Role of Antioxidants in Mitigating Abiotic Stresses in Plants: Current Trends and Mechanisms

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

Deadline for manuscript submissions: closed (31 October 2022) | Viewed by 10230

Special Issue Editor

Department of Agronomy, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611, USA
Interests: plant-microbe interactions; biofertilizer technology; abiotic stresses; plant breeding; plant protection; soil microbiology; phytohormones; phytoremediation and metabolic responses of plants to environmental stresses
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Special Issue Information

Dear Colleagues,

Abiotic stresses adversely affect plant growth and productivity. They negatively impact physiological and biochemical mechanisms and eventually reduce crop growth and productivity. Accumulation of reactive oxygen species (ROS), such as superoxide (O2), hydrogen peroxide (H2O2), and hydroxyl (OH) radical takes place through the exposure of plants to various abiotic stresses. Reactive oxygen species (ROS) are mostly generated in chloroplasts, mitochondria, peroxisomes, apoplast, and plasma membranes and are formed as part of normal cellular metabolism, but their overaccumulation severely damages cellular ingredients including carbohydrates, proteins, lipids, and DNA. However, it has now become apparent that plants actively produce reactive oxygen intermediates (ROIs) as signaling molecules to control abiotic stress responses, pathogen defense, and systemic signaling in plants. Reactive oxygen species (1O2, O−2, and OH) can act as a secondary signaling molecule and transport the signal to the nucleus through redox reactions for increasing tolerance against diverse abiotic stresses. In addition to this, hydrogen peroxide (H2O2) is an important component of stress response regulation in crop plants. Glutathione is also an important water-soluble antioxidant that regulates sulfur transport and expression of stress defense genes. Plants produce compatible organic solutes and osmoprotectants under water-deficit conditions. In these osmoprotectants, proline and glycine betaine are most common. The exogenous application of these two osmoprotectants helps plants to withstand drought stress conditions. Therefore, it is important to study the crosstalk among different antioxidants under abiotic stresses and the underlying mechanisms determining how these antioxidants help plants to withstand harsh environmental conditions. This Special Issue therefore aims to collect research papers and reviews that deal with this aspect of antioxidants.

Dr. Naeem Khan
Guest Editor

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Keywords

  • abiotic stresses
  • antioxidants
  • ROS
  • signal transduction
  • oxidative stress
  • plant stress tolerance

Published Papers (4 papers)

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Research

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21 pages, 2707 KiB  
Article
Application of Plant Growth-Promoting Bacteria from Cape Verde to Increase Maize Tolerance to Salinity
by Catarina Cruz, Paulo Cardoso, Jacinta Santos, Diana Matos, Carina Sá and Etelvina Figueira
Antioxidants 2023, 12(2), 488; https://0-doi-org.brum.beds.ac.uk/10.3390/antiox12020488 - 15 Feb 2023
Cited by 7 | Viewed by 1591
Abstract
Salinity constitutes a major abiotic factor that negatively affects crop productivity. Inoculation with plant growth-promoting bacteria (PGPB) is proven to increase plant tolerance to abiotic stresses and enhance plant growth, development and productivity. The present study aims to increase the resilience of crops [...] Read more.
Salinity constitutes a major abiotic factor that negatively affects crop productivity. Inoculation with plant growth-promoting bacteria (PGPB) is proven to increase plant tolerance to abiotic stresses and enhance plant growth, development and productivity. The present study aims to increase the resilience of crops to salinity using bacteria from the microbiome of plants growing in saline environments. For that, the halotolerance of bacteria present in the roots of natural plants growing on Sal Island, which is characterized by its arid environment and maritime influence, was determined, with some strains having extreme halotolerance. Their ability to produce plant growth-promoting traits was evaluated, with most strains increasing indole acetic acid (26–418%), siderophore (>300%) and alginate (2–66%) production and phosphate solubilization (13–100%) under salt stress. The strains evidencing the best performance were inoculated in maize (Zea mays L.) plants and their influence on plant growth and biochemical status was evaluated. Results evidenced bacterial ability to especially increase proline (55–191%), whose osmotic, antioxidant and protein-protecting properties reduced protein damage in salt-stressed maize plants, evidencing the potential of PGPB to reduce the impact of salinity on crops. Enhanced nutrition, phytohormone production and osmolyte synthesis along with antioxidant response all contribute to increasing plant tolerance to salt stress. Full article
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14 pages, 1180 KiB  
Article
Do Volatiles Affect Bacteria and Plants in the Same Way? Growth and Biochemical Response of Non-Stressed and Cd-Stressed Arabidopsis thaliana and Rhizobium E20-8
by Carina Sá, Diana Matos, Paulo Cardoso and Etelvina Figueira
Antioxidants 2022, 11(11), 2303; https://0-doi-org.brum.beds.ac.uk/10.3390/antiox11112303 - 21 Nov 2022
Cited by 1 | Viewed by 1332
Abstract
Plant roots are colonized by rhizobacteria, and these soil microorganisms can not only stimulate plant growth but also increase tolerance to stress through the production of volatile organic compounds. However, little is known about the effect that these plant beneficial volatiles may have [...] Read more.
Plant roots are colonized by rhizobacteria, and these soil microorganisms can not only stimulate plant growth but also increase tolerance to stress through the production of volatile organic compounds. However, little is known about the effect that these plant beneficial volatiles may have on bacteria. In this study, the effects on growth and oxidative status of different concentrations of three volatiles already reported to have a positive influence on plant growth (2-butanone, 3-methyl-1-butanol, and 2,3-butanediol) were determined in A. thaliana and Rhizobium sp. strain E20-8 via airborne exposure in the presence and absence of Cd. It was expected to ascertain if the plant and the bacterium are influenced in the same way by the volatiles, and if exposure to stress (Cd) shifts the effects of volatiles on plants and bacteria. Results showed the antioxidant activity of the volatiles protecting the plant cell metabolism from Cd toxicity and increasing plant tolerance to Cd. Effects on bacteria were less positive. The two alcohols (3-methyl-1-butanol and 2,3-butanediol) increased Cd toxicity, and the ketone (2-butanone) was able to protect Rhizobium from Cd stress, constituting an alternative way to protect soil bacterial communities from stress. The application of 2-butanone thus emerges as an alternative way to increase crop production and crop resilience to stress in a more sustainable way, either directly or through the enhancement of PGPR activity. Full article
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16 pages, 4299 KiB  
Article
Transcriptome and Metabolome Analyses Reveal Complex Molecular Mechanisms Involved in the Salt Tolerance of Rice Induced by Exogenous Allantoin
by Juan Wang, Yingbo Li, Yinxiao Wang, Fengping Du, Yue Zhang, Ming Yin, Xiuqin Zhao, Jianlong Xu, Yongqing Yang, Wensheng Wang and Binying Fu
Antioxidants 2022, 11(10), 2045; https://0-doi-org.brum.beds.ac.uk/10.3390/antiox11102045 - 18 Oct 2022
Cited by 5 | Viewed by 1812
Abstract
Allantoin is crucial for plant growth and development as well as adaptations to abiotic stresses, but the underlying molecular mechanisms remain unclear. In this study, we comprehensively analyzed the physiological indices, transcriptomes, and metabolomes of rice seedlings following salt, allantoin, and salt + [...] Read more.
Allantoin is crucial for plant growth and development as well as adaptations to abiotic stresses, but the underlying molecular mechanisms remain unclear. In this study, we comprehensively analyzed the physiological indices, transcriptomes, and metabolomes of rice seedlings following salt, allantoin, and salt + allantoin treatments. The results revealed that exogenous allantoin positively affects the salt tolerance by increasing the contents of endogenous allantoin with antioxidant activities, increasing the reactive oxygen species (ROS)–scavenging capacity, and maintaining sodium and potassium homeostasis. The transcriptome analysis detected the upregulated expression genes involved in ion transport and redox regulation as well as the downregulated expression of many salt-induced genes related to transcription and post-transcriptional regulation, carbohydrate metabolism, chromosome remodeling, and cell wall organization after the exogenous allantoin treatment of salt-stressed rice seedlings. Thus, allantoin may mitigate the adverse effects of salt stress on plant growth and development. Furthermore, a global metabolite analysis detected the accumulation of metabolites with antioxidant activities and intermediate products of the allantoin biosynthetic pathway in response to exogenous allantoin, implying allantoin enhances rice salt tolerance by inducing ROS scavenging cascades. These results have clarified the transcript-level and metabolic processes underlying the allantoin-mediated salt tolerance of rice. Full article
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Review

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26 pages, 2662 KiB  
Review
Insight into Recent Progress and Perspectives in Improvement of Antioxidant Machinery upon PGPR Augmentation in Plants under Drought Stress: A Review
by Hittanahallikoppal Gajendramurthy Gowtham, Sudarshana Brijesh Singh, Natarajamurthy Shilpa, Mohammed Aiyaz, Kalegowda Nataraj, Arakere Chunchegowda Udayashankar, Kestur Nagaraj Amruthesh, Mahadevamurthy Murali, Peter Poczai, Abdul Gafur, Waleed Hassan Almalki and R. Z. Sayyed
Antioxidants 2022, 11(9), 1763; https://0-doi-org.brum.beds.ac.uk/10.3390/antiox11091763 - 07 Sep 2022
Cited by 37 | Viewed by 4423
Abstract
Agriculture has a lot of responsibility as the rise in the world’s population demands more food requirements. However, more than one type of biotic and abiotic stress continually impacts agricultural productivity. Drought stress is a major abiotic stress that significantly affects agricultural productivity [...] Read more.
Agriculture has a lot of responsibility as the rise in the world’s population demands more food requirements. However, more than one type of biotic and abiotic stress continually impacts agricultural productivity. Drought stress is a major abiotic stress that significantly affects agricultural productivity every year as the plants undergo several morphological, biochemical, and physiological modifications, such as repressed root and shoot growth, reduced photosynthesis and transpiration rate, excessive production of reactive oxygen species (ROS), osmotic adjustments, and modified leaf senescence regulating and stress signaling pathways. Such modifications may permanently damage the plants; therefore, mitigation strategies must be developed. The use of drought resistant crop cultivars is more expensive and labor-intensive with few advantages. However, exploiting plant growth promoting rhizobacteria (PGPR) is a proven alternative with numerous direct and indirect advantages. The PGPR confers induced systemic tolerance (IST) mechanisms in plants in response to drought stress via multiple mechanisms, including the alteration of root architecture, maintenance of high relative water content, improvement of photosynthesis rate, production of phytohormones, exopolysaccharides, ACC deaminase, carotenoids and volatiles, induction of antioxidant defense system, and alteration in stress-responsive gene expression. The commercial application of PGPR as bioinoculants or biostimulants will remain contingent on more robust strain selection and performance under unfavorable environmental conditions. This review highlights the possible mechanisms of PGPR by activating the plant adaptive defense systems for enhancing drought tolerance and improving overall growth and yield. Full article
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