This special issue of The Enzymes is targeted towards researchers in biochemistry, molecular and cell biology, pharmacology, and cancer. This volume discusses signaling pathways in plants. Contributions from leading authorities Informs and updates on all the latest developments in the field
Front Cover 1
Signaling Pathways in Plants 4
Copyright 5
Contents 6
Contributors 10
Preface 12
Chapter One: Regulatory Networks Acted Upon by the GID1-DELLA System After Perceiving Gibberellin 16
1. Gibberellin Perception System in Higher Plants 17
2. Suppression of DNA-Binding Activity of TFs by DELLA (Trapping Function of DELLA) 20
2.1. Phytochrome-Interacting Factor Family of Proteins Involved in Hypocotyl Elongation and Chlorophyll Biosynthesis 20
2.2. Alcatraz and Spatula Involved in Valve Margin Development and Cotyledon Expansion, Respectively 22
2.3. Squamosa Promoter Binding-Like Proteins Involved in Floral Transition 23
2.4. Ethylene-Insensitive 3 and EIN3-Like 1 Involved in the GA-Ethylene Crosstalk for Apical Hook Development 23
2.5. Brassinazole-Resistant 1 Involved in the GA-Brassinosteroid Crosstalk for Hypocotyl Elongation 24
2.6. Jasmonate ZIM Domain and MYC2 Proteins Involved in the GA-Jasmonate Acid Crosstalk Under Certain Conditions 25
3. Transcriptional Regulation of Downstream Genes Via the Interaction of DELLA with Their Promoters (Direct Targeting Fun... 26
3.1. Backgrounds 26
3.2. ABA-Insensitive 3 and ABI5 Involved in GA-Abscisic Acid Crosstalk 28
3.3. Indeterminate Domain Proteins Involved in the Feedback Regulation of GA Signaling 28
3.4. Botrytis-Susceptible Interactor and Its Related Proteins Involved in the Transrepression Activity of DELLA 30
4. Other Functions of DELLA Besides Transcriptional Regulation 31
4.1. Prefoldin 3 and PFD5 Involved in Cortical Microtubule Arrangement 31
4.2. D14 Involved in GA-Strigolactone Crosstalk 32
5. Future Perspectives 33
References 34
Chapter Two: Phosphorylation Networks in the Abscisic Acid Signaling Pathway 42
1. Introduction 43
2. SnRK2: A Core Component in ABA Signaling 45
2.1. Upstream Regulation of SnRK2 Activation 46
2.2. Diverse SnRK2 Substrates 47
2.3. CDPK Interacts with the SnRK2 Pathway 49
3. MAPK Cascades in ABA Signaling 50
3.1. MAPK Activation for Antioxidant Defense in ABA Signaling 53
3.2. MAPK Regulation in ABA-Mediated Seedling Development 54
3.3. Function of ABA-Inducible MAPKs 55
3.4. Regulation of MAPK Signaling in Guard Cells 56
4. Phosphoproteomic Approach to the Phosphorylation Network in ABA Signaling 57
4.1. Comparative Phosphoproteomics Using SnRK2 Mutants 59
4.2. Motif Analysis to Narrow Down SnRK2 Substrates 59
4.3. Prediction of the SnRK2-Dependent Protein Phosphorylation Network 60
5. Future Perspectives 61
Acknowledgments 62
References 62
Chapter Three: Action of Strigolactones in Plants 72
1. Introduction 73
2. Biosynthesis and Distribution of Strigolactones 73
2.1. Biosynthesis of SLs 73
2.2. Transport of SLs 75
3. The Strigolactone Signaling Pathway 75
3.1. The Leu-Rich Repeat F-Box Protein 75
3.2. The a/ß-Fold Hydrolase 78
3.3. The Clp Protease Family Protein 80
3.4. Other Proteins Involved in SL Signaling 82
3.5. Downstream Responses of SL Signaling in Shoot Branching 83
3.5.1. The SL-Mediated Transcription Response 83
3.5.2. SL-Regulated Auxin Polar Transport 84
3.6. Similarities and Differences of Signaling Pathways Between SLs and Other Plant Hormone 86
3.6.1. Ubiquitin Proteasome Systems of Plant Hormones 86
3.6.2. TPL/TPR Corepressors 90
4. Effect of Strigolactones on Plant Adaption to Environments 91
4.1. SLs Act as Communication Molecules in Plant Development 91
4.2. Cross talk Between SLs and Other Plant Hormones 93
References 94
Chapter Four: Peptide Ligands in Plants 100
1. Introduction 101
2. Clavata3/Embryo surrounding region 102
2.1. CLV3 102
2.2. TDIF 105
2.3. CLE40 105
2.4. CLE45 105
2.5. Other CLE Peptides 106
2.6. CLE Peptides in Other Species 106
3. Systemin 106
4. Hydroxyproline-Rich SlSys 107
5. Plant Elicitor Peptide 108
6. Phytosulfokine 108
7. Plant Peptide Containing Sulfated Tyrosine 1 109
8. Root Meristem Growth Factor 109
9. Inflorescence deficient in abscission 110
10. C-Terminally Encoded Peptide 111
11. Epidermal patterning factor/EPF Like 111
12. Lure 113
13. S-Locus Cysteine-Rich Protein/S-Locus Protein 11 114
14. Rapid Alkalinization Factor 115
15. Xylogen 116
16. Tapetum determinant1 116
17. Conclusions 117
References 118
Chapter Five: Florigen Signaling 128
1. Introduction 129
2. Identification of Florigen 131
3. Structure of the FT Protein 132
4. FT-Interacting Factors 134
5. Florigen Activation Complex 135
6. Molecular Mechanisms of FAC Formation: 14-3-3 as a Florigen Receptor 138
7. Gene Networks Downstream of Florigen 139
7.1. Direct Targets for FAC 139
7.2. Downstream Genes Identified in Transcriptome Analyses 140
8. Pleiotropic Functions of the FT Family 140
9. Molecular Function of the FT Protein 143
10. Intercellular Transport of FT 144
11. Photoperiodic Regulation of Florigen Gene Expression 145
11.1. Arabidopsis 146
11.2. Rice 149
12. Natural Variation in Flowering Time Genes 150
13. Conclusions 151
Acknowledgments 152
References 152
Chapter Six: Signaling Pathway that Controls Plant Cytokinesis 160
1. Introduction 161
2. The NACK-PQR Pathway: A MAP Kinase Cascade that Positively Regulates Plant Cytokinesis 165
2.1. A MAP Kinase Cascade Involved in Plant Cytokinesis 165
2.2. NPK1 MAPKKK and NACK1 Kinesin 165
2.3. Components in the MAPK Cascade Downstream of NPK1 168
3. Functions of Cytokinetic Kinesin NACK Are Dually Regulated by CDKs 169
3.1. Amplification of M-Phase-Specific NACK1 Transcription by CDKs 170
3.2. Repression of NACK1 Functions by CDKs During the Early M Phase 172
4. Effectors Controlled by the NACK-PQR Pathway 173
5. Future Prospects 174
Acknowledgments 175
References 175
Chapter Seven: Cryptochrome-Mediated Light Responses in Plants 182
1. Introduction 183
2. Physiological Responses Mediated by Plant Cryptochromes 185
2.1. Blue Light-Stimulated Photomorphogenesis 185
2.2. Photoperiodic Control of Flowering Time 187
2.3. Cryptochromes and Clock: Light Entrainment and Temperature Compensation 189
2.4. Light-Controlled Stomatal Opening and Development 191
2.5. The Functions of Cryptochrome in Other Plants 193
3. Perspectives 196
Acknowledgments 197
References 197
Chapter Eight: Multiple Roles of the Plasma Membrane H+-ATPase and Its Regulation 206
1. Introduction 207
2. H+-ATPase and Stomatal Movements 207
2.1. H+-ATPase Is a Key Enzyme in the Blue-Light-Induced Stomatal Opening Process 207
2.1.1. Blue-Light-Induced Stomatal Opening 207
2.1.2. Mechanism of Blue-Light-Induced Activation of the H+-ATPase 209
2.1.3. H+-ATPase Is the Limiting Factor of Light-Induced Stomatal Opening 210
2.2. H+-ATPase Is Involved in ABA-Induced Stomatal Closure 212
2.3. Other Factors Regulating the H+-ATPase in Guard Cells 213
2.3.1. Flowering Locus T 213
2.3.2. RPM1-Interacting Protein 4 213
3. H+-ATPase and Hypocotyl Elongation 214
4. Evolution of the H+-ATPase 216
5. Concluding Remarks 218
Acknowledgments 219
References 219
Chapter Nine: Structure and Function of the ZTL/FKF1/LKP2 Group Proteins in Arabidopsis 228
1. Introduction 228
2. The Circadian Clock Regulation by ZTL 229
3. Photoperiodic Flowering Regulation by FKF1 234
4. General LOV Chemistry 236
5. LOV Domain Photocycle 238
6. ZTL Group Protein Structure and Function 242
7. Perspectives 248
Acknowledgments 249
References 249
Author Index 256
Subject Index 292
Color Plate 300
Phosphorylation Networks in the Abscisic Acid Signaling Pathway
Taishi Umezawa*; Fuminori Takahashi†; Kazuo Shinozaki†,1 * Faculty of Agriculture, Tokyo University of Agriculture and Technology, Tokyo, Japan
† RIKEN Center for Sustainable Resource Science, Tsukuba, Japan
1 Corresponding author: email address: kazuo.shinozaki@riken.jp
Abstract
Abscisic acid (ABA) is one of the major phytohormones and regulates various processes in the plant life cycle, for example, seed development and abiotic/biotic stress responses. Recent studies have made significant progress in elucidating ABA signaling and established a simple ABA signaling model consisting of three core components: PYR/PYL/RCAR receptors, 2C-type protein phosphatases, and SnRK2 protein kinases. This model highlights the importance of protein phosphorylation mediated by SnRK2, but the downstream substrates of SnRK2 remain to be determined to complete the model. Previous studies have identified several SnRK2 substrates involving transcription factors and ion channels. Recently, SnRK2 substrates have been further surveyed by a phosphoproteomic approach, giving new insights on the SnRK2 downstream pathway. Other protein kinases, e.g., Ca2 +-dependent protein kinase (CDPK) and mitogen-activated protein kinase (MAPK), have been identified as ABA signaling factors. Some evidence suggests that the SnRK2 pathway partially interacts with CDPK or MAPK pathways. In this chapter, recent advances in ABA signaling study are summarized, primarily focusing on two major protein kinases, SnRK2 and MAPK. Challenges for further study of the ABA-dependent protein phosphorylation network are also discussed.
Keywords
Abscisic acid
Protein phosphorylation
Protein kinase
Phosphoproteomics
Signal transduction
1 Introduction
In the 1960s, abscisic acid (ABA) was discovered as one of the phytohormones [1]. Although ABA had been originally isolated as a growth-inhibiting substance, it was subsequently determined a phytohormone with widespread roles in various processes in the plant life cycle (Fig. 2.1). For example, ABA is essential for seed dormancy, maturation, germination, and postgermination growth [2]. Another important role of ABA is to induce stress responses in plants. ABA is necessary for drought tolerance in plants, because it regulates stomatal movement to prevent water loss and triggers gene expression, leading to cellular adaptation to low water potential [2–4]. Because such ABA responses are strictly regulated by cellular signal transduction systems, it is important to understand what is ABA signaling and how it is regulated in plant cells.
Initially, the study of ABA signaling was advanced by genetic screening of Arabidopsis mutants showing altered ABA response [2]. For example, a series of ABA-insensitive (ABI) mutants were isolated in the 1990s. Interestingly, the abi1-1 and abi2-1 mutants defected multiple ABA responses from seeds to adult plants, and ABI1 and ABI2 encode closely related 2C-type protein phosphatases (PP2Cs) [5–8]. Since these discoveries, the importance of protein phosphorylation in ABA signaling has been widely accepted.
Recently, ABA signaling pathways are clearly identified and a core signaling model has emerged (Fig. 2.2). In a current model, three core components, PYR/PYL/RCAR, PP2C, and SNF1-related protein kinase 2 (SnRK2), compose the central module of ABA signaling [2,4,9–11]. The three components coordinate ABA signal output by regulating SnRK2 activity to induce cellular responses to ABA. It is believed that active SnRK2 can phosphorylate various substrates comprising a major protein phosphorylation network in ABA signaling.
Although SnRK2 must be a major regulator in ABA signaling, some evidence suggests that other protein kinases, such as Ca2 +-dependent protein kinase (CDPK) and mitogen-activated protein kinase (MAPK), are also involved in ABA responses [12,13]. MAPK cascades are key signaling components in cellular responses to internal and external stimuli. A number of MAPK cascade components were isolated from various plants. In addition, a recent study has suggested that some MAPK cascades are regulated by the SnRK2 pathway in ABA signaling [14]. Each protein kinase is expected to be differentially activated to regulate its own protein phosphorylation cascade; therefore, it is important to understand how multiple protein kinases generate protein phosphorylation networks in ABA signaling.
In general, to elucidate a signal transduction pathway involving protein kinases/phosphatases, it is necessary to characterize their upstream and downstream regulation. In the case of ABA signaling, a key protein kinase is SnRK2 and its upstream regulation has been mostly determined. The next question is to identify the downstream factors of SnRK2—its substrates—and the signal crosstalk of SnRK2 with other phosphorylation networks [11,15]. Although it is difficult to identify protein kinase substrates, progress has been made recently by a technical breakthrough in phosphoproteomics [14,16]. In this chapter, we review recent advances in ABA signaling studies, focusing primarily on the SnRK2 and MAPK protein phosphorylation networks.
2 SnRK2: A Core Component in ABA Signaling
The SnRK superfamily consists of three groups: SnRK1, SnRK2, and SnRK3 [17]. Each SnRK group has a well-conserved kinase domain similar to those of yeast sucrose nonfermenting 1 (SNF1) or mammalian AMPK (AMP-activated protein kinase). SnRK1 shows high similarity to SNF1 and AMPK and is believed to be a functional ortholog of SNF1 or AMPK [18]. However, SnRK2 and SnRK3 are likely to be different from SnRK1, considering both retain some specific C-terminal regions. In SnRK2, the C-terminal region contains a stretch of acidic residues, called the “acidic patch.” There is evidence that the C-terminal region plays an essential role in SnRK2 activation [19,20]. SnRK3 is quite different from other SnRKs, being regulated by Ca2 +-binding proteins, calcineurin B-like (CBL)/SCaBP. The C-terminal stretch of SnRK3 consists of regulatory domains functioning in autoinhibition [21,22]. These three SnRK families are well conserved in higher plants. For more details of the SnRK superfamily, refer to reviews [4,17,18,21,22].
Among SnRK superfamily proteins, SnRK2 plays a major part in ABA signaling. As stated above, the SnRK2 family is a plant-specific and well-conserved protein kinase family [4,17]. In the 1990s, an SnRK2 gene, PKABA1, was cloned from an ABA-treated wheat embryo cDNA library [23], and another SnRK2 gene, AAPK, was isolated from fava bean as an ABA-activated protein kinase in guard cells [24]. In both cases, further studies revealed that PKABA1 and AAPK are functional in ABA signaling, using a transient expression system in barley aleurone layers or guard cell protoplasts, respectively [25,26].
There are 10 members of SnRK2 in the Arabidopsis and rice genomes. Arabidopsis SnRK2s are designated as SRK2A–J and SnRK2.1–2.10 [17,27], and rice SnRK2s are designated as SAPK1–10 [20]. They are classified into three subclasses I, II, and III, and each subclass shows a different pattern of activation [20,28]. All SnRK2s are activated by osmotic stress, suggesting that SnRK2s play some role in osmotic stress signaling. Subclass III SnRK2s are strongly activated by ABA and are believed to be major ABA-activated protein kinases in plants. Subclass II SnRK2s are also activated by ABA, but their kinase activity is weaker than those of subclass III [20,28].
Physiological functions of SnRK2 in ABA signaling have been intensively investigated primarily in Arabidopsis. In Arabidopsis, subclass III contains three members, SRK2E, SRK2D, and SRK2I. These names may be confusing, considering SRK2E is also known as OPEN STOMATA 1 (OST1) or SnRK2.6 [17,27,29], and SRK2D and SRK2I are alternatively designated as SnRK2.2 and SnRK2.3, respectively [17]. In this review, they are abbreviated as SRK2E/OST1, SRK2D/SnRK2.2, and SRK2I/SnRK2.3, respectively. First, SRK2E/OST1 was identified as an ABA-activated protein kinase acting in guard cells...
| Erscheint lt. Verlag | 9.9.2014 |
|---|---|
| Sprache | englisch |
| Themenwelt | Naturwissenschaften ► Biologie ► Biochemie |
| Naturwissenschaften ► Biologie ► Botanik | |
| Naturwissenschaften ► Biologie ► Genetik / Molekularbiologie | |
| Naturwissenschaften ► Biologie ► Zellbiologie | |
| Technik | |
| ISBN-10 | 0-12-802015-6 / 0128020156 |
| ISBN-13 | 978-0-12-802015-9 / 9780128020159 |
| Haben Sie eine Frage zum Produkt? |
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