant genes 1

Introduction 1 DNA, chromatin, and chromosome structure 1 Chromatin 4

An introduction to gene structure and gene expression 6 Gene structure and expression in a eukaryotic protein-coding gene 6 Translation 10 Regulation of gene expression 16 Chromatin conformation 16 Gene transcription '6 RNA modification, splicing, turnover, and transport 18 Translation 20 Post-translational modification 21 Localization 21 Protein turnover 21 Conclusions 22 Implications for plant transformation 22 Examples of promoter elements used to drive transgene expression 26 Protein targeting 26 Heterologous promoters 26 Genome size and organization 27 Arabidopsis and the new technologies 28 Genome-sequencing projects—technology, findings, and applications 28 Biotechnological implications of the AGI 31 Crop plant genome sequencing 31 Summary 33 Further reading 34


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Số hóa bởi Trung tâm Học liệu – ĐHTN · application of plant genetic manipulation to agronomic traits (herbicide, pest, and disease resistance), which can be considered