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Antioxidant Defenses in Plants

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A special issue of Antioxidants (ISSN 2076-3921). This special issue belongs to the section "ROS, RNS and RSS".

Deadline for manuscript submissions: closed (30 November 2020) | Viewed by 78933

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Dr. Massimiliano Tattini

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Guest Editor

Institute for Sustainable Plant Protection, National Research Council, Turin, Italy
Interests: secondary metabolites; photoprotection; photosynthesis; plant physiology; plant environmental stress physiology; flavonoids; anthocyanins; reactive oxygen species
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Lucia Guidi

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Co-Guest Editor

Department of Agriculture, Food and Environment, University of Pisa, 56124 Pisa, Italy
Interests: antioxidant compounds; chlorophyll fluorescence; environmental stress; photosynthesis
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

We are leading the following Special Issue entitled: “Antioxidant Defenses in Plants” in the journal Antioxidants.

A common effect of different environmental stimuli on plants, not necessarily resulting in stressful conditions sensu stricto, is the generation of Reactive Oxygen Species (ROS). For instance, plants face large changes in ROS homeostasis on a daily basis, even when growing under both optimal water and nutrient availability, because of large variation in light irradiance. Deviations from ROS homeostasis become considerable when plants are challenged against multiple environmental pressures, due to their sessile nature (plants do not possess the ‘flight strategy’ displayed by other organisms). Plants faced multiple stress agents from their appearance on land and, hence, are well equipped with a modular and integrated network of antioxidant defenses which is, indeed, much more efficient than that displayed by other organisms. Plants have indeed ‘evolved’ a system of antioxidant defenses to keep the ROS levels within a sub-lethal range, being capable, at the same time, of activating a range of ROS-mediated signaling pathways to offer further protection to stress events. For instance, ROS-mediated signaling pathways are likely the main drivers for the biosynthesis of a wide range of secondary metabolites, the significance of which in countering oxidative stress and damage increases with the severity of stress. It is not surprising that plants have long been used as sources of powerful antioxidants for the care of human health, although most phytochemicals may play roles that go well beyond the mere quenching of ROS. For instance, flavonoids behave as ‘signalling molecules’ capable of modulating ROS-mediated signaling pathways acting not only on ROS, but also on downstream components, such as the large number of protein kinases, including the mitogen-activated protein kinases (MAPK) class family. There is also relatively recent evidence that metabolites synthesized through the methyl D-erythritol 4-phosphate (MEP) pathway, such as isoprene and carotenoids, may effectively counter photooxidative stress because of drought- and heat-induced decline in the use of radiant energy into the photosynthetic process. There is increasing evidence supporting the idea that isoprene and zeaxanthin may serve complementary antioxidant functions depending on drought stress severity, with isoprene acting effectively at mild-to-moderate drought and zeaxanthin offering effective protection at severe drought, when the large pool of violaxanthin cycle pigments fully saturates the binding sites in the light‐harvesting chlorophyll‐protein complexes in the photosystem II.

Signaling pathways following alterations in ROS homeostasis are also long known to activate an integrated network of primary antioxidants, mostly consisting of antioxidant enzymes (superoxide dismutase, ascorbate peroxidase, catalase) and metabolites derived from primary metabolism, such as ascorbate and glutathione. So-called soluble carbohydrates, mostly polyols (e.g., mannitol, sorbitol) have long been reported as effective scavengers of ROS, as is the case of mannitol-hydroxyl radical.

The aim of this Special Issue “Antioxidant Defenses in Plants” is to explore the network of antioxidant defenses plants activate in response to the wide range of environmental pressures. Here we are interested in publishing articles focusing on the antioxidant functions of metabolites, originated from both the primary (e.g., soluble carbohydrates, ascorbate and glutathione) and secondary metabolism (e.g., volatile and non-volatile isoprenoids, flavonoids), in plants challenged by stressors of different origin. Papers dealing with the role of antioxidant enzymes in plants exposed to a wide range of stressors are also included in this special issue. Research papers, short (such as opinion pieces) as well as full review articles, both critically reviewing and not merely listing the pertinent literature are welcome.

Dr. Massimiliano Tattini
Prof. Dr. Lucia Guidi
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Antioxidants is an international peer-reviewed open access monthly journal published by MDPI.

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Keywords

Primary and secondary metabolism
Abiotic and biotic stressors
Antioxidant enzymes
Ascorbate-glutathione cycle
Climate change
Oxidative stress and damage
Photooxidative stress
Reactive oxygen species
ROS-mediated signaling pathways
Sugars

Published Papers (11 papers)

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Editorial

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8 pages, 228 KiB

Open AccessEditorial

Antioxidant Defenses in Plants: A Dated Topic of Current Interest

by Lucia Guidi and Massimiliano Tattini

Antioxidants 2021, 10(6), 855; https://doi.org/10.3390/antiox10060855 - 27 May 2021

Cited by 10 | Viewed by 2253

Abstract

Plants have been challenged against oxidative stress since their appearance on land [...] Full article

(This article belongs to the Special Issue Antioxidant Defenses in Plants)

Research

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15 pages, 2470 KiB

Open AccessArticle

Grafting Enhances Pepper Water Stress Tolerance by Improving Photosynthesis and Antioxidant Defense Systems

by Yaiza Gara Padilla, Ramón Gisbert-Mullor, Lidia López-Serrano, Salvador López-Galarza and Ángeles Calatayud

Antioxidants 2021, 10(4), 576; https://doi.org/10.3390/antiox10040576 - 08 Apr 2021

Cited by 15 | Viewed by 2587

Abstract

Currently, limited water supply is a major problem in many parts of the world. Grafting peppers onto adequate rootstocks is a sustainable technique used to cope with water scarcity in plants. For 1 month, this work compared grafted peppers by employing two rootstocks (H92 and H90), with different sensitivities to water stress, and ungrafted plants in biomass, photosynthesis, and antioxidant response terms to identify physiological–antioxidant pathways of water stress tolerance. Water stress significantly stunted growth in all the plant types, although tolerant grafted plants (variety grafted onto H92, Var/H92) had higher leaf area and fresh weight values. Var/H92 showed photosynthesis and stomata conductance maintenance, compared to sensitive grafted plants (Var/H90) and ungrafted plants under water stress, linked with greater instantaneous water use efficiency. The antioxidant system was effective in removing reactive oxygen species (ROS) that could damage photosynthesis; a significant positive and negative linear correlation was observed between the rate of CO₂ uptake and ascorbic acid (AsA)/total AsA (AsA_t) and proline, respectively. Moreover, in Var/H92 under water stress, both higher proline and ascorbate concentration were observed. Consequently, less membrane lipid peroxidation was quantified in Var/H92. Full article

(This article belongs to the Special Issue Antioxidant Defenses in Plants)

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14 pages, 3388 KiB

Open AccessEditor’s ChoiceArticle

Overexpression of the Golden SNP-Carrying Orange Gene Enhances Carotenoid Accumulation and Heat Stress Tolerance in Sweetpotato Plants

by So-Eun Kim, Chan-Ju Lee, Sul-U Park, Ye-Hoon Lim, Woo Sung Park, Hye-Jin Kim, Mi-Jeong Ahn, Sang-Soo Kwak and Ho Soo Kim

Antioxidants 2021, 10(1), 51; https://doi.org/10.3390/antiox10010051 - 04 Jan 2021

Cited by 29 | Viewed by 3771

Abstract

Carotenoids function as photosynthetic accessory pigments, antioxidants, and vitamin A precursors. We recently showed that transgenic sweetpotato calli overexpressing the mutant sweetpotato (Ipomoea batatas [L.] Lam) Orange gene (IbOr-R96H), which carries a single nucleotide polymorphism responsible for Arg to His substitution at amino acid position 96, exhibited dramatically higher carotenoid content and abiotic stress tolerance than calli overexpressing the wild-type IbOr gene (IbOr-WT). In this study, we generated transgenic sweetpotato plants overexpressing IbOr-R96H under the control of the cauliflower mosaic virus (CaMV) 35S promoter via Agrobacterium-mediated transformation. The total carotenoid contents of IbOr-R96H storage roots (light-orange flesh) and IbOr-WT storage roots (light-yellow flesh) were 5.4–19.6 and 3.2-fold higher, respectively, than those of non-transgenic (NT) storage roots (white flesh). The β-carotene content of IbOr-R96H storage roots was up to 186.2-fold higher than that of NT storage roots. In addition, IbOr-R96H plants showed greater tolerance to heat stress (47 °C) than NT and IbOr-WT plants, possibly because of higher DPPH radical scavenging activity and ABA contents. These results indicate that IbOr-R96H is a promising strategy for developing new sweetpotato cultivars with improved carotenoid contents and heat stress tolerance. Full article

(This article belongs to the Special Issue Antioxidant Defenses in Plants)

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16 pages, 2172 KiB

Open AccessArticle

The Biosynthesis of Phenolic Compounds Is an Integrated Defence Mechanism to Prevent Ozone Injury in Salvia officinalis

by Alessandra Marchica, Lorenzo Cotrozzi, Rebecca Detti, Giacomo Lorenzini, Elisa Pellegrini, Maike Petersen and Cristina Nali

Antioxidants 2020, 9(12), 1274; https://doi.org/10.3390/antiox9121274 - 14 Dec 2020

Cited by 19 | Viewed by 2976

Abstract

Specialized metabolites constitute a major antioxidant system involved in plant defence against environmental constraints, such as tropospheric ozone (O₃). The objective of this experiment was to give a thorough description of the effects of an O₃ pulse (120 ppb, 5 h) on the phenylpropanoid metabolism of sage, at both biochemical and molecular levels. Variable O₃-induced changes were observed over time among the detected phenylpropanoid compounds (mostly identified as phenolic acids and flavonoids), likely because of their extraordinary functional diversity. Furthermore, decreases in the phenylalanine ammonia-lyase (PAL), phenol oxidase (PPO), and rosmarinic acid synthase (RAS) activities were reported during the first hours of treatment, probably due to an O₃-induced oxidative damage to proteins. Both PAL and PPO activities were also suppressed at 24 h from the beginning of exposure, whereas enhanced RAS activity occurred at the end of treatment and at the recovery time, suggesting that specific branches of the phenolic pathways were activated. The increased RAS activity was accompanied by the up-regulation of the transcript levels of genes like RAS, tyrosine aminotransferase, and cinnamic acid 4-hydroxylase. In conclusion, sage faced the O₃ pulse by regulating the activation of the phenolic biosynthetic route as an integrated defence mechanism. Full article

(This article belongs to the Special Issue Antioxidant Defenses in Plants)

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22 pages, 2326 KiB

Open AccessArticle

Priming with γ-Aminobutyric Acid against Botrytis cinerea Reshuffles Metabolism and Reactive Oxygen Species: Dissecting Signalling and Metabolism

by Henry Christopher Janse van Rensburg and Wim Van den Ende

Antioxidants 2020, 9(12), 1174; https://doi.org/10.3390/antiox9121174 - 25 Nov 2020

Cited by 17 | Viewed by 2934

Abstract

The stress-inducible non-proteinogenic amino acid γ-aminobutyric acid (GABA) is known to alleviate several (a)biotic stresses in plants. GABA forms an important link between carbon and nitrogen metabolism and has been proposed as a signalling molecule in plants. Here, we set out to establish GABA as a priming compound against Botrytis cinerea in Arabidopsis thaliana and how metabolism and reactive oxygen species (ROS) are influenced after GABA treatment and infection. We show that GABA already primes disease resistance at low concentrations (100 µM), comparable to the well-characterized priming agent β-Aminobutyric acid (BABA). Treatment with GABA reduced ROS burst in response to flg22 (bacterial peptide derived from flagellum) and oligogalacturonides (OGs). Plants treated with GABA showed reduced H₂O₂ accumulation after infection due to increased activity of catalase and guaiacol peroxidase. Contrary to 100 µM GABA treatments, 1 mM exogenous GABA induced endogenous GABA before and after infection. Strikingly, 1 mM GABA promoted total and active nitrate reductase activity whereas 100 µM inhibited active nitrate reductase. Sucrose accumulated after GABA treatment, whereas glucose and fructose only accumulated in treated plants after infection. We propose that extracellular GABA signalling and endogenous metabolism can be separated at low exogenous concentrations. Full article

(This article belongs to the Special Issue Antioxidant Defenses in Plants)

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17 pages, 3154 KiB

Open AccessArticle

Cyst Nematode Infection Elicits Alteration in the Level of Reactive Nitrogen Species, Protein S-Nitrosylation and Nitration, and Nitrosoglutathione Reductase in Arabidopsis thaliana Roots

by Mateusz Labudda, Elżbieta Różańska, Marta Gietler, Justyna Fidler, Ewa Muszyńska, Beata Prabucka and Iwona Morkunas

Antioxidants 2020, 9(9), 795; https://doi.org/10.3390/antiox9090795 - 26 Aug 2020

Cited by 9 | Viewed by 2821

Abstract

Reactive nitrogen species (RNS) are redox molecules important for plant defense against pathogens. The aim of the study was to determine whether the infection by the beet cyst nematode Heterodera schachtii disrupts RNS balance in Arabidopsis thaliana roots. For this purpose, measurements of nitric oxide (NO), peroxynitrite (ONOO⁻), protein S-nitrosylation and nitration, and nitrosoglutathione reductase (GSNOR) in A. thaliana roots from 1 day to 15 days post-inoculation (dpi) were performed. The cyst nematode infection caused generation of NO and ONOO⁻ in the infected roots. These changes were accompanied by an expansion of S-nitrosylated and nitrated proteins. The enzyme activity of GSNOR was decreased at 3 and 15 dpi and increased at 7 dpi in infected roots, whereas the GSNOR1 transcript level was enhanced over the entire examination period. The protein content of GSNOR was increased in infected roots at 3 dpi and 7 dpi, but at 15 dpi, did not differ between uninfected and infected roots. The protein of GSNOR was detected in plastids, mitochondria, cytoplasm, as well as endoplasmic reticulum and cytoplasmic membranes. We postulate that RNS metabolism plays an important role in plant defense against the beet cyst nematode and helps the fine-tuning of the infected plants to stress sparked by phytoparasitic nematodes. Full article

(This article belongs to the Special Issue Antioxidant Defenses in Plants)

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Review

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13 pages, 905 KiB

Open AccessReview

Isoprene: An Antioxidant Itself or a Molecule with Multiple Regulatory Functions in Plants?

by Susanna Pollastri, Ivan Baccelli and Francesco Loreto

Antioxidants 2021, 10(5), 684; https://doi.org/10.3390/antiox10050684 - 27 Apr 2021

Cited by 25 | Viewed by 3699

Abstract

Isoprene (C₅H₈) is a small lipophilic, volatile organic compound (VOC), synthesized in chloroplasts of plants through the photosynthesis-dependent 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway. Isoprene-emitting plants are better protected against thermal and oxidative stresses but only about 20% of the terrestrial plants are able to synthesize isoprene. Many studies have been performed to understand the still elusive isoprene protective mechanism. Isoprene reacts with, and quenches, many harmful reactive oxygen species (ROS) like singlet oxygen (¹O₂). A role for isoprene as antioxidant, made possible by its reduced state and conjugated double bonds, has been often suggested, and sometimes demonstrated. However, as isoprene is present at very low concentrations compared to other molecules, its antioxidant role is still controversial. Here we review updated evidences on the function(s) of isoprene, and outline contrasting indications on whether isoprene is an antioxidant directly scavenging ROS, or a membrane strengthener, or a modulator of genomic, proteomic and metabolomic profiles (perhaps as a secondary effect of ROS removal) eventually leading to priming of antioxidant plant defenses, or a signal of stress for neighbor plants alike other VOCs, or a hormone-like molecule, controlling the metabolic flux of other hormones made by the MEP pathway, or acting itself as a growth and development hormone. Full article

(This article belongs to the Special Issue Antioxidant Defenses in Plants)

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14 pages, 639 KiB

Open AccessReview

The Oxidative Paradox in Low Oxygen Stress in Plants

by Chiara Pucciariello and Pierdomenico Perata

Antioxidants 2021, 10(2), 332; https://doi.org/10.3390/antiox10020332 - 23 Feb 2021

Cited by 23 | Viewed by 4300

Abstract

Reactive oxygen species (ROS) are part of aerobic environments, and variations in the availability of oxygen (O₂) in the environment can lead to altered ROS levels. In plants, the O₂ sensing machinery guides the molecular response to low O₂, regulating a subset of genes involved in metabolic adaptations to hypoxia, including proteins involved in ROS homeostasis and acclimation. In addition, nitric oxide (NO) participates in signaling events that modulate the low O₂ stress response. In this review, we summarize recent findings that highlight the roles of ROS and NO under environmentally or developmentally defined low O₂ conditions. We conclude that ROS and NO are emerging regulators during low O₂ signalling and key molecules in plant adaptation to flooding conditions. Full article

(This article belongs to the Special Issue Antioxidant Defenses in Plants)

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18 pages, 1844 KiB

Open AccessEditor’s ChoiceReview

Are Flavonoids Effective Antioxidants in Plants? Twenty Years of Our Investigation

by Giovanni Agati, Cecilia Brunetti, Alessio Fini, Antonella Gori, Lucia Guidi, Marco Landi, Federico Sebastiani and Massimiliano Tattini

Antioxidants 2020, 9(11), 1098; https://doi.org/10.3390/antiox9111098 - 09 Nov 2020

Cited by 132 | Viewed by 7751

Abstract

Whether flavonoids play significant antioxidant roles in plants challenged by photooxidative stress of different origin has been largely debated over the last few decades. A critical review of the pertinent literature and our experimentation as well, based on a free-of-scale approach, support an important antioxidant function served by flavonoids in plants exposed to a wide range of environmental stressors, the significance of which increases with the severity of stress. On the other side, some questions need conclusive answers when the putative antioxidant functions of plant flavonoids are examined at the level of both the whole-cell and cellular organelles. This partly depends upon a conclusive, robust, and unbiased definition of “a plant antioxidant”, which is still missing, and the need of considering the subcellular re-organization that occurs in plant cells in response to severe stress conditions. This likely makes our deterministic-based approach unsuitable to unveil the relevance of flavonoids as antioxidants in extremely complex biological systems, such as a plant cell exposed to an ever-changing stressful environment. This still poses open questions about how to measure the occurred antioxidant action of flavonoids. Our reasoning also evidences the need of contemporarily evaluating the changes in key primary and secondary components of the antioxidant defense network imposed by stress events of increasing severity to properly estimate the relevance of the antioxidant functions of flavonoids in an in planta situation. In turn, this calls for an in-depth analysis of the sub-cellular distribution of primary and secondary antioxidants to solve this still intricate matter. Full article

(This article belongs to the Special Issue Antioxidant Defenses in Plants)

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23 pages, 1991 KiB

Open AccessEditor’s ChoiceReview

ROS and NO Regulation by Melatonin Under Abiotic Stress in Plants

by Miriam Pardo-Hernández, Maria López-Delacalle and Rosa M. Rivero

Antioxidants 2020, 9(11), 1078; https://doi.org/10.3390/antiox9111078 - 03 Nov 2020

Cited by 81 | Viewed by 5816

Abstract

Abiotic stress in plants is an increasingly common problem in agriculture, and thus, studies on plant treatments with specific compounds that may help to mitigate these effects have increased in recent years. Melatonin (MET) application and its role in mitigating the negative effects of abiotic stress in plants have become important in the last few years. MET, a derivative of tryptophan, is an important plant-related response molecule involved in the growth, development, and reproduction of plants, and the induction of different stress factors. In addition, MET plays a protective role against different abiotic stresses such as salinity, high/low temperature, high light, waterlogging, nutrient deficiency and stress combination by regulating both the enzymatic and non-enzymatic antioxidant defense systems. Moreover, MET interacts with many signaling molecules, such as reactive oxygen species (ROS) and nitric oxide (NO), and participates in a wide variety of physiological reactions. It is well known that NO produces S-nitrosylation and NO₂-Tyr of important antioxidant-related proteins, with this being an important mechanism for maintaining the antioxidant capacity of the AsA/GSH cycle under nitro-oxidative conditions, as extensively reviewed here under different abiotic stress conditions. Lastly, in this review, we show the coordinated actions between NO and MET as a long-range signaling molecule, regulating many responses in plants, including plant growth and abiotic stress tolerance. Despite all the knowledge acquired over the years, there is still more to know about how MET and NO act on the tolerance of plants to abiotic stresses. Full article

(This article belongs to the Special Issue Antioxidant Defenses in Plants)

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52 pages, 2770 KiB

Open AccessEditor’s ChoiceReview

Reactive Oxygen Species and Antioxidant Defense in Plants under Abiotic Stress: Revisiting the Crucial Role of a Universal Defense Regulator

by Mirza Hasanuzzaman, M.H.M. Borhannuddin Bhuyan, Faisal Zulfiqar, Ali Raza, Sayed Mohammad Mohsin, Jubayer Al Mahmud, Masayuki Fujita and Vasileios Fotopoulos

Antioxidants 2020, 9(8), 681; https://doi.org/10.3390/antiox9080681 - 29 Jul 2020

Cited by 1267 | Viewed by 38702

Abstract

Global climate change and associated adverse abiotic stress conditions, such as drought, salinity, heavy metals, waterlogging, extreme temperatures, oxygen deprivation, etc., greatly influence plant growth and development, ultimately affecting crop yield and quality, as well as agricultural sustainability in general. Plant cells produce oxygen radicals and their derivatives, so-called reactive oxygen species (ROS), during various processes associated with abiotic stress. Moreover, the generation of ROS is a fundamental process in higher plants and employs to transmit cellular signaling information in response to the changing environmental conditions. One of the most crucial consequences of abiotic stress is the disturbance of the equilibrium between the generation of ROS and antioxidant defense systems triggering the excessive accumulation of ROS and inducing oxidative stress in plants. Notably, the equilibrium between the detoxification and generation of ROS is maintained by both enzymatic and nonenzymatic antioxidant defense systems under harsh environmental stresses. Although this field of research has attracted massive interest, it largely remains unexplored, and our understanding of ROS signaling remains poorly understood. In this review, we have documented the recent advancement illustrating the harmful effects of ROS, antioxidant defense system involved in ROS detoxification under different abiotic stresses, and molecular cross-talk with other important signal molecules such as reactive nitrogen, sulfur, and carbonyl species. In addition, state-of-the-art molecular approaches of ROS-mediated improvement in plant antioxidant defense during the acclimation process against abiotic stresses have also been discussed. Full article

(This article belongs to the Special Issue Antioxidant Defenses in Plants)

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