Plant Adaptation to Environmental Change: Significance of Amino Acids and their Derivatives

By Penna Suprasanna, Yoshikatsu Murooka, Antonio J Márquez and 10 more

Plants constantly cope with unfavourable ecosystem conditions, which often prevent them reaching their full genetic potential in terms of growth, development and productivity. This book covers plants' responses to these environmental changes, namely, the modulation of amino acids, peptides and amines to combat both biotic and abiotic stress factors. Bringing together the most recent developments, this book is an important resource for researchers and students of crop stress and plant physiology.

• Language: English
• Publisher: CAB International
• Release date: Jan 10, 2014
• ISBN: 9781789244335

Penna Suprasanna

Professor Suprasanna Penna has worked as Head of Nuclear Agriculture and Biotechnology Division, Bhabha Atomic Research Centre, Mumbai, and currently is a professor at the Homi Bhabha National Institute, Mumbai. He made significant contributions to plant science covering plant biotechnology, mutation breeding, stress tolerance and novel biopolymer. His work on technology development for radiation depolymerized oligo-chitosan has been successfully used in enhancing plant productivity in crop plants and vegetables. He has also contributed to molecular understanding of plant abiotic stress tolerance in crop plants and salinity-adaptive mechanisms in halophytes. He is on the editorial board of several national and international journals and published over 300 publications and has edited several books on salinity tolerance, genome editing and plant-metal interactions.

Book preview

Plant Adaptation to Environmental Change

Significance of Amino Acids and their Derivatives

Plant Adaptation to Environmental Change

Significance of Amino Acids and their Derivatives

Edited by

Naser A. Anjum

CESAM-Centre for Environmental and Marine Studies & Department of Chemistry, University of Aveiro, 3810-193 Aveiro, Portugal

Sarvajeet S. Gill and Ritu Gill

Centre for Biotechnology, MD University Rohtak — 124 001, Haryana, India

CABI is a trading name of CAB International

© CAB International 2014. All rights reserved. No part of this publication may be reproduced in any form or by any means, electronically, mechanically, by photocopying, recording or otherwise, without the prior permission of the copyright owners.

A catalogue record for this book is available from the British Library, London, UK.

Library of Congress Cataloging-in-Publication Data

Plant adaptation to environmental change : significance of amino acids and their derivatives / edited by Naser A. Anjum, Sarvajeet S. Gill and Ritu Gill.

        p. ; cm.

    Includes bibliographical references and index.

    ISBN 978-1-78064-273-4 (alk. paper)

    1. Crops--Effect of stress on. 2. Crops--Adaptation. 3. Crops--Physiology. 4. Amino acids. 5. Polyamines. I. Anjum, Naser A. II. Gill, Sarvajeet Singh. III. Gill, Ritu.

    QK754.P55 2013

   571.2-dc23

                                                     2013021988

ISBN-13: 978 1 78064 273 4

Commissioning editor: Sreepat Jain

Editorial assistant: Alexandra Lainsbury

Production editors: Shankari Wilford and Simon Hill

Typeset by AMA Dataset, Preston

Printed and bound by CPI Group (UK) Ltd, Croydon, CR0 4YY

Contents

Contributors

Preface

Acknowledgements

Abbreviations

PART I: INTRODUCTION

1 Environmental Change, and Plant Amino Acids and their Derivatives — An Introduction

Naser A. Anjum, Sarvajeet S. Gill, Imran Khan and Ritu Gill

PART II: AMINO ACIDS AND PEPTIDES, AND PLANT STRESS ADAPTATION

2 5-Aminolevulinic Acid (5-ALA) — A Multifunctional Amino Acid as a Plant Growth Stimulator and Stress Tolerance Factor

Yoshikatsu Murooka and Tohru Tanaka

3 Cysteine — Jack of All Glutathione-based Plant Stress Defence Trades

Naser A. Anjum, Sarvajeet S. Gill and Ritu Gill

4 Amino Acids and Drought Stress in Lotus: Use of Transcriptomics and Plastidic Glutamine Synthetase Mutants for New Insights in Proline Metabolism

Pedro Díaz, Marco Betti, Margarita García-Calderón, Carmen M. Pérez-Delgado, Santiago Signorelli, Omar Borsani, Antonio J. Márquez and Jorge Monza

5 Modulation of Proline: Implications in Plant Stress Tolerance and Development

P. Suprasanna, Archana N. Rai, P. HimaKumari, S. Anil Kumar and P.B. KaviKishor

6 Target Osmoprotectants for Abiotic Stress Tolerance in Crop Plants — Glycine Betaine and Proline

Sarvajeet S. Gill, Ritu Gill and Naser A. Anjum

PART III: AMINES AND BRASSINOSTEROIDS, AND PLANT STRESS ADAPTATION

7 Polyamines as Indicators and as Modulators of the Abiotic Stress in Plants

Pablo Ignacio Calzadilla, Ayelén Gazquez, Santiago Javier Maiale, Oscar Adolfo Ruiz and Menéndez Ana Bernardina

8 Polyamines in Stress Protection — Applications in Agriculture

Rubén Alcázar and Antonio F. Tiburcio

9 Functional Role of Polyamines and Polyamine-metabolizing Enzymes during Salinity, Drought and Cold Stresses

Aryadeep Roychoudhury and Kaushik Das

10 Regulatory Role of Polyamines in Growth, Development and Abiotic Stress Tolerance in Plants

Mirza Hasanuzzaman, Kamrun Nahar and Masayuki Fujita

11 Polyamines — Involvement in Plant Stress Tolerance and Adaptation

Dessislava Todorova, Zornitsa Katerova, Iskren Sergiev and Vera Alexieva

12 Role of Polyamines in Plant—Pathogen Interactions

Abhijit Dey, Kamala Gupta and Bhaskar Gupta

13 Role of Polyamines in Stress Management

Renu Bhardwaj, Indu Sharma, Neha Handa, Dhriti Kapoor, Harpreet Kaur, Vandana Gautam and Sukhmeen Kohli

14 Polyamines in Plant In Vitro Culture

Jose Luis Casas

15 Betaines and Related Osmoprotectants — Significance in Metabolic Engineering of Plant Stress Resistance

Renu Bhardwaj, Indu Sharma, Resham Sharma and Poonam

16 Brassinosteroids’ Role for Amino Acids, Peptides and Amines Modulation in Stressed Plants — A Review

B. Vidya Vardhini

PART IV: APPRAISAL AND PERSPECTIVES

17 Plant Adaptation to Environmental Change, and Significance of Amino Acids and their Derivatives — Appraisal and Perspectives

Naser A. Anjum, Sarvajeet S. Gill and Ritu Gill

Index

Contributors

Rubén Alcázar, Department of Natural Products and Plant Biology, University of Barcelona, Faculty of Pharmacy, Avda de Joan XXIII s/n, 08028 Barcelona, Spain

Vera Alexieva, Institute of Plant Physiology and Genetics, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bl. 21, 1113 Sofia, Bulgaria. e-mail: [e-mail]

Naser A. Anjum, CESAM-Centre for Environmental and Marine Studies & Department of Chemistry, University of Aveiro, Portugal. e-mail: [e-mail]; [e-mail]

Menéndez Ana Bernardina, IIB-INTECh (CONICET-UNSAM), Chascomús, Buenos Aires, Argentina; Department of Biodiversity and Experimental Biology, Faculty of Sciences, University of Buenos Aires (DBBE, FCEN, UBA)

Marco Betti, Department of Plant Biochemistry and Molecular Biology, Chemistry Faculty, University of Seville, Apartado 1203, 41071-Sevilla, Spain

Renu Bhardwaj, Department of Botanical and Environmental Sciences, Guru Nanak Dev University, Amritsar 143005, Punjab, India. e-mail: [e-mail]; [e-mail]

Omar Borsani, Biochemistry Laboratory, Department of Vegetal Biology, Agronomy Faculty, Research group: Plant Abiotic Stress, Av. E. Garzón 780, CP 12900 Montevideo, Uruguay

Pablo Ignacio Calzadilla, IIB-INTECh (CONICET-UNSAM), Chascomús, Buenos Aires, Argentina

Jose Luis Casas, Plant Biotechnology Laboratory, Institute of Biodiversity (CIBIO), University of Alicante, Crta. San Vicente del Raspeig s/n, E-03690 San Vicente del Raspeig, Alicante, Spain. e-mail: [e-mail]

Kaushik Das, Post Graduate Department of Biotechnology, St. Xavier’s College (Autonomous), 30, Mother Teresa Sarani, Kolkata — 700016, West Bengal, India

Abhijit Dey, Department of Botany, Presidency University, 86/1 College Street, Kolkata 700073, India

Pedro Díaz, Biochemistry Laboratory, Department of Vegetal Biology, Agronomy Faculty, Research group: Plant Abiotic Stress, Av. E. Garzón 780, CP 12900 Montevideo, Uruguay

Masayuki Fujita, Laboratory of Plant Stress Responses, Department of Applied Biological Science, Kagawa University, 2393 Ikenobe, Miki-cho, Kita-gun, Kagawa 761-0795, Japan. e-mail: [e-mail]

Margarita García-Calderón, Department of Plant Biochemistry and Molecular Biology, Chemistry Faculty, University of Seville, Apartado 1203, 41071-Sevilla, Spain

Vandana Gautam, Department of Botanical and Environmental Sciences, Guru Nanak Dev University, Amritsar 143005, Punjab, India

Ayelén Gazquez, IIB-INTECh (CONICET-UNSAM), Chascomús, Buenos Aires, Argentina

Ritu Gill, Centre for Biotechnology, MD University, Rohtak, Haryana, India

Sarvajeet S. Gill, Centre for Biotechnology, MD University, Rohtak, Haryana, India. e-mail: [e-mail]

Bhaskar Gupta, Molecular Biology Laboratory, Department of Biotechnology, Presidency University, 86/1 College Street, Kolkata 700073, India. e-mail: [e-mail]

Kamala Gupta, Plant Molecular Biology Laboratory, Department of Botany, Bethune College, 181 Bidhan Sarani, Kolkata 700006, India

Neha Handa, Department of Botanical and Environmental Sciences, Guru Nanak Dev University, Amritsar 143005, Punjab, India

Mirza Hasanuzzaman, Laboratory of Plant Stress Responses, Department of Applied Biological Science, Kagawa University, 2393 Ikenobe, Miki-cho, Kita-gun, Kagawa 761-0795, Japan; Department of Agronomy, Faculty of Agriculture, Sher-e-Bangla Agricultural University, Dhaka-1207, Bangladesh

Dhriti Kapoor, Department of Botanical and Environmental Sciences, Guru Nanak Dev University, Amritsar 143005, Punjab, India

Zornitsa Katerova, Institute of Plant Physiology and Genetics, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bl. 21, 1113 Sofia, Bulgaria

Harpreet Kaur, Department of Botanical and Environmental Sciences, Guru Nanak Dev University, Amritsar 143005, Punjab, India

P.B. KaviKishor, Department of Genetics, Osmania University, Hyderabad 500 007, India

Sukhmeen Kohli, Department of Botanical and Environmental Sciences, Guru Nanak Dev University, Amritsar 143005, Punjab, India

Imran Khan, Department of Chemistry, CICECO, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal

S. Anil Kumar, Department of Genetics, Osmania University, Hyderabad 500 007, India

P. Hima Kumari, Department of Genetics, Osmania University, Hyderabad 500 007, India

Santiago Javier Maiale, IIB-INTECh (CONICET-UNSAM), Chascomús, Buenos Aires, Argentina

Antonio J. Márquez, Department of Plant Biochemistry and Molecular Biology, Chemistry Faculty, University of Seville, Apartado 1203, 41071-Sevilla, Spain. e-mail: [e-mail]

Jorge Monza, Biochemistry Laboratory, Department of Vegetal Biology, Agronomy Faculty, Research group: Plant Abiotic Stress, Av. E. Garzón 780, CP 12900 Montevideo, Uruguay

Yoshikatsu Murooka, Emeritus Professor of Osaka University, Takaya, Higashi-Hiroshima 739-2125, Japan. email: [e-mail]

Kamrun Nahar, Laboratory of Plant Stress Responses, Department of Applied Biological Science, Kagawa University, 2393 Ikenobe, Miki-cho, Kita-gun, Kagawa 761-0795, Japan; Department of Agricultural Botany, Faculty of Agriculture, Sher-e-Bangla Agricultural University, Dhaka-1207, Bangladesh

Carmen M. Pérez-Delgado, Department of Plant Biochemistry and Molecular Biology, Chemistry Faculty, University of Seville, Apartado 1203, 41071-Sevilla, Spain

Poonam, Department of Botanical and Environmental Sciences, Guru Nanak Dev University, Amritsar 143005, Punjab, India

Archana N. Rai, Nuclear Agriculture Biotechnology, Bhabha Atomic Research Center, Trombay, Mumbai 400 085, India

Aryadeep Roychoudhury, Post Graduate Department of Biotechnology, St. Xavier’s College (Autonomous), 30, Mother Teresa Sarani, Kolkata — 700016, West Bengal, India. e-mail: [e-mail]

Oscar Adolfo Ruiz, IIB-INTECh (CONICET-UNSAM), Chascomús, Buenos Aires, Argentina. e-mail: [e-mail]; [e-mail]

Iskren Sergiev, Institute of Plant Physiology and Genetics, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bl. 21, 1113 Sofia, Bulgaria

Indu Sharma, Department of Botanical and Environmental Sciences, Guru Nanak Dev University, Amritsar 143005, Punjab, India

Resham Sharma, Department of Botanical and Environmental Sciences, Guru Nanak Dev University, Amritsar 143005, Punjab, India

Santiago Signorelli, Biochemistry Laboratory, Department of Vegetal Biology, Agronomy Faculty, Research group: Plant Abiotic Stress, Av. E. Garzón 780, CP 12900 Montevideo, Uruguay

P. Suprasanna, Nuclear Agriculture Biotechnology, Bhabha Atomic Research Center, Trombay, Mumbai 400 085, India. e-mail: [e-mail]

Tohru Tanaka, SBI Pharmaceuticals Co., Ltd., 1-6-1 Roppongi, Minato-ku, Tokyo 106-6017, Japan

Antonio F. Tiburcio, Department of Natural Products and Plant Biology, University of Barcelona, Faculty of Pharmacy, Avda de Joan XXIII s/n, 08028 Barcelona, Spain. e-mail: [e-mail]

Dessislava Todorova, Institute of Plant Physiology and Genetics, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bl. 21, 1113 Sofia, Bulgaria

B. Vidya Vardhini, Department of Botany, Telangana University, Nizamabad-503175, Andhra Pradesh, India. e-mail: [e-mail]

Preface

Plants are fundamental to all life on Earth. They provide us with oxygen, food, fuel, fibre, medicines and even shelter, either directly or indirectly. However, plant-based food production has always been linked to environmental changes. To this end, both naturally and human activities-influenced changes in the physical and biogeochemical environments contribute to global environmental changes which cumulatively create sub-optimal conditions for plant growth. Being sessile in nature, plants, in a variably changing environment, have to cope with a plethora of sub-optimal (adverse) growth conditions where the majority of these conditions can delay growth and development and most importantly prevent them reaching their full productivity genetic potential. Nevertheless, in the complex field environment with its heterogenic conditions, global environmental changes-mediated potential anomalies in plants are further aggravated with various abiotic stress combinations. However, plants develop a battery of highly sophisticated and efficient strategies to acclimate, grow and produce under gradual change in their environment. Understanding of the global environmental change-led impacts on plants and also the exploration of sustainable ways to counteract these impacts have become thrust areas of utmost significance.

Through authoritative contributions, the present volume entitled Plant Adaptation to Environmental Change: Significance of Amino Acids and their Derivatives overviews varied amino acids and their derivatives’ significance for plant stress adaptation/tolerance, discusses significant biotechnological strategies for the manipulation of amino acids and their major derivatives (hence to improve biotic/ abiotic stress tolerance in crop plants), provides state-of-the-art knowledge of recent developments in the understanding of amino acids and their derivatives emphasizing mainly on the cross-talks on amino acids, peptides and amines, and fills the gap in the knowledge gained on the subject obtained through extensive research in the last one and half decades.

In particular, the role of important amino acids, peptides and amines as potential selection criteria for improving plant tolerance to adverse growth conditions has been critically discussed at length in different chapters contributed by experts from over the globe working in the field of crop improvement, genetic engineering and abiotic stress tolerance. Though occasional overlaps of information between chapters could not be avoided, they reflect the central and multiple aspects of major amino acids, peptides and amines-based strategies for enhancing tolerance to environmental change in the light of the advances in molecular biology.

Chapter 1 introduces major factors responsible for environmental change and its implication for plant growth and development, and amino acids and their important derivatives in context mainly with their significance for plant adaptation and/or tolerance to varied environmental stress factors. Focusing on 5-aminolevulinic acid (5-ALA) Chapter 2 deals with the biosynthetic pathway and chemical synthesis of 5-ALA, the biosynthetic pathway of tetrapyrrole compounds from 5-ALA, industrial strains development for 5-ALA over-production and 5-ALA important biological activity significance in different stressed plants. Chapter 3 summarizes available data on the structure, occurrence, biosynthesis, regulation and significance of cysteine, peptides (glutathione, phytochelatins) and cysteine-rich, gene-encoded low-molecular weight proteins — metallothioneines in plant metabolism and stress defense as well. Considering the significance of legumes for both humans and animals as a source of protein-rich food Chapter 4 discusses transcriptomics and plastidic glutamine synthetase mutants for new insights in proline metabolism in drought exposed Lotus japonicus. In Chapter 5, information about physiological functions and regulations of proline in plant systems is summarized and diverse roles of proline including the signalling events involved in proline synthesis are presented. Chapter 6 reviews the knowledge that has been gathered over the last couple of decades with respect to glycine betaine and proline — extensively explored as target osmoprotectants for enhancing abiotic stress tolerance in crop plants.

The central focus of Chapters 7–11 is polyamines. In particular, Chapter 7 critically discusses polyamines as indicators and modulators in the abiotic stress in plants. By exploring the natural variation for polyamine levels, and how these interact with the environment, Chapter 8 looks for developing tools that will facilitate the manipulation of polyamine levels that can lead to practical applications in agriculture. Chapter 9 emphasizes the mechanism of polyamine metabolism and their multifunctional role in plants under major environmental stresses like salinity, drought and cold. In addition, in this chapter, the regulation of expression of genes, encoding polyamine-metabolizing enzymes under such stress conditions, their promoter structures and overexpression of such genes through transgenic approaches for enhanced tolerance is also highlighted. Chapter 10 summarizes some recent data concerning changes in polyamine metabolism (biosynthesis, catabolism and regulation) in higher plants subjected to a wide array of environmental stress conditions, and describes and discusses some new advances concerning the different proposed mechanisms of polyamine actions implicated in plants’ responses to abiotic stress. Furthermore, this chapter also discusses progress made in genetic engineering in polyamine-induced stress tolerance in plants. Polyamines involvement in plant tolerance and adaptation to stress is discussed in Chapter 11. The role of polyamines in the biotic stress of plants as a result of plant—pathogen interaction with a note on current research tendencies and future perspectives is critically discussed in Chapter 12; whereas, Chapter 13 highlights the role of polyamines in the management of important stresses. Chapter 14 deals with polyamines significance in plant in vitro culture. Betaines and related osmoprotectants’ significance in metabolic engineering of plant stress resistance is highlighted in Chapter 15; whereas, Chapter 16 throws lights on brassinosteroids’ role for amino acids, peptides and amines modulation in stressed plants. Chapter 17 presents a critical appraisal of the manuscripts covered in the current book and also highlights important aspects so far less explored in the current context.

The outcome of the present treatise will be a resourceful guide suited for scholars and researchers exploring sustainable strategies for crop improvement and abiotic stress tolerance.

Naser A. Anjum

Sarvajeet S. Gill

Ritu Gill

Acknowledgements

We are thankful to the competent scientists for their sincere efforts, invaluable contributions and full faith and cooperation that eventually made the present volume possible.

We extend our appreciation to Dr. Sreepat Jain, CABI Commissioning Editor for South Asia and his team at CABI, United Kingdom for their exceptional kind support, which made our efforts successful.

We gratefully acknowledge the Foundation for Science & Technology (FCT), Portugal, the Aveiro University Research Institute/Centre for Environmental and Marine Studies (CESAM), University Grants Commission (UGC) and Council for Scientific and Industrial Research, Govt. of India, New Delhi, India for financial supports to our research.

Last but not least, we thank all the well-wishers, teachers, seniors, research students, colleagues and our families. Without their unending moral support, motivation, endurance and encouragements, the gruelling task would have never been accomplished. Special thanks go to Zoya, Simar Gill and Naznee who supported us during the course of this book project.

Naser A. Anjum

Sarvajeet S. Gill

Ritu Gill

Abbreviations

1 Environmental Change, and Plant Amino Acids and their Derivatives — An Introduction

Naser A. Anjum¹,*, Sarvajeet S. Gill², Imran Khan³ and Ritu Gill²

¹CESAM-Centre for Environmental and Marine Studies & Department of Chemistry, University of Aveiro, Portugal; ²Centre for Biotechnology, MD University, Rohtak, Haryana, India; ³Department of Chemistry, CICECO, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal

1.1 Background

Being sessile in nature, plants, in a variably changing environment, have to cope with a plethora of adverse growth conditions (hereafter called stress) where the majority of these conditions can delay growth and development and most importantly prevent them reaching their full genetic potential in terms of productivity. Therefore, identifying the major factors responsible for environmental changes and understanding their cumulative potential effects on plant growth would be promising in sustainably protecting the agricultural ecosystem, and hence extract enough food for the burgeoning global population. The interactions between plants and environmental stresses reflect a complex system where plant stress responses occur at all levels of organization. At the cellular level, though a variety of reactive oxygen species (ROS), including hydrogen peroxide (H2O2), superoxide (O2−) and hydroxyl radical (OH-), are by-products of the normal aerobic plant cell metabolism, varied adverse growth conditions lead to significantly elevated generation of ROS and its reaction products (Apel and Hirt, 2004; Gill and Tuteja, 2010b). Subsequently, an imbalance between the pro-oxidants (ROS and its reaction products) generation and their antioxidants-mediated metabolism/scavenging occurs leading to a physiological condition called oxidative stress. Unmetabolized ROS and its reaction products are highly toxic due to their capacity to induce oxidative damage to vital cellular organelles, lipids, proteins, nucleic acids and pigments leading ultimately to cellular metabolism arrest.

Plants respond to the continuous environmental fluctuations with appropriate physiological, developmental and biochemical changes to cope with and/or acclimatize/adapt to these stress conditions. Plants exposed to stress factors often synthesize a set of diverse metabolites that accumulate to concentrations in the millimolar range, particularly specific amino acids (such as asparagine, histidine, proline and serine), peptides (such as glutathione and phytochelatins, PCs), and the amines (such as spermine, spermidine, putrescine, nicotianamine and mugineic acids). A credible number of studies have shown the significant changes in the contents of the majority of amino acids, peptides and amines, thus indicating their functional significance in the context of stress tolerance and/or adaptations. Multiple highly regulated and interwoven metabolic networks occur in plant cells where these networks largely play central regulatory roles in plant growth and development. Because the amino acids are vital for the synthesis of proteins and also serve as precursors for a large array of metabolites with multiple functions in plant growth and response to various stresses, the amino acids synthesis-related metabolic networks have gained considerable interest (Less and Galili, 2008).

This chapter introduces: (a) the major factors responsible for environmental change and its implication for plant growth and development, and (b) amino acids and their important derivatives in context mainly with their significance for plant adaptation and/or tolerance to varied environmental stress factors.

1.2 Environmental Change

Agricultural food production has always been linked to environmental conditions; however, growing demands for food in turn affect the global environment in many ways. According to recent estimates, global food security has been projected to face a severe threat from global environmental change, which includes naturally or human activities-influenced changes in the physical and biogeochemical environments (Steffen et al., 2003; Carpenter et al., 2009; Ericksen et al., 2009; Liverman and Kapadia, 2010). Moreover, different elements of environmental change are interlinked through a complex set of physical, chemical and biological processes; where natural or human activities-led changes in one component can ramify for other components as well (IPEC, 2003).

Changes in atmospheric CO2 concentration, increase in ambient temperatures and regional changes in annual precipitation are expected to significantly influence future agricultural production (Mittler and Blumwald, 2010). During the past two centuries the atmospheric CO2 concentration increased significantly from ≈ 270 μmol/ mol to current concentrations greater than 385 μmol/mol (Intergovernmental Panel Climate Change, 2007; Le Quéré et al., 2009; reviewed by Mittler and Blumwald, 2010). Elevated atmospheric CO2 generally increases plant productivity and alters nutrient element cycling. However, there is a report that experimental CO2 enrichment in a sandy soil with low organic matter content can cause plants to accumulate contaminants in plant biomass, with declines in the extractable contaminant element pools in surface soils (Duval et al., 2011). Combined ambient greenhouse gas concentrations (including methane, ozone and nitrous oxide) are now expected to exceed concentrations of 550 μmol/ mol by 2050 (Raven and Karley, 2006; Brouder and Volenec, 2008). Moreover, atmospheric temperature is rapidly being changed with the climate change and global warming. To this end, the Intergovernmental Panel Climate Change (2007) has projected average annual mean warming increases of 3–5°C in the next 50–100 years due to the increase in greenhouse gases (reviewed by Mittler and Blumwald, 2010).

Seven percent of the electromagnetic radiation emitted from the sun is in the UV range (200–400 nm). A great reduction in and modification of UV radiation takes place as it passes through the atmosphere. Radiation of range 200–280 nm (UV-C radiation) is completely absorbed by atmospheric gases, 280–320 nm (UV-B radiation) is additionally absorbed by stratospheric ozone (thus only a very small proportion is transmitted to the earth’s surface); whereas, the radiation of range 320–400 nm (UV-A radiation) is hardly absorbed by ozone (Frohnmeyer and Staiger, 2003). The depletion of the stratospheric ozone layer is leading to an increase in UV-B radiation reaching the earth’s surface with serious implications for all living organisms. In this context, the release of anthropogenic pollutants such as chlorofluorocarbons has earlier been regarded as a major factor contributing a decrease of about 5% in ozone concentration observed during the last 50 years (Pyle, 1996). This has raised interest in the possible consequence of increased UV-B levels on plant growth and development and the mechanisms underlying these responses (Mackerness, 2000; Frohnmeyer and Staiger, 2003). Moreover, UV-B radiation has also been regarded as a key environmental signal that initiates diverse responses in plants that affect metabolism, development and viability. Many effects of UV-B involve the differential regulation of gene expression (Jenkins, 2009). Tropospheric ozone (O3) is currently viewed as a widespread and growing problem that suppresses crop productivity. Being a strong oxidant, O3 can interact with constituents of the apoplast to generate ROS (Hasanuzzaman et al., 2012). The antioxidant system in plant tissues plays an important role in conferring plants’ tolerance to O3 exposure (Tausz et al., 2007). This increase in UV radiation is predicted to increase in the near future, which may cause a negative impact on plants and other biological organisms. Extended exposure to UV-B radiation is especially harmful to plants due to their requirement for light (Sinha et al., 2003). It also increases ROS and causes oxidative stress and hence the antioxidant defense under UV-stress is a matter of concern (Hasanuzzaman et al., 2012).

1.2.1 Environmental changes-accrued anomalies-aggravation in plants — Significance of abiotic stresses

In the complex field environment with its heterogenic conditions, global environmental changes-mediated potential anomalies are further aggravated with varied abiotic stress combinations, all together severely impacting modern agriculture (Witcombe et al., 2008; Mittler and Blumwald, 2010) (Fig. 1.1). Drought, temperature extremes and saline soils are the most common abiotic stresses that plants encounter. Plant life and primary productivity depend on water availability. On earth, nearly 20% of the global land surface is too dry to be cultivated and areas under drought are already expanding and this is expected to increase further (Burke et al., 2006). In this context, among the most severe environmental stresses, drought has been considered a major constraint for plant productivity worldwide causing great damage to rain-fed and irrigated farming (Sadat Noori et al., 2011). Drought stress may lead to stomatal closure, which reduces CO2 availability in the leaves and inhibits carbon fixation, exposing chloroplasts to excessive excitation energy, which in turn could increase the generation of ROS and induce oxidative stress (de Carvalho, 2008; Hasanuzzaman and Fujita, 2011).

Fig. 1.1. Schematic representation of: (a) environmental change — biotic and abiotic stress factors relatedness in terms of their cumulative negative impacts on plants, and (b) the significance of amino acids, peptides and amines in the control of plant adaptation/tolerance to environmental change, biotic and abiotic stress factors and their cumulative positive impacts on plant growth, metabolism and productivity.

Land degradation is a decline in land quality caused by human activities, has been a major global issue since the 20th century and is expected to remain high on the international agenda in the 21st century (Eswaran et al., 2001). Though land degradation is reflected in an increasing use of fertilizers, and spreading pests increases the use of expensive agricultural chemicals, land salinization is one of the major factors of land degradation. Globally, approximately 22% of agricultural land is saline (FAO, 2004). According to UNEP (2009), ≈ 950 million ha of salt-affected lands occur in arid and semiarid regions, nearly 33% of the potentially arable land area of the world. Additionally, worldwide, some 20% of irrigated land (450,000 km²) is salt-affected, with 2,500–5,000 km² of lost production every year as a result of salinity (UNEP, 2009). Hence, salt stress is becoming a major concern for crop production as increased salinity of agricultural land is expected to have devastating global effects, resulting in up to 50% loss of cultivable lands (Mahajan and Tuteja, 2005). In most of the cases, the negative effects of salt stress are ionic stress (Na+ and Cl–) and osmotic stress, which interrupt many plant processes. Nutrient depletion as a form of land degradation has a severe economic impact at the global scale. Erosion is very significant in land degradation where the productivity of some lands has declined by 50% due to soil erosion and desertification (FAO, 2004; Burke et al., 2006).

Heavy metal (HM) contamination of agricultural soils has emerged as a major environmental problem severely impacting both the productivity of plants and the safety of plant products as foods and feeds. Moreover, the rapid increase in population together with fast industrialization causes serious environmental problems, including the production and release of considerable amounts of HMs in the environment (Hasanuzzaman and Fujita, 2012). There is enough evidence that exposure of plants to excess concentrations of redox active HMs results in oxidative injury (Sharma and Dietz, 2008; Hasanuzzaman and Fujita, 2012). High temperature (HT) is another major environmental factor that often affects plant growth and crop productivity and leads to substantial crop losses (Hasanuzzaman et al., 2012). The cellular changes induced by HT include responses that lead to the excess accumulation of toxic compounds, especially ROS that cause oxidative stress (Mittler, 2002; Suzuki and Mittler, 2006). Low temperature (LT) conditions aggravate the imbalance between light absorption and light use by inhibiting the activity of the Calvin-Benson cycle and enhanced photo-synthetic electron flux to O2 and the over-reduction of the respiratory electron transport chain that causes ROS accumulation during chilling (Hu et al., 2008). In addition, the solubility of a gas increases, which leads to a higher [O2] and thus enhances the risk of increased production of ROS (Guo et al., 2006).

In a recent review, Mittler and Blumwald (2010) revealed that drought—heat, salinity—heat, ozone—salinity, ozone—heat, nutrient stress—drought, nutrient stress—salinity, UV—heat, UV—drought, and high light intensity combined—heat, drought, or chilling are the stress interactions that have a deleterious effect on crop productivity. On the contrary, drought—zone, ozone—UV and high CO2 combined with drought, ozone or high light are the environmental interactions that do not have a deleterious effect on yield and could actually have a beneficial impact on the effects of each other (Mittler and Blumwald, 2010). The global challenge will be to devise and implement a sustainable balance between meeting the food security needs of the poor and minimizing the impacts of environmental changes (IPEC, 2003). In this context, continued technological developments have been anticipated to facilitate the adaptation of crops to changing environments (Gregory et al., 2005).

Plants have evolved very clever and fascinating adaptive mechanisms at the cellular, organ and whole plant level that together help them to survive and produce under adverse conditions. As said also above these varied environmental unfavourable changes or environmental stress factors may impact plants both individually and/ or more commonly, in combination. Therefore, plant responses to these environmental insults are dynamic and involve complex cross-talk between different regulatory levels, including adjustment of metabolism and gene expression for physiological and morphological adaptation (Ahuja et al., 2010; Krasenky and Jonak, 2012). In this context, involvement of coordinated adjustments of a large array of metabolic networks in the plant adaptation mechanisms is known. Among those are metabolic networks containing different amino acids as intermediate metabolites, which either as themselves or incorporated into proteins, accumulate to high levels in response to specific cues, or serve as precursors for a large array of metabolites with multiple functions. The following sections highlight amino acids and their major derivatives, and critically discuss their significance for adaptation/tolerance of plants under non-optimum growth conditions.

1.3 Amino Acids

All organisms are constituted essentially by proteins where these molecules are required by living cells for the execution of diverse functions as metabolic regulation, transport, defence and catalysis. Chemically, proteins are polypeptides of 50 or more amino acids where they can be joined via amide bonds to give peptides. Amino acids are biologically important organic compounds made from amine (-NH2) and carboxylic acid (-COOH) functional groups, along with a side-chain specific to each amino acid. The key elements of an amino acid are carbon, hydrogen, oxygen and nitrogen. Plants and bacteria synthesize all 20 common amino acids. Mammals can synthesize about half; the others are required in the diet (essential amino acids). About 500 amino acids are known (Wagner and Musso, 1983) which can be classified in many ways. Structurally they can be classified according to the functional groups’ locations as alpha- (α-), beta- (β-), gamma- (γ-) or delta- (δ-) amino acids; other categories relate to polarity, acid/base/neutral and side-chain group type (including aliphatic, acyclic, hydroxyl or sulfur-containing, aromatic). In the form of proteins, amino acids comprise the second largest component other than water of human muscles, cells and other tissues (Latham, 1997).

1.3.1 Classification of amino acids

Although there are many ways to classify amino acids, these molecules can be assorted into six main groups, on the basis of their structure and the general chemical characteristics of their R groups (Table 1.1; Figs 1.2–1.7).

In plants, nitrogen is first assimilated into organic compounds in the form of glutamate, formed from alpha-ketoglutarate and ammonia in the mitochondrion. In order to form other amino acids, the plant uses transaminases to move the amino group to another alpha-keto carboxylic acid. For example, aspartate aminotransferase converts glutamate and oxaloacetate to alpha-ketoglutarate and aspartate (Buchanan et al., 2000). Other organisms too use transaminases for amino acid synthesis. Nonstandard amino acids are usually formed through modifications to standard amino acids. For example, homocysteine is formed through the transsulfuration pathway or by the demethylation of methionine via the intermediate metabolite S-adenosyl methionine (Brosnan and Brosnan, 2006, while hydroxyproline is made by a posttranslational modification of proline (Kivirikko and Pihlajaniemi, 1998). Because of their biological significance, amino acids are important in nutrition and are commonly used in nutritional supplements, fertilizers and food technology. Industrial uses include the production of biodegradable plastics, drugs and chiral catalysts.

Table 1.1. Summary of amino acid classification.

Fig. 1.2. Aliphatic amino acids (neutral non-polar amino acids).

Fig. 1.3. Hydroxyl or sulfur-containing amino acids.

Fig. 1.4. Aromatic amino acids.

Fig. 1.5. Acidic and their amide amino acids.

Fig. 1.6. Basic amino acids.

Fig. 1.7. Cyclic amino acid.

A number of processes of nitrogen assimilation, associated carbon metabolism, photorespiration, export of organic nitrogen from the leaf and the synthesis of nitrogenous end-products have been reported to revolve around a hub of amino acids (Foyer et al., 2003). Moreover, specific major amino acids or their relative ratios have been considered as potentially powerful markers for metabolite profiling and metabolomic approaches to the study of plant biology (Foyer et al., 2003).

1.4 Amino Acid Derivatives

In layman’s language, an amino acid derivative is a molecule that is generated using an amino acid as a starting point (precursor). It is important to emphasize here that apart from an amino acid’s significance as a vital component of the protein synthesis, these compounds also serve as precursors for a large array of amino acid derivatives with multiple functions in plant growth, development and response to various stresses (Less and Galili, 2008).

A credible number of reports and reviews have evidenced an extensive shift in plant metabolism, including metabolic networks associated with amino acids as stressed plants’ adaptive/ survival strategy (Galili et al., 2001; Amir et al., 2002; Galili, 2002; Stepansky and Galili, 2003; Less and Galili, 2008). In this perspective, specific amino acids (such as asparagine, histidine, proline and serine) and peptides (such as glutathione (GSH), phytochelatins (PCs)) (Sharma and Dietz, 2006; Krasensky and Jonak, 2012), and the amines (such as spermine, spermidine, putrescine, nicotianamine and mugineic acids) (Sharma and Dietz, 2006; Gill and Tuteja, 2010a; Anjum et al., 2010, 2012a,b) have been extensively reported and reviewed for their involvement in plant stress tolerance. Additionally, aromatic amino acids have extensively been evidenced as precursors for numerous metabolites, such as hormones, cell wall components and a large group of multiple functional secondary metabolites (Radwanski and Last, 1995; Wittstock and Halkier, 2002; Pichersky et al., 2006; Tempone et al., 2007; cited in Less and Galili, 2008). Amir et al. (2002), Wittstock and Halkier (2002), Rebeille et al. (2006), Goyer et al. (2007) evidenced Met to provide a methyl group to DNA methylation, chlorophyll biosynthesis and cell wall biosynthesis. Moreover, these authors have also reported the significance of Met as a precursor for the synthesis of the hormone ethylene, polyamines and cellular energy glucosinolates. To the other, Jander et al. (2004) and Joshi et al. (2006) reported the involvement of Thr conversion into Gly in seed development; while Mooney et al. (2002) evidenced Ile catabolism-mediated production of cellular energy.

Cysteine (Cys) is a sulfur-containing amino acid and a central precursor of all reduced sulfur-containing organic molecules including the amino acid methionine (Met), proteins, vitamins, cofactors (e.g. S-adenosylmethionine, SAM), multiple secondary metabolites and peptides (e.g. glutathione, phytochelatins) significant for plant biotic-abiotic stress tolerance and/or adaptation. Hence because of its prominent tasks performed (in conjunction with Met), Cys has now been considered essential for the entire biological kingdom. Proline is a proteinogenic amino acid, contains a secondary amino group, has cyclic structure, a restricted conformational flexibility and stabilizes or destabilizes protein conformation secondary structures. Vital roles of Cys, GSH and PCs for plant stress tolerance are credibly available in literature (Cobbett, 2000, 2003; Hall, 2002; Heiss et al., 2003; Landberg and Greger, 2004; Sharma and Dietz, 2006; Anjum et al., 2010, 2012a,b).

γ-aminobutyric acid (GABA) is a non-protein amino acid. Apart from GABA significance for in-plant metabolism (including carbon—nitrogen metabolism, energy balance, signalling and development), its rapid accumulation to high levels in plants under different adverse environmental conditions has been reported (Kinnersley and Turano, 2000; Kaplan and Guy, 2004; Kempa et al., 2008; Renault et al., 2010; Krasensky and Jonak, 2012; Seher et al., 2013). Amino acids and derivatives are able to chelate metals conferring to plants resistance to toxic levels of metal ions. Histidine consists of carboxyl, amino and imidazole groups and is considered the most important free amino acid in heavy metal metabolism in plants where it acts as a versatile metal chelator and confers metal tolerance (Kramer et al., 1996; Callahan et al., 2006). Nicotianamine (NA) is an amino acid derivative, it occurs in all plants, is involved in the movement of micronutrients in plants (Stephan and Scholz, 1993) and chelates Fe, Cu and Zn in complexes (Stephan et al., 1996) and then accumulates within vacuoles (Pich et al., 1997).

Increasing evidence suggests that osmoprotectants (osmolytes, compatible solutes) play multiple critical roles in increasing plant tolerance to the abiotic stress factors. Osmoprotectants occur in all organisms from bacteria to higher plants and animals. These solutes of low molecular weight are non-toxic even at high concentrations and are able to stabilize proteins and cellular structures and/or to maintain cell turgor by osmotic adjustment, and redox metabolism to remove excess levels of ROS and re-establish the cellular redox balance (Krasenky and Jonak, 2012). The accumulation of osmoprotectants under abiotic stress differs among plant species and chemically, these are of three types: betaines and related compounds; amino acids, such as proline, ecotine and their derivatives and polyols and sugars, such as fructans, trehalose, mannitol, sorbitol, onoitol and pinitol. In plant cells, osmoprotectants are typically confined mainly to the cytosol, chloroplasts and other cytoplasmic compartments that together occupy 20% or less of the volume of mature cells (the other 80% is the large central vacuole) (Rhodes and Samaras, 1994). The free amino acid proline is considered to act as an osmolyte, a ROS scavenger and a molecular chaperone stabilizing the structure of proteins, thereby protecting cells from damage caused by adverse environmental conditions such as drought, high salinity or low temperatures (Rontein et al., 2002; Sleator and Hill, 2002; Verbruggen and Hermans, 2008; Szabados and Savoure, 2010; Krasensky and Jonak, 2012). Glycine betaine (GB) [(CH3)3N+CH2COO−], a quaternary ammonium compound, is a very effective osmoprotectant, which is naturally synthesized and accumulated in response to various abiotic stresses by plants, animals and bacteria (Chen et al., 2000; Zhang et al., 2009). GB has been reported to protect higher plants against salt/ osmotic stresses by maintaining osmotic adjustment (Pollard and Wyn Jones, 1979; Jagendorf and Takabe, 2001), protecting the photosystem II (PSII) complex by stabilizing the connection of extrinsic PSII complex proteins in the presence of salt or under extremes of temperature or pH, and also by protecting membranes against heat-induced destabilization and enzymes such as Rubisco against osmotic stress (Jolivet et al., 1982; Murata et al., 1992; Mohanty et al., 1993; Makela et al., 2000; Chen and Murata, 2011).

Polyamines (PA) stand second to none among amine osmoprotectants and in terms of their significance in plant stress tolerance and/or adaptation. PA are small aliphatic molecules positively charged at cellular pH. The protonated amino and imino groups in polyamines have a positive charge that allows electrostatic interactions with negatively charged groups in macromolecules and cellular substructures, providing a stabilizing effect. Putrescine, spermidine and spermine are the most common PAs in higher plants. Various stresses, such as drought, salinity and cold, modulate PA levels, and high PA levels have been positively correlated with stress tolerance; where PA have been implicated in protecting membranes and alleviating oxidative stress (Groppa and Benavides, 2008; Alcazar et al., 2011; Hussain et al., 2011; Krasenky and Jonak, 2012; Marco et al., 2012). Additionally, reports suggest that electrostatic interactions of polyamines with phosphoric acid residues in DNA, uronic acid residues in the cell wall matrix, and negative groups on membrane surfaces help maintain their functional and structural integrity (Edreva et al., 2007; Marco et al., 2012).

The accumulation of carbohydrates (such as starch and fructans) has been reported in plants as ‘storage substances’ that are mobilized during periods of limited energy supply or enhanced energetic demands (Hendry, 1993). Carbohydrates such as mannitol, sorbitol, inositol and fructans play an important role in osmoprotection. They stabilize membranes, subcellular components, protein complexes or enzymes, preserve dry membranes, liposomes and labile proteins and protect them by ROS scavenging in plants under varied abiotic stresses including drought and salinity (Tuteja and Sopory, 2008; Valluru and Van den Ende, 2008; Livingston et al., 2009). Fructans exhibit high water solubility and are resistant to crystallization at freezing temperatures; therefore, fructan synthesis is very important normally under low temperatures (Vijn and Smeekens, 1999; Livingston et al., 2009), where these compounds can stabilize membranes (Valluru and Van den Ende, 2008) and/or may indirectly contribute to osmotic adjustment upon freezing and dehydration by the release of hexose sugars (Spollen and Nelson, 1994; Olien and Clark, 1995). Mannitol, a six-carbon non-cyclic sugar alcohol, is the most widely distributed sugar alcohol in nature and has been reported in 4100 species of vascular plants of several families, including the Rubiaceae (coffee), Oleaceae (olive, privet) and Apiaceae (celery, carrot, parsley) where it acts as storage of carbon and energy and helps in regulating coenzymes, osmoregulation and free-radical scavenging (Stoop et al., 1996; Bohnert and Jensen, 1996; Prabhavathi and Rajam, 2007). The non-reducing disaccharide trehalose accumulates to high amounts in some desiccation-tolerant plants. Trehalose accumulation in plants has been reported only in Selaginella lepidophylla (Adams et al., 1990) and Myrothamnus flabellifolia (Bianchi et al., 1993). At sufficient levels, trehalose can function as an osmolyte and stabilize proteins and membranes (Paul et al., 2008). The accumulation of raffinose family oligosaccharides (RFOs) (such as raffinose, stachyose and verbascose) has been reported in plants during seed desiccation (Peterbauer and Richter, 2001) and in leaves of plants experiencing environmental stress like cold, heat, drought or high salinity; where RFOs have been implicated in membrane protection and radical scavenging (Hincha, 2003; Nishizawa et al., 2008; reviewed by Krasenky and Jonak, 2012).

Nitrogen (alkaloids, cyanogenic glucosides and non-protein amino acids) and sulfur (GSH, glucosinolates, phytoalexins, thionins, defensins and allinin) containing secondary metabolite compounds are synthesized principally from common amino acids (Rosenthal and Berenbaum, 1992; Van Etten et al., 2001). These compounds have been linked directly or indirectly with the defence of plants against biotic and abiotic stress factors.

1.5 Conclusions and Perspectives

Life on earth relies directly or indirectly on plants where humans harness them for food, feed, fibre, fuel and fun. Food production and environmental conditions are intricately linked; where growing demands for food in turn affect the global environment in many ways. Global food security has been projected to face a severe threat from global environmental change which includes naturally or human activities-influenced changes in the physical and biogeochemical environments. Nevertheless, in the complex field environment with its heterogenic conditions, global environmental changes-mediated potential anomalies are further aggravated with varied abiotic stress combinations, all together severely impacting modern agriculture. Being sessile in nature, plants, in a variably changing environment, have to cope with a plethora of adverse growth conditions (hereafter called stress) where the majority of these conditions can delay growth and development and most importantly prevent them reaching their full genetic potential in terms of productivity. Employing multiple highly regulated and interwoven metabolic networks, plants exposed to stress factors often synthesize a set of diverse metabolites that accumulate to concentrations in the millimolar range, particularly specific amino acids (such as asparagine, histi-dine, proline and serine), peptides (such as glutathione and phytochelatins), and the amines (such as spermine, spermidine, putrescine, nicotianamine and mugineic acids). A credible number of studies have shown significant changes in the contents of the majority of amino acids, peptides and amines thus indicating their functional significance in the context of stress tolerance and/or adaptations.

In the current volume, most of the highlighted above aspects will be covered in significant contributions from renowned experts and researchers working directly or indirectly on the theme of Plant Adaptation to Environmental Change: Significance of Amino Acids and their Derivatives. The outcome of the deliberations will help improve crop tolerance to rapidly mounting varied stress factors; hence to sustainably achieve enough food to feed burgeoning world population.

Acknowledgements

NAA is grateful to the Portuguese Foundation for Science and Technology (FCT) (SFRH/BPD/ 64690/2009; SFRH/BPD/84761/2012) and the Aveiro University Research Institute/Centre for Environmental and Marine Studies (CESAM) for partial financial support. IK is indebted to the Portuguese Foundation for Science and Technology (FCT) (SFRH/BPD/76850/2011). SSG and RG would like to acknowledge the receipt of funds from DBT, DST and UGC, Government of India, New Delhi.

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