Search Results (121)

The mechanism of cadmium (Cd) accumulation was analyzed in the marine alga Ulva compressa. The alga was cultivated with 10 µM Cd, with 10 µM of Cd and increasing concentrations of a sulfide donor (NaHS), or with a sulfide acceptor (hypotaurine), and intracellular Cd levels were monitored for 7 d. Glutathione (GSH) and phytochelatins (PCs) levels, and metallothioneins (MTs) transcript levels were also quantified, along with the extrusion of Cd, GSH, and PCs to the culture medium. The results showed that the sulfide donor increased intracellular Cd levels, whereas the sulfide acceptor decreased them. GSH, PCs, and MTs levels did not correlate with intracellular Cd contents. Both Cd and GSH were extruded to the culture medium, along with lower amounts of PCs. TEM-EDXS analysis revealed electron-dense nanoparticles containing Cd and O, likely CdO or Cd bound to fatty acids; in the presence of NaHS, nanoparticles containing Cd and S (likely CdS) or Cd, S, and N (likely Cd bound to GSH) were also observed. In conclusion, Cd accumulates as insoluble nanoparticles—probably not bound to GSH, PCs, or MTs—and is extruded to the culture medium together with GSH in the marine alga U. compressa. Full article

Agricultural soils worldwide are facing escalating contamination by heavy metals, which present high risks for health due to their persistence, being non-biodegradable, accumulating across the soil profile, and being easily transferred into edible plant tissues, thus propagating through the food chain, with serious consequences for human health and ecosystem integrity. Conventional physical and chemical remediation approaches are costly, ecologically disruptive and operationally complex for the extent of contamination of agricultural land. Thus, there is an urgent need for sustainable and scalable alternatives. This review addresses the need by providing an integrated, mechanistically grounded synthesis of plant-based bioremediation strategies for heavy metal contamination removal, emphasizing the links between soil chemistry, plant physiology, and soil microbiology. First, the principal contamination pathways and controls on metal speciation and bioavailability are summarized, highlighting how parameters such as pH, organic matter, clay minerals, and redox conditions govern the metal fraction available for the plants. The molecular basis of plant heavy metal uptake, translocation and detoxification is examined in detail, including transporter-mediated root uptake, xylem loading and long-distance transport, and chelation by phytochelatins and metallothioneins. The performance and limitations of the main phytoremedation strategies are evaluated across representative hyperaccumulator species, then two major enhancement solutions are discussed: chemical enhancement using synthetic and biodegradable agents, and biological enhancement through plant growth-promoting rhizobacteria, arbuscular mycorrhizal fungi, and mycoremediation fungi. Integrating these perspectives, this review provides a critical assessment of when and how phytoremediation can offer a realistic and agronomically compatible route for managing heavy metal contamination in agricultural soils. Full article

Cadmium (Cd) is a potentially toxic element that impairs plant growth and threatens food safety and human health. This study aimed to investigate the effects of sulfur (S) supplementation on Cd uptake and tolerance in rice under hydroponic conditions. Rice seedlings were exposed to Cd stress and treated with S at different concentrations. Physiological traits, oxidative damage markers, thiol compounds, and ionomic profiles in rice plants were assessed. S supplementation reduced Cd-induced growth inhibition, restoring plant biomass. Although Cd accumulation increased with S treatment, it was accompanied by enhanced antioxidant responses, scavenging reactive oxygen species (ROS) and malondialdehyde. S application increased the production of thiol-containing compounds, including γ-glutamylcysteine, glutathione, and phytochelatins, which helped chelate Cd and sequester it in vacuoles, particularly in roots. Additionally, S supplementation altered the essential nutrient composition in rice tissues, particularly the uptake of N, P, and K, while influencing levels of Ca, Mg, and other essential elements. S supplementation enhanced rice tolerance to Cd stress by reestablishing ROS balance, activating thiol-based detoxification pathways, and regulating mineral nutrient balance. Furthermore, sulfur (S) exhibited a dual effect in plants, enhancing cadmium (Cd) uptake while also promoting its detoxification, underscoring its role in improving crop resilience in contaminated soils. Full article

Phytochelatin synthase (PCS) is crucial for synthesizing phytochelatins, cysteine-rich peptides vital for heavy metal detoxification in plants. Potato, a key staple crop in China, faces risks from soil heavy metal contamination, yet the genes involved in its detoxification, particularly PCS genes, remain underexplored. This study systematically identified and characterized the StPCS gene family in potato using genomic databases, uncovering five StPCS members distributed across three of the 12 potato chromosomes. Phylogenetic analysis classified StPCS proteins into three clades, while gene structure and motif analyses revealed high conservation in domain organization. Promoter region investigations identified stress-responsive elements in nearly all StPCS genes. Under cadmium (Cd) stress conditions, qPCR analysis indicated a significant upregulation of StPCS1 (5.73-fold) and StPCS2 (1.61-fold) transcript levels after 21 days compared to the control, whereas no obvious differences were observed at 7 days post-stress. Subsequent functional verification in yeast revealed that StPCS1 overexpression markedly improved Cd tolerance in transgenic yeast. In addition, analysis of cis-acting elements in the StPCS gene promoter combined with qPCR verification under MeJA and ABA stress conditions suggested that StPCS1 might be involved in Cd stress responses in potato through certain hormone signaling pathways. This study represents the first comprehensive analysis of the StPCS gene family in potato, clarifying its structural characteristics and characterizing the function of StPCS1 as a long-term Cd stress-responsive gene, which lays a solid foundation for investigating its role in heavy metal detoxification. Full article

Phytochelatin synthases (PCSs) are pivotal enzymes in heavy metal detoxification, yet also implicated in sulfur homeostasis and redox regulation. In this study, we report the molecular and functional characterization of the PCS gene from the green alga Scenedesmus acutus (SaPCS), comparing wild-type and chromium-tolerant strains of this microalga. RT-qPCR, immunoblotting and mass spectrometry analyses revealed that SaPCS expression and protein abundance are primarily regulated by sulfur availability rather than by chromium stress. Two protein isoforms (~70 kDa full-length and ~34 kDa truncated) were detected, both more abundant in the chromium-tolerant strain than the wild-type and responsive to sulfur availability. Furthermore, three alternatively spliced transcript variants (SaPCSa, SaPCSb, SaPCSc) lacking the C-terminal domain coding region but retaining a functional or partially disrupted N-terminal catalytic domain were identified, contributing to the post-transcriptional diversification of PCSs. Mass spectrometry analyses showed negligible phytochelatin production in response to chromium treatment, indicating that detoxification of this metal in S. acutus relies mainly on glutathione (GSH) conjugation and the ascorbate–GSH antioxidant cycle. Overall, these results suggest that SaPCS may promote chromium tolerance by modulating sulfur and redox metabolism rather than by driving phytochelatin accumulation, highlighting the remarkable functional plasticity of PCSs in algal stress responses. Full article

Soil heavy metal (HM) pollution poses a severe threat to ecological security and human health. Selenium (Se) is an essential trace element for the human body and can regulate crop growth and development as well as HM uptake in HM-contaminated soils. The regulatory mechanisms of Se on HMs are mainly reflected in four aspects: Geochemical immobilization promotes the formation of metal selenide precipitates and the adsorption of HMs by soil colloids by regulating the rhizosphere redox potential (Eh) and pH value. Rhizosphere microbial remodeling drives the enrichment of functional microorganisms such as Se redox bacteria, plant growth-promoting rhizobacteria (PGPR), and arbuscular mycorrhizal fungi (AMF) through the dual selective pressure of Se toxicity and root exudates, in order to synergistically realize Se speciation transformation and HM adsorption/chelation. Root barrier reinforcement constructs physical and chemical dual defense barriers by inducing the formation of iron plaques on the root surface, remodeling root morphology and strengthening cell wall components such as lignin and polysaccharides. Intracellular transport regulation down-regulates the genes encoding HM uptake transporters, up-regulates the genes encoding HM efflux proteins, and promotes the synthesis of phytochelatins (PCs) to form HM complexes and lastly realizes vacuolar sequestration. Finally, we summarize current research gaps in the interaction mechanisms of different Se species, precise application strategies, and long-term environmental risk assessment, providing a theoretical basis and technical outlook for the green remediation of HM-contaminated farmlands and Se biofortification of crops. Full article

Cadmium (Cd) is a toxic heavy metal that impairs plant growth and induces oxidative stress. In this study, we compared the physiological, biochemical, and molecular responses of two durum wheat (Triticum turgidum ssp. durum) cultivars, Razek and Chili, to Cd stress. Seedlings were exposed to 0, 5, and 50 µM Cd (Cd²⁺; supplied as CdCl₂) under controlled hydroponic and Petri assay conditions. Cd reduced radicle elongation, biomass accumulation, and water uptake in both cultivars, but the relative inhibition of growth was lower in Razek than in Chili, indicating a better capacity to maintain growth under Cd stress. This was accompanied by milder oxidative stress symptoms and more stable antioxidant enzyme activity, particularly for catalase (CAT) and ascorbate peroxidase (APX). Gene expression analyses revealed that Razek maintained a higher expression of antioxidant and stress-related genes under acute Cd stress, while Chili exhibited pronounced downregulation. Histochemical analyses showed increased H₂O₂ accumulation and lignin deposition in Chili roots, suggesting a stronger stress response. Notably, Chili also showed a sharp depletion of reduced glutathione (GSH) under high Cd concentrations, with limited upregulation of GSH synthesis and phytochelatin-related genes. Together, these findings indicate that Razek activates more efficient detoxification, redox regulation, and hormonal signaling pathways under Cd stress, indicating its potential suitability for cultivation in slightly Cd-contaminated soils. Full article

Citrus trees are mainly cultivated in acidic soils. Excessive manganese (Mn) is the second most limiting factor for crop productivity in acidic soils after aluminum toxicity. The roles of reactive oxygen species (ROS) and methylglyoxal (MG) detoxification systems in augmented pH-mediated amelioration of excessive Mn are poorly understood. ‘Sour pummelo’ (Citrus grandis (L.) Osbeck) seedlings were exposed to nutrient solution at a Mn concentration of 500 (Mn500) or 2 (Mn2) μM and a pH of 3 (P3) or 5 (P5). The increase in pH attenuated Mn500-induced increases in ROS production and MG and malondialdehyde accumulation in roots and leaves. Additionally, the increase in pH enhanced the coordinated detoxification capability of both ROS and methylglyoxal scavenging systems in these tissues under Mn500. These findings corroborated the hypothesis that augmenting pH enhances the capability of these tissues to detoxify ROS and methylglyoxal under Mn excess. Therefore, this study provided new evidence on the roles of ROS and MG detoxification systems in the augmented pH-mediated amelioration of oxidative damage in ‘Sour pummelo’ leaves and roots caused by Mn excess, as well as a basis for correcting Mn toxicity by augmenting soil pH. Full article

Heavy metal (HM) contamination threatens environmental sustainability, food safety, and agricultural productivity worldwide. HM toxicity adversely affects plant growth, reducing germination rates by 20–50%, impairing seedling establishment, and inhibiting shoot and root development by 30–60% in various crops. HM disrupts key physiological processes, including photosynthesis, stomatal regulation, membrane integrity, nutrient uptake, and enzymatic and nonenzymatic antioxidant activities. These disruptions largely result from oxidative stress, caused by the excessive accumulation of reactive oxygen species, which damage cellular components. To counteract HM toxicity, plants deploy a complex defense network involving antioxidant enzymes, metal chelation by phytochelatins and metallothioneins, vacuolar sequestration, and symbiotic interactions with arbuscular mycorrhizal fungi, which can retain 40–70% of metals in roots and reduce translocation to shoots. At the molecular level, MAPK (Mitogen-Activated Protein Kinase) signaling pathways, transcription factors (e.g., WRKY, MYB, bZIP, and NAC), and phytohormonal crosstalk regulate the expression of stress-responsive genes expression to enhance HM stress tolerance. Advances in nanotechnology offer promising strategies for the remediation of HM-contaminated soils and water sources (HM remediation); engineered and biogenic nanoparticles (e.g., ZnO, Fe₃O₄) improve metal immobilization, reduce bioavailability, and enhance plant growth by 15–35% under HM stresses, although excessive doses may induce phytotoxicity. Future applications of nanotechnology in HM remediation should consider nanoparticle transformation (e.g., dissolution and agglomeration) and environmentally relevant concentrations to ensure efficacy and minimize phytotoxicity. Integrating phytoremediation with nanoparticle-enabled strategies provides a sustainable approach for HM remediation. This review emphasizes the need for a multidisciplinary framework linking plant science, biotechnology, and nanoscience to advance HM remediation and safeguard agricultural productivity. Full article

Arsenic (As) contamination poses a major challenge to sustainable crop production, particularly in legumes such as peanut (Arachis hypogaea L.), where it disrupts growth, nodulation, and redox homeostasis. This study evaluated the potential of circular-economy-based amendments derived from spent mushroom substrate (SMS) of Pleurotus djamor and plant growth-promoting bacteria (PGPB) to mitigate As stress in peanut plants. Six growth conditions were tested under 20 µM arsenate, including single and combined inoculations with P. djamor and Pseudomonas fluorescens, as well as a residue-only benchmark (E). Results showed that the unamended control (AP) exhibited the highest As accumulation, oxidative stress (H₂O₂, TBARs), and biomass loss, whereas SMS-based amendments attenuated these effects. Treatments HB (SMS + P. djamor + PGPB) and B (SMS + PGPB) combined low As translocation with enhanced antioxidant performance (SOD, CAT), maintaining growth and pigment stability. Amendment H (SMS + P. djamor) preferentially activated phytochelatin-related genes (PCS2, CAD1), while E minimized As uptake but lacked circular applicability. Overall, SMS-PGPB interactions promoted As retention in roots and strengthened ROS-scavenging defenses. These findings highlight SMS-based amendments as viable, sustainable strategies to enhance peanut quality and resilience under As stress, supporting their integration into circular agronomic systems. Full article

The uptake and accumulation of nanoplastics by plants have emerged as a major research focus. Exogenous selenium nanoparticles (SeNPs) are widely used to mitigate the toxicity of abiotic stresses, such as nanoplastics (NPs) and polyethylene (PE—NPs) nanoplastics, and represent a feasible strategy to enhance plant performance. However, the molecular mechanisms by which SeNPs alleviate the phytotoxicity of microplastics and nanoplastics remain poorly defined. To address this gap, we used Pistia stratiotes L. (P. stratiotes) as a model and silicon dioxide nanoparticles (SiO₂NPs) as a comparator, integrating physiological assays, ultrastructural observations, and proteomic analyses. We found that NP stress caused ultrastructural damage in root tips, exacerbated oxidative stress, and intensified membrane lipid peroxidation. SeNPs treatment significantly mitigated NP-induced oxidative injury and metabolic suppression. Compared to the NPs group, SeNPs increased T-AOC by 38.2% while reducing MDA and ·OH by 33.3% and 89.6%, respectively. Antioxidant enzymes were also elevated, with CAT and POD rising by 47.1% and 39.2%. SeNPs further enhanced the photosynthetic capacity and osmotic adjustment, reflected by increases in chlorophyll a, chlorophyll b, and soluble sugar by 49.7%, 43.8%, and 27.0%, respectively. In contrast, proline decreased by 17.4%, indicating stress alleviation rather than an osmotic compensation response. Overall, SeNPs outperformed SiO₂NPs. These results indicate that SeNPs broadly strengthen anti-oxidative defenses and metabolic regulation in P. stratiotes, effectively alleviating NP-induced oxidative damage. Proteomics further showed that SeNPs specifically activated the MAPK signaling cascade, phenylpropanoid biosynthesis, and energy metabolic pathways, enhancing cell-wall lignification to improve the mechanical barrier and limiting NPs translocation via a phytochelatin-mediated vacuolar sequestration mechanism. SiO₂NPs produced similar but weaker alleviative effects. Collectively, these findings elucidate the molecular basis by which SeNPs mitigate NPs’ phytotoxicity and provide a theoretical foundation and practical outlook for using nanomaterials to enhance phytoremediation in aquatic systems. Full article

While the molecular mechanisms of cadmium (Cd) uptake are well-studied in rice and tobacco, hexaploid wheat remains less explored. Elucidating the roles of transporter genes in Cd uptake and translocation in wheat is critical for minimizing Cd accumulation in grains. This study compared the differences in the expression levels of Cd transporter families (including the natural resistance-associated macrophage protein (NRAMP), heavy metal ATPase (HMA), zinc-regulated transporter/iron-regulated transporter (ZIP), and yellow stripe-like (YSL) families) between two high Cd-accumulating wheat varieties and two low Cd-accumulating wheat varieties using qPCR. We found that low Cd-accumulating wheat varieties had higher expression levels of TaNRAMP5 and TaHMA2 in roots and TaHMA3 in aboveground tissues, and lower expression levels of TaNRAMP6, TaZIP5, and TaYSL6 in both roots and aboveground tissues compared to the high Cd-accumulating wheat varieties. Mantel test analysis revealed that the root expression levels of TaNRAMP5 and TaNRAMP6 and aboveground expression levels of TaZIP6 and TaHMA2 were significantly correlated with the Cd content of wheat tissues. Furthermore, the expression levels of TaZIP5 in roots and TaZIP5 and TaHMA3 in aboveground tissues were significantly correlated with the Cd translocation factor from roots to aboveground tissues, suggesting that TaNRAMP5, TaNRAMP6, TaZIP6, and TaHMA2 played key roles in Cd uptake and accumulation in wheat, and TaZIP5 and TaHMA3 were closely associated with Cd translocation from roots to aboveground tissues. Compared to low Cd-accumulating varieties, high Cd-accumulating wheat varieties exhibit significantly elevated levels of thiol-containing compounds for Cd chelation, including glutathione (7.65%~75.5% higher), phytochelatins (2.35%~47.2% higher), and non-protein thiols (13.2%~37.1% higher). These findings deepen insights into wheat Cd absorption processes. The identified transporter genes could serve as foundational resources for future breeding strategies aimed at reducing Cd accumulation in wheat, pending further functional validation. Full article

Lead (Pb) is a widespread environmental pollutant that severely threatens plant growth and development. While the mechanisms of Pb uptake and accumulation have been extensively studied in herbaceous plants, the glutathione (GSH)-mediated biochemical responses in woody species remain largely unexplored. This knowledge gap limits our understanding of the detoxification strategies of perennial plants with high phytoremediation potential. In this study, two Salix integra clones (P336 and P646) with contrasting Pb tolerance were used to investigate the temporal regulation of GSH metabolism under Pb stress. P336 displayed both early and sustained increases in cysteine (Cys), GSH, ascorbic acid (AsA), phytochelatins (PCs), and the activities of γ-ECS and APX, conferring stronger antioxidant and detoxification capacity than P646. Notably, glutathione reductase (GR) activity remained unchanged in both clones, indicating that GSH homeostasis was maintained mainly through de novo synthesis rather than GR-mediated recycling. These findings demonstrate that Pb tolerance in P336 is achieved through γ-ECS–driven de novo GSH biosynthesis, which sustains both the AsA–GSH cycle and PC synthesis for efficient ROS detoxification and Pb sequestration. By providing the first detailed evidence of GSH-centered detoxification dynamics in a woody phytoremediant, this study advances our mechanistic understanding of Pb tolerance in S. integra and highlights its application potential in the phytoremediation of Pb-contaminated environments. Full article

This study aims to investigate the role of exogenous spermidine (Spd) in mitigating the adverse effects of cadmium (Cd) stress on the growth and development of cucumber (Cucumis sativus). The cucumber cultivar “Xintaimici” was used as the experimental material, and a hydroponic experiment was carried out. Based on a baseline Cd concentration of 10 mg·L⁻¹, Spd was supplemented at concentrations of 0.05, 0.1, 0.2, 0.4, and 0.5 mM, resulting in seven treatment groups: control group (CK), S0 group (Cd-only treatment, 10 mg·L⁻¹ Cd + 0 mM Spd), S1+ Cd group (10 mg·L⁻¹ Cd + 0.05 mM Spd), S2+ Cd group (10 mg·L⁻¹ Cd + 0.1 mM Spd), S3+ Cd group (10 mg·L⁻¹ Cd + 0.2 mM Spd), S4+ Cd group (10 mg·L⁻¹ Cd + 0.4 mM Spd), and S5+ Cd group (10 mg·L⁻¹ Cd + 0.5 mM Spd). This study analyzed the regulatory effects of Spd on the growth and development, antioxidant capacity and cadmium accumulation characteristics of cucumber seeds and seedlings. It was found that cadmium stress significantly inhibited their growth process and led to a decline in multiple physiological indicators. Under a Cd concentration of 10 mg·L⁻¹, the application of 0.2 mM Spd significantly improved these parameters. During the seedling stage, the application of 0.2 mM Spd under Cd stress significantly enhanced the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX), as well as the content of soluble proteins, while significantly reducing malondialdehyde (MDA) levels. Cd content analysis revealed that 0.2 mM Spd promoted Cd accumulation in roots while suppressing its translocation to young leaves, thereby reducing Cd accumulation in aboveground tissues. Gene expression analysis demonstrated that this treatment significantly upregulated the expression levels of the phytochelatin synthase gene (CsPCS1) and the gene associated with reduced glutathione synthesis (CsGSHS). In conclusion, the exogenous application of 0.2 mM Spd effectively alleviates oxidative damage and osmotic stress induced by Cd stress in cucumber, promotes plant growth, and significantly enhances Cd tolerance. Full article

Cadmium and arsenic co-contamination found in mining actions indicates major effluence in adjacent farmland soils, disturbing the plant physiology and soil’s microbial community. Phosphorus (P) plays a vital role in reducing soil contamination from Cd and As bioavailability and uptake by plants. However, the right P sources for remediation approaches are critical and still require further research in Cd- and As-contaminated soil. This study aimed to explore the effects of different phosphorus fertilizer sources on Lolium perenne growth and its physiological and rhizosphere microbial diversity under combined contamination with Cd and As. Pot experiments were performed with seven treatments including SSP (single super phosphate), DAP (diammonium phosphate), MAP (monoammonium phosphate), CaP (calcium phosphate), HighCaP (high calcium phosphate), RP (rock phosphate), and no phosphorus fertilizer application (CK) with five replications in the RCB design. The SSP treatment showed the greatest plant height (15.7 cm), hay yield (3567.6 kg·ha⁻¹), and enhanced antioxidant defense activities. It also achieved the highest phosphorus accumulation rate (0.63 g·kg⁻¹) with reduced Cd and As uptake. In addition, SSP promoted higher non-protein sulfhydryl (NPT) and phytochelatin synthetase (PCs) contents along with γ-glutamylcysteine synthetase (γ-ECS) activity, and enriched the rhizosphere microbial community, where the Sphingomonas abundance was 7.08% higher than for other treatments. Therefore, this result indicates that SSP can improve the yield and physiology in L. perenne, as well as soil the rhizosphere microbial community structure, while reducing Cd and As accumulation in plants under Cd and As stress. Full article