Ion Channels and Plant Stress Responses (eBook)

Preface 6
Contents 7
Ion Channels and Plant Stress: Past, Present, and Future 9
Introduction 10
Plasma Membrane K+ Channels in Guard Cells 12
Characterization of K+ Channel and Transporter cDNAs 13
Critical Roles of Plasma Membrane Anion Channels in Plant Stress Responses 14
Roles of Anion Channels in Stress Responses and Identification of Anion Channel Gene Families 15
Ca2+ Channels and Intracellular Ca2+ Elevations 16
Gene Candidates for Plasma Membrane Ca2+ Channels 17
Properties of Vacuolar Cation Channels 18
Sodium Transport Systems in Plants 18
Future Prospects 21
References 22
The Role of Ion Channels in Plant Salt Tolerance 31
Introduction 32
The Role of Ion Channels in Na+ Uptake: A Simple Model 33
Electrochemical Gradients and Fluxes 33
Fundamental Characteristics of Different Channel Types 35
Contribution of Different Channel Types to Na+ Uptake 37
The Role of Ion-Channels in Salt Tolerance: Experimental Evidence 43
Ion Channels and Salt Tolerance in Crops 43
Ion Channels and Salt Tolerance in Arabidopsis thaliana 44
Ion Channels and Salt Tolerancesalt tolerance in Halophytic Higher Plants 45
Ion Channels and Salt Tolerance in Charophytescharophytes 47
Summary and Conclusions 50
References 50
Cation Channels and the Uptake of Radiocaesium by Plants 55
Background 56
Historical Studies 57
Caesium Transport Proteins in Root Cells 58
Molecular Mechanisms for Cs Uptake by Roots of Non-Mycorrhizal Plants 63
K-Replete Plants 63
K-Starved Plants 65
Differences between Plant Species 66
Molecular Mechanisms for Cs Uptake by Roots of Mycorrhizal Plants 67
Prospects for the Generation of Safer Crops 68
References 69
Ion Channels in Plant Development 76
Ion Channels in Plant Development 77
Molecular Identification of K+- and Anion Channels in Plant Development 77
Molecular Identification of Mechanosensitive Channels 78
Glutamate Receptor-Like Channels and Cyclic-Nucleotide Gated Channels 79
Ion Channels Acting in Concert 82
Ion Channels in Root Hair Development 82
Ion Channels in Pollen Tube Growth 84
Ion Channels in Algal Development 86
Ion Channels in Nodule Development 86
Conclusions 87
References 88
Potassium and Potassium-Permeable Channels in Plant Salt Tolerance 94
Introduction 95
Salinity as an Issue 95
Physiological Constraints Imposed by Salinity 96
Potassium Homeostasis in Plants 96
Potassium Essentiality and Functions in Plants 96
Tissue- and Organelle-Specific Potassium Compartmentation 97
Major Potassium Transport Systems: A Brief Overview 98
Potassium and Potassium-Permeable Channels 98
Regulation of K+ Channel Activity Under Saline Conditions 99
K+ Channels and ``Osmotic´´ and ``Ionic´´ Components of Salt Stress 99
GORK and AKT Channels as Downstream Targets of Salinity Effects 101
Voltage Gating and the Role of H+-ATPases 102
Maintaining the Optimal Cytosolic K+/Na+ Ratio 102
Long-term Salinity Exposure and Regulation of K+ Transport 103
Tonoplast (Vacuolar) Channels 105
Properties of K+-Permeable Vacuolar Channels 105
Vacuolar Channels and Cytosolic K+ Homeostasis 106
Regulation of Vacuolar Channel Activity Under Saline Conditions 106
Chloroplasts and Mitochondria 108
Salinity and Photosynthesis 108
Photosynthetic Activity, Stromal pH, and Membrane Transport in Chloroplasts 108
Role of the Envelope K+(Na+)/H+ Antiport in Salt Tolerance 109
Mitochondrial Channels 109
Concluding Remarks and Future Prospects 110
References 111
Regulation of Ion Channels by the Calcium Signaling Network in Plant Cells 118
Introduction 118
CDPKs, Plant Calcium ``Sensor-Responders´´ that Regulate Ion Channels 120
Structural Diversity and Regulation of CDPK Superfamily 121
Functional Diversity of CDPKs and CCaMKs 122
Ion Channel Regulation by CDPKs 124
Calmodulins : Small Calcium Sensors that Target a Family of Ion Channels (CNGCs) 124
Plant Genomes Encode a Large Number of CaMs and CaM-Related Proteins 124
Calmodulin Targets a Large Array of Proteins Including Ion Channels 126
Regulation of Cyclic Nucleotide-Gated Channels by CaMs 128
The CBL-CIPK Network 129
Plant CBLs are Related to Calcineurin B but have Significantly Diverged into a Group of Proteins with New Functions 129
The CBL-Type Calcium Sensors Target a Family of Protein Kinases-a Shift-of-Paradigm from Calcineurin in Yeast and Anima 130
Physiological Pathways Involving CBL-CIPK Signaling Modules that Regulate Ion Channels and Transporters 132
Plant Calcium Signaling Network in Response to Abiotic Stresses 133
References 135
The Role of Cyclic Nucleotide-Gated Channels in Cation Nutrition and Abiotic Stress 143
Introduction 144
Molecular Characteristics of Plant CNGCs 146
Transport of Monovalent and Divalent Cations 146
Regulation by CN Monophosphates 149
Regulation by Calmodulin 150
CNGC Expression and Subcellular Localization 151
Tissue-Specific Expression Patterns 151
Responses to Abiotic Stress 153
Subcellular Localization 155
Physiological Roles in Plant Nutrition 156
Cation Uptake and Homeostasis 156
Ca2+ Signaling 158
Conclusions and Future Perspectives 159
References 160
The Function of Cyclic Nucleotide-Gated Channels in Biotic Stress 164
Introduction 165
CNGC Structure and Function8.2 CNGC structure and function 166
Ca2+ Signaling, CNGCs, and Pathogen Defense Responses8.3 Ca2+ signaling, CNGCs, and pathogen defense responses. 169
CaM and Ca2+ Signaling During Pathogen Defense Responses8.4 CaM and Ca2+ signaling during pathogen defense responses. 171
Activation of CNGCs During Immune Signaling Cascades8.5 Activation of CNGCs during immune signaling cascades. 173
Cyclic Nucleotide Generation and Its Role in Biotic Stress Responses8.6 Generation of cyclic nucleotides in plants. 173
Summary and Perspectives for the Future8.7 Summary and perspectives for the future. 175
ReferencesReferences 176
New Approaches to Study the Role of Ion Channels in Stress-Induced Signalling: Measuring Calcium Permeation in Plant Cells and 180
Introduction 181
Plant Cell Impalement 182
Aequorin 182
Fura-2 184
Green-Fluorescent-Protein-Based Calcium Indicators 185
Patch-Clamp 185
Whole-Cell Measurements 186
Fluorescence Combined with Excised Patch (FLEP) 186
New Prospects in Investigating Calcium Permeable Channels 189
Voltage-Clamp and TIRF 189
Voltage-Sensitive Dyes 190
Voltage-Clamp Fluorometry 190
Far-Field Fluorescence Nanoscopy 190
Conclusion 191
References 191
Vacuolar Ion Channels: Roles as Signalling Mechanisms and in Plant Nutrition 196
Introduction 197
The Role of Vacuoles in Plant Nutrition 197
Vacuoles and Signalling 198
The Role of Vacuoles in Detoxification 198
TonoplastTonoplast Membrane Transporters 199
The Slow Vacuolar Channel 201
The Vacuolar K+ Channel 203
The Fast Vacuolar Channel 206
Ligand-Gated Vacuolar Cation Channels 206
Vacuolar Anion Channels 208
Concluding Remarks 208
References 209
Reactive Oxygen Species, Oxidative Stress and Plant Ion Channels 212
Introduction 213
Synthesis of ROS and Free Radicals and Their Effect on Ion Channels 215
Oxygen and Radicals 215
Singlet Oxygen 216
Superoxide Radical 217
The Chemistry of Superoxide 217
Superoxide Generation during Stress Conditions 218
Superoxide and Ca2+ Channels Form a Stress Signalling ``Hub´´ in Plant Cells 220
Hydroxyl Radical 220
Hydrogen Peroxide 222
Transition Metals 223
Properties of Plant Ion Channels Regulated by ROS and Free Radicals 224
Physiological Properties and Involvement in Stress Responses 224
Transition Metal-Activated Cation Channels in Green Algae 225
Hydroxyl Radical-Activated Channels in Roots of Higher Plants 225
Hydrogen Peroxide-Activated Channels in Roots and Leaves 226
ROS-Activated NSCCs Could be Constitutive Hyperpolarisation-Activated Ca2+ Channels Involved in Stress Reactions 228
ROS-Activated K+ Efflux Channels and Their Role in Plant Stress Response 228
Molecular Properties 230
Concluding Remarks 231
References 231
Index 238