Rhizobiology: Molecular Physiology of Plant Roots

Preface
Contents
Root Apex Cognition: From Neuronal Molecules to Root-Fungal Networks
	1 Introduction
	2 Root Apex Transition Zone: Oscillatory Brain-Like Cognitive Organ in Soil Exploration
	3 Neuronal Molecules Relevant for Root Apex Cognitive Navigation and Soil Exploration
	4 Synaptic Principles Relevant for Root Apex Cognitive Navigation
	5 Transition Zone Energides in the Driver’s Seat to Control Root Apex Navigation
	6 Changing Metaphor for Transition Zone Energide: From ‘Bug in Cage’ to ‘Spider in Web’
	7 Evolution of the Root Apex Brain: From Ancient Roots Towards Complex Root Systems
	8 Root-Fungal Networks Control Underground Supracellular Life
	9 Conclusions and Gaian Outlook
	References
Root Architectural Plasticity in Changing Nutrient Availability
	1 Introduction
	2 RSA and Nitrogen Mediated Root Remodeling
	3 Root System Architecture in Response to Phosphate (Pi)
		3.1 Primary Root Growth Under Pi Deficiency
		3.2 Lateral Root Growth in Pi Deficiency
		3.3 Role of Root Hairs in Pi Deficiency
	4 Conclusion and Future Perspective
	References
Molecular Physiology of Nitrate Sensing by Roots
	1 NUE and Roots for a Second Green Revolution
	2 Root Morphology: Maize Root Versus Arabidopsis Root
	3 Main Molecular Actors for Nitrate Sensing in Arabidopsis Root
	4 Regulation of Root Development by Nitrate Availability: Maize Versus Arabidopsis
	5 Maize Transition Zone and Nitrate Sensing
	References
Role of Arbuscular Mycorrhizal Fungi in Root Development with a New Dimension in the Root Web Network
	1 Introduction
	2 Improved Nutrient Uptake
	3 Promotes Growth
	4 Improves Photosynthetic Efficiency
	5 Alters the Level of Phytohormone
	6 Provides Resistance from Abiotic Stress
		6.1 Salinity
	7 Drought Stress
	8 Metals
	9 Temperature Stress
	10 Provides Resistance from Biotic Stress
	11 Arbuscular Mycorrhizal Fungi (AMF) as (Agro) Ecosystem Engineers
	12 Relationship Between Strigolactone and AM Fungi
	13 Conclusions
	References
Ally or Foe: Role of Soil Microbiota in Shaping Root Architecture
	1 Introduction
	2 Different Microorganisms that Modulate Root Architecture
		2.1 Bacteria as Modulators
		2.2 Fungi as Modulators
		2.3 Nematodes as Modulators
		2.4 Insects as Modulators
		2.5 Parasitic Plants as Modulators
		2.6 Viruses as Modulators
	3 Different Levels of Modulation of Root Architecture
		3.1 Anatomical and Structural Changes
		3.2 Physiological Changes
		3.3 Hormonal Changes
		3.4 Molecular Changes
	4 Evolutionary Pressure between the Plant and Rhizobiome
	5 Strategies to Improve Plant Health by Manipulating Microbiome
	6 Conclusion
	References
miRNA Mediated Signaling Involved in Arabidopsis thaliana Root Development
	1 Introduction
	2 Role of miRNAs in Primary Root Development
	3 miRNA Mediated Regulation of Lateral Root Development
	4 Role of miRNA in Adventitious Root Development
	5 Conclusion and Future Perspectives
	References
Rooting the Right Way: Role of Glucose Signaling in Regulating Root Development in Plants
	1 Introduction
	2 Role of HXK1 Dependent Pathway in Regulating Root Development
	3 Role of RGS1 Mediated Heterotrimeric G-protein Signalling (HXK1-Independent) in Regulating Root Development
	4 Role of Glucose Mediated TOR-SnRK1 Energy Signalling in Regulating Root Development
	5 Crosstalk Between Glucose and Phytohormones in Regulating Root Development
	6 Conclusions
	References
Plant Hormonal Crosstalk: A Nexus of Root Development
	1 Introduction
	2 Auxin and Its Crosstalk in Root Development
	3 Gibberellins and Their Crosstalk in Root Development
	4 Strigolactones and Their Crosstalk in Root Development
	5 Brassinosteroids and Their Crosstalk in Root Development
	6 Conclusion
	References
Dynamic Pool of Nitric Oxide (NO) in Rhizosphere Modulates Root Architecture, Nutrient Acquisition and Stress Tolerance in Plants
	1 Introduction
	2 Sources of NO Generation and Its Distribution in the Rhizosphere
	3 Rhizosphere Composition Regulates Apoplastic and Symplastic NO Production in Roots
	4 Rhizospheric Organic Matter Elevates NO Biosynthesis and Subsequent Upregulation of Plant Growth Hormones
	5 Rhizospheric NO Regulates Nitrate Assimilation and Root Architecture in Plants
	6 Nitric Oxide Mediated Abiotic Stress Tolerance in Plants is Partially Regulated by Rhizospheric Interactions
	7 Rhizobacteria Mediated NO Formation in the Rhizosphere Regulates Abiotic Stress Tolerance in Plants
	8 Future Perspectives: Rhizospheric NO Regulates Symbiotic Associations with Plant Roots
	References
Role of Nitric Oxide as a Double Edged Sword in Root Growth and Development
	1 Introduction
	2 Chemical Nature of Nitric Oxide
	3 Different Routes of NO Synthesis
	4 Ways and Means to Study NO in Plants
	5 Where is NO Produced in a Plant Cell
	6 Role of NO in Root Growth and Development
	7 Role of NO in Adventitious Rooting
	8 Role of NO in Lateral Root Formation
	9 Role of NO in Root Hair Development
	10 Role of NO During Different Stages of the Legume Rhizobium Interaction
	11 Role of NO in Protecting Plant Roots from Stress
	12 Crosstalk Between NO and Other Plant Hormones in Terms of Root Growth and Development
	13 NO a Double Edged Secondary Sword
	14 Conclusion
	References
Interaction of Cytokinin and Ethylene in the Regulation of Primary Root Growth and Development
	1 Introduction
	2 Signal Transduction by Cytokinin, Ethylene, and Auxin
		2.1 Cytokinin Signaling
		2.2 Ethylene Signaling
		2.3 Auxin Signaling
	3 Mechanisms for Crosstalk Between Cytokinin and Ethylene
		3.1 Transcriptional Cross-Talk
		3.2 Induction of Ethylene Biosynthesis by Cytokinin
		3.3 Signaling by Ethylene Through the Multi-step Phosphorelay
	4 The Arabidopsis Root System
	5 Auxin-Dependent Mechanisms by Which Cytokinin and Ethylene Regulate Cell Proliferation in the Primary Root
		5.1 Auxin-Dependent Mechanisms by Which Cytokinin Regulates Cell Proliferation in the Primary Root
		5.2 Auxin-Dependent Mechanisms by Which Ethylene Regulates Cell Proliferation in the Primary Root
	6 Regulation of the Cell Cycle by Cytokinin and Ethylene
		6.1 Regulation of the Cell Cycle by Cytokinin
		6.2 Regulation of the Cell Cycle by Ethylene
	7 Auxin-Dependent Mechanisms by Which Cytokinin and Ethylene Regulate Cell Expansion in the Primary Root
		7.1 Auxin-Dependent Mechanisms by Which Ethylene Regulates Cell Expansion in the Primary Root
		7.2 Auxin-Dependent Mechanisms by Which Cytokinin Regulates Cell Expansion in the Primary Root
	8 Ethylene and Cytokinin Regulate Cell Division in the QC
	9 Conclusion
	References
Role of Brassinosteroids in Root Growth and Development
	1 Introduction
	2 Brassinosteroids
	3 Biosynthesis of Brassinolide
	4 Brassinosteroid Signaling Pathway
	5 Physiological Roles of Brassinosteroid
		5.1 Maintenance of Meristem Size in Roots
		5.2 Growth of Root by Cell Elongation
		5.3 Root Hair Formation
		5.4 Initiation of Lateral Roots
		5.5 Gravitotropic Responses Shown by Roots
		5.6 Nodulation and Mycorrhiza Formation
	6 Crosstalk of BRs with Other Phytohormones Operating During Root Development
	7 Conclusions
	References
Precise Role of Strigolactones and Its Crosstalk Mechanisms in Root Development
	1 Introduction
	2 Structure, Diversity and Biosynthesis of Strigolactones
	3 Spatial Expression Analysis of SL Biosynthesis Genes in Roots
	4 Strigolactones and Root Development
		4.1 Strigolactones and Primary Root Development
		4.2 Strigolactones and Lateral Root Development
		4.3 Strigolactones and Adventitious Root Formation
		4.4 Strigolactones and Root Hair Elongation
	5 Conclusion
	References
Crosstalk of Jasmonates with Phytohormones Accompanying Root Growth, Development and Microbe-Interaction
	1 Introduction
	2 Jasmonates
	3 Biosynthesis of Jasmonates
	4 Biosignalling of Jasmonates
	5 Role of Jasmonates in Root Growth and Development
		5.1 Gravitotropism Response
		5.2 Inhibition of Primary Root Growth
		5.3 Effect on Nodulation
		5.4 Jasmonate Mediated Root Curling
		5.5 Disruption of Root Mitochondria
		5.6 Regulation of Beneficial Microbe—Root Interaction
	6 Crosstalk of Jasmonates with Other Phytohormones During Root Development
	7 Conclusions
	References
Jasmonates: A Thorough Insight into the Mechanism of Biosynthesis, Signaling and Action in Root Growth and Development
	1 Introduction
	2 Initial Isolation and Identification
	3 Biosynthesis of Jasmonates
	4 Regulation of JA Biosynthesis
	5 Jasmonic Acid Metabolism
	6 Jasmonic Acid Signalling
	7 From JA-Ile Perception to Transcriptional Activation- Mechanism of JA-Induced Gene Expression
	8 Role of Jasmonates in Modulating Root System Architecture (RSA)
	9 Conclusions and Perspective
	References
Serotonin and Melatonin: Role in Rhizogenesis, Root Development and Signaling
	1 Introduction
	2 Biosynthetic Pathway
	3 Role of Melatonin and Serotonin in Rooting
	4 Melatonin and Serotonin—Auxin like Function in Root Induction?
	5 Insights from Gene Expression Patterns
	6 Gravitropic Response—An Auxin Like Response to Melatonin
	7 Nitric Oxide, Auxin and Melatonin Signaling Pathways in Root Induction
	8 Tryptophan as an Inductive Signal
	9 Stress and Rhizobiology: Role of Melatonin and Serotonin
	10 Is Melatonin a Phytohormone?
	References
Suberin in Monocotyledonous Crop Plants: Structure and Function in Response to Abiotic Stresses
	1 Introduction
	2 Suberin
		2.1 Localization
		2.2 Composition and Structure
		2.3 Biosynthesis
		2.4 Regulation of Suberin Biosynthesis
		2.5 Function of Suberin
	3 The Effect of Suberized Barriers on Water and Solute Transport
	4 Environmental Stimuli
		4.1 Water Deficiency and Osmotic Stress
		4.2 Salt Stress
		4.3 Exogenous Abscisic Acid Treatment
		4.4 Nitrogen, Phosphorus, and Potassium Excess and Deficiency
		4.5 Heavy Metal Accumulation
		4.6 Silicon Fertilization
		4.7 Hypoxia
	5 Conclusion
	References
Hitting Hard Times: Effect of Abiotic Stress on Root Physiology
	1 Introduction
	2 Perception of Abiotic Stress by Roots
	3 Activation of Signaling Cascade
	4 Hormone Signaling in Roots During Abiotic Stress
	5 Root Morphology and Anatomy
	6 Changes in Root System Architecture in Response to Abiotic Stress
	7 Tools for the Study of Root Responses to Abiotic Stresses
	8 Conclusions
	References
An Approach in Updating Plant Metabolomics in Roots to Tolerate Anaerobic Submergence Stress
	1 Introduction
	2 Metabolomics Approaches for Deciphering the Stress Tolerance Under Submergence
	3 Submergence Stress: A Significant Scope for Metabolomics Study
	4 Areas Under Coverage of Root Metabolomics Under Submergence Stress
	5 Compartmentalization of Metabolic Flux in Roots Under Submergence
	6 Metabolic Fluxes of Reaction Oxygen Species in Roots Under Submergence
	7 Metabolomics in Roots for Re-Oxygenation Phenomena on Post Submergence
	References
Role of Heavy-Metal Resistant Bacteria Isolated from Rhizosphere in Bioremediation and Plant Development
	1 Introduction
	2 Response of Different Organisms to Metal Intoxication and Metal Starvation
	3 Molecular Mechanism of Heavy Metal Resistance in Bacteria
		3.1 Mechanism of Mercury Resistance in Bacteria
		3.2 Mechanism of Arsenic Resistance in Bacteria
		3.3 Mechanism of Copper Resistance in Bacteria
		3.4 Mechanism of Cobalt Resistance in Bacteria
	4 Application of Heavy Metal Hypertolerant Bacteria in Bioremediation of Heavy Metal Toxicity
	5 Phytoremediation of Heavy Metal Pollution
	6 Role of Rhizospheric Heavy-Metal Resistant Bacteria in Enhancement of Plant Growth
	7 Mechanism of Action of Heavy-Metal Resistant Plant Growth Promoting Bacteria
		7.1 Phosphate Solubilization
		7.2 Potassium Solubilization
		7.3 Nitrogen Fixation
		7.4 Siderophore Production
		7.5 Production of Phytohormones
		7.6 Production of 1-Aminocyclopropane-1-Carboxylate (ACC) Deaminase
		7.7 Production of Volatile Organic Compounds
		7.8 Production of Hydrolytic Enzyme
		7.9 Miscellaneous Actions of Plant Growth Promoting Bacteria
	8 Conclusion
	References
Understanding the Regulation of Root Development Towards Environmental Stresses for Crop Improvement
	1 Introduction
	2 Root Development
		2.1 Embryonic Development (ED) Phase
		2.2 Post-embryonic Development (PED) Phase
	3 Phytohormonal Regulation and the Genetic Control of Root Development
	4 Effect of Environmental Stresses on Root Development
		4.1 Abiotic Factors
		4.2 Biotic Factors
	5 Strategies for Crop Improvement by Modulating Root-Specific Traits
		5.1 Root Modification by Microbial Consortia
		5.2 Root Architectural Engineering for Crop Improvement
		5.3 Recent Techniques for the Modification of Root-Architecture
	6 Epilogue
	References
In Vitro Biosynthesis of Natural Products in Plant Roots
	1 Introduction
	2 In vitro Production of Secondary Metabolites
	3 Elicitation
	4 Physical Factors
		4.1 pH
		4.2 Temperature and Duration
		4.3 Light
		4.4 Combination
	5 Chemical Factors
		5.1 Heavy Metals
		5.2 Organic Compounds
		5.3 Salts
	6 Hormones
	7 Beneficial Microorganisms
		7.1 Bacteria
		7.2 Fungi
	8 Conclusion
	References
Author Index
Subject Index