The Chloroplast (eBook)

Advances in Photosynthesis and Respiration 8
The Chloroplast: Basics and Applications 4
Contents 16
Preface 26
Contributors 38
Chapter 1: Investigation of Possible Relationships Between the Chlorophyll Biosynthetic Pathway, the Assembly of Chlorophyll– 42
I Introduction 44
II Agricultural Productivity and Photosynthetic Efficiency 44
A The Primary Photochemical Act of Photosystem I (PS I) I and II 44
B Conversion of Carbon Dioxide into Carbohydrates 45
C Theoretical Maximal Energy Conversion Efficiency of the Photosynthetic Electron Transport System of Green Plants 45
D Actual Energy Conversion Efficiency of the PETS of Green Plants Under Field Conditions 46
III Molecular Basis of the Discrepancy Between the Theoretical Maximal Efficiency of the Photosynthetic Electron Transport Cha 46
A Contribution of Extrinsic Photosynthetic Electron Transport System Parameters to the Discrepancy between the Theoretical Phot 46
B Contribution of Intrinsic Photosynthetic Electron Transport Chain Parameters to the Discrepancy Between the Theoretical Pho 46
IV Correction of the Antenna/Photosystem Chlorophyll Mismatch 47
A State of the Art in Our Understanding of Chlorophyll Biosynthesis 47
1 The Single-Branched Chl Biosynthetic Pathway Does Not Account for the Formation of All the Chlorophyll in Green Plants 47
2 The Chlorophyll of Green Plants Is Formed Via a Multibranched Biosynthetic Pathway 48
B Thylakoid Apoprotein Biosynthesis 49
C Assembly of Chlorophyll–Protein Complexes 50
1 Assembly of Chlorophyll–Protein Complexes: The Single-Branched Chlorophyll Biosynthetic Pathway (SBP)-Single Location Model 50
2 Assembly of Chlorophyll–Protein Complexes: The Single- Branched Chlorophyll Biosynthetic Pathway-Multilocation Model 51
3 Assembly of Chlorophyll–Protein Complexes: The Multi-Branched Chlorophyll Biosynthetic Pathway (MBP)-Sublocation Model 51
D Which Chl–Thylakoid Apoprotein Assembly Model Is Validated by Experimental Evidence 52
1 Can Resonance Excitation Energy Transfer Between Anabolic Tetrapyrroles and ­Chlorophyll–Protein Complexes be ­Demonstrated? 53
(a) Induction of Tetrapyrrole Accumulation 53
(b) Selection of Appropriate Chlorophyll .a. Acceptors 54
(c) Acquisition of In Situ Emission and Excitation Spectra at 77 K 54
(d) Generation of Reference In Situ tetrapyrrole Excitation Spectra 54
(e) Processing of Acquired Excitation Spectra 54
(f) Demonstration of Resonance Excitation Energy Transfer Between Anabolic Tetrapyrroles and Chlorophyll–Protein Complexes 54
2 Development of Analytical Tools for Measuring Distances Separating Various Chlorophyll–Protein Complexes from Anabolic Tetr 55
(a) Determination of the Molar Extinction Coefficients of Total Chl .a. In Situ at 77 K 55
(b) Estimation of the Molar Extinction Coefficients of Chl a ~F685, ~F695 and ~F735 at 77 K 55
(c). Calculation of Distances R Separating Anabolic Tetrapyrroles from Various Chl a–protein Complexes 55
(d) Calculation of R.0 57
(e) Calculation of k, the Orientation Dipole 57
(f) Calculation of the Overlap Integral .Ju at 77K 57
(g) Calculation of n0., the Mean Wavenumber of Absorption and Fluorescence Peaks of the Donor at 77 .K 57
(h) Calculation of t0., the Inherent Fluorescence Lifetime of Donors at 77 K 58
(i) Calculation of Fy.Da. the Relative Fluorescence Yield of Tetrapyrrole Donors in the Presence of Chl Acceptors In Situ at 77 58
(j) Calculation of tD., the Actual Mean Fluorescence Lifetime of the Excited Donor in the Presence of Acceptor at 77 K 59
(k) Calculation of R.0. for Proto, Mp(e) and Pchlide .a. donors-Chl .a. Acceptors Pairs at 77 K 59
(l) Calculation of E, the Efficiency of Energy Transfer In Situ at 77 K 59
(m) Calculation of the Distances That Separate Proto, Mp(e), DV Pchlide .a., and MV Pchlide .a. from Various Chl .a. Acceptors 60
3 Testing the Functionalities of the Various Chl–Thylakoid Biogenesis Models 60
(a) The Single-Branched Pathway-Single Location Model Is Not Compatible with Resonance Excitation Energy Transfer Between An 61
(b) The SBP-Multilocation Model Is Not Compatible with the Realities of Chl Biosynthesis in Green Plants 61
(c) The MBP-Sublocation Model Is Compatible with the Realities of Chl Biosynthesis in Green Plants, and with Resonance Excitati 61
E Guidelines and Suggestions to Bioengineer Plants with Smaller Photosynthetic Unit Size 62
1 Selection of Mutants 62
(a) Mutants of Higher Plants Other Than Arabidopsis 62
(b) Arabidopsis Mutants 62
(c) Lower Plant Mutants 62
2 Preparation of Photosynthetic Particles 62
3 Determination of Biosynthetic Routes Functional in a Specific Mutant or Photosynthetic Particle 62
References 63
Chapter 2: Evidence for Various 4-Vinyl Reductase Activities in Higher Plants 66
I Introduction 67
II Materials and Methods 70
A Plant Material 70
B Light Pretreatment 70
C Chemicals 70
D Preparation of Divinyl Protochlorophyllide .a 70
E Preparation of Divinyl Chlorophyllide .a 70
F Preparation of Divinyl Mg-Protoporphyrin Mono Methyl Ester 70
G Isolation of Crude and Purified Plastids 70
H Preparation of Plastid Membranes and Stroma 71
I Preparation of Envelope Membranes 71
J Solubilization of [4-Vinyl] Reductase(s) by 3-[(3-Cholamidopropyl)dimethylammonio]-1-Propanesulfonate 71
K Assay of [4-Vinyl] Reductase Activities 71
L Protein Determination 71
M Extraction and Determination of the Amounts of Divinyl and Monovinyl Tetrapyrroles 71
III Results 71
A Experimental Strategy 71
B Detection of [4-Vinyl]Protochlorophyllide .a. Reductase, [4-Vinyl]Mg-Protoporphyrin Monoester Reductase and [4-Vinyl]Mg-Prot 72
C Solubilization of [4-Vinyl]Protochlorophyllide .a. Reductase, [4-Vinyl]Mg-Protoporphyrin Monoester Reductase and [4-Vinyl]Mg- 72
D 4-Vinyl Side Chain Reduction Occurs Before Isocycle Ring Formation in Photoperiodically-Grown Barley 72
E [4-Vinyl] Chlorophyllide .a. Reductase and [4-Vinyl]Protochlorophyllide .a. Reductase Activities do not Occur in Barley Et 73
F [4-Vinyl] Protochlorophyllide .a. Reductase Activity Is Detectable in Greening Barley 73
G NADPH, but Not NADH is a Cofactor for [4-Vinyl]Chlorophyllide Reductase and [4-Vinyl]Protochlorophyllide Reductase Solubilize 73
H The Presence of NADP or Vitamin B.3. in the Incubation Buffer Has No Effect on the Activities of [4-Vinyl]Chlorophyllide .a. 74
I Demonstration of [4-Vinyl] Protochlorophyllide a Reductase and [4-Vinyl] Chlorophyllide .a. Reductase Activities in Barley Ch 74
J Effects of Various Light Treatments on [4-Vinyl] Clorophyllide .a. Reductase Activity 75
IV Discussion 75
References 78
Chapter 3: Control of the Metabolic Flow in Tetrapyrrole Biosynthesis: Regulation of Expression and Activity of Enzymes in th 80
I Introduction 81
II Mg Protoporphyrin IX Chelatase 81
A Structure and Catalytic Activity 81
B Control of Expression, Activity and Localisation 83
C Analysis of Mutants and Transgenic Plants 84
III S-Adenosyl-L-Methionine:Mg Protoporphyrin IX Methyltransferase 85
IV Mg Protoporphyrin IX Monomethylester Cyclase 86
V Divinyl Reductase 87
VI Regulatory Aspects of Mg Porphyrin Synthesis 87
References 90
Chapter 4: Regulation and Functions of the Chlorophyll Cycle 95
I Introduction 96
A Distribution of Chlorophyll .b 96
B Establishment of the Chl Cycle 98
1 Chl .b. Synthesis 98
2 Chl .b. to Chl .a. Conversion 99
3 Why Is the Interconversion of Chl .a. and Chl .b. Called the Chl Cycle? 100
II Pathway and Enzymes of the Chlorophyll (Chl) CycleA Pathway of the Chl Cycle 100
B Enzymes of the Chl Cycle 102
1 Chlorophyllide .a. Oxygenase 102
2 Chl .b. Reductase 103
3 HM-Chl .a. Reductase 103
III Diversity and Evolutionary Aspects of Chlorophyllide .a. Oxygenase 103
A Diversity of CAO Sequences 103
B Domain Structure of CAO 106
C Distribution of Chl .b. Reductase 106
IV Regulation of the Chl Cycle 107
A Regulation of the Chl .a. to .b. Conversion 107
1 Transcriptional Control 107
2 The Signal Transduction Pathway 107
3 Post-transcriptional Control 108
B Regulation of the Chl .b. to .a. Conversion 108
V Roles of the Chl Cycle in the Construction of the Photosynthetic Apparatus 109
A Coordination of the Chl cycle and the Construction of the Photosynthetic Apparatus 109
B Construction and Deconstruction of the Photosynthetic Apparatus and Its Coordination with the Chl .b. to .a. Conversion Syste 112
References 113
Chapter 5: Magnesium Chelatase 118
I Introduction 119
II The 40 kDa Subunit 119
III Comparision of 40 kDa Subunit with the Golgi Membrane Protein NSF-D2, Heat Shock Locus Protein HslU and the .d¢. Subun 120
IV The 70 kDa Subunit and Its Complex Formation with the 40 kDa Subunit 122
V The 140 kDa Subunit 124
VI The Gun4 Protein 125
References 126
Chapter 6: The Enigmatic Chlorophyll .a. Molecule in the Cytochrome .b6f. Complex 128
I Introduction: On the Presence of Two Pigment Molecules in the Cytochrome .b6f. Complex 129
II Crystal Structures of the Cyt .b6f. Complex: The Environment of the Bound Chlorophyll 129
III Additional Function(s) of the Bound Chlorophyll 130
IV Additional Function of the .b.-Carotene 131
References 131
Chapter 7: The Non-mevalonate DOXP/MEP (Deoxyxylulose 5-Phosphate/Methylerythritol 4-Phosphate) Pathway of Chloroplast Isopre 133
I Introduction 134
II The Cytosolic Acetate/Mevalonate (MVA) Pathway of Isopentenyl Pyro phosphate (IPP) Biosynthesis and Its Inhibition 135
III The Plastidic DOXP/MEP Pathway of IPP and Its Inhibition 137
IV Labeling Experiments of Chloroplast Prenyllipids 138
V Compartmentation of Isoprenoid Biosynthesis in Plants 139
VI Branching Point of DOXP/MEP Pathway with Other Chloroplast Pathways 140
VII Cross-Talk Between Both Cellular Isoprenoid Pathways 142
VIII Earlier Observations on Cooperation of Both Isoprenoid Pathways 143
IX Distribution of the DOXP/MEP and the MVA Pathways in Photosynthetic Algae and Higher Plants 144
X Evolutionary Aspects of the DOXP/MEP Pathway 147
XI Biosynthesis of Isoprene and Methylbutenol 147
XII Level of Chlorophylls, Carotenoids and Prenylquinones in Sun and Shade Leaves 149
XIII Inhibition of Chlorophyll and Carotenoid Biosynthesis by 5-Ketoclomazone 150
XIV Conclusion 151
References 152
Chapter 8: The Methylerythritol 4-Phosphate Pathway: Regulatory Role in Plastid Isoprenoid Biosynthesis 157
I Introduction 158
II Regulatory Role of the MEP Pathway in Plastid Isoprenoid Biosynthesis 159
III Crosstalk Between the MVA and the MEP Pathways 161
IV Perspectives for Metabolic Engineering of Plastid Isoprenoids 162
References 162
Chapter 9: The Role of Plastids in Protein Geranylgeranylation in Tobacco BY-2 Cells 165
I Introduction 166
II Protein Isoprenylation in Plants 167
A The Chemical Modification of a C-Terminal Cysteine 167
B Functions of Protein Prenylation in Plants 167
C Isoprenylation of Proteins in Tobacco BY-2 Cells 167
D Origin of the Prenyl Residue Used for Protein Modification 167
1 A Double Origin of Prenyl Diphosphates 167
2 Construction of a Tool to Test the Origin of Geranylgeranyl Residues in Prenylated Proteins 168
(a) State of the Art 168
(b) Tobacco BY-2 Cell Suspensions as a Suitable Tool 168
(c) Description of the System and Results 169
III Conclusion and Perspectives 172
References 172
Chapter 10: The Role of the Methyl-Erythritol-Phosphate (MEP)Pathway in Rhythmic Emission of Volatiles 176
I Introduction 177
II The MEP Pathway and Rhythmic Emission of Floral Volatiles 178
III The MEP Pathway and Rhythmic Emission of Leaf Volatiles 184
IV The MEP Pathway and Rhythmic Emission of Herbivore-Induced Plant Volatiles 185
V The MEP Pathway and Rhythmic Emission of Isoprene 185
VI Conclusions 187
References 187
Chapter 11: Tocochromanols: Biological Function and Recent Advances to Engineer Plastidial Biochemistry for Enhanced Oil Seed 191
I Introduction 192
II Tocochromanol Biosynthesis and Regulation 195
III Tocochromanol Pathway Engineering for Enhancement of Vitamin E 197
IV Optimized Tocochromanol Composition 197
V Enhancement of Total Tocochromanol Content 198
VI Enhancement of Tocotrienol Biosynthesis 200
VII Conclusions and Outlook 200
References 202
Chapter 12: The Anionic Chloroplast Membrane Lipids: Phosphatidylglycerol and Sulfoquinovosyldiacylglycerol 206
I Introduction 207
II Biosynthesis of Plastidic Phosphatidylglycerol 209
III Biosynthesis of Sulfoquinovosyldiacylglycerol 210
IV Functions of Plastid Phosphatidylglycerol 211
V Functions of Sulfoquinovosyldiacylglycerol 212
VI The Importance of Anionic Lipids in Chloroplasts 213
VII Future Perspectives 214
References 215
Chapter 13: Biosynthesis and Function of Monogalactosyldiacylglycerol (MGDG), the Signature Lipid of Chloroplasts 219
I Introduction 220
II Identification of MGDG Synthase in Seed Plants 220
III Biochemical Properties of MGDG Synthase 221
A Enzymatic Features of MGDG Synthase 221
B Subcellular Localization of MGDG Synthase 221
C Three-Dimensional Structure of MGDG Synthase 222
D Two Types of MGDG Synthase in Arabidopsis 222
E MGDG Synthesis in Non-photosynthetic Organs 223
IV Function and Regulation of MGDG Synthase 223
A Regulation of Type A MGDG Synthase 223
B Regulation of Type B MGDG Synthase 224
C In Vivo Function of MGDG Synthase by Mutant Analyses 225
V Substrate Supply Systems for MGDG Synthesis 226
A DAG Supply to the Outer Envelope 227
B DAG Supply to the Inner Envelope 229
VI MGDG Synthesis in Photoautotrophic Prokaryotes 230
VII Future Perspectives 231
References 232
Chapter 14: Synthesis and Function of the Galactolipid Digalactosyldiacylglycerol 237
I Introduction 238
II Structure and Occurrence of Digalactosyldiacylglycerol 238
III Synthesis of Digalactosyldiacylglycerol and Oligogalactolipids 239
IV Function of Digalactosyldiacylglycerol in Photosynthesis 240
V Digalactosyldiacylglycerol as Surrogate for Phospholipids 241
VI Changes in Galactolipid Content During Stress and Senescence 242
VII Conclusions 243
References 243
Chapter 15: The Chemistry and Biology of Light-Harvesting Complex II and Thylakoid Biogenesis: .raison d’etre. of Chlorophyll 246
I Introduction 247
A Chlorophyll .a 248
B Chlorophyll .b 249
C Chlorophyll .c 249
D Chlorophyll .d 249
II Coordination Chemistry of Chlorophyll and Ligands 250
III Binding of Chlorophyll to Proteins 251
IV Chlorophyll Assignments in Light Harvesting Complex II (LHCII) 253
V Cellular Location of Chlorophyll .b. Synthesis and LHCII Assembly 255
VI Chlorophyllide .a. Oxygenase 257
VII Conclusions 258
References 259
Chapter 16: Folding and Pigment Binding of Light-Harvesting Chlorophyll .a/b. Protein (LHCIIb) 263
I Introduction 264
II Time-Resolved Measurements of LHCIIb Assembly In Vitro 265
A Fluorescence as a Monitor for LHCIIb Assembly 265
B A Two-step Model of Pigment Binding 267
C Protein Folding During LHCIIb Assembly 270
III Concluding Remarks 273
References 273
Chapter 17: The Plastid Genome as a Platform for the Expression of Microbial Resistance Genes 277
I Introduction 278
II Yield and Resistance 279
III .Aspergillus flavus.: Managing a Food and Feed Safety Threat 280
A Economic and Health Impacts 280
B Approaches to Intervention 280
IV The Case for Transgenic Interventions 282
A Modifying the Nuclear Genome for Resistance 282
V Plastid Transformation 283
B Features of the Plastid Expression System 283
1 The Plastome 284
(a) Integration of Foreign Sequences 284
(b) Maternal Inheritance 284
C Moving Beyond the Model System 284
VI Identifying Candidate Genes for Aflatoxin Resistance 284
A Chloroperoxidase 285
1 Antimicrobial Potential 285
2 Expression of CPO-P in Transgenic Plants 285
VII An Environmentally Benign Approach 285
A Plastid Transformation Vector 285
B Determinants of Foreign Gene Expression in Plastids 286
1 The .psbA. 5.¢. UTR 286
(a) The Potential of .psbA. 5.¢. UTR Stems From Its Endogenous Role in Plastids 286
(b) Translational Control Is Highly Regulated and Dependent on Imported Trans-acting Protein Factors 286
(c) Light Regulation of Translation Via the .psbA. 5.¢. UTR 287
C The CPO-P Transplastomic Lines 287
1 Evaluating CPO-P Expression 287
(a) Protein Expression 287
(b) Analysis of Foreign Transcripts 287
(c) Continued Analysis 287
VIII Future Challenges: Control of Aflatoxin Contamination in Cottonseed 288
A Taking a Direct Approach 288
B Taking an Indirect Approach 288
1 Drought Tolerance 289
2 Resistance to Herbivory 289
C Generation of Transplastomic Cotton 289
IX Conclusion 289
References 289
Chapter 18: Chloroplast Genetic Engineering: A Novel Technology for Agricultural Biotechnology and Bio-pharmaceutical Industr 295
I Introduction 296
II Genome and Organization 297
III Concept of Chloroplast Transformation 298
IV Advantages of Plastid Transformation 299
V Chloroplast Transformation Vectors and Mode of Transgene Integration into Chloroplast Genome 301
VI Methods of Plastid Transformation and Recovery of Transplastomic Plants 302
VII Current Status of Plastid Transformation 304
VIII Application of Chloroplast Technology for Agronomic Traits 305
IX Chloroplast-Derived Vaccine Antigens 307
X Chloroplast-Derived Biopharmaceutical Proteins 309
XI Chloroplast-Derived Industrially Valuable Biomaterials 310
References 312
Chapter 19: Engineering the Sunflower Rubisco Subunits into Tobacco Chloroplasts: New Considerations 317
I Introduction 319
II Transforming the Tobacco Plastome with Sunflower Rubisco Genes 320
A Replacing the Tobacco .rbc.L with Sunflower .rbc.L.S 320
B Co-transplanting .rbc.L.S. and a Codon-Modified Sunflower .cmrbc.S Gene 320
1 A Need to Co-engineer Cognate L- and S-Subunits 320
2 Altering the Codon Bias of a Sunflower .Rbc.S.s. Gene 321
3 Using the T7g10 5.¢.UTR to Regulate Sunflower S-Subunit Translation 322
C Transformation, Selection and Growth of the Transplastomic Lines 322
III Inadvertent Gene Excision by Recombination of Duplicated .psb.A 3.¢.UTR Sequence 322
A Preferential Loss of Plastome Copies Containing .cmrbc.S.S 322
B Why Were the .cmrbc.S.S. Containing Plastome Copies Lost? 323
IV Simple Removal of .aad.A in T.0. t.Rst.SLA by Transient CRE Recombinase Expression 323
A Bacteriophage P1 CRE-.lox. Site-specific Recombination 323
B Removing .aad.A by Bombarding with Plasmid pKO27 324
1 Selection and Screening for .Daad.A Lines 324
2 Screening the T.1. Progeny for .aad.A Loss and No Incorporation of the pKO27 T-DNA 325
V Growth Phenotypes of the tob.Rst., t.Rst.LA and t.Rst.L Lines 325
A Elevated CO.2. Partial Pressures Augment the Growth of the Juvenile Transformants 325
B The Comparable Phenotype and Growth Rates of the Transgenic Lines 325
1 Differences in Leaf and Apical Meristem Development 325
2 Shoot Development 327
C Leaf and Floral Development 327
VI Expression of the Hybrid L.s.S.t. Rubisco in Mature Leaves 328
A Steady-State .rbc.L.S. mRNA Levels 328
B Rubisco and Protein Content 328
C Translational Efficiency and/or Folding and Assembly Limit L.s.S.t. Production 330
VII Whole Leaf Gas Exchange Measurements of the L.s.S.t. Kinetics 330
A Measuring Gamma Star (.G.*) 330
B Measuring the L.s.S.t. Michaelis Constants for CO.2. and O.2 331
VIII Future Considerations for Transplanting Foreign Rubiscos into Tobacco Plastids 331
A Improving L.s.S.t. Synthesis 331
1 Limitations to Translational Processing of .rbc.L.S 331
2 Subunit Assembly Limitations 333
B The Assembly and Kinetic Capacity of Other Hybrid Rubiscos 333
C Constraints on S-Subunit Engineering in Tobacco 334
D Rubisco Activase Compatibility 334
IX Quicker Screening of the Assembly and Kinetics of Genetically Modified L.8.S.8. Enzymes in Tobacco Chloroplasts 334
References 335
Chapter 20: Engineering Photosynthetic Enzymes Involved in CO.2.–Assimilation by Gene Shuffling 339
I Introduction 340
II Potential Targets for Improving Plant Photosynthesis 340
III Directed Molecular Evolution Provides a Useful Tool to Engineer Selected Enzymes 342
IV Improving Rubisco CatalyticEfficiency by Gene Shuffling 344
A Attempts to Express .Arabidopsis thaliana. Rubisco in .Chlamydomonas reinhardtii 344
B Shuffling the .Chlamydomonas reinhardtii. Rubisco Large Subunit 346
V Improving Rubisco Activase Thermostability by Gene Shuffling 348
VI Future Prospects 350
References 352
Chapter 21: Elevated CO.2. and Ozone: Their Effects on Photosynthesis 355
I Introduction 356
II Regulation of the Photosynthetic Apparatus: Metabolic and Environmental Signals 357
III Possible Scenarios Explaining Effects of Elevated [CO.2.] and [O.3.] on Plant Behavior in the Altered Earth Atmosphere 359
A Plant Responses to Elevated [CO.2] 360
B Plant Responses to Tropospheric [O.3.] 361
C Combined Effects of [CO.2] and [O.3] 362
IV Benefits from Model Species:.Arabidopsis thaliana. and .Thellungiella halophila 363
V Discussion 368
A The Importance of Model Species 368
B Gene Networks Explaining Transcript Behavior 368
VI Conclusions 372
Chapter 22: Regulation of Photosynthetic Electron Transport 379
I Introduction 380
II Chlorophyll Fluorescence: A Non-disruptive Tool for Electron Transport Analysis 381
III Thermal Dissipation of Absorbed Excessive Light Energy from PSII 382
IV Balancing Excitation Energy Between Photosystems by State Transition 382
V Photorespiration and the Water–Water Cycle: Alternative Electron Sinks? 383
VI The Discovery of PGR5-Dependent PSI Cyclic Electron Transport 384
VII PSI Cyclic Electron Transport Mediated by Chloroplast NAD(P)H Dehydrogenase 386
VIII PSI Cyclic Electron Transport and Thermal Dissipation 387
IX PSI Cyclic Electron Transport and State Transition 388
X The Water–Water Cycle and PSI Cyclic Electron Transport 388
XI Concluding Remarks 388
References 389
Chapter 23: Mechanisms of Drought and High Light Stress Tolerance Studied in a Xerophyte, .Citrullus lanatus. (Wild Watermelon) 394
I Introduction 395
II Experimental Procedures 396
III Physiological Response of Wild Watermelon 397
IV Enzymes for Scavenging Reactive Oxygen Species 399
V Cytochrome .b561. and Ascorbate Oxidase 400
VI Global Changes in the Proteomes 402
VII Citrulline Metabolism and Function 402
VIII Concluding Remarks 404
References 405
Chapter 24: Antioxidants and Photo-oxidative Stress Responses in Plants and Algae 409
I Types of Reactive Oxygen Species 410
II Sources of Reactive Oxygen Species in Algae and Plants 411
III Functions of Reactive Oxygen Species 411
IV Oxidative Damage in Chloroplasts 412
V Avoidance of Reactive Oxygen Species Production 413
VI Non-enzymatic Mechanisms for Scavenging Reactive Oxygen Species 413
A Hydrophilic Antioxidants 414
1 Ascorbate 414
2 Glutathione 415
B Lipophilic Antioxidants 415
1 Tocopherol 415
2 Carotenoids 416
C Antioxidant Interactions 417
VII Enzymatic Mechanisms for Scavenging Reactive Oxygen Species 418
A Superoxide Dismutase 418
B Catalase 419
C Ascorbate Peroxidase 419
D Glutathione Peroxidase 419
E Thioredoxin 420
F Glutaredoxin 421
G Peroxiredoxin 421
References 422
Chapter 25: Singlet Oxygen-Induced Oxidative Stress in Plants 427
I Introduction 428
II Formation of Singlet Oxygen in Plants 428
III Generation of Singlet Oxygen from Chlorophyll Biosynthesis Intermediates 430
IV Porphyrin-Generating Compounds 430
A 5-Aminolevulinic Acid 430
B Diphenyl Ethers 431
V Type I and Type II Photosensitization Reactions of Tetrapyrroles 431
VI Intracellular Destruction of Singlet Oxygen 432
VII Singlet Oxygen-Mediated Oxidative Damage to the Photosynthetic Apparatus 432
A Generation of Tetrapyrrole-Induced Singlet Oxygen in Chloroplasts 433
B Singlet Oxygen-Induced Impairment of the Electron Transport Chain 433
C Role of Singlet Oxygen Scavengers 434
D Impact of .1.O.2. on Chlorophyll a Fluorescence 434
E Effect of Singlet Oxygen on Thermoluminiscence 436
VIII Singlet Oxygen-induced Oxidative Damage in Mutants 436
A Chlorophyll Anabolic Mutants 436
B Chlorophyll Catabolic Mutants 438
IX Future Prospects 438
References 439