Root Hairs (eBook)

Prof. Anne Mie C. Emons Studied Biology (MSc 1969, cum laude) at the Radboud University of Nijmegen, the Netherlands, and after a family break completed her PhD at the same university in 1986. Postdoctoral studies at Wageningen University in 1987, and at the John Innes Centre, Norwich, UK, on an EMBO grant in 1988 in the department of Dr. Keith Roberts. From 1988 Assistant, Associate and later Full Professor at Wageningen University, laboratory of Plant Cell Biology and since 2002 Advisor Bio-organization FOM Institute AMOLF, Theory Biomolecular Matter group. Major research interests: Plant cell biology, cell polymers: actin filaments, microtubules and cellulose microfibrils, plant cell cyto-architecture, tip growth, legume root hair, rhizobium interaction Dr. Tijs Ketelaar Studied Plant Breeding (MSc 1996) at Wageningen University, the Netherlands, followed by a PhD at the Laboratory of Plant Cell Biology at Wageningen University in 2002. From 2001 to 2004 Postdoctoral research in the laboratory of Professor Patrick Hussey at the University of Durham, UK, followed by a VENI fellowship of the Dutch Science Foundation (NWO) at the Laboratory of Plant Cell Biology of Wageningen University (2004-2007). Since 2007 Assistant Professor at the same laboratory. Research interests: cytoskeleton, plant cell cyto-architecture, polar cell expansion, root hairs

Editors 6
Preface 7
Contents 9
Contributors 11
Genetics of Root Hair Formation 15
1 Introduction 15
2 Genetics of Root Hair Cell Specification 20
3 Genetics of Root Hair Initiation 24
4 Genetics of Root Hair Elongation 25
5 Environmental Regulation of Root Hair Development 30
6 Protocol: Rapid Preparation of Transverse Sections of Plant Roots 31
References 31
Intracellular Organization: A Prerequisite for Root Hair Elongation and Cell Wall Deposition 41
1 Introduction: The “Tip-Growth Unit” Concept 41
2 The Vacuole 43
3 The Nucleus Must Be at a Certain Distance from the Growing Root Hair Tip for Fast Tip Growth 44
4 The Subapical Cytoplasmic Dense Area 46
5 The Cytoskeleton 48
6 Plasma Membrane, Cellulose Synthase Complex, Cellulose Microfibril 50
7 Cell Wall Texture 51
7.1 Root Hair Cell Wall Texture 52
7.2 Comparison of Methods for Cell Wall Texture Evaluation 53
References 55
Auxin and Root Hair Morphogenesis 59
1 Root Hairs Provide an Auxin-Responsive In Planta Single Cell System 59
2 Auxin Signaling and Root Hair Development 64
3 Auxin Transport and Root Hair Development 68
4 Protein Phosphorylation, Auxin, and the Root Hair 70
5 Auxin and Polarity in Root Hair Morphogenesis 71
6 The Root Hair Cell System to Study Auxin Transport 72
7 Measurement of Root Hair Length 73
References 74
The Membrane Dynamics of Root Hair Morphogenesis 79
1 Introduction 79
2 The Secretory Pathway 80
3 Membrane Traffic 82
3.1 Five Steps in Vesicle Trafficking 82
3.2 Membrane Fusion 88
3.3 The Gating of Membrane Fusion 89
3.4 The Role of Calcium in Membrane Fusion 90
3.5 Fidelity, Speed, and Efficiency in Membrane Fusion 90
4 The Establishment and Maintenance of Polarity 90
4.1 An Intrinsic Positional Cue 91
4.2 Lipid Rafts 91
4.3 ROP Signaling 93
4.4 The Exocyst 94
4.5 The Maintenance of Polarity 94
5 Open Questions and Conclusions 96
References 96
Plant Cell Wall Biogenesis During Tip Growth in Root Hair Cells 99
1 Introduction: Plant Cell Walls and Tip Growth 99
2 Synthesis and Delivery of Cell Wall Components in Plants 102
3 Tip Growth: Cell Wall Deposition vs. Cell Wall Expansion 102
4 Cellulose Biosynthesis: Cellulose Synthases 103
5 Cellulose-Synthase-Like Proteins 104
6 Xyloglucan Synthesis and Remodeling 105
7 Pectins 107
8 Structural Cell Wall Proteins 108
9 Conclusions and Directions 110
10 Root Hair Immunolocalization Protocol 110
References 112
Modeling Tip Growth: Pushing Ahead 117
1 Introduction 117
2 The Delivery of the Vesicles 121
3 The Biomechanics of the Cell Wall 127
4 Outlook 131
References 133
Root Hair Electrophysiology 137
1 Introduction 137
2 In Situ Vacuolar Electrophysiology Using Root Hairs 138
2.1 Electrical Model of the Root Hair 139
2.2 Electrophysiological Measurements 142
2.3 Cable Properties and Electrical Coupling 143
2.4 Beyond Potential and Resistance 143
3 Ion Transport in Root Hairs 145
4 Ion Transport and Root Hair Morphogenesis 152
5 Concluding Remarks 153
References 153
Calcium in Root Hair Growth 159
1 Introduction 159
2 Calcium Gradients in Root Hair Development 160
3 Establishment of Tip-Focused Calcium Gradient 164
4 Ca 2+ -Dependent Regulation of Apical Growth 169
5 Conclusions and Perspectives 174
6 Methods: Ca 2+ Imaging in Root Hairs 175
References 178
Phospholipid Signaling in Root Hair Development 185
1 Introduction 185
2 Overview of Phospholipids as Site-Specific Signals 186
3 Phosphoinositide Signaling in Root Hair Development 191
4 Phosphatidic Acid Signaling in Root Hair Development 193
5 Other Lipid-Related Signals in Root Hair Development 194
6 A Hypothesis of the Signaling Network Sustaining Root Hair Tip Growth 195
7 Conclusion 197
References 197
ROP (Rho-Related Protein from Plants) GTPases for Spatial Control of Root Hair Morphogenesis 205
1 Introduction 205
2 The ROP GTPase Family 207
3 ROP Regulators: The Roles of GDIs, GAPs, and GEFs in the Regulation of Specific PM Domains 209
4 ROP Effectors: RICs (Actin and Calcium), PIP Kinase ( PLC and PLD), NADPH Oxidase ( ROS), and ICR1 – Exocyst 211
5 Speculative Model of ROP Function at the Growth Domain Selection and Bulge Formation 214
6 ROPs in Initiation and Maintenance of Root Hair Tip Growth 217
7 Conclusions 218
References 219
The Actin Cytoskeleton in Root Hairs: A Cell Elongation Device 225
1 Introduction 225
2 Actin Visualization in Root Hairs 226
2.1 Actin Visualization in Fixed Root Hairs 226
2.2 Actin Visualization in Live Cells 228
3 Actin Organization and Function in Root Hairs 229
4 Prospects 240
References 240
Microtubules in Plant Root Hairs and Their Role in Cell Polarity and Tip Growth 247
1 Methods to Visualize MTs in Root Hairs 247
2 MT Organization in Developing Root Hairs 248
3 MT Dynamics in Root Hairs 250
4 The Function of MTs in Elongating Root Hairs 251
5 MTs in Legume Root Hairs During Early Stages of Infection by Rhizobia 253
6 MTs and Their Putative Role in Targeting Polarity Markers to the Very Tip of Elongating Root Hairs 255
7 Remaining Questions and Future Work 256
References 258
Nod Factor Signal Transduction in the Rhizobium – Legume Symbiosis 263
1 Introduction 263
2 Legumes Can Establish a Rhizobial Symbiosis 264
3 Rhizobia and Nod Factors 265
4 Infection 266
5 Nod-Factor-Signaling Pathway 267
6 The Nod-Factor-Signaling Genes in the Epidermis 272
7 Epidermis to Inner Root Signaling 279
8 Concluding Remarks 282
References 283
Architecture of Infection Thread Networks in Nitrogen- Fixing Root Nodules 291
1 Introduction 291
2 Infection Thread Development in Root Hairs 293
2.1 Infection Thread Development in Cortical Tissue and Young Indeterminate Nodules 295
2.2 Lessons from Three-Dimensional Reconstructions of Infection Thread Networks 296
2.3 Two Questions Concerning the Development of Infection Threads in Indeterminate Nodules 299
3 Materials and Methods 303
4 Methods 304
References 305
Microbial Encounters of a Symbiotic Kind: Attaching to Roots and Other Surfaces 309
1 Introduction 310
2 Docking Components 313
2.1 Rhicadhesin 313
2.2 Flagella 314
2.3 Lectin-Mediated Attachment 315
3 Locking Components 316
3.1 Polysaccharides 316
3.2 Proteins 319
3.3 Additional Components Involved in Attachment 320
4 Concluding Remarks 321
5 Method: Growing Rhizobia in Microtiter Plate Wells 322
References 324
Root Hair Colonization by Mycorrhizal Fungi 329
1 A Short Overview of Mycorrhizas 330
1.1 Ectomycorrhizas 331
1.2 Endomycorrhizas 332
2 The Role of Root Hairs in Mycorrhizal Establishment 335
3 Root Anatomy, Root Hairs, and Mycorrhizas: The Baylis Hypothesis 337
4 Lessons from the Mutants 339
5 The Input of Confocal Microscopy and In Vivo Imaging 342
6 Conclusions 345
Appendix: How to Study the Interactions Between Root Hairs and Arbuscular Mycorrhizal Fungi: Technical Aspects 346
Morphological and Quantitative Analysis on Fixed Material Mycorrhizal Synthesis 346
Mycorrhizal Intensity Evaluation 346
Morphological Observation 347
Cytochemical Localization of Polysaccharides (Thiéry et al. 1967) 347
In Vivo Analysis In Vivo Microscopic Observation of Mycorrhizal Infection 347
References 348
Index 353