MIPs and Their Roles in the Exchange of Metalloids (eBook)

Thomas P. Jahn is an Associate Professor and group leader at the Department of Agriculture and Ecology, Faculty of Life Sciences, University of Copenhagen. He studied biology at the University of Bonn, Germany. From early on in his scientific career he was interested in transport processes in plants and the molecular mechanisms behind these processes. More recently his group contributed to the field of aquaporin research culminating in the identification of several new substrates for members of this superfamily of channel proteins. The overall scope of his current research focuses on the elucidation of networks comprising molecular components engaged in the responses to nutritional stresses, including elements of transport, assimilation, storage and stress signaling. Gerd P. Bienert is currently a Marie Curie Fellow at the Institute of Life Science at the Université Catholique de Louvain in Louvain la Neuve, Belgium. His work focuses on the molecular characterisation of the intracellular trafficking and hetero‑oligomerisation of aquaporins in plants. In 2008, he received his PhD in Molecular Plant Nutrition from the University of Copenhagen, Denmark. During his PhD, Gerd Patrick Bienert made significant advances in the scientific understanding on the substrate selectivity of plant aquaporins for uncharged solutes. The work resulted in the molecular identification of the first arsenite, antimonite and hydrogen peroxide channels in plants. Gerd P. Bienert studied biology at the Julius‑Maximilians‑University Würzburg and at the Technical University Darmstadt, Germany. During his education he emphasized molecular plant physiology and biophysics, genetics and biotechnology. His main research interests focus on the molecular transmembrane transport processes involved in the uptake, translocation and extrusion of compounds that are relevant for plant physiology. In addition, intracellular regulation and trafficking of the transport proteins themselves are also contemplated. In his home region, Tauber‑Franken, he began to develop his enthusiastic curiosity for biology by exploring and studying nature. He became fascinated by insects, especially the members of the order of hymenoptera to which he still devotes his free‑time. The existing overlap between entomology and botany has aroused his interest in understanding the physiology of plants.

Title Page 3
Copyright Page 4
PREFACE 5
ABOUT THE EDITORS... 7
ABOUT THE EDITORS... 8
PARTICIPANTS 9
Table of Contents 11
Chapter 1 Aquaporins: A Family of Highly Regulated Multifunctional Channels 15
Introduction—The Discovery of Aquaporins 15
Topology of Aquaporins 17
Selectivity of Aquaporins 17
Measurement of Aquaporin Activity and Water Movement 18
Cell Swelling Assays 18
Stopped-Flow Spectrophotometry 19
Cell Pressure Probe Measurements 19
Proton NMR 20
Aquaporin Inhibition 20
Phenotype Analysis Reveals Involvement of Aquaporins in Key Physiological Processes 20
Aquaporin Regulation: Gating and Localization 21
Phosphorylation 22
pH and Divalent Cations 23
Hetero-Oligomerization 24
Modification of the Subcellular Localization 24
Conclusion 25
References 25
Chapter 2 Phylogeny of Major Intrinsic Proteins 33
Introduction 33
A Historical Account of the MIP Phylogeny 33
Plant MIPs 35
Phylogenetic Analysis of NIPs 38
Solute Transport 40
NIP-Like Bacterial MIPs and Ancestral State of ar/R Filter 40
Conclusion 41
References 41
Chapter 3 Metalloids, Soil Chemistry and the Environment 47
Introduction 47
Historical Perspective 48
Environmental Relevance 49
Environmental Toxicity of Metalloids 49
Factors Controlling Bioavailability 50
Solid: Solution Partitioning of Metalloids 50
Speciation of Metalloids in the Environment 51
Assessing Soil Bioavailability of Metalloids 54
Conclusion 55
References 56
Chapter 4 Arsenic Transport in Prokaryotes and Eukaryotic Microbes 60
Introduction 60
Metalloid Transport in Prokaryotes 60
Metalloid Transport in Eukaryotic Microbes 64
Metalloid Uptake in Yeast 64
Metalloid Efflux in Yeast 64
Metalloid Transport in Parasites 65
Conclusion 66
References 66
Chapter 5 Metalloid Transport by Aquaglyceroporins: Consequences in the Treatment of Human Diseases 70
Introduction 70
Metalloids and Cancer 72
Uptake of Metalloids via Human Aquaglyceroporins 72
Metalloids in Protozoan Parasitic Infections 73
Parasite Aquaglyceroporins Facilitate Metalloid Transport 74
Therapeutic Modulation of AQP Permeability 76
Conclusion 79
References 79
Chapter 6 Roles of Vertebrate Aquaglyceroporins in Arsenic Transport and Detoxification 84
Introduction 84
Expression of Vertebrate Aquaglyceroporins 84
Arsenic Is Both an Environmental Toxin and Human Carcinogen 86
Uptake of Organic and Inorganic Arsenic via Aquaglyceroporins 87
Molecular Mechanisms for Arsenic Translocation by Aquaglyceroporins 90
Arsenic Toxicity in Relation of Aquaglyceroporins Regulation 91
Perspectives 92
Conclusion 92
References 92
Chapter 7 Molecular Mechanisms of Boron Transport in Plants: Involvement of Arabidopsis NIP5 1 and NIP61
Essentiality of Boron in Plants 96
Rhamnogalacturonan-II Binds Boron 97
Involvement of Rhamnogalacturonan-II in B Function 98
Roles of B Other Than Binding to RG-II 99
Physiological Analysis of B Transport 99
Passive Diffusion 99
Channel-Mediated B Transport 100
“Active” B Transport against Concentration Gradients 100
Molecular Mechanisms of B Transport 101
BOR1, a Transport Protein Responsible for Xylem Loading 101
B-Deficiency Sensitive Mutant of Arabidopsis thaliana, bor1-1 101
B Transport Properties of bor1-1 101
BOR1 is an Efflux Transporter of Boron 101
BOR1 Degradation via Endocytosis in Response to High B Supply 102
BOR1 Paralogs in A. thaliana 103
A. thaliana NIP5 1, a Channel for Boric Acid Mediates B Uptake under B Limitation103
Complementary Roles of BOR1 and NIP5 1 in Efficient B Transport under BLimitation104
NIP6 1, a Channel for Boric Acid Responsible for B Distribution to Leaves under B Limitation104
Improvement of Plant Growth Property through BOR and NIP Transporters 105
Low B Tolerant Plants 105
High B Tolerant Plants Can Be Generated through Overexpression of BOR4 105
Growth Improvement by Enhanced Expression of NIP5 1
References 106
Chapter 8 Silicon Transporters in Higher Plants 111
Introduction 111
Silicon Transporters 112
Influx Si Transporters 112
Influx Si Transporter (OsLsi1) in Rice 112
Isolation of Rice Si Transporter (OsLsi1) 112
Expression Pattern of OsLsi1 112
Cellular and Subcellular Localization of OsLsi1 113
Characteristics of Rice Si Transporter 113
Influx Si Transporters in Barley and Maize 115
Efflux Transporter of Silicon 115
Efflux Si Transporters in Rice 115
Isolation of Rice Efflux Si Transporter (OsLsi2) 115
Expression Pattern of OsLsi2 115
Localization of Rice Si Efflux Transporter OsLsi2 115
Characteristics of Rice Si Efflux Transporter OsLsi2 115
Efflux Transporters in Barley and Maize 116
Difference in Si Uptake System between Paddy and Field Crops 116
Silicon Transporters for Xylem Unloading 118
Conclusion 118
References 120
Chapter 9 Major Intrinsic Proteins and Arsenic Transport in Plants: New Players and Their Potential Role 123
Introduction 123
The Challenge of As Speciation in Plants 125
Transport of As in Plants 126
As(V) Uptake 126
As(III) Transport Via NIPs—Gateway for Good and Bad 126
Genetic Evidence 127
Uptake and Distribution of As in Rice and the Consequences for the Food Chain 128
Rice NIP2 1 Mediates the Uptake of Methylated As Species129
Transport of Conjugated As Species in Plants 131
What Do the Different “Omics” Tell Us About NIP-Mediated As Transmembrane Transport? 131
The Physiological Role of NIPs 132
Do MIPs Play a Physiological Role in the Translocation of Toxic Compounds Such as As(III)? 132
Regulating Bi-Directional Flux Through MIPs 133
Plant NIPs Transport Trivalent Antimony 134
Conclusion 134
References 135
Chapter 10 Major Intrinsic Proteins in Biomimetic Membranes 139
Introduction 139
Biomimetic Membranes 140
Sensor Applications 141
Separation Applications 142
MIP Biomimetic Membranes and Osmotic Processes 142
MIP Basic Properties 142
Considerations Regarding Permeability 143
Osmotic Processes 146
Polarization Effects 148
Conclusion 148
References 150
Index 155