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.

Auteur

Professor Peter Hedden graduated with BSc (1969) and PhD (1973) degrees in chemistry from the University of Bristol. After post-doctoral positions at the University of Göttingen, Germany, with Jan Graebe and at UCLA, USA, with Bernard Phinney, he joined East Malling Research Station, in Kent, United Kingdom in 1981. He moved to Long Ashton Research Station (LARS), Bristol, UK, in 1984 and then to Rothamsted Research after the closure of LARS in 2003. His main research interest throughout his career has been the biosynthesis of the gibberellin plant hormones, working initially on delineating the biosynthetic pathways, then on the isolation and characterization of the biosynthetic enzymes and latterly on their regulation by developmental and environmental factors. Current research includes exploiting the gibberellin biosynthesis and signal transduction pathways for the introduction of desirable traits into crop species.

Dr Steve Thomas graduated BSc from the University of Southampton in 1991. He gained a PhD in biochemistry at Bristol University in 1996. In the same year he started postdoctoral work at Long Ashton Research Station where he spent four years investigating the regulation of gibberellin biosynthesis and inactivation in sugar beet and Arabidopsis. He then spent three and a half years in Tai-ping Sun's Laboratory at Duke University dissecting the signalling pathways controlling gibberellin-mediated degradation of DELLA proteins in Arabidopsis. In 2004, he returned to the UK to work with Dr Andy Phillips and Prof. Peter Hedden in the Hormone Signalling Group at Rothamsted Research as a Senior Scientist. He is currently a member of the 20:20 Wheat® Institute Strategic Programme at Rothamsted Research, with his research focused on improving grain yields in wheat by manipulating plant hormone signalling.

Contenu

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 12-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 &...