Plant Signaling Molecules

Role and Regulation under Stressful Environments

M. Iqbal R. Khan, Palakolanu Sudhakar Reddy, Antonio Ferrante, Nafees A Khan, Nafees A. Khan

• Publisher: Woodhead Publishing
• Year: 2019
• Print ISBN: 9780128164518
• eBook ISBN: 9780128164525
• Topic: Technology & Engineering
• Subtopic: Botany
• Index: Technology & Engineering

Plant Signaling Molecule: Role and Regulation under Stressful Environments explores tolerance mechanisms mediated by signaling molecules in plants for achieving sustainability under changing environmental conditions. Including a wide range of potential molecules, from primary to secondary metabolites, the book presents the status and future prospects of the role and regulation of signaling molecules at physiological, biochemical, molecular and structural level under abiotic stress tolerance. This book is designed to enhance the mechanistic understanding of signaling molecules and will be an important resource for plant biologists in developing stress tolerant crops to achieve sustainability under changing environmental conditions.- Focuses on plant biology under stress conditions- Provides a compendium of knowledge related to plant adaptation, physiology, biochemistry and molecular responses- Identifies treatments that enhance plant tolerance to abiotic stresses- Illustrates specific physiological pathways that are considered key points for plant adaptation or tolerance to abiotic stresses

Chapter 1

Signaling Molecules in Ecophysiological Response Mechanisms of Salt-Stressed Plants

Daniele Massa¹ and Sara Melito², ¹CREA, Research Centre for Vegetable and Ornamental Crops, Council for Agricultural Research and Economics, Pescia (PT), Italy, ²Department of Agriculture, University of Sassari, Sassari, Italy

Abstract

The world’s cultivated lands suffer the intrusion of marine water in coastal areas and secondary salinization related to intensive use of arable soils and agrochemical products. It has been estimated that roughly half of irrigated lands are supplied with saline water. Generally, plants grown in saline environments show reduced growth and yield for most cultivated species. Crops that are more tolerant may take advantage from moderate saline stress showing increased produce quality. The different ability of plants in signaling salinity stress is a key factor to improve their tolerance to salt conditions. The temporal pattern of the signal induced the activation of physiological response mechanisms, which limited the detrimental effects of saline environments. The chapter provides an overview of the most important signaling molecules involved in the ecophysiological response of plants to salinity and their interaction mechanisms.

Keywords

Abscisic acid; jasmonic acid; nitrogen oxide; photosynthesis; plant growth; reactive nitrogen species; reactive oxygen species; salinity; sodium chloride; stomatal movements

Outline

• 1.1 Introduction 1
• 1.2 Growth and Development 2
  • 1.2.1 Plant Response to Salinity: Signaling Pathway at Tissue and Organ Level 2
  • 1.2.2 Temporal Signature and Related Cell Response Mechanisms 4
• 1.3 Leaf Gaseous Exchanges 8
  • 1.3.1 Stomatal Conductance and Water Relations 8
  • 1.3.2 Photosynthesis 11
• References 12

1.1 Introduction

The signaling pathways involved in the response to salinity are very complex and highly heterogeneous due to the many biological, botanical, and environmental variables that actively interact with one another. Salinity produces several changes in plant physiology that range from osmotic effect to ion toxicity and nutritional disorders (Läuchli and Grattan, 2007; Munns, 2002; Khan et al., 2014a,b) thus causing a number of growth and development alterations from seed germination to plant maturity. It has been observed that saline soils (with at least 4 dS/m electrical conductivity, roughly equivalent to 40 mM NaCl) significantly affect the growth rate of most crops, thus causing significant decreases in produce yield (Shrivastava and Kumar, 2015). The plant response to salinity depends on several factors such as genotypes, plant age, stress duration, salt concentration, and the plant organ involved. Under salinity, plants show typical morphological traits: reduction of leaves numbers, reduction of plant size and of roots length and biomass production (Shannon and Grieve, 1999). These traits are the consequence of the negative effects of high salt concentration on membrane permeability, ions imbalance, stomatal conductance, and lower photosynthesis efficiency (Ivanova et al., 2014). Tolerant species generally show high capacity in sensing saline environments and prompt reaction to change their physiological status. Stomatal closure indeed is one of the first mechanisms to counteract the detrimental effects of osmotic stress (Munns and Tester, 2008; Robinson et al., 1997).

Based on their salt-tolerance capacity, plant species are classified into glycophytes and halophytes. The plant tolerance to Na⁺ largely varies among plant species; Flowers (2004) reported a low tolerance to Na⁺ in tomato, citrus, and avocado species, while a high tolerance was found for barley and cotton. In general, most of the crops require water with a very low Na⁺ concentration (micromolar) and are referred to as glycophytes. Growth alteration, lack of fruiting and seed germination, occur for several crops under 100 mM NaCl (Flowers, 2004; Park et al., 2016; Zhu, 2001). For other plants (i.e., halophytes), such as Atriplex, Salicornia, Rhizophora, and Suaeda, growth and development depend on high NaCl concentration (200 mM) (Bohnert and Cushman, 2000; Flowers et al., 2010). The NaCl cellular concentration is the result of the dynamic fluxes in and out of the plant cell. Halophytes show high capacity of controlling NaCl concentration, because of specific ion-gated channels while glycophytes have a more limited ability to regulate the NaCl fluxes (Glenn et al., 1999). To control the Na⁺ level inside the cell, a plasma-membrane antiport Na⁺/H⁺ is required (Horie and Schroeder, 2004). Some halophytic species use this antiport system to compartmentalize Na⁺ and Cl⁻ ions in vacuoles within the cell, maintaining a low NaCl level in the cytosol (Zhang et al., 2010a). Both glycophytes and halophytes are not able to tolerate high salinity in their cytoplasm; consequently they regulate the salt concentration in the cytosol compartmentalizing ions in vacuoles or translocating them in different plant tissues (Turkan and Demiral, 2009).

1.2 Growth and Development

1.2.1 Plant Response to Salinity: Signaling Pathway at Tissue and Organ Level

Each phenological stage responds differently to the salinity stress (Munns, 2002; Sairam and Tyagi, 2004). For instance, germination and seedling growth are deeply sensitive to ion imbalance, while the following stage of vegetative growth, in general, shows less sensitivity to salt concentration. Finally, the salinity stress is more damaging during the initial flowering stage as compared with seeds that are already set. Overall, in susceptible plants the shoot growth showed a greater size reduction compared with the root size (Läuchli and Grattan, 2007).

At the germination level, the first signal-molecule received as stress signal is NaCl. High salinity, due to the accumulation of Na⁺ and Cl⁻, affects the germination because it induces a variation of the osmotic potential that decreases the water uptake, thus leading to a reduction in seed water absorption. In this case, salinity enforces the “dormancy” seed status inhibiting water absorption and the metabolic processes associated with the first stage of germination (Hannachi and Van Labeke, 2018). In addition to the osmotic effect, also the toxic effect of ion accumulation showed to negatively affect plant germination (Bajji et al., 2002). High Na⁺ and Cl⁻ levels inhibit the expanding and division cell process, causing reductions in the germination percentage and further lengthening the time of germination in several plant species such as tomato and eggplant (Cuartero and Fernandez-Munoz, 1999; Hannachi and Van Labeke, 2018). Halophyte and glycophite plant seeds present different germination response. In both groups, salinity induces a reduction of germination: in halophytes the altered osmotic potential is the main cause, while for glycophytes the ion toxicity has an additive role (Bajji et al., 2002). As an adaptive mechanism, seeds of salt-tolerant species have a low osmotic potential inside the seed coat, which ensures adequate water absorption. Two principal strategies are used to create a water potential difference between the environment and the seeds: the use of organic solutes, to keep the osmotic potential, and the NaCl compartmentalization (Zhang et al., 2010b).

Osmotic adjustment, ion flux regulation, and Na⁺ and Cl⁻ compartmentalization are salt tolerance strategies with a high-energy cost that compete with the seed germination and plant growth and development (Zhang et al., 2010b). The metabolic cost for the salt tolerance absorbs carbon reserves and energy otherwise required for the germination and seedling development, inducing a reduction of successful germination and an increase of the germination time. As well as the ion concentration and the quantitative variation of endogenous plant hormone regulates the plant response to salt stress.

One of the principal factors involved in salt stress response is abscisic acid (ABA). ABA is a plant hor...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• List of Contributors
• Chapter 1. Signaling Molecules in Ecophysiological Response Mechanisms of Salt-Stressed Plants
• Chapter 2. Stress Responsive Signaling Molecules and Genes Under Stressful Environments in Plants
• Chapter 3. Engineering Signaling Molecules to Improve Abiotic Stress Tolerance in Crop Plants
• Chapter 4. Genetic Engineering/Genome Editing Approaches to Modulate Signaling Processes in Abiotic Stress Tolerance
• Chapter 5. Measurement of Signaling Molecules Calcium Ion, Reactive Sulfur Species, Reactive Carbonyl Species, Reactive Nitrogen Species, and Reactive Oxygen Species in Plants
• Chapter 6. Drought Tolerance in Plants: Molecular Mechanism and Regulation of Signaling Molecules
• Chapter 7. Crop Improvement of Cereals Through Manipulation of Signaling Pathways in Response to Drought Stress
• Chapter 8. Role and Regulation of ROS and Antioxidants as Signaling Molecules in Response to Abiotic Stresses
• Chapter 9. Role and Regulation of Plants Phenolics in Abiotic Stress Tolerance: An Overview
• Chapter 10. Bioactive Molecules as Regulatory Signals in Plant Responses to Abiotic Stresses
• Chapter 11. Biochemical and Molecular Regulation of Phenylpropanoids Pathway Under Abiotic Stresses
• Chapter 12. Role and Regulation of Glucose as a Signal Molecule to Salt Stress
• Chapter 13. Role of Sugars in Abiotic Stress Signaling in Plants
• Chapter 14. Methylglyoxal: A Novel Signaling Molecule in Plant Responses to Abiotic Stresses
• Chapter 15. Role of Trehalose and Regulation of its Levels as a Signal Molecule to Abiotic Stresses in Plants
• Chapter 16. Sugar Regulates Plant Growth and Development Under In Vitro Conditions
• Chapter 17. Role of Mineral Nutrients in Abiotic Stress Tolerance: Revisiting the Associated Signaling Mechanisms
• Chapter 18. Sulfur Availability Potentiates Phytohormones-Mediated Action in Plants
• Chapter 19. Role and Regulation of Plant Hormones as a Signal Molecule in Response to Abiotic Stresses
• Chapter 20. Role and Regulation of Auxin Signaling in Abiotic Stress Tolerance
• Chapter 21. The Regulatory Signaling of Gibberellin Metabolism and Its Crosstalk With Phytohormones in Response to Plant Abiotic Stresses
• Chapter 22. Abscisic Acid, a Principal Regulator of Plant Abiotic Stress Responses
• Chapter 23. Salicylic Acid–Mediated Defense Mechanisms to Abiotic Stress Tolerance
• Chapter 24. Role of Methyl Jasmonates in Salt Stress Tolerance in Crop Plants
• Chapter 25. Insights Into the Nitric Oxide Mediated Stress Tolerance in Plants
• Chapter 26. Brassinosteroid Signaling and Complex Interplay of ROS, NADPH Oxidase, and MAPK Mediated Biotic and Abiotic Stress Acclimation in Plants
• Chapter 27. Role and Regulation of Osmolytes and ABA Interaction in Salt and Drought Stress Tolerance
• Chapter 28. Regulatory Role of Proline in Heat Stress Tolerance: Modulation by Salicylic Acid
• Chapter 29. Osmolyte Diversity, Distribution, and Their Biosynthetic Pathways
• Chapter 30. Role and Regulation of Osmolytes as Signaling Molecules to Abiotic Stress Tolerance
• Chapter 31. Proteomics Insights Into Salt Stress Signaling in Plants
• Chapter 32. Heat Shock Proteins (Hsps) Mediated Signalling Pathways During Abiotic Stress Conditions
• Chapter 33. C4/CAM Facultative Photosynthesis as a Means to Improve Plant Sustainable Productivity Under Abiotic-Stressed Conditions: Regulatory Mechanisms and Biotechnological Implications
• Chapter 34. Protein Kinases and Phosphatases in Stress Transduction: Role in Crop Improvement
• Chapter 35. Nanoparticles and Abiotic Stress Tolerance in Plants: Synthesis, Action, and Signaling Mechanisms
• Index