Plant Biotechnology and Transgenic Plants (Books in Soils, Plants, and the Environment, 92)

Biology EEn 1 PLANT BIOTECHNOLOGY AND TRANSBENIC PLANTS 2 Back Cover 3 Copyright Info 5 Preface 10 TOC 12 Contributors 15 Chapter 1: Plant Biotechnology—An Emerging Field 19 I. INTRODUCTION 19 II. A LONG HISTORY TO REACH A HIGH STANDARD 20 III. PLANT TISSUE AND CELL CULTURES—A VERY VERSATILE SYSTEM 23 IV. FROM GENES TO PATHWAYS TO BIOTECHNOLOGICAL APPLICATION 25 V. THE PLANT CELL ORGANELLES CONTAINING GENETIC INFORMATION 31 VI. METABOLISM OF XENOBIOCHEMICALS 32 VII. CROP PLANTS AND RENEWABLE RESOURCES 35 VIII. CONCLUSIONS 36 REFERENCES 37 Chapter 2: Plant-Derived Drugs and Extracts 40 I. INTRODUCTION 40 II. DRUGS ISOLATED FROM PLANTS 41 A. Artemisinin 41 B. Cardiac Glycosides 42 C. Opium 42 D. B-Sitosterol 44 E. Steroids 45 F. Taxol 45 G. Tropane Alkaloids 46 H. Vinblastine and Vincristine 47 III. PLANT PRODUCTS AND EXTRACTS 48 A. Chamomile 48 B. Echinacea 49 C. Evening Primrose Oil 50 D. Garlic 50 E. Linseed Oil 52 F. Mint Oils and Menthol 52 G. Saw Palmetto 53 IV. STANDARDIZED EXTRACTS 54 A. Ginger 54 B. Ginkgo 55 C. Ginseng 56 D. Hawthorn 56 E. St. John's Wort 57 V. CONCLUSIONS 58 REFERENCES 59 Chapter 3: Industrial Strategies for the Discovery of Bioactive Compounds from Plants 62 I. INTRODUCTION 62 II. CHANGING PARADIGMS: INDUSTRIALIZATION OF DISCOVERY 63 III. AUTOMATION FOR DRUG DISCOVERY 66 IV. PLANT PRODUCTS IN THE INDUSTRIALIZED DRUG DISCOVERY PROCESS 68 V. OPPORTUNITIES FROM TRADITIONAL MEDICINE 71 VI. OUTLOOK 72 REFERENCES 73 Chapter 4: Plant Cell and Tissue Culture Techniques Used in Plant Breeding 75 I. INTRODUCTION 75 II. SOMATIC HYBRIDIZATION 77 III. GENE TRANSFER TO PLANTS 78 IV. MICROPROPAGATION AND SOMATIC EMBRYOGENESIS 80 V. IN VITRO SELECTION 82 VI. THE NEED FOR A COMPREHENSIVE PLANT BREEDING STRATEGY 83 VII. BREEDING FOR SELF-POLLINATED PLANTS 84 VIII. BREEDING HYBRID VARIETIES OF OUT-CROSSING PLANTS 86 IX. BREEDING CLONALLY PROPAGATED PLANTS 86 X. BREEDING HYBRID VARIETIES OF SELFING PLANTS 87 XI. CELL AND TISSUE CULTURE IN TREE BREEDING 88 XII. FOREST TREE POPULATION STRUCTURES AND THE ADOPTION OF CLONING 89 XIII. ECOLOGICAL ASPECTS IN TREE BREEDING 90 XIV. THE CLONAL FORESTRY OPTION 91 REFERENCES 92 Chapter 5: Plant Cell Cultures as Producers of Secondary Compounds 93 I. INTRODUCTION 93 II. CELL CULTURE SYSTEMS USED FOR PRODUCTION OF PHYTOCHEMICALS 94 A. Callus and Cell Suspension Cultures 94 B. Immobilized Cultures 94 C. Organ Cultures 94 1. Shoot Cultures 95 2. Root Culture 95 D. Bioreactor Cultures 96 III. FACTORS AFFECTING SECONDARY METABOLITE PRODUCTION BY PLANT CELL CULTURES 96 A. Plant Growth Regulators 96 B. Medium Nutrients 97 C. Elicitors 98 D. Physical Factors 99 E. Biological Factors 99 IV. PRODUCTION OF PLANT PIGMENTS 100 A. Anthocyanin 100 1. Cell Line Selection 102 2. Physical Environment 103 3. Chemical Factors 103 4. Bioreactor Culture 104 5. Engineering Anthocyanin Production Using Recombinant DNA Technology 104 B. Shikonin 104 1. Large-Scale Production of Shikonin Derivatives by Lithospermum erythrorhizon Cell Cultures 106 2. Regulatory Mechanism of Shikonin Biosynthesis 107 3. Intracellular Localization of Shikonin Biosynthesis 110 4. Engineering Shikonin Biosynthesis in Cultured Plant Cells 110 V. PRODUCTION OF CLINICALLY USED ANTINEOPLASTIC COMPOUNDS 110 A. Catharanthus Alkaloids 110 B. Camptothecin 112 C. Paclitaxel (Taxol) 114 D. Podophyllotoxin 114 VI. FUTURE PROSPECTS 116 ACKNOWLEDGMENTS 116 REFERENCES 116 Chapter 6: Genetic Transformation of Plants and Their Cells 126 I. INTRODUCTION 126 II. REQUIREMENTS FOR PLANT TRANSFORMATION 127 A. Overview 127 B. DNA Transfer Methods 127 C. Cell and Tissue Culture and Plant Regeneration 128 D. Selectable Marker Genes 129 III. AGROBACTERIUM-MEDlKTED TRANSFORMATION 131 A. Agrobacterium tumefaciens: A Natural Gene Transfer System 131 B. Development of Ti-Plasmid Vectors 131 C. General Protocol for Agrobacterium-Mediated Transformation 133 D. Recent Advances—Expanding the Agrobacterium Host Range 134 E. Recent Advances—Increasing the Capacity of T-DNA 136 F. Conjugation Systems and Ri Plasmids 136 IV. PARTICLE BOMBARDMENT 136 A. Advantages and Disadvantages of Particle Bombardment 137 B. Recent Advances 138 V. TRANSFORMATION OF PROTOPLASTS 140 VI. OTHER DIRECT TRANSFORMATION METHODS 141 VII. TRANSFORMATION WITHOUT TISSUE CULTURE 142 VIII. PLANT VIRUSES AS GENE TRANSFER VECTORS 143 IX. ORGANELLE TRANSFORMATION 144 X. FUTURE PROSPECTS—CONTROLLED TRANSGENE INTEGRATION AND EXPRESSION 144 A. Overview 144 B. Clean DMA Transformation 145 C. Toward Marker-Free Transgenic Plants 147 D. Toward Precise Integration and Control of Expression 149 XI. CONCLUDING REMARKS 149 REFERENCES 150 Chapter 7: Properties and Applications of Hairy Root Cultures 157 I. INTRODUCTION 157 II. PROPERTIES OF HAIRY ROOTS 158 A. Genotype and Phenotype Stability 158 B. Autotrophy in Plant Hormones 159 C. Fast Growth 159 D. High Levels of Secondary Metabolites 159 E. Species Resistant to Hairy Root Transformation 160 F. Clonal Variation 161 III. COCULTURES USING HAIRY ROOTS 161 IV. PRODUCTION OF FOREIGN PROTEINS USING HAIRY ROOTS 162 V. HAIRY ROOTS IN PHYTOREMEDIATION AND PHYTOMINING STUDIES 165 VI. CONCLUSIONS 170 ACKNOWLEDGMENTS 170 REFERENCES 170 Chapter 8: Bioreactors for Plant Cell and Tissue Cultures 176 I. INTRODUCTION 176 II. BACKGROUND 177 III. GENERAL REQUIREMENTS FOR THE CULTIVATION OF PLANT CELLS IN BIOREACTORS 177 IV. INSTRUMENTATION OF BIOREACTORS FOR PLANT CELL AND TISSUE CULTURES 179 V. GENERAL CLASSIFICATION OF BIOREACTOR TYPES 182 A. Stirred Reactor 186 B. Rotating Drum Reactor 186 C. Bubble Column 186 D. Airlift Reactor 186 E. Packed Bed Reactor 189 F. Fluidized Bed Reactor 189 G. Trickle Bed Reactor 189 H. Membrane Reactor 189 VI. SUITABLE BIOREACTORS FOR PLANT CELL AND TISSUE CULTURES 192 A. Reactors for Plant Cell Suspensions 192 B. Reactors for Hairy Root Cultures 197 C. Reactors for Embryogenic and Shoot Cultures 198 VII. ECONOMIC FEASIBILITY AND TRENDS IN REACTOR DEVELOPMENT FOR PLANT CELL AND TISSUE CULTURES 200 VIII. OPERATIONAL STRATEGIES OF PLANT CELL AND TISSUE CULTURE BIOREACTORS 204 IX. CONCLUSIONS 206 REFERENCES 206 Chapter 9: The Potential Contribution of Plant Biotechnology to Improving Food Quality 213 I. INTRODUCTION 213 II. PRIORITIES FOR THE FOOD SECTOR 216 A. The Developing World 216 1. Improvements in Protein Quality 217 2. Reduction in Antinutritional Factors 217 B. The Developed World 218 III. APPLICATION OF GENETIC ENGINEERING TO FOOD QUALITY IMPROVEMENT 221 IV. PLANT SECONDARY METABOLITES AS DETERMINANTS OF QUALITY 222 V. THE PHENYLPROPANOID PATHWAY 222 A. Flavonoids and Isoflavonoids 224 B. The Isoprenoid Pathway 228 1. Sterol Biosynthesis 232 2. Carotenoid Biosynthesis 234 VI. RELATIONSHIP OF STRUCTURE TO NUTRITIONAL QUALITY (BIOAVAILABILITY) 235 VII. SAFETY AND REGULATORY ISSUES 236 A. Food Chemical Risk Assessment 238 VIII. CONCLUSIONS 240 REFERENCES 240 Chapter 10: Engineering Plant Biochemical Pathways for Improved Nutritional Quality 245 I. INTRODUCTION 245 II. STRATEGIES TO MANIPULATE PLANT METABOLIC PATHWAYS TOWARD THE PRODUCTION OF A DEFINED COMPOUND OF NUTRITIONAL VALUE 246 III. MANIPULATING ESSENTIAL AMINO ACID METABOLIC PATHWAYS TO INCREASE THE NUTRITIONAL VALUE OF CROPS 248 A. Biochemical Regulation of Lysine and Threonine Biosynthesis 249 B. Mutants Overproducing Free Lysine or Threonine 250 C. Key Genes of the Lysine and Threonine Pathways 251 1. Aspartate Kinase Genes 251 2. Cloning and Characterization of Wild-Type and Mutant Genes Encoding Dihydrodipicolinate Synthase 252 D. Improving Lysine and Threonine Accumulation via Transfer of Bacterial Genes 254 E. Improving Lysine Content Using Plant Gene Transfer 255 F. Manipulating Plant Micronutrients to Benefit Human Health and Nutrition 259 IV. CONCLUSIONS AND PERSPECTIVES FOR THE FUTURE 260 ACKNOWLEDGMENTS 261 REFERENCES 261 Chapter 11: Transgenic Plants as Producers of Modified Starch and Other Carbohydrates 266 I. INTRODUCTION 266 II. APPROACHES TO STARCH AND CARBOHYDRATE MODIFICATION 267 III. STARCH STRUCTURE 268 A. Amylose and Amylopectin, the Two Components of Starch 268 B. Starch Granules 268 IV. STARCH DEPOSITION 270 A. Source of Photosynthate for Starch Biosynthesis 270 B. The Committed Pathway of Starch Biosynthesis 272 C. Synthesis of Amylose 274 D. Synthesis of Amylopectin 274 V. TRANSGENIC MODIFICATION OF CARBOHYDRATE BIOSYNTHESIS 276 A. Alteration of Starch Quantity 277 B. Production of Simple Sugars in Storage Organs 278 C. Alteration of the Amylose Complement in Starch 280 D. Alteration of Amylopectin Structure 280 E. Production of Nonstarch Carbohydrates 282 VI. CONCLUSIONS 284 REFERENCES 285 Chapter 12: Improving the Nutritional Quality and Functional Properties of Seed Proteins by Genetic Engineering 294 I. INTRODUCTION 294 II. SEED PROTEINS 295 III. GLOBULIN STORAGE PROTEINS 295 IV. PROLAMINS 296 V. 2S ALBUMINS 296 VI. NUTRITIONAL QUALITY OF SEED PROTEINS 297 VII. HIGH-LYSINE CEREALS 297 A. Manipulation of the Amino Acid Composition of Prolamins 298 B. Expression of Specific Lysine-Rich Proteins 298 C. Increased Accumulation of Free Lysine 300 VIII. HIGH-METHIONINE LEGUMES 302 IX. SEED PROTEINS AND FUNCTIONALITY 304 X. GEL FORMATION AND EMULSIFICATION PROPERTIES OF SOYBEAN GLOBULINS 305 XI. THE VISCOELASTICITY OF WHEAT GLUTEN 305 XII. CONCLUSIONS 308 ACKNOWLEDGMENTS 309 REFERENCES 309 Chapter 13: Transgenic Plants as Sources of Modified Oils 316 I. INTRODUCTION 316 II. SHORT- AND MEDIUM-CHAIN SATURATED FATTY ACIDS 317 III. LONG CHAIN SATURATED FATTY ACIDS 318 IV. MONOUNSATURATED FATTY ACIDS 321 V. POLYUNSATURATED FATTY ACIDS 323 VI. VARIATIONS ON THE METHYLENE-INTERRUPTED DOUBLE BOND 325 VII. COMMERCIAL PRODUCTION OF NEW OILS FROM TRANSGENIC PLANTS 327 REFERENCES 327 Chapter 14: Flavors and Fragrances from Plants 333 I. INTRODUCTION 333 II. RECOMBINANT DMA TECHNOLOGY 336 A. Genetically Engineered Food Plants 336 B. Plant Enzymes and Genomics 338 III. PLANT CELL, TISSUE, AND ORGAN CULTURES 341 A. Tissue Cultures 341 B. Organ Cultures 345 C. Biotransformation by Plant Cell Cultures 346 IV. PROCESS DEVELOPMENTS 349 V. CONCLUSIONS 350 REFERENCES 351 Chapter 15: Fine Chemicals from Plants 357 I. INTRODUCTION 357 II. PRODUCTION OF PHYTOCHEMICALS 358 III. METABOLIC ENGINEERING FOR IMPROVEMENT OF PRODUCTIVITY 361 IV. TRANSFORMATION AND REGENERATION OF MEDICINAL PLANTS 367 V. APPLICATION OF BIOTECHNOLOGY TO DUBOIS1A FOR SCOPOLAMINE PRODUCTION 368 A. Conventional Breeding 370 B. Tissue Culture Applications 370 C. Agronomical Performance of Hairy Root-Derived Plants 371 D. Genetic Transformation 371 E. Other Traits of Interest 373 F. Molecular Markers 374 VI. CONCLUSIONS 375 REFERENCES 376 Chapter 16: Genetic Engineering of the Plant Cell Factory for Secondary Metabolite Production: Indole Alkaloid Production in Catharanthus roseus as a Model 382 I. INTRODUCTION 382 II. CATHARANTHUS ROSEUS AS A SOURCE OF TERPENOID INDOLE ALKALOID PRODUCTION 384 A. Aspects of TIA Formation by Transgenic Cell Lines of C. roseus Overexpressing Tdc and Str 394 B. Effect of Culture Conditions on the Productivity of the Transgenic Cell Lines 399 C. Precursor Feeding Experiments: Identification of Bottlenecks and Determination of the Capacity of the Transgenic Cell Lines for TIA Accumulation 400 D. Stability of the Transgenic Cell Lines over a Period of 30 Months of Subculture 402 E. Conclusions and Prospects 404 III. THE FUTURE 406 REFERENCES 406 Chapter 17: Transgenic Plants for Production of Immunotherapeutic Agents 413 I. PLANT BIOREACTORS FOR IMMUNOTHERAPEUTIC PROTEINS 413 II. ISSUES REGARDING TRANSGENIC PLANT EXPRESSION OF IMMUNOTHERAPEUTIC PROTEINS 414 A. Production Costs 414 B. Glycosylation of Transgenic Plant Proteins; Plant Antibody Glycosylation 416 C. Gene Silencing: A Potential Problem of Plant Expression 418 D. Purification and Process Development 419 III. ANTIBODIES FROM PLANTS: PLANTIBODIES 421 IV. SlgA: A NOVEL ANTIBODY ISOTYPE 421 V. CLINICAL STUDIES OF CaroRx™, AN ANTISTREPTOCOCCUS MUTANS SIgA TO PREVENT DENTAL CARIES 423 VI. SUMMARY 426 REFERENCES 427 Chapter 18: Signal Transduction Elements 435 I. INTRODUCTION 435 II. HORMONE LEVELS 436 III. RECEPTOR-LIGAND INTERACTIONS 437 IV. GTP-BINDING PROTEINS 439 V. CALCIUM SIGNALING 440 VI. MITOGEN-ACTIVATED PROTEIN KINASES 441 VII. TRANSCRIPTION FACTORS 443 VIII. CONCLUSIONS AND OUTLOOK 445 REFERENCES 446 Chapter 19: The Plant Cell Wall—Structural Aspects and Biotechnological Developments 453 I. INTRODUCTION 453 II. FUNCTIONS OF PLANT CELL WALLS IN PLANTA 455 III. COMPONENTS AND ARCHITECTURE OF PLANT CELL WALLS 460 IV. BIOSYNTHESIS AND ASSEMBLY OF PLANT CELL WALLS 465 V. BIOTECHNOLOGICAL APPROACHES TO OPTIMIZE CELL WALL PERFORMANCE IN PLANTA 468 VI. BIOTECHNOLOGICAL APPROACHES TO OPTIMIZE CELL WALL COMPONENTS FOR USES EX PLANTA 471 VII. PROSPECTS FOR THE FUTURE OF PLANT CELL WALL BIOTECHNOLOGY 474 ACKNOWLEDGMENTS 476 REFERENCES 476 Chapter 20: Lignin Genetic Engineering: A Way to Better Understand Lignification beyond Applied Objectives 484 I. INTRODUCTION 484 II. RECENT ACHIEVEMENTS IN THE FIELD OF LIGNIN GENETIC ENGINEERING 485 A. Down-regulation of O-Methyltransferases 486 B. Down-regulation of 4-Coumarate CoA Ligase (4CL) 489 C. Cinnamoyl CoA Reductase (CCR) Down-regulation 490 D. Cinnamyl Alcohol Dehydrogenase (CAD) Down-regulation 491 E. Double Transformants 492 III. POTENTIAL SIDE EFFECTS AND COMPENSATION MECHANISMS ASSOCIATED WITH LIGNIN MODIFICATIONS 492 IV. FUTURE TARGETS FOR ENGINEERING NEW LIGNINS 494 V. A SOCIOECONOMIC PERSPECTIVE 495 VI. CONCLUDING REMARKS AND PROSPECTS 497 ACKNOWLEDGMENT 499 REFERENCES 499 Chapter 21: Transgenic Plants Expressing Tolerance Toward Oxidative Stress 503 I. OXIDATIVE STRESS 504 A. Foe . . . 504 B. ... And Friend 505 II. OXIDATIVE STRESS DEFENSE MECHANISMS IN PLANTS 506 A. Superoxide Dismutases 506 B. Ascorbate Peroxidase 507 C. Catalases 508 III. TRANSGENIC PLANTS WITH MODIFIED ANTIOXIDANT ENZYME LEVELS 509 A. Transgenic Plants with Elevated Superoxide Dismutase Levels 509 B. Transgenic Plants with Modulated Ascorbate Peroxidase or Catalase Levels 514 IV. PERSPECTIVES 515 ACKNOWLEDGMENTS 516 REFERENCES 516 Chapter 22: Transgenic Plants with Increased Resistance and Tolerance against Viral Pathogens 523 I. INTRODUCTION 523 A. Definition of Terms 524 II. DEFENSE RESPONSES OF PLANTS 525 A. General Responses 525 B. Virus-Specific Responses 525 C. Recovery 527 III. HOST RESISTANCE GENES 527 A. N Gene 528 B. Rx Gene 529 C. Avr Genes as Tools for Resistance Breeding 530 IV. PATHOGEN-DERIVED RESISTANCE 531 A. Classical Cross-Protection 531 B. Protein-Mediated Protection 532 1. Coat Proteins 532 2. Dominant Negative Mutations 533 C. RNA-Mediated Protection 533 1. Antisense and Sense RNAs 533 D. Interfering Replicons 534 1. Defective Interfering (DI) Nucleic Acids 534 2. Satellites 536 V. GENE SILENCING 536 A. Transcriptional Gene Silencing (TGS) 537 B. Posttranscriptional Gene Silencing (PTGS) 537 C. Virus-Induced Gene Silencing (VIGS) 538 D. Systemic Acquired Gene Silencing (SAS) 538 E. Mechanistic Aspects of Posttranscriptional Gene Silencing 538 F. Suppressors of PTGS 539 VI. SUSTAINABILITY CONCERNS 541 A. Tolerance 541 B. Resistance Breakage 542 C. Transcapsidation 542 D. Recombination 542 E. Synergism 543 VII. PERSPECTIVES 543 ACKNOWLEDGMENTS 544 REFERENCES 544 Chapter 23: Transgenic Plants with Enhanced Tolerance against Microbial Pathogens 555 I. SINGLE-GENE DEFENSE MECHANISMS 556 A. Pathogenesis-Related Proteins 556 B. Defense Peptides 558 C. Ribosome-lnactivating Proteins 559 D. Plants with Elevated Levels of Antimicrobial Secondary Compounds 560 II. MULTIGENE DEFENSE MECHANISMS 561 A. Elevation of Endogenous Levels of Salicylic Acid 561 B. Constitutive Systemic Acquired Resistance 561 C. Hydrogen Peroxide 561 D. Cell Death as a Trigger of Plant Resistance 563 1. Mutants with Spontaneous Cell Death 563 2. Transgenic Plants with Induced Limited Cell Death 564 III. SALICYLIC ACID FUNCTION IN PROGRAMMED CELL DEATH 565 IV. CONCLUSIONS AND FUTURE PERSPECTIVES 568 REFERENCES 569 Chapter 24: Transgenic Crop Plants with Increased Tolerance to Insect Pests 576 I. INTRODUCTION 576 II. BACILLUS THURINGIENSIS CRY GENES AS A SOURCE OF INSECTICIDAL GENES FOR CROPS 577 III. COMMERCIALIZED BACILLUS THURINGIENSIS (Bt) CROPS 577 A. Bt-Corn 577 B. Bt-Cotton 580 C. Bt-Potatoes 584 D. Resistance Management and Bt Crops 585 E. Nontarget Effects of Bt Crops 585 IV. OTHER SOURCES OF INSECTICIDAL GENES FOR CROP PROTECTION 586 A. New Oral Toxins 587 B. Inhibitors of Digestion 588 1. Protease Inhibitors 588 2. Alpha Amylase Inhibitors 589 3. Lectins and Assorted Insecticidal Proteins 590 C. Secondary Metabolites 592 V. CONCLUSIONS 593 REFERENCES 594 Chapter 25: Transgenic Herbicide-Resistant Crops—Advantages, Drawbacks, and Failsafes 601 I. INTRODUCTION 601 II. CONTRIBUTIONS OF WEED SCIENCE TO BIOCHEMISTRY AND MOLECULAR BIOLOGY 603 III. NEEDS FOR TRANSGENICS NOT BEING MET 604 IV. THE SUCCESS OF TRANSGENIC HERBICIDE-RESISTANT CROPS 605 A. Metabolically Resistant T-HRCs 607 B. Target Site Resistant Crops 608 V. RESISTANCE MANAGEMENT—THE NEED FOR STACKED GENES 611 VI. INTROGRESSION OF TRANSGENES FROM CROPS TO WEEDS 613 A. Vertical, Horizontal, and Diagonal Gene Transfer 615 B. Generalizing from Hazards to Risks 616 1. Risks of Introgression of Transgenes to Related Weeds 616 C. Assaying Introgression in the Field 619 VII. PREVENTING AND MITIGATING INTROGRESSION FROM T-HRCs TO WEEDS 622 A. Gene Placement Failsafes 622 1. Chromosomal 622 2. Hybrids 622 3. Plastome or Chondriome 622 4. Transient Transgenics 623 B. Transgenetic Mitigation (TM) 623 1. Traits for Transgenetic Mitigation 624 2. Balancing Primary and TM Traits 625 3. TM Genes Are Available to Mitigate Movement of Resistance 626 VIII. CONCLUDING REMARKS 627 ACKNOWLEDGMENTS 628 REFERENCES 628 Chapter 26: Plants and Environmental Stress Adaptation Strategies 638 I. INTRODUCTION 638 II. DEFINING THE PROBLEM AND SEARCHING FOR SOLUTIONS 639 III. ENVIRONMENTAL STRESS ADAPTATION STRATEGIES 640 A. How Many Strategies Are There? 640 B. Protection of Downstream Reactions 642 1. Osmotic Adjustment 642 2. Radical Scavenging Capacity 643 3. Water and Ion Relations 644 C. Ubiquitous Cellular Stress Tolerance Mechanisms— Comparison of Models 649 IV. STRESS PROTECTION BASED ON SENSING AND SIGNAL TRANSDUCTION 651 V. CHANGES IN GROWTH AND MORPHOLOGY UNDER STRESS 652 VI. STRESS GENOMICS 653 VII. CONCLUSIONS 655 ACKNOWLEDGMENTS 656 REFERENCES 656 Chapter 27: Molecular Mechanisms that Control Plant Tolerance to Heavy Metals and Possible Roles in Manipulating Metal Accumulation 668 I. INTRODUCTION 668 II. TOLERANCE MECHANISMS 670 A. Chelation 671 1. Phytochelatins and GSH Metabolism 671 2. Metallothioneins 672 3. Other Proteinaceous Chelators 674 4. Organic Acids, Amino Acids 675 B. Sequestration 677 1. Roles of ABC-type Transporters in Sequestration 677 2. Cation Diffusion Facilitators (CDFs) 677 3. Other Transporters 678 C. Efflux 679 D. Engineering Metal Uptake Systems 679 1. The ZIP Family of Transporters 680 2. Nramp Metal Transporters 680 3. The Uptake of Nonessential Metal Ions 681 E. Biotransformation and Direct Removal 682 F. Repair Mechanisms 684 III. MECHANISMS OF HYPERTOLERANCE 684 IV. CONCLUSIONS 685 ACKNOWLEDGMENTS 686 REFERENCES 686 Biology EEn 1 PLANT BIOTECHNOLOGY AND TRANSBENIC PLANTS 2 Back Cover 3 Copyright Info 5 Preface 10 TOC 12 Contributors 15 Chapter 1: Plant Biotechnology—An Emerging Field 19 I. INTRODUCTION 19 II. A LONG HISTORY TO REACH A HIGH STANDARD 20 III. PLANT TISSUE AND CELL CULTURES—A VERY VERSATILE SYSTEM 23 IV. FROM GENES TO PATHWAYS TO BIOTECHNOLOGICAL APPLICATION 25 V. THE PLANT CELL ORGANELLES CONTAINING GENETIC INFORMATION 31 VI. METABOLISM OF XENOBIOCHEMICALS 32 VII. CROP PLANTS AND RENEWABLE RESOURCES 35 VIII. CONCLUSIONS 36 REFERENCES 37 Chapter 2: Plant-Derived Drugs and Extracts 40 I. INTRODUCTION 40 II. DRUGS ISOLATED FROM PLANTS 41 A. Artemisinin 41 B. Cardiac Glycosides 42 C. Opium 42 D. B-Sitosterol 44 E. Steroids 45 F. Taxol 45 G. Tropane Alkaloids 46 H. Vinblastine and Vincristine 47 III. PLANT PRODUCTS AND EXTRACTS 48 A. Chamomile 48 B. Echinacea 49 C. Evening Primrose Oil 50 D. Garlic 50 E. Linseed Oil 52 F. Mint Oils and Menthol 52 G. Saw Palmetto 53 IV. STANDARDIZED EXTRACTS 54 A. Ginger 54 B. Ginkgo 55 C. Ginseng 56 D. Hawthorn 56 E. St. John's Wort 57 V. CONCLUSIONS 58 REFERENCES 59 Chapter 3: Industrial Strategies for the Discovery of Bioactive Compounds from Plants 62 I. INTRODUCTION 62 II. CHANGING PARADIGMS: INDUSTRIALIZATION OF DISCOVERY 63 III. AUTOMATION FOR DRUG DISCOVERY 66 IV. PLANT PRODUCTS IN THE INDUSTRIALIZED DRUG DISCOVERY PROCESS 68 V. OPPORTUNITIES FROM TRADITIONAL MEDICINE 71 VI. OUTLOOK 72 REFERENCES 73 Chapter 4: Plant Cell and Tissue Culture Techniques Used in Plant Breeding 75 I. INTRODUCTION 75 II. SOMATIC HYBRIDIZATION 77 III. GENE TRANSFER TO PLANTS 78 IV. MICROPROPAGATION AND SOMATIC EMBRYOGENESIS 80 V. IN VITRO SELECTION 82 VI. THE NEED FOR A COMPREHENSIVE PLANT BREEDING STRATEGY 83 VII. BREEDING FOR SELF-POLLINATED PLANTS 84 VIII. BREEDING HYBRID VARIETIES OF OUT-CROSSING PLANTS 86 IX. BREEDING CLONALLY PROPAGATED PLANTS 86 X. BREEDING HYBRID VARIETIES OF SELFING PLANTS 87 XI. CELL AND TISSUE CULTURE IN TREE BREEDING 88 XII. FOREST TREE POPULATION STRUCTURES AND THE ADOPTION OF CLONING 89 XIII. ECOLOGICAL ASPECTS IN TREE BREEDING 90 XIV. THE CLONAL FORESTRY OPTION 91 REFERENCES 92 Chapter 5: Plant Cell Cultures as Producers of Secondary Compounds 93 I. INTRODUCTION 93 II. CELL CULTURE SYSTEMS USED FOR PRODUCTION OF PHYTOCHEMICALS 94 A. Callus and Cell Suspension Cultures 94 B. Immobilized Cultures 94 C. Organ Cultures 94 1. Shoot Cultures 95 2. Root Culture 95 D. Bioreactor Cultures 96 III. FACTORS AFFECTING SECONDARY METABOLITE PRODUCTION BY PLANT CELL CULTURES 96 A. Plant Growth Regulators 96 B. Medium Nutrients 97 C. Elicitors 98 D. Physical Factors 99 E. Biological Factors 99 IV. PRODUCTION OF PLANT PIGMENTS 100 A. Anthocyanin 100 1. Cell Line Selection 102 2. Physical Environment 103 3. Chemical Factors 103 4. Bioreactor Culture 104 5. Engineering Anthocyanin Production Using Recombinant DNA Technology 104 B. Shikonin 104 1. Large-Scale Production of Shikonin Derivatives by Lithospermum erythrorhizon Cell Cultures 106 2. Regulatory Mechanism of Shikonin Biosynthesis 107 3. Intracellular Localization of Shikonin Biosynthesis 110 4. Engineering Shikonin Biosynthesis in Cultured Plant Cells 110 V. PRODUCTION OF CLINICALLY USED ANTINEOPLASTIC COMPOUNDS 110 A. Catharanthus Alkaloids 110 B. Camptothecin 112 C. Paclitaxel (Taxol) 114 D. Podophyllotoxin 114 VI. FUTURE PROSPECTS 116 ACKNOWLEDGMENTS 116 REFERENCES 116 Chapter 6: Genetic Transformation of Plants and Their Cells 126 I. INTRODUCTION 126 II. REQUIREMENTS FOR PLANT TRANSFORMATION 127 A. Overview 127 B. DNA Transfer Methods 127 C. Cell and Tissue Culture and Plant Regeneration 128 D. Selectable Marker Genes 129 III. AGROBACTERIUM-MEDlKTED TRANSFORMATION 131 A. Agrobacterium tumefaciens: A Natural Gene Transfer System 131 B. Development of Ti-Plasmid Vectors 131 C. General Protocol for Agrobacterium-Mediated Transformation 133 D. Recent Advances—Expanding the Agrobacterium Host Range 134 E. Recent Advances—Increasing the Capacity of T-DNA 136 F. Conjugation Systems and Ri Plasmids 136 IV. PARTICLE BOMBARDMENT 136 A. Advantages and Disadvantages of Particle Bombardment 137 B. Recent Advances 138 V. TRANSFORMATION OF PROTOPLASTS 140 VI. OTHER DIRECT TRANSFORMATION METHODS 141 VII. TRANSFORMATION WITHOUT TISSUE CULTURE 142 VIII. PLANT VIRUSES AS GENE TRANSFER VECTORS 143 IX. ORGANELLE TRANSFORMATION 144 X. FUTURE PROSPECTS—CONTROLLED TRANSGENE INTEGRATION AND EXPRESSION 144 A. Overview 144 B. Clean DMA Transformation 145 C. Toward Marker-Free Transgenic Plants 147 D. Toward Precise Integration and Control of Expression 149 XI. CONCLUDING REMARKS 149 REFERENCES 150 Chapter 7: Properties and Applications of Hairy Root Cultures 157 I. INTRODUCTION 157 II. PROPERTIES OF HAIRY ROOTS 158 A. Genotype and Phenotype Stability 158 B. Autotrophy in Plant Hormones 159 C. Fast Growth 159 D. High Levels of Secondary Metabolites 159 E. Species Resistant to Hairy Root Transformation 160 F. Clonal Variation 161 III. COCULTURES USING HAIRY ROOTS 161 IV. PRODUCTION OF FOREIGN PROTEINS USING HAIRY ROOTS 162 V. HAIRY ROOTS IN PHYTOREMEDIATION AND PHYTOMINING STUDIES 165 VI. CONCLUSIONS 170 ACKNOWLEDGMENTS 170 REFERENCES 170 Chapter 8: Bioreactors for Plant Cell and Tissue Cultures 176 I. INTRODUCTION 176 II. BACKGROUND 177 III. GENERAL REQUIREMENTS FOR THE CULTIVATION OF PLANT CELLS IN BIOREACTORS 177 IV. INSTRUMENTATION OF BIOREACTORS FOR PLANT CELL AND TISSUE CULTURES 179 V. GENERAL CLASSIFICATION OF BIOREACTOR TYPES 182 A. Stirred Reactor 186 B. Rotating Drum Reactor 186 C. Bubble Column 186 D. Airlift Reactor 186 E. Packed Bed Reactor 189 F. Fluidized Bed Reactor 189 G. Trickle Bed Reactor 189 H. Membrane Reactor 189 VI. SUITABLE BIOREACTORS FOR PLANT CELL AND TISSUE CULTURES 192 A. Reactors for Plant Cell Suspensions 192 B. Reactors for Hairy Root Cultures 197 C. Reactors for Embryogenic and Shoot Cultures 198 VII. ECONOMIC FEASIBILITY AND TRENDS IN REACTOR DEVELOPMENT FOR PLANT CELL AND TISSUE CULTURES 200 VIII. OPERATIONAL STRATEGIES OF PLANT CELL AND TISSUE CULTURE BIOREACTORS 204 IX. CONCLUSIONS 206 REFERENCES 206 Chapter 9: The Potential Contribution of Plant Biotechnology to Improving Food Quality 213 I. INTRODUCTION 213 II. PRIORITIES FOR THE FOOD SECTOR 216 A. The Developing World 216 1. Improvements in Protein Quality 217 2. Reduction in Antinutritional Factors 217 B. The Developed World 218 III. APPLICATION OF GENETIC ENGINEERING TO FOOD QUALITY IMPROVEMENT 221 IV. PLANT SECONDARY METABOLITES AS DETERMINANTS OF QUALITY 222 V. THE PHENYLPROPANOID PATHWAY 222 A. Flavonoids and Isoflavonoids 224 B. The Isoprenoid Pathway 228 1. Sterol Biosynthesis 232 2. Carotenoid Biosynthesis 234 VI. RELATIONSHIP OF STRUCTURE TO NUTRITIONAL QUALITY (BIOAVAILABILITY) 235 VII. SAFETY AND REGULATORY ISSUES 236 A. Food Chemical Risk Assessment 238 VIII. CONCLUSIONS 240 REFERENCES 240 Chapter 10: Engineering Plant Biochemical Pathways for Improved Nutritional Quality 245 I. INTRODUCTION 245 II. STRATEGIES TO MANIPULATE PLANT METABOLIC PATHWAYS TOWARD THE PRODUCTION OF A DEFINED COMPOUND OF NUTRITIONAL VALUE 246 III. MANIPULATING ESSENTIAL AMINO ACID METABOLIC PATHWAYS TO INCREASE THE NUTRITIONAL VALUE OF CROPS 248 A. Biochemical Regulation of Lysine and Threonine Biosynthesis 249 B. Mutants Overproducing Free Lysine or Threonine 250 C. Key Genes of the Lysine and Threonine Pathways 251 1. Aspartate Kinase Genes 251 2. Cloning and Characterization of Wild-Type and Mutant Genes Encoding Dihydrodipicolinate Synthase 252 D. Improving Lysine and Threonine Accumulation via Transfer of Bacterial Genes 254 E. Improving Lysine Content Using Plant Gene Transfer 255 F. Manipulating Plant Micronutrients to Benefit Human Health and Nutrition 259 IV. CONCLUSIONS AND PERSPECTIVES FOR THE FUTURE 260 ACKNOWLEDGMENTS 261 REFERENCES 261 Chapter 11: Transgenic Plants as Producers of Modified Starch and Other Carbohydrates 266 I. INTRODUCTION 266 II. APPROACHES TO STARCH AND CARBOHYDRATE MODIFICATION 267 III. STARCH STRUCTURE 268 A. Amylose and Amylopectin, the Two Components of Starch 268 B. Starch Granules 268 IV. STARCH DEPOSITION 270 A. Source of Photosynthate for Starch Biosynthesis 270 B. The Committed Pathway of Starch Biosynthesis 272 C. Synthesis of Amylose 274 D. Synthesis of Amylopectin 274 V. TRANSGENIC MODIFICATION OF CARBOHYDRATE BIOSYNTHESIS 276 A. Alteration of Starch Quantity 277 B. Production of Simple Sugars in Storage Organs 278 C. Alteration of the Amylose Complement in Starch 280 D. Alteration of Amylopectin Structure 280 E. Production of Nonstarch Carbohydrates 282 VI. CONCLUSIONS 284 REFERENCES 285 Chapter 12: Improving the Nutritional Quality and Functional Properties of Seed Proteins by Genetic Engineering 294 I. INTRODUCTION 294 II. SEED PROTEINS 295 III. GLOBULIN STORAGE PROTEINS 295 IV. PROLAMINS 296 V. 2S ALBUMINS 296 VI. NUTRITIONAL QUALITY OF SEED PROTEINS 297 VII. HIGH-LYSINE CEREALS 297 A. Manipulation of the Amino Acid Composition of Prolamins 298 B. Expression of Specific Lysine-Rich Proteins 298 C. Increased Accumulation of Free Lysine 300 VIII. HIGH-METHIONINE LEGUMES 302 IX. SEED PROTEINS AND FUNCTIONALITY 304 X. GEL FORMATION AND EMULSIFICATION PROPERTIES OF SOYBEAN GLOBULINS 305 XI. THE VISCOELASTICITY OF WHEAT GLUTEN 305 XII. CONCLUSIONS 308 ACKNOWLEDGMENTS 309 REFERENCES 309 Chapter 13: Transgenic Plants as Sources of Modified Oils 316 I. INTRODUCTION 316 II. SHORT- AND MEDIUM-CHAIN SATURATED FATTY ACIDS 317 III. LONG CHAIN SATURATED FATTY ACIDS 318 IV. MONOUNSATURATED FATTY ACIDS 321 V. POLYUNSATURATED FATTY ACIDS 323 VI. VARIATIONS ON THE METHYLENE-INTERRUPTED DOUBLE BOND 325 VII. COMMERCIAL PRODUCTION OF NEW OILS FROM TRANSGENIC PLANTS 327 REFERENCES 327 Chapter 14: Flavors and Fragrances from Plants 333 I. INTRODUCTION 333 II. RECOMBINANT DMA TECHNOLOGY 336 A. Genetically Engineered Food Plants 336 B. Plant Enzymes and Genomics 338 III. PLANT CELL, TISSUE, AND ORGAN CULTURES 341 A. Tissue Cultures 341 B. Organ Cultures 345 C. Biotransformation by Plant Cell Cultures 346 IV. PROCESS DEVELOPMENTS 349 V. CONCLUSIONS 350 REFERENCES 351 Chapter 15: Fine Chemicals from Plants 357 I. INTRODUCTION 357 II. PRODUCTION OF PHYTOCHEMICALS 358 III. METABOLIC ENGINEERING FOR IMPROVEMENT OF PRODUCTIVITY 361 IV. TRANSFORMATION AND REGENERATION OF MEDICINAL PLANTS 367 V. APPLICATION OF BIOTECHNOLOGY TO DUBOIS1A FOR SCOPOLAMINE PRODUCTION 368 A. Conventional Breeding 370 B. Tissue Culture Applications 370 C. Agronomical Performance of Hairy Root-Derived Plants 371 D. Genetic Transformation 371 E. Other Traits of Interest 373 F. Molecular Markers 374 VI. CONCLUSIONS 375 REFERENCES 376 Chapter 16: Genetic Engineering of the Plant Cell Factory for Secondary Metabolite Production: Indole Alkaloid Production in Catharanthus roseus as a Model 382 I. INTRODUCTION 382 II. CATHARANTHUS ROSEUS AS A SOURCE OF TERPENOID INDOLE ALKALOID PRODUCTION 384 A. Aspects of TIA Formation by Transgenic Cell Lines of C. roseus Overexpressing Tdc and Str 394 B. Effect of Culture Conditions on the Productivity of the Transgenic Cell Lines 399 C. Precursor Feeding Experiments: Identification of Bottlenecks and Determination of the Capacity of the Transgenic Cell Lines for TIA Accumulation 400 D. Stability of the Transgenic Cell Lines over a Period of 30 Months of Subculture 402 E. Conclusions and Prospects 404 III. THE FUTURE 406 REFERENCES 406 Chapter 17: Transgenic Plants for Production of Immunotherapeutic Agents 413 I. PLANT BIOREACTORS FOR IMMUNOTHERAPEUTIC PROTEINS 413 II. ISSUES REGARDING TRANSGENIC PLANT EXPRESSION OF IMMUNOTHERAPEUTIC PROTEINS 414 A. Production Costs 414 B. Glycosylation of Transgenic Plant Proteins; Plant Antibody Glycosylation 416 C. Gene Silencing: A Potential Problem of Plant Expression 418 D. Purification and Process Development 419 III. ANTIBODIES FROM PLANTS: PLANTIBODIES 421 IV. SlgA: A NOVEL ANTIBODY ISOTYPE 421 V. CLINICAL STUDIES OF CaroRxTM, AN ANTISTREPTOCOCCUS MUTANS SIgA TO PREVENT DENTAL CARIES 423 VI. SUMMARY 426 REFERENCES 427 Chapter 18: Signal Transduction Elements 435 I. INTRODUCTION 435 II. HORMONE LEVELS 436 III. RECEPTOR-LIGAND INTERACTIONS 437 IV. GTP-BINDING PROTEINS 439 V. CALCIUM SIGNALING 440 VI. MITOGEN-ACTIVATED PROTEIN KINASES 441 VII. TRANSCRIPTION FACTORS 443 VIII. CONCLUSIONS AND OUTLOOK 445 REFERENCES 446 Chapter 19: The Plant Cell Wall—Structural Aspects and Biotechnological Developments 453 I. INTRODUCTION 453 II. FUNCTIONS OF PLANT CELL WALLS IN PLANTA 455 III. COMPONENTS AND ARCHITECTURE OF PLANT CELL WALLS 460 IV. BIOSYNTHESIS AND ASSEMBLY OF PLANT CELL WALLS 465 V. BIOTECHNOLOGICAL APPROACHES TO OPTIMIZE CELL WALL PERFORMANCE IN PLANTA 468 VI. BIOTECHNOLOGICAL APPROACHES TO OPTIMIZE CELL WALL COMPONENTS FOR USES EX PLANTA 471 VII. PROSPECTS FOR THE FUTURE OF PLANT CELL WALL BIOTECHNOLOGY 474 ACKNOWLEDGMENTS 476 REFERENCES 476 Chapter 20: Lignin Genetic Engineering: A Way to Better Understand Lignification beyond Applied Objectives 484 I. INTRODUCTION 484 II. RECENT ACHIEVEMENTS IN THE FIELD OF LIGNIN GENETIC ENGINEERING 485 A. Down-regulation of O-Methyltransferases 486 B. Down-regulation of 4-Coumarate CoA Ligase (4CL) 489 C. Cinnamoyl CoA Reductase (CCR) Down-regulation 490 D. Cinnamyl Alcohol Dehydrogenase (CAD) Down-regulation 491 E. Double Transformants 492 III. POTENTIAL SIDE EFFECTS AND COMPENSATION MECHANISMS ASSOCIATED WITH LIGNIN MODIFICATIONS 492 IV. FUTURE TARGETS FOR ENGINEERING NEW LIGNINS 494 V. A SOCIOECONOMIC PERSPECTIVE 495 VI. CONCLUDING REMARKS AND PROSPECTS 497 ACKNOWLEDGMENT 499 REFERENCES 499 Chapter 21: Transgenic Plants Expressing Tolerance Toward Oxidative Stress 503 I. OXIDATIVE STRESS 504 A. Foe . . . 504 B. ... And Friend 505 II. OXIDATIVE STRESS DEFENSE MECHANISMS IN PLANTS 506 A. Superoxide Dismutases 506 B. Ascorbate Peroxidase 507 C. Catalases 508 III. TRANSGENIC PLANTS WITH MODIFIED ANTIOXIDANT ENZYME LEVELS 509 A. Transgenic Plants with Elevated Superoxide Dismutase Levels 509 B. Transgenic Plants with Modulated Ascorbate Peroxidase or Catalase Levels 514 IV. PERSPECTIVES 515 ACKNOWLEDGMENTS 516 REFERENCES 516 Chapter 22: Transgenic Plants with Increased Resistance and Tolerance against Viral Pathogens 523 I. INTRODUCTION 523 A. Definition of Terms 524 II. DEFENSE RESPONSES OF PLANTS 525 A. General Responses 525 B. Virus-Specific Responses 525 C. Recovery 527 III. HOST RESISTANCE GENES 527 A. N Gene 528 B. Rx Gene 529 C. Avr Genes as Tools for Resistance Breeding 530 IV. PATHOGEN-DERIVED RESISTANCE 531 A. Classical Cross-Protection 531 B. Protein-Mediated Protection 532 1. Coat Proteins 532 2. Dominant Negative Mutations 533 C. RNA-Mediated Protection 533 1. Antisense and Sense RNAs 533 D. Interfering Replicons 534 1. Defective Interfering (DI) Nucleic Acids 534 2. Satellites 536 V. GENE SILENCING 536 A. Transcriptional Gene Silencing (TGS) 537 B. Posttranscriptional Gene Silencing (PTGS) 537 C. Virus-Induced Gene Silencing (VIGS) 538 D. Systemic Acquired Gene Silencing (SAS) 538 E. Mechanistic Aspects of Posttranscriptional Gene Silencing 538 F. Suppressors of PTGS 539 VI. SUSTAINABILITY CONCERNS 541 A. Tolerance 541 B. Resistance Breakage 542 C. Transcapsidation 542 D. Recombination 542 E. Synergism 543 VII. PERSPECTIVES 543 ACKNOWLEDGMENTS 544 REFERENCES 544 Chapter 23: Transgenic Plants with Enhanced Tolerance against Microbial Pathogens 555 I. SINGLE-GENE DEFENSE MECHANISMS 556 A. Pathogenesis-Related Proteins 556 B. Defense Peptides 558 C. Ribosome-lnactivating Proteins 559 D. Plants with Elevated Levels of Antimicrobial Secondary Compounds 560 II. MULTIGENE DEFENSE MECHANISMS 561 A. Elevation of Endogenous Levels of Salicylic Acid 561 B. Constitutive Systemic Acquired Resistance 561 C. Hydrogen Peroxide 561 D. Cell Death as a Trigger of Plant Resistance 563 1. Mutants with Spontaneous Cell Death 563 2. Transgenic Plants with Induced Limited Cell Death 564 III. SALICYLIC ACID FUNCTION IN PROGRAMMED CELL DEATH 565 IV. CONCLUSIONS AND FUTURE PERSPECTIVES 568 REFERENCES 569 Chapter 24: Transgenic Crop Plants with Increased Tolerance to Insect Pests 576 I. INTRODUCTION 576 II. BACILLUS THURINGIENSIS CRY GENES AS A SOURCE OF INSECTICIDAL GENES FOR CROPS 577 III. COMMERCIALIZED BACILLUS THURINGIENSIS (Bt) CROPS 577 A. Bt-Corn 577 B. Bt-Cotton 580 C. Bt-Potatoes 584 D. Resistance Management and Bt Crops 585 E. Nontarget Effects of Bt Crops 585 IV. OTHER SOURCES OF INSECTICIDAL GENES FOR CROP PROTECTION 586 A. New Oral Toxins 587 B. Inhibitors of Digestion 588 1. Protease Inhibitors 588 2. Alpha Amylase Inhibitors 589 3. Lectins and Assorted Insecticidal Proteins 590 C. Secondary Metabolites 592 V. CONCLUSIONS 593 REFERENCES 594 Chapter 25: Transgenic Herbicide-Resistant Crops—Advantages, Drawbacks, and Failsafes 601 I. INTRODUCTION 601 II. CONTRIBUTIONS OF WEED SCIENCE TO BIOCHEMISTRY AND MOLECULAR BIOLOGY 603 III. NEEDS FOR TRANSGENICS NOT BEING MET 604 IV. THE SUCCESS OF TRANSGENIC HERBICIDE-RESISTANT CROPS 605 A. Metabolically Resistant T-HRCs 607 B. Target Site Resistant Crops 608 V. RESISTANCE MANAGEMENT—THE NEED FOR STACKED GENES 611 VI. INTROGRESSION OF TRANSGENES FROM CROPS TO WEEDS 613 A. Vertical, Horizontal, and Diagonal Gene Transfer 615 B. Generalizing from Hazards to Risks 616 1. Risks of Introgression of Transgenes to Related Weeds 616 C. Assaying Introgression in the Field 619 VII. PREVENTING AND MITIGATING INTROGRESSION FROM T-HRCs TO WEEDS 622 A. Gene Placement Failsafes 622 1. Chromosomal 622 2. Hybrids 622 3. Plastome or Chondriome 622 4. Transient Transgenics 623 B. Transgenetic Mitigation (TM) 623 1. Traits for Transgenetic Mitigation 624 2. Balancing Primary and TM Traits 625 3. TM Genes Are Available to Mitigate Movement of Resistance 626 VIII. CONCLUDING REMARKS 627 ACKNOWLEDGMENTS 628 REFERENCES 628 Chapter 26: Plants and Environmental Stress Adaptation Strategies 638 I. INTRODUCTION 638 II. DEFINING THE PROBLEM AND SEARCHING FOR SOLUTIONS 639 III. ENVIRONMENTAL STRESS ADAPTATION STRATEGIES 640 A. How Many Strategies Are There? 640 B. Protection of Downstream Reactions 642 1. Osmotic Adjustment 642 2. Radical Scavenging Capacity 643 3. Water and Ion Relations 644 C. Ubiquitous Cellular Stress Tolerance Mechanisms— Comparison of Models 649 IV. STRESS PROTECTION BASED ON SENSING AND SIGNAL TRANSDUCTION 651 V. CHANGES IN GROWTH AND MORPHOLOGY UNDER STRESS 652 VI. STRESS GENOMICS 653 VII. CONCLUSIONS 655 ACKNOWLEDGMENTS 656 REFERENCES 656 Chapter 27: Molecular Mechanisms that Control Plant Tolerance to Heavy Metals and Possible Roles in Manipulating Metal Accumulation 668 I. INTRODUCTION 668 II. TOLERANCE MECHANISMS 670 A. Chelation 671 1. Phytochelatins and GSH Metabolism 671 2. Metallothioneins 672 3. Other Proteinaceous Chelators 674 4. Organic Acids, Amino Acids 675 B. Sequestration 677 1. Roles of ABC-type Transporters in Sequestration 677 2. Cation Diffusion Facilitators (CDFs) 677 3. Other Transporters 678 C. Efflux 679 D. Engineering Metal Uptake Systems 679 1. The ZIP Family of Transporters 680 2. Nramp Metal Transporters 680 3. The Uptake of Nonessential Metal Ions 681 E. Biotransformation and Direct Removal 682 F. Repair Mechanisms 684 III. MECHANISMS OF HYPERTOLERANCE 684 IV. CONCLUSIONS 685 ACKNOWLEDGMENTS 686 REFERENCES 686