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.
Being sessile organisms, plants are frequently exposed to various environmental stresses that cause several physiological disorders and even death. Oxidative stress is one of the common consequences ...of abiotic stress in plants, which is caused by excess generation of reactive oxygen species (ROS). Sometimes ROS production exceeds the capacity of antioxidant defense systems, which leads to oxidative stress. In line with ROS, plants also produce a high amount of methylglyoxal (MG), which is an α-oxoaldehyde compound, highly reactive, cytotoxic, and produced via different enzymatic and non-enzymatic reactions. This MG can impair cells or cell components and can even destroy DNA or cause mutation. Under stress conditions, MG concentration in plants can be increased 2- to 6-fold compared with normal conditions depending on the plant species. However, plants have a system developed to detoxify this MG consisting of two major enzymes: glyoxalase I (Gly I) and glyoxalase II (Gly II), and hence known as the glyoxalase system. Recently, a novel glyoxalase enzyme, named glyoxalase III (Gly III), has been detected in plants, providing a shorter pathway for MG detoxification, which is also a signpost in the research of abiotic stress tolerance. Glutathione (GSH) acts as a co-factor for this system. Therefore, this system not only detoxifies MG but also plays a role in maintaining GSH homeostasis and subsequent ROS detoxification. Upregulation of both Gly I and Gly II as well as their overexpression in plant species showed enhanced tolerance to various abiotic stresses including salinity, drought, metal toxicity, and extreme temperature. In the past few decades, a considerable amount of reports have indicated that both antioxidant defense and glyoxalase systems have strong interactions in conferring abiotic stress tolerance in plants through the detoxification of ROS and MG. In this review, we will focus on the mechanisms of these interactions and the coordinated action of these systems towards stress tolerance.
Among the plant nutrients, potassium (K) is one of the vital elements required for plant growth and physiology. Potassium is not only a constituent of the plant structure but it also has a regulatory ...function in several biochemical processes related to protein synthesis, carbohydrate metabolism, and enzyme activation. Several physiological processes depend on K, such as stomatal regulation and photosynthesis. In recent decades, K was found to provide abiotic stress tolerance. Under salt stress, K helps to maintain ion homeostasis and to regulate the osmotic balance. Under drought stress conditions, K regulates stomatal opening and helps plants adapt to water deficits. Many reports support the notion that K enhances antioxidant defense in plants and therefore protects them from oxidative stress under various environmental adversities. In addition, this element provides some cellular signaling alone or in association with other signaling molecules and phytohormones. Although considerable progress has been made in understanding K-induced abiotic stress tolerance in plants, the exact molecular mechanisms of these protections are still under investigation. In this review, we summarized the recent literature on the biological functions of K, its uptake, its translocation, and its role in plant abiotic stress tolerance.
The physiological roles of PAs (putrescine, spermidine, and spermine) were investigated for their ability to confer salt tolerance (200 mM NaCl, 48 h) in mung bean seedlings (Vigna radiata L. cv. ...BARI Mung-2). Salt stress resulted in Na toxicity, decreased K, Ca, Mg, and Zn contents in roots and shoots, and disrupted antioxidant defense system which caused oxidative damage as indicated by increased lipid peroxidation, H2O2 content, Formula: see text generation rate, and lipoxygenase activity. Salinity-induced methylglyoxal (MG) toxicity was also clearly evident. Salinity decreased leaf chlorophyll (chl) and relative water content (RWC). Supplementation of salt affected seedlings with exogenous PAs enhanced the contents of glutathione and ascorbate, increased activities of antioxidant enzymes (dehydroascorbate reductase, glutathione reductase, catalase, and glutathione peroxidase) and glyoxalase enzyme (glyoxalase II), which reduced salt-induced oxidative stress and MG toxicity, respectively. Exogenous PAs reduced cellular Na content and maintained nutrient homeostasis and modulated endogenous PAs levels in salt affected mung bean seedlings. The overall salt tolerance was reflected through improved tissue water and chl content, and better seedling growth.
Reactive oxygen species (ROS) generation is a usual phenomenon in a plant both under a normal and stressed condition. However, under unfavorable or adverse conditions, ROS production exceeds the ...capacity of the antioxidant defense system. Both non-enzymatic and enzymatic components of the antioxidant defense system either detoxify or scavenge ROS and mitigate their deleterious effects. The Ascorbate-Glutathione (AsA-GSH) pathway, also known as Asada-Halliwell pathway comprises of AsA, GSH, and four enzymes viz. ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase, and glutathione reductase, play a vital role in detoxifying ROS. Apart from ROS detoxification, they also interact with other defense systems in plants and protect the plants from various abiotic stress-induced damages. Several plant studies revealed that the upregulation or overexpression of AsA-GSH pathway enzymes and the enhancement of the AsA and GSH levels conferred plants better tolerance to abiotic stresses by reducing the ROS. In this review, we summarize the recent progress of the research on AsA-GSH pathway in terms of oxidative stress tolerance in plants. We also focus on the defense mechanisms as well as molecular interactions.
Chromium (Cr) toxicity is hazardous to the seed germination, growth, and development of plants. γ-aminobutyric acid (GABA) is a non-protein amino acid and is involved in stress tolerance in plants. ...To investigate the effects of GABA in alleviating Cr toxicity, we treated eight-d-old mustard (
Brassica juncea
L.) seedlings with Cr (0.15 and 0.3 mM K
2
CrO
4
, 5 days) alone and in combination with GABA (125 µM) in a semi-hydroponic medium. The roots and shoots of the seedlings accumulated Cr in a dose-dependent manner, which led to an increase in oxidative damage lipid peroxidation; hydrogen peroxide (H
2
O
2
) content; superoxide (O
2
•−
) generation; lipoxygenase (LOX) activity, methylglyoxal (MG) content, and disrupted antioxidant defense and glyoxalase systems. Chromium stress also reduced growth, leaf relative water content (RWC), and chlorophyll (chl) content but increased phytochelatin (PC) and proline (Pro) content. Furthermore, supplementing the Cr-treated seedlings with GABA reduced Cr uptake and upregulated the non-enzymatic antioxidants (ascorbate, AsA; glutathione, GSH) and the activities of the enzymatic antioxidants including ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), glutathione reductase (GR), glutathione peroxidase (GPX), superoxide dismutase (SOD), catalase (CAT), glyoxalase I (Gly I), and glyoxalase II (Gly II), and finally reduced oxidative damage. Adding GABA also increased leaf RWC and chl content, decreased Pro and PC content, and restored plant growth. These findings shed light on the effect of GABA in improving the physiological mechanisms of mustard seedlings in response to Cr stress.
Selenium in plants: Boon or bane? Hasanuzzaman, Mirza; Bhuyan, M.H.M. Borhannuddin; Raza, Ali ...
Environmental and experimental botany,
October 2020, 2020-10-00, Letnik:
178
Journal Article
Recenzirano
•Se has both positive and negate impact on plants’ life.•At higher dose, Se exerts many negative consequence and both growth and physiology are affected.•At lower concentration, Se ac as stimulants ...and promote plant growth and physiology and increase yield.•Se confers abiotic stress tolerance in plants.•Se shows its role as antioxidant and protects plants from oxidative damages.•Selenium biofortification can enhance crop quality.
Selenium (Se) is yet to be confirmed as essential for plants, but it has proven to be an essential trace element for humans and other animals. However, it is well documented that Se is a beneficial element for plants. Recent studies show that Se treatment at a low concentration exerts positive effects on plant growth, development, and yield. Thus, Se may act as a vital element by altering several physiological and biochemical processes. Remarkably, Se also acts as a plant antioxidant and pro-oxidant, and confers tolerance against different abiotic stresses, including salinity, drought, extreme temperature, and toxic metals/metalloids stresses. Its protective mechanism involves the enhancement of photosynthetic pigment synthesis, photosynthetic rate, gas exchange, accumulation of osmoprotectants, and secondary metabolites. Another important role of Se is the enhancement of the antioxidant defense system, which reduces reactive oxygen species (ROS) accumulation and thus oxidative stress. Moreover, Se also induces and modulates stress-responsive proteins/genes. Notably, an excessive Se concentration in growing media shows phytotoxicity associated with the overproduction of ROS as pro-oxidative Se activity, inhibition of the biosynthesis of photosynthetic pigments, and suppression of growth, developmental, and physiological processes. On the other hand, as a phytofortifier, Se may improve the nutritional quality of food crops and fodder. Moreover, plants can play important roles in overwhelming the Se deficiency and toxicity in various areas of the world; thus, a comprehensive mechanism of Se metabolism is crucial for effective Se-biofortification. Therefore, this review focuses on the recent advancement in the beneficial and harmful physiological role of Se in plants under abiotic stresses.
High temperature and drought stress often occur simultaneously, and due to global climate change, this kind of phenomenon occurs more frequently and severely, which exerts devastating effects on ...plants. Polyamines (PAs) play crucial roles in conferring abiotic stress tolerance in plants. Present study investigated how exogenous pretreatment of spermine (Spm, 0.2 mM) enhances mung bean (
Vigna radiata
L. cv. BARI Mung-2) seedlings tolerance to high temperature (HT, 40 °C) and drought induced by 5 % polyethyleneglycol (PEG) stress individually and in combination. Spm pretreatment reduced reactive oxygen species (ROS) production including H
2
O
2
and O
2
•−
, lipoxygenase (LOX) activity, and membrane lipid peroxidation (indicated by malondialdehyde, MDA) under HT and/or drought stress. Histochemical staining of leaves with diaminobenzidine and nitro blue tetrazolium chloride also confirmed that Spm-pretreated seedlings accumulated less H
2
O
2
and O
2
•−
under HT and/or drought stress. Spermine pretreatment maintained the ascorbate (AsA) and glutathione (GSH) levels high, and upregulated the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), dehydroascorbate reductase (DHAR), and glutathione reductase (GR) which were vital for imparting ROS-induced oxidative stress tolerance under HT and/or drought stress. The cytotoxic compound methylglyoxal (MG) was overproduced due to HT and/or drought, but exogenous Spm pretreatment reduced MG toxicity enhancing the glyoxalase system. Spermine pretreatment modulated endogenous PA levels. Osmoregulation and restoration of plant water status were other major contributions of Spm under HT and/or drought stress. Preventing photosynthetic pigments and improving seedling growth parameters, Spm further confirmed its influential roles in HT and/or drought tolerance.
Cadmium (Cd) is a serious environmental threat because it accumulates in plants from soil and is subsequently transported into the food cycle. Increased Cd uptake in plants disrupts plant metabolism ...and hampers crop growth and development. Therefore, remediation of Cd from soil and enhancing plant tolerance to metal toxicity is vital. In the present study, we investigated the function of different doses of citric acid (CA) on Cd toxicity in terms of metal accumulation and stress tolerance in mustard (Brassica juncea L.). Brassica juncea seedlings (12-day-old) were treated with Cd (0.5mMCd and 1.0mM CdCl2) alone and in combination with CA (0.5mM and 1.0mM) in a semi-hydroponic medium for three days. Cadmium accumulation in the roots and shoots of the mustard seedlings increased in a dose-dependent manner and was higher in the roots. Increasing the Cd concentration led to reduced growth, biomass, water status, and chlorophyll (chl) content resulting from increased oxidative damage (elevated malondialdehyde, MDA content; hydrogen peroxide, H2O2 level; superoxide, O2•− generation; lipoxygenase, LOX activity; and methylglyoxal, MG content) and downregulating of the major enzymes of the antioxidant defense and glyoxalase systems. Under Cd stress, both doses of CA improved the growth of the plants by enhancing leaf relative water content (RWC) and chl content; reducing oxidative damage; enhancing the pool of ascorbate (AsA) and glutathione (GSH) and the activities of the antioxidant enzymes (ascorbate peroxidase, APX; monodehydroascorbate reductase, MDHAR; dehydroascorbate reductase, DHAR; glutathione reductase, GR; glutathione peroxidase, GPX; superoxide dismutase, SOD; catalase, CAT); improving the performance of the glyoxalase system (glyoxalase I, Gly I and glyoxalase II, Gly II activity); and increasing the phytochelatin (PC) content. Exogenous CA also increased the root and shoot Cd content and Cd translocation from the roots to the shoots in a dose-dependent manner. Our findings suggest that CA plays a dual role in mustard seedlings by increasing phytoremediation and enhancing stress tolerance through upregulating the antioxidant defense and glyoxalase systems.
•Cadmium (Cd) toxicity decreased plant growth and biomass through oxidative stress.•Citric acid reduced Cd-induced oxidative stress through activating antioxidants.•Citric acid also increased phytoremediation capacity of Brassica juncea L.•Citric acid functioned dose dependently to increase tolerance or phytoremediation.
This study aims at investigate how exogenous glutathione (GSH, 1.0 mM) affects the oxidative stress and antioxidant defense in wheat seedlings under lead (Pb) stress 0.5 and 1.0 mM Pb(NO
3
)
2
. Lead ...treatment decreased growth, leaf relative water content, and chlorophyll (chl) content whereas raised proline (Pro) level. Lead stress increased H
2
O
2
content,
generation rate, and membrane lipid peroxidation. Addition of Pb also disrupted antioxidant enzyme activities and status of endogenous ascorbate and GSH pool. The increase of methylglyoxal was evident under Pb stress. Glutathione supplementation under Pb stress increased antioxidant redox pool and augmented the activities of antioxidant enzymes, and decreased ROS production. Exogenous supplementation of GSH reverted the increase in the methylglyoxal level due to Pb stress due to increased activities of glyoxalase enzymes. Exogenous GSH also regulated Pro, well-maintained tissue water status and prevented chl degradation and increased plant growth and biomass. Abbreviations: AO- ascorbate oxidase; APX- ascorbate peroxidase; AsA- ascorbic acid (ascorbate); BSA- bovine serum albumin; CAT- catalase; CDNB-1-chloro-2, 4-dinitrobenzene; chl- chlorophyll; DHA- dehydroascorbate; DHAR- dehydroascorbate reductase; DTNB- 5,5′-dithio-bis (2-nitrobenzoic acid); EDTA- ethylenediaminetetraacetic acid; Gly I- glyoxalase I; Gly II- glyoxalase II; GR- glutathione reductase; GSH- reduced glutathione; GSSG- oxidized glutathione; GPX- glutathione peroxidase; GST- glutathione S-transferase; MDA- malondialdehyde; MDHA- monodehydroascorbate; MDHAR- monodehydroascorbate reductase; MG- methylglyoxal; NADPH- nicotinamide adenine dinucleotide phosphate; NBT- nitroblue tetrazolium chloride; Pb- lead; PEG- polyethylene glycol; Pro- proline, ROS- reactive oxygen species; RWC- relative water content; SLG- S-d-lactoylglutathione; SOD- superoxide dismutase; TBA- thiobarbituric acid; TCA- trichloroacetic acid.
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