The evidence reviewed indicates that As can induce changes in both primary and secondary metabolic pathways, and future research should integrate genomics, transcriptomics, proteomics, and metabolomics to elucidate the molecular basis of As tolerance and support modern crop breeding programs aimed at developing arsenic-tolerant cultivars.
Abstract
Arsenic (As) is a highly toxic metalloid that can be absorbed by plants, inducing stress that disrupts vital physiological processes. In response, plants activate defense mechanisms that allow them to cope with As-induced stress. This review provides a comprehensive overview of the metabolic pathways involved in plant responses to As stress, focusing on the mechanisms of As uptake and transport, metabolic and antioxidant responses, molecular regulation, and mitigation strategies that contribute to plant adaptation and tolerance. As exposure disrupts primary metabolism by impairing photosynthesis, the Calvin cycle, and carbon and energy metabolism, while also altering aquaporin-mediated transport and phosphate homeostasis. In addition, As induces oxidative stress, leading to increased lipid peroxidation and enhanced activities of antioxidant enzymes, including superoxide dismutase (SOD), ascorbate peroxidase (APX), and glutathione reductase (GR). It also affects secondary metabolism by modifying the biosynthesis and accumulation of specialized metabolites involved in stress tolerance. Overall, the evidence reviewed indicates that As can induce changes in both primary and secondary metabolic pathways. Although primary metabolic alterations are relatively well documented, information regarding changes in secondary metabolites, including phenolics and flavonoids, remains limited. Therefore, future research should integrate genomics, transcriptomics, proteomics, and metabolomics to elucidate the molecular basis of As tolerance and support modern crop breeding programs aimed at developing arsenic-tolerant cultivars. Moreover, this knowledge is fundamental for mitigating the impact of As on major food crops such as rice, wheat, maize, and vegetables, where arsenic contamination can reduce productivity, compromise crop quality, and increase the risk of As entry into the food chain. Furthermore, the mechanistic insights gained from these crops may serve as a basis for developing mitigation strategies applicable to other agriculturally important species.
Heavy metal contamination poses a major constraint to plant growth and agricultural productivity by disrupting cellular metabolism and inducing oxidative stress. Exposure to toxic metals results in excessive accumulation of reactive oxygen species (ROS), which damage biomolecules and destabilise cellular homeostasis. Plants mitigate this challenge through a coordinated network of redox-mediated defence mechanisms that includes metal chelation and sequestration, enzymatic antioxidant detoxification, and metabolic adjustment. Beyond these direct responses, ROS also function as key signalling intermediates that activate stress-responsive transcriptional pathways, modulate ion transport, and remodel cell-wall architecture. Crosstalk between redox cues and phytohormones such as abscisic acid, ethylene and jasmonic acid further integrates environmental perception with long-term acclimation. This review synthesises current understanding of the biochemical, structural, and regulatory roles of redox molecules in heavy-metal tolerance, and highlights emerging avenues in omics-driven discovery, genetic enhancement, and microbial strategies. Improved insight into redox-centred defence systems will support the development of resilient crop varieties and sustainable approaches for agriculture in metal-polluted environments.
D. Holman, A. Barker, R. Wu et al.· Journal of Plant Biochemistr...· 0 citations
Heavy metal contamination is a major environmental constraint that negatively affects plant growth, metabolism, and agricultural productivity. Excess metals such as cadmium, lead, and copper disturb cellular functions mainly by inducing oxidative stress, disrupting nutrient balance, and causing toxicity at multiple levels of organization. To cope with these stresses, plants activate complex defense systems, among which melatonin (MT) (N-acetyl-5-methoxytryptamine) has recently emerged as a key regulatory molecule. This review highlights MT's central role in coordinating plant responses to heavy metal stress. MT strengthens redox homeostasis by enhancing both enzymatic and non-enzymatic antioxidant systems, thereby reducing reactive oxygen species (ROS) accumulation and limiting oxidative damage to cellular components. In addition to its antioxidant function, MT regulates metal uptake, transport, and sequestration by modulating transporter families such as NRAMP, ZIP, and HMA, while also promoting detoxification through phytochelatin (PC) and metallothionein (MT) pathways. MT also plays an important role in hormonal crosstalk, interacting with abscisic acid (ABA), jasmonic acid (JA), and salicylic acid (SA) signaling pathways to fine-tune stress perception and downstream defense responses. Furthermore, recent multi-omics studies have shown that MT induces broad transcriptional, proteomic, and metabolomic reprogramming, leading to coordinated adjustments in gene expression, protein activity, and metabolic pathways under heavy metal stress. Overall, MT functions as a central signaling hub that integrates redox regulation, hormonal signaling, and multi-omics networks to enhance plant tolerance to heavy metal stress. These insights deepen understanding of plant stress biology and offer promising strategies to improve crop resilience and phytoremediation efficiency in contaminated environments.
Si-Xi Zhu, Yu-Tian Lv, Shao-Xiong Lin et al.· Plant physiology and biochem...· 0 citations
Integrating molecular insights with breeding and metabolic engineering approaches facilitates the development of climate-resilient crops adapted to increasingly water-limited environments, supporting global food security and climate adaptation efforts.
Arsenic (As) contamination is a major environmental constraint that impairs wheat growth and productivity by disrupting cellular redox homeostasis, photosynthesis, and metabolic processes. Melatonin (MT), a multifunctional plant signaling molecule, has emerged as a promising regulator of plant tolerance to abiotic stresses; however, its role in mitigating As toxicity in wheat remains insufficiently understood. Wheat seedlings of three cultivars (Anaj-17, Galaxy-13, and Nayab-11) were grown in pots containing dried sand and exposed to As stress (20 mg L⁻¹) with or without MT supplementation (75 and 150 µM). Arsenic stress markedly increased As accumulation in grains, malondialdehyde (MDA), hydrogen peroxide (H₂O₂), and electrolyte leakage (EL%), while significantly reducing biomass, chlorophyll content, and gas exchange parameters. In contrast, MT application, particularly at 150 µM, effectively alleviated As-induced oxidative damage by enhancing the activities of catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD). Melatonin also promoted the accumulation of glycine betaine, proline, total soluble sugars, total soluble proteins, and phenolic compounds, contributing to improved physiological performance and stress tolerance. Among the tested cultivars, Anaj-17 exhibited the greatest resilience to As stress and the strongest response to MT treatment, followed by Galaxy-13 and Nayab-11, indicating considerable genotypic variation in As tolerance. These findings demonstrate that melatonin enhances wheat tolerance to arsenic toxicity by strengthening antioxidant defenses, improving osmotic adjustment, and promoting the accumulation of protective metabolites, highlighting its potential as an effective strategy for enhancing heavy-metal stress resilience in wheat and other crop species.
F. Farhat, Arneeb Tariq, Ali Liaquat et al.· Ecotoxicology and Environmen...· 0 citations
Recent researches focus on intensive high-input agricultural practices for maximizing crop yield, involve heavy use of fertilizers, pesticides, and irrigation. These methods increase food production but often lead to environmental degradation, including soil erosion, and increased soil salinity. On the cellular level, salinity elevates the formation of reactive oxygen species (ROS), which cause oxidative damage to lipids, proteins, and nucleic acids, and also serve as signalling molecules and trigger stress responses in plants. Plants counteract these challenges by integrating cellular, biochemical, and molecular adaptations that help to sustain cellular homeostasis. The major component of this whole mechanism is the antioxidant defense system, which consists of various enzymatic components (superoxide dismutase (SOD), catalase (CAT), peroxidases (POD), ascorbate peroxidase (APX), glutathione reductase (GR), and non-enzymatic antioxidants (ascorbate, glutathione, tocopherols, carotenoids, phenolics, compatible osmolytes). These systems synergize to control the ROS levels and maintain redox balance in a saline environment. Moreover, salinity stress triggers intricate networks of molecular signalling, which comprise ROS, calcium signalling, and kinase-mediated pathways. Other pathways that maintain ion homeostasis include the SOS signalling system. A combination of these mechanisms helps plants maintain metabolic stability and adapt to saline conditions. The present review aims to provide in-depth critical insights into these interdependent responses in plants to understand how they contribute to enhancing stress tolerance and improving crop productivity. Such understanding will be highly valuable for developing strategies to optimize plant responses under rising salinity levels and, consequently, improve crop yield.
Apurva Ahlawat, N. Mishra, M. Bajpai· BIO Web of Conferences· 0 citations
Reactive oxygen species (ROS) serve as both critical signalling molecules and potent cytotoxins. Generated predominantly in chloroplasts, mitochondria, peroxisomes, and the apoplast, ROS arise as by-products of aerobic metabolism and are further induced under environmental stresses. This dual nature positions ROS at the interface of plant stress responses, development, and immunity. At low concentrations, ROS act as secondary messengers regulating processes such as seed germination, root hair elongation, stomatal closure, and systemic acquired acclimation. They mediate complex interactions with phytohormones, including abscisic acid (ABA), ethylene (ET), auxins (IAA), and cytokinins, modulating developmental and stress responses. Conversely, excessive ROS accumulation under drought, salinity, extreme temperatures, or pathogen attack leads to oxidative damage, impairing macromolecules and triggering programmed cell death. Plants counteract this through robust antioxidant systems comprising enzymatic (SOD, CAT, APX) and non-enzymatic (ascorbate, glutathione, carotenoids) components. Beyond localized responses, ROS can function as systemic signals through self-propagating RBOH-dependent ROS waves, coordinating whole-plant acclimation and defence, while MAPK cascades act as intracellular effectors that transduce ROS signals into transcriptional and physiological responses. This review elucidates the multifaceted roles of ROS in plant physiology, emphasizing their context-dependent effects as either beneficial regulators or detrimental agents, thus underscoring their identity as both boon and bane. ROS are double-edged molecules vital for signalling, yet harmful at high levels. ROS hormone crosstalk fine-tunes growth, stress responses, and developmental transitions. ROS guides key processes like seed germination, root growth, and programmed cell death. ROS waves enable systemic stress signalling, integrating MAPK, calcium, and retrograde pathways. Antioxidant systems maintain ROS balance, safeguarding plant health under stress. ROS are double-edged molecules vital for signalling, yet harmful at high levels. ROS hormone crosstalk fine-tunes growth, stress responses, and developmental transitions. ROS guides key processes like seed germination, root growth, and programmed cell death. ROS waves enable systemic stress signalling, integrating MAPK, calcium, and retrograde pathways. Antioxidant systems maintain ROS balance, safeguarding plant health under stress.
Aditi Mishra, Anjali Bhardwaj, U. Bhatt et al.· Discover Plants· 0 citations
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