Seed development, dormancy and germination

✍ Scribed by Kent Bradford, Hiro Nonogaki

• Publisher: Blackwell Pub
• Year: 2007
• Tongue: English
• Leaves: 389
• Series: Annual plant reviews 27
• Edition: 1
• Category: Library

✦ Synopsis

The formation, dispersal and germination of seeds are crucial stages in the life cycles of gymnosperm and angiosperm plants. The unique properties of seeds, particularly their tolerance to desiccation, their mobility, and their ability to schedule their germination to coincide with times when environmental conditions are favorable to their survival as seedlings, have no doubt contributed significantly to the success of seed-bearing plants. Humans are also dependent upon seeds, which constitute the majority of the world’s staple foods (e.g., cereals and legumes). Seeds are an excellent system for studying fundamental developmental processes in plant biology, as they develop from a single fertilized zygote into an embryo and endosperm, in association with the surrounding maternal tissues. As genetic and molecular approaches have become increasingly powerful tools for biological research, seeds have become an attractive system in which to study a wide array of metabolic processes and regulatory systems.

Seed Development, Dormancy and Germination provides a comprehensive overview of seed biology from the point of view of the developmental and regulatory processes that are involved in the transition from a developing seed through dormancy and into germination and seedling growth. It examines the complexity of the environmental, physiological, molecular and genetic interactions that occur through the life cycle of seeds, along with the concepts and approaches used to analyze seed dormancy and germination behavior. It also identifies the current challenges and remaining questions for future research. The book is directed at plant developmental biologists, geneticists, plant breeders, seed biologists and graduate students.

✦ Table of Contents

Cover Page......Page 1
Contents......Page 6
List of Contributors......Page 14
Preface......Page 16
1.2 Overview of seed development in angiosperms......Page 22
1.3.1 Central regulators of embryogenesis......Page 24
1.3.2 Genes involved in the morphogenesis phase of embryo development......Page 25
1.3.3 Regulators of the maturation phase of embryo development......Page 26
1.4 Genetic control of endosperm development......Page 27
1.4.2 Genes that repress autonomous endosperm development......Page 28
1.5 Genetic aspects of testa development......Page 29
1.5.2 Regulators of mucilage biosynthesis and accumulation......Page 30
1.6.1 Genetic factors affecting seed mass......Page 31
1.6.3 Endosperm development and seed mass......Page 32
1.6.4 Sugar transport and metabolism during seed development......Page 34
1.6.5 Metabolic control of seed development and size......Page 36
References......Page 38
2.2.1 The seed envelopes......Page 46
2.2.2 The Arabidopsis testa......Page 48
2.3.1 Constraints imposed by the seed coat......Page 50
2.3.2.1 Main flavonoid end-products present in seeds......Page 52
2.3.2.2 Molecular genetics of flavonoid metabolism......Page 53
2.3.2.3 Effects of flavonoids on seed dormancy and germination......Page 56
2.3.3.1 Solanaceae......Page 59
2.3.3.3 Flavonoids and other phenolics as direct and indirect germination inhibitors......Page 60
2.3.3.5 Heteromorphism and physiological heterogeneity among seeds......Page 61
2.4 Link between seed coat-imposed dormancy and longevity......Page 62
2.5 Concluding remarks......Page 63
References......Page 64
3.2 Classifications of dormancy......Page 71
3.2.1 Endogenous dormancy......Page 73
3.2.2 Exogenous dormancy......Page 74
3.3 Definitions of dormancy......Page 75
3.4.1.1 Role of ABA in dormancy induction......Page 78
3.4.1.2 Developmental programs and dormancy induction......Page 79
3.4.2.1 After-ripening......Page 80
3.4.2.2 Regulation of dormancy in imbibed seeds......Page 81
3.5 Secondary dormancy......Page 84
3.6.1 Stress signaling......Page 85
3.6.3 Environmental signals......Page 86
References......Page 88
4.1 Introduction......Page 93
4.2 Types and phenology of seed dormancy......Page 94
4.3.1.1 Temperature......Page 97
4.3.1.2 After-ripening......Page 99
4.3.1.3 Stratification......Page 100
4.3.2.1 Fluctuating temperature......Page 101
4.3.2.2 Light......Page 102
4.4 Approaches to modeling seed dormancy......Page 103
4.4.1 Temperature response models and thermal time......Page 104
4.4.2 Water potential responses and hydrotime models......Page 108
4.4.3 Interactions of temperature and water potential......Page 110
4.4.4 Modeling responses to other factors affecting dormancy and germination......Page 111
4.5.1 Solanum tuberosum......Page 112
4.5.2 Bromus tectorum......Page 113
4.5.3 Polygonum aviculare......Page 117
4.5.3.1 Modeling seed germination responses to temperature......Page 118
4.6 Population-based threshold models of seed dormancy......Page 121
4.7 Conclusions and future directions......Page 126
References......Page 127
5.1 Introduction......Page 134
5.2 Mutant approaches in Arabidopsis......Page 135
5.3 Mutant approaches in other species......Page 139
5.4 Genetic analyses of natural variation......Page 140
5.4.2 Natural variation for dormancy in grasses......Page 141
5.5 What do the genetics teach us about dormancy and germination?......Page 146
References......Page 148
6.1 Introduction......Page 154
6.2.2 Import of fatty acids into the peroxisome......Page 156
6.2.3 Activation of fatty acids to acyl-CoA thioesters for • -Oxidation......Page 157
6.2.4.2 Multifunctional protein......Page 158
6.2.5 Glyoxylate cycle and gluconeogenesis......Page 159
6.2.5.3 Phosphoenolpyruvate carboxylase......Page 160
6.3.1 Importance of the ABC transporter for the transition from dormancy to germination......Page 161
6.3.2 Defects in B-oxidation enzymes, but not in LACS, affect seed dormancy......Page 163
6.3.3 Storage lipid mobilization (glyoxylate cycle and gluconeogenesis) is not required for seed dormancy release......Page 165
6.4.2 B-Oxidation and hormonal signaling......Page 166
6.4.3 Possible biosynthetic roles for • -oxidation in regulating germination......Page 168
6.4.4 B-Oxidation, reactive oxygen species, and redox control......Page 169
References......Page 170
7.2 Challenges in NO chemistry and biology......Page 174
7.3 Tools used in NO research......Page 175
7.4 Roles of NO and other N-containing compounds in seed dormancy and germination......Page 178
7.4.1 Nitrate, nitrite, and ammonium......Page 179
7.4.2 Cyanide and azide......Page 180
7.4.3 NO donors and germination......Page 181
7.5.1 Synthesis of NO by plants......Page 183
7.5.2 NO binding to metal-containing proteins......Page 185
7.5.3 NO as an antioxidant......Page 187
7.6 Interactions between NO and phytochrome or ABA......Page 188
7.7.1 Nitrogen and vegetation gap sensing......Page 189
7.8 Unresolved questions and concluding remarks......Page 190
References......Page 192
8.1 Introduction......Page 197
8.2.1 ABA in seed maturation and the induction of primary dormancy......Page 198
8.2.2 Transcription factors and combinatorial control of seed development and maturation......Page 201
8.2.3.1 ABA synthesis and homeostasis during dormancy maintenance and termination......Page 203
8.2.3.2 ABA signaling factors and the control of dormancy maintenance and termination......Page 207
8.3.1 GA is antagonistic to ABA during seed development......Page 211
8.3.2 GA promotes the transition to germination......Page 212
8.4.1 GA synthesis and signaling are promoted by light through the action of phytochrome......Page 216
8.4.2 ABA-associated signaling processes are opposed by light signaling......Page 217
8.5.1 Ethylene counteracts ABA during seed development......Page 218
8.5.2 Ethylene promotes the transition from dormancy to germination......Page 219
8.6.1 Auxin and cytokinin establish the embryo body plan during seed development......Page 222
8.6.2 Auxin and cytokinins have not been intimately linked to dormancy maintenance or termination......Page 223
8.7 Brassinosteroids......Page 224
8.8 G-protein signaling reveals integration of GA, BR, ABA, and sugar responses......Page 226
8.9 Profiling of hormone metabolic pathways in Arabidopsis mutants reveals cross-talk......Page 227
8.10 Summary and future directions......Page 229
References......Page 232
9.1 Introduction......Page 245
9.2.1 ABA biosynthesis......Page 246
9.2.2 ABA deactivation......Page 250
9.2.4 GA biosynthesis......Page 251
9.2.6 GA-deficient mutants and seed germination......Page 252
9.3.1 Drugs to reduce endogenous ABA levels......Page 253
9.3.2 Drugs to increase endogenous ABA levels......Page 255
9.3.4 Side effects of drugs......Page 256
9.4.1.2 FUS3, a balancer of ABA and GA levels......Page 257
9.4.1.3 AGL15, a transcriptional regulator of a GA deactivation gene......Page 259
9.4.2 Regulation of ABA metabolism during seed imbibition in Arabidopsis......Page 260
9.4.3.1 Regulation of GA biosynthesis by light......Page 261
9.5 Conclusions and perspectives......Page 262
References......Page 263
10.2 Control of germination by GA signaling......Page 269
10.3 The role of the ubiquitin–proteasome pathway in GA signaling......Page 273
10.4 Is RGL2 a ‘master regulator’ of seed germination?......Page 276
10.5 Sleepy1 is a positive regulator of seed germination in Arabidopsis......Page 278
10.6 Do DELLA proteins have a conserved role in seed germination?......Page 279
References......Page 281
11.2 Imbibition and water relations of seed germination......Page 285
11.3.1 Testa and pericarp......Page 293
11.3.2 Endosperm......Page 294
11.3.3.1 Expansins......Page 297
11.3.3.2 Xyloglucan endotransglycosylase/ hydrolases......Page 298
11.3.3.3 Endo-B -mannanase, A-galactosidase, and B-mannosidase......Page 300
11.3.3.4 Cellulase, arabinosidase, xylosidase......Page 303
11.3.3.6 B-1,3-Glucanase and chitinase......Page 304
11.3.3.7 Concerted action of cell wall hydrolases and expansins......Page 306
11.3.4.1 Generation of embryo growth potential......Page 307
11.3.4.2 Gene expression associated with embryo growth......Page 309
11.4.1 Transcriptome and proteome analyses......Page 310
11.4.2 Activation tagging and enhancer trapping......Page 313
11.4.3 Potential involvement of microRNAs in seed germination......Page 315
References......Page 316
12.2.1 ABA response mutants isolated in germination-based screens......Page 326
12.2.2 ABA inhibition of seed germination is suppressed by sugars......Page 327
12.2.3 ABA blocks the transition from embryonic to vegetative growth......Page 328
12.3.1 Plant sugar signaling and the identification of sugar-response mutants......Page 330
12.3.2 The glucose-insensitive response pathway......Page 332
12.3.3 Other factors affecting the glucose response during early seedling development......Page 335
12.3.4 Sugar delays seed germination in Arabidopsis......Page 336
12.3.5 Imbibed seeds rapidly lose sensitivity for the glucose-induced germination delay......Page 340
12.4 Conclusions......Page 342
References......Page 343
Index......Page 350