Annual Plant Reviews, The Gibberellins

First discovered as fungal metabolites, the gibberellins were recognised as plant hormones over 50 years ago. They regulate reproductive development in all vascular plants, while their role in flowering plants has broadened to include also the regulation of growth and other developmental processes. This timely book covers the substantial and impressive recent advances in our understanding of the gibberellins and their roles in plant development, including the biosynthesis, inactivation, transport, perception and signal transduction of these important hormones. An introductory chapter traces the history of gibberellin research, describing the many discoveries that form the basis for the recent progress. The exciting emerging evidence for the interaction of gibberellin signalling with that of the other hormones is critically evaluated. The occurrence of gibberellins in fungal, bacterial and lower plant species is also discussed, with emphasis on evolution. Manipulation of gibberellin metabolism and signal transduction through chemical or genetic intervention has been an important aspect of crop husbandry for many years. The reader is presented with important information on the advances in applying gibberellin research in agriculture and horticulture. Annual Plant Reviews, Volume 49: The Gibberellins is an important resource for plant geneticists and biochemists, as well as agricultural and horticultural research workers, advanced students of plant science and university lecturers in related disciplines. It is an essential addition to the shelves of university and research institute libraries and agricultural and horticultural institutions teaching and researching plant science.

Table of Contents:
List of Contributors xv Preface xvii 1 Signal Achievements in Gibberellin Research: The Second Half-Century 1 Valerie M. Sponsel 1.1 Introduction 1 1.2 Gibberellin biosynthesis 6 1.3 Gibberellin signalling 17 1.4 Physiological responses to gibberellins 25 References 29 2 Gibberellin Biosynthesis in Higher Plants 37 Peter Hedden 2.1 Introduction 37 2.2 Synthesis of ent-kaurene 39 2.2.1 Formation of trans-geranylgeranyl diphosphate 39 2.2.2 Formation of ent-kaurene from trans-geranylgeranyl diphosphate 40 2.3 Reactions catalysed by cytochrome P450 mono-oxygenases 42 2.4 Reactions catalysed by 2-oxoglutarate-dependent dioxygenases 45 2.5 Sites of gibberellin biosynthesis 49 2.6 Regulation of gibberellin biosynthesis 50 2.6.1 Developmental control 50 2.6.2 Gibberellin homoeostasis 51 2.6.3 Regulation by other hormones 54 2.6.4 Regulation by environmental factors 55 2.7 Concluding remarks 59 Acknowledgements 60 References 60 3 Inactivation Processes 73 Hiroshi Magome and Yuji Kamiya 3.1 Introduction 73 3.2 Gibberellin inactivation 75 3.2.1 Gibberellin 2-oxidase 75 3.2.2 Gibberellin methyltransferase 77 3.2.3 Gibberellin 16,17-oxidase 78 3.2.4 Gibberellin 13-oxidase and 12α-oxidase 78 3.2.5 Conjugation with sugar 80 3.3 Regulation of gibberellin inactivation 80 3.3.1 Developmental regulation 81 3.3.2 Gibberellin homoeostasis 82 3.3.3 Regulation by other hormones 83 3.3.4 Environmental regulation 84 3.4 Concluding remarks 87 References 88 4 Gibberellin Transport 95 Jonathan Dayan 4.1 Introduction 95 4.2 Gibberellins can be translocated along plant bodies 96 4.3 Gibberellin transport in seeds 100 4.4 Pattern of gibberellin biosynthesis in transport analysis 101 4.5 Grafting experiments 103 4.6 Significance for secondary growth 104 4.7 Orientation of gibberellin signal flow: source and sink tissues 107 4.8 Monitoring intra- and intercellular gibberellin concentration 110 4.9 Conclusion: new aspects for gibberellin transport 111 4.9.1 Potential transporters 111 4.9.2 Analysis through perception 112 4.9.3 Links to sugar transport 112 Acknowledgements 113 References 114 5 Gibberellins in Fungi, Bacteria and Lower Plants: Biosynthesis, Function and Evolution 121 Bettina Tudzynski, Lena Studt and María Cecilia Rojas 5.1 Introduction 122 5.2 Gibberellin biosynthesis in fungi 122 5.2.1 The biosynthetic pathway in F. fujikuroi: genes and enzymes 122 5.2.2 Gibberellin production in distantly related fungi 126 5.2.3 Evolution of the gibberellin biosynthetic gene cluster in fungi 128 5.2.4 The role of gibberellins in plant infection 131 5.2.5 Strain improvement 132 5.3 Gibberellin biosynthesis in bacteria 133 5.3.1 Free-living rhizobacteria 133 5.3.2 Symbiotic rhizobacteria: genes and reactions of the gibberellin biosynthetic pathway 134 5.3.3 Function and evolution 137 5.4 Gibberellin biosynthesis and signalling components in lower plants 139 5.5 Concluding remarks 143 References 144 6 Gibberellin Hormone Signal Perception: Down-Regulating DELLA Repressors of Plant Growth and Development 153 Sven K. Nelson and Camille M. Steber 6.1 Introduction 154 6.2 DELLA proteins are repressors of gibberellin responses 154 6.3 Gibberellin signalling lifts DELLA repression of gibberellin responses 157 6.4 The gibberellin receptor GID1 (GA-INSENSITIVE DWARF1) 159 6.5 The structural requirements for gibberellin binding by GID1 161 6.6 The structural requirements for the GID1-DELLA protein–protein interaction 162 6.7 The DELLA destruction model: negative regulation of DELLA repressors by SLY1/GID2 and the ubiquitin-proteasome pathway 166 6.8 Regulation of DELLA by phosphorylation and O-GlcNAc modification 169 6.9 Evidence for gibberellin-independent DELLA regulation 173 6.10 Evidence for gibberellin signalling without DELLA destruction 175 6.11 Concluding remarks 177 Acknowledgements 179 References 179 7 DELLA Proteins: Master Regulators of Gibberellin-Responsive Growth and Development 189 Stephen G. Thomas, Miguel A. Blázquez and David Alabadí 7.1 Introduction 190 7.2 DELLAs regulate downstream gibberellin signalling 191 7.3 Gibberellins relieve DELLA-growth repression by targeting their degradation 193 7.4 Functional diversification of DELLA genes 194 7.5 DELLA activity invokes rapid changes in the transcriptome 197 7.6 DELLA proteins activate transcription 198 7.7 DELLAs regulate transcription by physical interaction with transcriptional regulators 199 7.7.1 DELLAs sequester bona fide TFs by physical interaction 200 7.7.2 DELLAs interact with TFs in the context of promoters 204 7.7.3 DELLAs interact with other transcriptional regulators 206 7.7.4 DELLAs regulate chromatin dynamics 208 7.8 A non-genomic response regulated by DELLAs 209 7.9 Analysis of DELLA protein structure-function 210 7.10 GAMYB: A transcriptional regulator of gibberellin responses during cereal grain germination and pollen development 213 7.10.1 GAMYB positively regulates gene expression in cereal aleurone cells 214 7.10.2 GAMYB regulates gibberellin-dependent anther development 216 7.11 Concluding remarks 217 Acknowledgements 218 References 218 8 Interactions Between Gibberellins and other Hormones 229 John J. Ross, Asemeh Miraghazadeh, Amelia H. Beckett, Laura J. Quittenden and Erin L. McAdam 8.1 Introduction 229 8.2 Interactions involving effects of other hormones on gibberellin levels 230 8.2.1 Auxin promotes gibberellin biosynthesis 230 8.2.2 Ethylene inhibits gibberellin biosynthesis 231 8.2.3 Do gibberellin and abscisic acid inhibit each other’s synthesis? 232 8.2.4 Do brassinosteroids act by affecting gibberellin levels? 234 8.2.5 Possible effects of other hormones on gibberellin synthesis 234 8.3 Interactions between hormone signal transduction pathways 234 8.3.1 Do other hormones affect DELLA stability? 235 8.3.2 DELLAs interact with proteins from the signaling pathways of other hormones 237 8.4 Gibberellins and auxin transport 245 8.5 Conclusion 246 Acknowledgements 247 References 247 9 Gibberellins and Seed Germination 253 Terezie Urbanova and Gerhard Leubner-Metzger 9.1 Introduction 254 9.2 Spatiotemporal expression of gibberellin metabolism during Brassicaceae seed germination 254 9.3 Gibberellin signalling and seed germination 264 9.3.1 The GID1ac and GID1b pathways in seeds 264 9.3.2 DELLA proteins and seed germination 268 9.4 Gibberellin and abiotic stress factors: thermoinhibition of seed germination 270 9.5 Gibberellin and biotic stress factors: allelochemical interference of gibberellin biosynthesis during seed germination 273 9.6 Conclusions and perspectives 276 Acknowledgements 277 References 277 10 Gibberellins and Plant Vegetative Growth 285 Cristina Martínez, Ana Espinosa-Ruiz and Salomé Prat 10.1 Introduction 285 10.2 Gibberellins and shoot development 288 10.2.1 Control of SAM function and leaf size 289 10.2.2 Elongation of the hypocotyl 290 10.2.3 Apical hook formation 295 10.3 Gibberellin function in root development 298 10.3.1 Hormonal control of root growth 298 10.3.2 Gibberellin signalling from the endodermis 302 10.3.3 DELLAs downstream signalling in the root 304 10.3.4 DELLAs promote mycorrhizal symbiosis 306 10.4 Growth under unfavourable conditions 308 10.4.1 DELLAs promote resistance to abiotic stress 308 10.4.2 DELLAs and biotic stress 310 10.5 Concluding remarks 311 References 312 11 Gibberellins and Plant Reproduction 323 Andrew R.G. Plackett and Zoe A. Wilson 11.1 Introduction 323 11.2 The floral transition 324 11.2.1 Gibberellin promotes flowering through multiple interacting pathways 324 11.2.2 Sites of gibberellin biosynthesis and action during the floral transition 329 11.2.3 Gibberellin and flowering in perennial species 331 11.3 Floral development 331 11.3.1 Floral patterning and early development 332 11.3.2 Gibberellin and fertility 334 11.4 Seed and fruit development 340 11.4.1 Fruit development 341 11.4.2 Embryo and seed development 345 Acknowledgements 348 References 348 12 Chemical Regulators of Gibberellin Status and their Application in Plant Production 359 Wilhelm Rademacher 12.1 Introduction 359 12.2 Gibberellins 361 12.3 Inhibitors of gibberellin biosynthesis 363 12.3.1 Quaternary ammonium compounds 365 12.3.2 Compounds with a nitrogen-containing heterocycle 366 12.3.3 Structural mimics of 2-oxoglutaric acid 369 12.3.4 16,17-Dihydro-gibberellins 371 12.4 Uses for gibberellins and inhibitors of gibberellin biosynthesis in crop production 372 12.4.1 Wheat, barley, rye, oats and other small-grain cereals 373 12.4.2 Rice 376 12.4.3 Sugarcane 377 12.4.4 Pasture and turf grasses 377 12.4.5 Oilseed rape 379 12.4.6 Cotton 379 12.4.7 Peanuts 381 12.4.8 Opium poppy 382 12.4.9 Fruit trees growing in temperate climate 382 12.4.10 Fruit and nut trees growing in subtropical and tropical climates 385 12.4.11 Grapevines 387 12.4.12 Ornamentals 389 12.4.13 Hybrid seed production 391 12.5 Outlook 391 References 391 13 Genetic Control of Gibberellin Metabolism and Signalling in Crop Improvement 405 Andrew L. Phillips 13.1 Introduction 405 13.2 The REDUCED HEIGHT-1 (Rht-1) alleles of wheat 406 13.2.1 Pleiotropic effects of Rht-1 alleles 410 13.2.2 Rht-1 orthologues in other crop species 412 13.3 The SEMI-DWARF-1(SD-1) alleles of rice 413 13.4 The ELONGATED UPPERMOST INTERNODE (EUI) gene of rice 415 13.5 Commercially useful alleles of other genes from the gibberellin pathway 416 13.6 Transgenic approaches to manipulation of gibberellin-dependent processes in crops 419 13.6.1 Cereals 419 13.6.2 Other crop species 420 13.7 Conclusions 423 Acknowledgements 424 References 424 Appendix The structures of the gibberellins 431 Index 437