Copper: uptake, toxicity and tolerance in plants and management of Cu-contaminated soil

Copper and cadmium co-contamination increases the risk of nitrogen loss in red paddy soils

The microbiome plays a crucial role in soil nitrogen (N) cycling and in regulating its bioavailability. However, the functional and genomic information of microorganisms encoding N cycling in response to copper (Cu) and cadmium (Cd) contamination is largely unknown. Here, metagenomics and genome binning were used to examine microbial N cycling in Cu and Cd co-contaminated red paddy soils collected from a polluted watershed in southern China. The results showed that soil Cu and Cd concentrations induced more drastic changes in microbial N functional and taxonomic traits than soil general properties. Soil Cu and Cd co-contamination stimulated microbial nitrification, denitrification, and dissimilatory nitrate reduction processes mainly by increasing the abundance of Nitrospira (phylum Nitrospirota), while inhibiting N fixation by decreasing the abundance of Desulfobacca. These contrasting changes in microbial N cycling processes suggested a potential risk of N loss in paddy soils. A high-quality genome was identified as belonging to Nitrospirota with the highest abundance in heavily contaminated soils. This novel Nitrospirota strain possessed metabolic capacities for N transformation and metal resistance. These findings elucidate the genetic mechanisms underlying soil N bioavailability under long-term Cu and Cd contamination, which is essential for maintaining agricultural productivity and controlling heavy metal pollution.

Copper stress in rice: Perception, signaling, bioremediation and future prospects

Copper (Cu) is an indispensable micronutrient for plants, animals, and microorganisms and plays a vital role in different physiological processes. However, excessive Cu accumulation in agricultural soil, often through anthropogenic action, poses a potential risk to plant health and crop productivity. This review article provided a comprehensive overview of the available information regarding Cu dynamics in agricultural soils, major sources of Cu contamination, factors influencing its mobility and bioavailability, and mechanisms of Cu uptake and translocation in rice plants. This review examined the impact of Cu toxicity on the germination, growth, and photosynthesis of rice plants. It also highlighted molecular mechanisms underlying Cu stress signaling and the plant defense strategy, involving chelation, compartmentalization, and antioxidant responses. This review also identified significant areas that need further research, such as Cu uptake mechanism in rice, Cu signaling process, and the assessment of Cu-polluted paddy soil and rice toxicity under diverse environmental conditions. The development of rice varieties with reduced Cu accumulation through comprehensive breeding programs is also necessary. Regulatory measures, fungicide management, plant selection, soil and environmental investigation are recommended to prevent Cu buildup in agricultural lands to achieve sustainable agricultural goals.

The protective role of quercetin against copper-induced female reproductive toxicity: Insights from transcriptome analysis

Quercetin has been shown to mitigate the cytotoxic effects of heavy metals. While copper is an essential trace element for bodily functions, excessive intake has been linked to impaired female reproductive function. Transcriptome analysis was employed to identify genes that are differentially expressed in response to high copper and were validated through qRT-PCR and western blotting. ATP content and Tunel were used to identify the damage of mitochondrial and cell apoptosis. PPI analysis revealed that MKI67, TOPII, ASPM, CASP3, PLK1, and TTK are central proteins within the network. Additionally, exposure to elevated levels of copper resulted in the dysregulation of 86 genes associated with mitochondria. Conversely, treatment with quercetin (QUE) in combination with high copper led to the normalization of 42 mitochondria-related genes previously affected by high copper levels. Furthermore, CuSO4 decreases ATP content and induces cell apoptosis, which can be reversed by QUE. Results suggest that elevated copper levels could lead to oxidative stress and apoptosis by inducing mitochondrial damage, while QUE has the potential to mitigate these effects, ultimately safeguarding granulosa cells and halting the progression of cell death. This study provides novel insights into the molecular pathways involved in female reproductive toxicity caused by excessive copper exposure.

Biochar improves growth and physiology of Swietenia macrophylla king in contaminated soil by copper

The production of açaí seed waste from the commercial and extractive exploitation of the Euterpe oleraceae palm tree is a serious problem that contributes to environmental contamination and production of greenhouse gases, a fact that suggests the need for an environmentally correct destination for this waste produced on a large scale. To this end, this study was conducted to evaluate the potential of acaí seed biochar (BCA) in mitigating the toxic effects of copper in Brazilian mahogany plants, analyzing biometrics and gas exchange. The experimental design was in randomized blocks, with five blocks, in a 4 × 3 factorial scheme, corresponding to the control (without Cu) and three concentration of Cu (200, 400, and 600 mg Cu kg-1) and three levels of BCA (0%, 5% and 10%) proportional to the amount of soil in the pots, totaling sixty experimental units. The use of 5% BCA in soils contaminated with up to 200 mg kg-1 Cu promoted biometric increase (height, diameter, number of leaves), maintaining gas exchange (photosynthesis, stomatal conductance, transpiration, internal carbon and internal/external carbon), and consequently, maintaining water use efficiency in plants under abiotic stress, resulting in plant growth. The findings of this study allow us to indicate the use of biochar in remediating and improving the growth of plants grown in copper-contaminated soils. The production of biochar from açaí seeds is an ecologically sustainable alternative, because it reduces its accumulation on public roads and contributes to reducing soil pollution. In the context of public policies, biochar production could be a source of income in the context of the bioeconomy and circular economy practiced in the Amazon, because it is produced in large quantities.

Novel approach evaluating powdered raw and hydrothermally treated syenite as stonemeal for tropical environments: Potential effects on groundwater quality and agricultural suitability

Soluble fertilizers, particularly potash, are often prohibitively expensive or unavailable in Africa. Consequently, alternatives such as powdered silicate rocks, both raw and hydrothermally treated, are being explored as potential solutions, especially for acidic tropical soils. This study investigates the possible impacts of these rocks (syenite) on groundwater quality, which is a critical factor for agricultural activities. The powdered raw material underwent chemical and mineralogical characterization, including X-ray fluorescence and X-ray diffraction, followed by quantitative evaluation of materials by scanning electron microscopy. Both raw and 46 hydrothermally treated materials were subjected to sequential leaching cycles (1, 24, and 192 h) using deionized water, and the resulting leachates were analyzed by inductively coupled plasma atomic emission spectroscopy. Parameters such as electrical conductivity, total dissolved solids, soluble sodium percentage, sodium adsorption ratio, magnesium hazard, Kelly's ratio, and permeability index were also evaluated. Results from the 47 leachates indicated that 64 % of the samples exhibited excellent to acceptable water quality for irrigation purposes across all parameters. Conversely, 6 % to 13 % fell into the doubtful category, and 2 % to 24 % were classified as unsuitable. Consistency index and ratios of approximately 0.07 and 0.042, respectively, were determined using multi-criteria decision analysis (analytic hierarchy process: AHP), confirming the coherence of the decision and pairwise comparison matrix. The weighted coefficients for each criterion ranged from 0.06 to 0.2. Consequently, the optimal sample (Treatment 23) was identified, showing a hydrothermal temperature of 176 °C, a time of 3.9 h, a normality of 4.62, and a liquid-solid ratio of 0.24. This treatment met all high-water quality standards, including low salinity and sodium hazard, as corroborated by the US salinity laboratory and Wilcox diagrams. Furthermore, due to their nutrient release, low concentration of toxic elements, and effective buffering capacity (pH ∼ 10.6), these powdered syenites are suitable for application in acidic soils.

Superoxide dismutase positively regulates Cu/Zn toxicity tolerance in Sorghum bicolor by interacting with Cu chaperone for superoxide dismutase

Heavy metal stress threatens plant growth and productivity. In this study, we investigated the effects of CuSO4 and ZnSO4 toxicity on sorghum seedlings, focusing on their impact on biomass, germination rates, growth parameters, antioxidant enzyme activities, gene expression profiles, and stress resistance mechanisms. As a result, eight sorghum superoxide dismutase (SOD) genes were identified, and their evolutionary relationships with cis-acting regulatory elements and their expressional patterns were evaluated. Integrating transcriptomic data revealed a key SOD member SbCSD1 that might contribute to plant abiotic stress resistance. Furthermore, SbCSD1 overexpression enhanced plant tolerance to CuSO4 and ZnSO4 stress by regulating SOD activity and interacting with copper chaperone for superoxide dismutase 1 (CCS1) in the plant nucleus and cytoplasm. Meanwhile, silencing CCS1 in SbCSD1-overexpressing plants revealed that SbCSD1 and CCS1 synergistically contribute to Cu stress tolerance. By integrating transcriptomic and genetic data, herein we provide novel insights into the orchestration of plant responses to heavy-metal stress in sorghum by SOD.

Metabolite responses of cucumber on copper toxicity in presence of fullerene C60 derivatives

Copper (Cu) toxicity in crops is a result of excessive release of Cu into environment. Little is known about mitigation of Cu toxicity through the application of carbon-based nanomaterials including water-soluble fullerene C60 derivatives. Two derivatives of fullerene were examined: polyhydroxylated C60 (fullerenol) and arginine C60 derivative. In order to study the response of Cu-stressed plants (Cucumis sativus L.) to these nanomaterials, metabolomics analysis by gas chromatography-mass spectrometry (GC-MS) was performed. Excess Cu (15 μM) caused substantial increase in xylem sap Cu, retarded dry biomass and leaf chlorosis of hydroponically grown cucumber. In Cu-stressed leaves, metabolomes was disturbed towards suppression metabolism of nitrogen (N) compounds and activation metabolism of hexoses. Also, upregulation of some metabolites involving in antioxidant defense system, such as ascorbic acid, tocopherol and ferulic acid, was occurred in Cu-stressed leaves. Hydroponically added fullerene adducts decreased the xylem sap Cu and alleviated Cu toxicity with effectiveness has been most pronounced for arginine C60 derivative. Metabolic responses of plants subjected to high Cu with fullerene derivatives were opposite to that observed under Cu alone. Fatty acids up-regulation (linolenic acid) and antioxidant molecules (tocopherol) down-regulation might indicate that arginine C60 adduct can alleviate Cu induced oxidative stress. Although fullerenol slightly improved cucumber growth, its effect on metabolic state of Cu-stressed plants was not statistically significant. We suggest that tested fullerene C60 adducts have a potential to prevent Cu toxicity in plants through a mechanism associated with their capability to restrict xylem transport of Cu from roots to shoot, and to maintain antioxidative properties of plants.

Integrated physiological, biochemical, and transcriptomic analyses of Bruguiera gymnorhiza leaves under long-term copper stress: Stomatal size, wax crystals and composition

Copper (Cu) is a necessary mineral nutrient for plant growth and development and is involved in several morphological, physiological, and biochemical processes; however, high concentrations of Cu can negatively impact these processes. The role of stomata in responding to various biotic and abiotic stimuli has not been studied in Bruguiera gymnorhiza, particularly in terms of their coordinated interactions at the molecular, physiological, and biochemical levels. Moreover, numerous plants employ strategies such as the presence of thick waxy cuticles on their leaf epidermis and the closing of stomata to reduce water loss. Thus, this study investigates the accumulation of Cu in B. gymnorhiza and its effect on leaf morphology and the molecular response under different Cu treatments (0, 200, and 400 mg L⁻¹, Cu0, Cu200, and Cu400, respectively) during a two years stress period. The results show that Cu stress affected accumulation and transport, increased the activities of peroxidase and ascorbate peroxidase, concentrations of soluble sugar, proline, and H2O2, and decreased the activity of catalase and content of malondialdehyde. Also, Cu-induced stress decreased the uptake of phosphorus and nitrogen and inhibited plant photosynthesis, which consequently led to reduced plant growth. Scanning electron microscopy combined with gas chromatography-mass spectrometry showed that B. gymnorhiza leaves had higher wax crystals and compositions under increased Cu stress, which forced the leaf's stomata to be closed. Also, the contents of alkanes, alcohols, primary alcohol levels (C26:0, C28:0, C30:0, and C32:0), n-Alkanes (C29 and C30), and other wax loads were significantly higher, while fatty acid (C12, C16, and C18) was lower in Cu200 and Cu400 compared to Cu0. Furthermore, the transcriptomic analyses revealed 1240 (771 up- and 469 downregulated), 1000 (723 up- and 277 down-regulated), and 1476 (808 up- and 668 downregulated) differentially expressed genes in Cu0 vs Cu200, Cu0 vs Cu400, and Cu200 vs Cu400, respectively. RNA-seq analyses showed that Cu mainly affected eight pathways, including photosynthesis, cutin, suberin, and wax biosynthesis. This study provides a reference for understanding mangrove response to heavy metal stress and developing novel management practices.

Innovative indenone-derivative colorimetric fluorescent probe: A approach for copper ion detection in water

Copper (Cu2+) is a metal chemical element closely related to human life and is widely used in many fields. However, with the discharge of copper wastewater, the water quality will be seriously affected, leading to excessive intake of Cu2+ and a variety of diseases. Hence, there is a pressing need for an effective detection method for Cu2+ in aqueous environments. Leveraging the remarkable attributes of GFP chromophores and indenone derivatives, we have created a novel colorimetric fluorescent probe P-Cu2+, tailored for efficient copper ion detection. The addition of Cu2+ causes the solution to visibly change from colorless to a pronounced yellow, enabling naked-eye detection and offering promise for real sample analysis.

Effects of exogenous copper on microbial metabolic function and carbon use efficiency of Panax notoginseng planting soil

Soil copper (Cu) pollution is a serious environmental risk in the Panax notoginseng planting area. However, the effect of Cu on soil microbial metabolism and nutrient cycling in this area remains unknown. Therefore, Biolog ECO-plate and enzyme stoichiometry methods were utilized in this study to investigate the impact of exogenous Cu (control: 0 mg·kg-1; Cu100: 100 mg·kg-1; Cu400: 400 mg·kg-1; and Cu600: 600 mg·kg-1) on the metabolic function of soil microbial and nutrient limitation in the P. notoginseng soil. The results indicated that Cu100 significantly increased soil organic carbon (SOC), total phosphorus (TP), soil C:N, microbial biomass carbon (MBC), and microbial biomass nitrogen (MBN) 9.89%, 15.65%, 17.91%, 61.87%, and 90.56% higher than the control, respectively. Moreover, the carbon source utilization ratio of carbohydrates, amino acids, and amphiphilic compounds of Cu100 also increased by 7.16%, 25.47%, and 84.68%, respectively, compared with the control. The activities of β-1,4-glucosidase, cellobiohyrolase, leucine amino peptidase, β-1,4-N-acetylglucosaminidase, and phosphatase significantly decreased with increasing Cu concentration. Soil enzyme stoichiometry showed that all treatments were limited by nitrogen (vector angle < 45°; 19.045-22.081). Cu600 led to the lowest carbon limitation (1.798) and highest carbon use efficiency (CUE:0.267). The PLS-SEM model also showed that MBC, MBN, MBP, and microbial diversity positively affected carbon and nitrogen limitation (0.654 and 0.424). Soil carbon, nitrogen, phosphorus, stoichiometric ratio, MBC, MBN, and MBP positively affected CUE (0.527 and 0.589). The microbial diversity index significantly negatively affected CUE (-1.490). Multiple linear stepwise regression analyses showed that CUE was mainly influenced by MBC, AP, C:P, and LAP. Thus, P. notoginseng soil can benefit soil microbial carbon and nitrogen limitations at low Cu concentrations. Clarifying the metabolic activity and nutritional status of microorganisms under Cu stress can provide some theoretical basis for realizing China's comprehensive and effective management and control policies for environmental risks from metals by 2035.

Molecular Mechanisms of Plant Responses to Copper: From Deficiency to Excess

Copper (Cu) is an essential nutrient for plant growth and development. This metal serves as a constituent element or enzyme cofactor that participates in many biochemical pathways and plays a key role in photosynthesis, respiration, ethylene sensing, and antioxidant systems. The physiological significance of Cu uptake and compartmentalization in plants has been underestimated, despite the importance of Cu in cellular metabolic processes. As a micronutrient, Cu has low cellular requirements in plants. However, its bioavailability may be significantly reduced in alkaline or organic matter-rich soils. Cu deficiency is a severe and widespread nutritional disorder that affects plants. In contrast, excessive levels of available Cu in soil can inhibit plant photosynthesis and induce cellular oxidative stress. This can affect plant productivity and potentially pose serious health risks to humans via bioaccumulation in the food chain. Plants have evolved mechanisms to strictly regulate Cu uptake, transport, and cellular homeostasis during long-term environmental adaptation. This review provides a comprehensive overview of the diverse functions of Cu chelators, chaperones, and transporters involved in Cu homeostasis and their regulatory mechanisms in plant responses to varying Cu availability conditions. Finally, we identified that future research needs to enhance our understanding of the mechanisms regulating Cu deficiency or stress in plants. This will pave the way for improving the Cu utilization efficiency and/or Cu tolerance of crops grown in alkaline or Cu-contaminated soils.

Copper dynamics in vineyard topsoils as affected by the supply of aerated compost tea: insights from a batch experiment

Aerated compost teas (ACTs) are rich in soluble humic substances (SHS) that have high affinity for metals, notably Cu. Using a batch experiment, we measured the extent to which two ACTs altered Cu dynamics in vineyard topsoils one day and 21 days after their addition. Soils were extracted with 0.01 M KCl, and total Cu concentration, free Cu ion fraction and size distribution of Cu ligands were measured in the extraction solution to assess the impact of ACT on the mobility of Cu. Diffusive gradient in thin film (DGT) measurements were carried out to assess the effect of ACT on Cu bioavailability, and the dissociation rate of Cu-SHS complexes was measured. The results revealed that ACT increased the mobility of Cu from a factor 1.2 to 5.8 depending on the soil, the ACT and the incubation time. Cu mobilization was associated with an increase in absorbance at 254 nm and a decrease in the free Cu ion fraction in the KCl extract. Associated with the strong agreement between the size distribution of SHS and that of Cu ligands in the KCl extract of soils treated with ACT, these results showed that Cu was mobilized through complexation by the SHS present in ACTs. A fraction of the SHS supplied with ACTs sorbed onto the soil constituents, notably in calcareous soils where this fraction reached 86% for ACT B. Between 15% and 50% of the SHS remaining in solution degraded between day one and day 21 under the presumed action of microflora. This explains why the Cu mobilization efficiency of ACTs was on average lower in calcareous soils than in non-calcareous soils, and decreased with time. Lastly, ACT increased the bioavailability of Cu in soils from a factor 1.3 to 4.2, due to the relatively high dissociation rate of Cu-SHS complexes.

Isotopic insights and integrated analysis for heavy metal levels, ecological risks, and source apportionment in river sediments of the Qinghai-Tibet Plateau

The research was carried out to examine the pollution characteristics, ecological risk, and origins of seven heavy metals (Hg, As, Pb, Cu, Cd, Zn, and Ni) in 51 sediment samples gathered from 8 rivers located on the Qinghai-Tibet Plateau (QTP) in China. The contents of Hg and Cd were 5.0 and 1.1 times higher than their background values, respectively. The mean levels of other measured heavy metals were below those found naturally in the local soil. The enrichment factor showed that the study area exhibited significantly enriched Hg with 70.6% sampling sites. The Cd contents at 19.6% of sampling sites were moderately enriched. The other sampling sites were at a less enriched level. The sediments of all the rivers had a medium level of potential ecological risk. Hg was the major ecological risk factor in all sampling sites, followed by Cd. The findings from the positive matrix factorization (PMF) analysis shown agricultural activities, industrial activities, traffic emissions, and parent material were the major sources. The upper, middle, and low reaches of the Quanji river had different Hg isotope compositions, while sediments near the middle reaches were similar to the δ202Hg of the industrial source. At the upstream sampling sites, the Hg isotope content was very close to the background level. The results of this research can establish a strong scientific sound to improve the safety of the natural circumstances of rivers on the QTP.

Effects of gold and copper mining on the structure and diversity of the surrounding plant communities in Northeast Tiger and Leopard National Park

Introduction

Northeast China Tiger and Leopard National Park is home to the largest and only breeding family of wild tigers and leopards in China. The mining of open-pit gold and copper mines in the core zone might affect the surrounding forest ecosystem and the survival activities of wild tigers and leopards.

Methods

In order to understand the impacts of gold and copper mining on the structure and diversities of the surrounding plant communities, the vegetation of the forest layer, shrub layer and herb layer of the forest community in the original forest area, mining area, tailings area and restoration area of the Northeast China Tiger and Leopard National Park were investigated, and the influence of plant community structure on species diversity was also evaluated.

Results

This study concluded that there are 25 species belonging to 11 families, 16 genera of trees, 43 species belonging to 22 families, 35 genera of shrubs, and 57 species belonging to 23 families, 46 genera of herb in the sampling sites. There were no significant differences in the community structure characteristics and species diversities of the tree layer and the shrub layer in different operational areas. However, in herb layer, the heights, the coverage and the species diversity index were higher in the restoration area. Additionally, the community structure was one of the major factors that influence the diversity indices, which might be an important way for mining to impact plant diversity.

Discussion

Therefore, mining had some impacts on the structure and diversity of the surrounding plant communities, but the impacts did not reach a significant level. These results could provide scientific support for the management of the forest ecosystems around the mining area of Northeast Tiger and Leopard Park.

Exogenous GABA Enhances Copper Stress Resilience in Rice Plants via Antioxidant Defense Mechanisms, Gene Regulation, Mineral Uptake, and Copper Homeostasis

The importance of gamma-aminobutyric acid (GABA) in plants has been highlighted due to its critical role in mitigating metal toxicity, specifically countering the inhibitory effects of copper stress on rice plants. This study involved pre-treating rice plants with 1 mM GABA for one week, followed by exposure to varying concentrations of copper at 50 μM, 100 μM, and 200 μM. Under copper stress, particularly at 100 μM and 200 μM, plant height, biomass, chlorophyll content, relative water content, mineral content, and antioxidant activity decreased significantly compared to control conditions. However, GABA treatment significantly alleviated the adverse effects of copper stress. It increased plant height by 13%, 18%, and 32%; plant biomass by 28%, 52%, and 60%; chlorophyll content by 12%, 30%, and 24%; and relative water content by 10%, 24%, and 26% in comparison to the C50, C100, and C200 treatments. Furthermore, GABA treatment effectively reduced electrolyte leakage by 11%, 34%, and 39%, and the concentration of reactive oxygen species, such as malondialdehyde (MDA), by 9%, 22%, and 27%, hydrogen peroxide (H2O2) by 12%, 38%, and 30%, and superoxide anion content by 8%, 33, and 39% in comparison to C50, C100, and C200 treatments. Additionally, GABA supplementation led to elevated levels of glutathione by 69% and 80%, superoxide dismutase by 22% and 125%, ascorbate peroxidase by 12% and 125%, and catalase by 75% and 100% in the C100+G and C200+G groups as compared to the C100 and C200 treatments. Similarly, GABA application upregulated the expression of GABA shunt pathway-related genes, including gamma-aminobutyric transaminase (OsGABA-T) by 38% and 80% and succinic semialdehyde dehydrogenase (OsSSADH) by 60% and 94% in the C100+G and C200+G groups, respectively, as compared to the C100 and C200 treatments. Conversely, the expression of gamma-aminobutyric acid dehydrogenase (OsGAD) was downregulated. GABA application reduced the absorption of Cu2+ by 54% and 47% in C100+G and C200+G groups as compared to C100, and C200 treatments. Moreover, GABA treatment enhanced the uptake of Ca2+ by 26% and 82%, Mg2+ by 12% and 67%, and K+ by 28% and 128% in the C100+G and C200+G groups as compared to C100, and C200 treatments. These findings underscore the pivotal role of GABA-induced enhancements in various physiological and molecular processes, such as plant growth, chlorophyll content, water content, antioxidant capacity, gene regulation, mineral uptake, and copper sequestration, in enhancing plant tolerance to copper stress. Such mechanistic insights offer promising implications for the advancement of safe and sustainable food production practices.

Potential of amino acids-modified biochar in mitigating the soil Cu and Ni stresses - Targeting the tomato growth, physiology and fruit quality

Trace heavy metals (HMs) such as copper (Cu) and nickel (Ni) are toxic to plants, especially tomato at high levels. In this study, biochar (BC) was treated with amino acids (AA) to enhance amino functional groups, which effectively alleviated the adverse effects of heavy metals (HMs) on tomato growth. Hence, this study aimed to evaluate the effect of glycine and alanine modified BC (GBC/ABC) on various tomato growth parameters, its physiology, fruit yield and Cu/Ni uptake under Cu and Ni stresses. In a pot experiment, there was 21 treatments with three replications having two rates of simple BC and glycine/alanine enriched BC (0.5% and 1% (w/w). Cu and Ni stresses were added at 150 mg kg-1 respectively. Plants were harvested after 120 days of sowing and subjected to various analysis. Under Cu and Ni stresses, tomato roots accumulated more Cu and Ni than shoots and fruits, while GBC and ABC application significantly enhanced the root and shoot dry weight irrelevant to the stress conditions. Both rates of GBC decreased the malondialdehyde and hydrogen peroxide levels in plants. The addition of 0.5% GBC with Cu enhanced the tomato fruit dry weight by 1.3 folds in comparison to the control treatment; while tomato fruit juice content also increased (50%) in the presence of 0.5% GBC with Ni as compared to control. In summary, these results demonstrated that lower rate of GBC∼0.5% proved to be the best in mitigating the Cu and Ni stress on tomato plant growth by enhancing the fruit production.

Construction of Chitosan-Modified Naphthalimide Fluorescence Probe for Selective Detection of Cu2

A chitosan-based Cu2+ fluorescent probe was designed and synthesized independently using the C-2-amino group of chitosan with 1, 8-naphthalimide derivatives. A series of experiments were conducted to characterize the optical properties of the grafted probe. The fluorescence quenching effect was investigated based on the interactions between the probe and common metals. It was found that the proposed probe displayed selective interaction with Cu2+ over other metal ions and anions, reaching equilibrium within 5 min.

Mechanistic insight into the impact of polystyrene microparticle on submerged plant during asexual propagules germination to seedling: Internalization in functional organs and alterations of physiological phenotypes

Asexual reproduction is one of the most important propagations in aquatic plants. However, there is a lack of information about the growth-limiting mechanisms induced by microplastics on the submerged plant during asexual propagule germination to seedling. Hence, we investigated the effects of two sizes (2 µm, 0.2 µm) and three concentrations (0.5 mg/L, 5 mg/L, and 50 mg/L) of polystyrene microplastics (PSMPs) on Potamogeton crispus turion germination and seedling growth. Both PSMPs sizes were found in P. crispus seedling tissues. Metabolic profile alterations were observed in leaves, particularly affecting secondary metabolic pathways and ATP-binding cassette transporters. Metal elements are indispensable cofactors for photosynthesis; however, alterations in the metabolic profile led to varying degrees of reduced concentrations in magnesium, iron, copper, and zinc within P. crispus. Therefore, the maximum quantum yield of photosystem II significantly decreased in all concentrations with 0.2 µm-PSMPs, and at 50 mg/L with 2 µm-PSMPs. These findings reveal that internalization of microplastics, nutrient absorption inhibition, and metabolic changes contribute to the negative impact on P. crispus seedlings.

Comparative effectiveness of carbon nanoparticles and biochar in alleviating copper stress in corn (Zea mays L.)

The application of carbon nanoparticles (CNPs) and biochar in agriculture for improving plant health and soil quality and alleviating metal stress offers alternative approaches to meet the ever-increasing demand for food. However, poor understanding of their roles in improving crop production under Cu stress represents a significant obstacle to their wide application in agriculture. To clarify how CNPs and biochar affect corn (Zea mays L.) seed germination, seedling growth, plant health, and nutrient uptake under different Cu stress levels, soil-less Petri-dish and greenhouse soil-based bioassays were conducted. The results revealed that CNPs and biochar stimulated corn seed germination and seedling growth. Besides, they were effective in immobilizing Cu2+ sorption in sandy soil and alleviating Cu stress for plant growth, as shown by the increased plant height and dry biomass. The plant nutrient uptake efficiency (NUE) was significantly increased by CNPs, with a maximum increase of 63.1% for N and 63.3% for K at the highest Cu2+ stress level (400 mg Cu2+ L-1). In contrast, non-significant effects on NUE were observed with biochar treatments regardless of Cu stress levels. Interestingly, CNPs significantly increased plant uptake of Cu in the Petri dish test, while biochar inhibited plant uptake of Cu under both experimental conditions. Principle component analysis (PCA) and Pearson correlation analysis indicated that CNPs mitigated Cu stress mainly by elevating antioxidant enzyme activities, enhancing plant photochemical efficiency, and increasing plant uptake of N and K, while biochar was more likely to reduce bioavailability and uptake of Cu in the plant. These findings have great implications for the application of CNPs and biochar as plant growth stimulators and de-toxicity agents in agriculture.

A modified cultivation strategy to enhance biomass production and lipid accumulation of Tetradesmus obliquus FACHB-14 with copper stress and light quality induction

In this study, a two-stage culture strategy was refined to concurrently enhance the growth and lipid accumulation of Tetradesmus obliquus. The results unveiled that, during the initial stage, the optimal conditions for biomass accumulation were achieved with 0.02 mg·L-1 Cu2+ concentration and red light. Under these conditions, biomass accumulation reached 0.628 g·L-1, marking a substantial 23.62 % increase compared to the control group. In the second stage, the optimal conditions for lipid accumulation were identified as 0.5 mg·L-1 Cu2+ concentration and red light, achieving 64.25 mg·g-1·d-1 and marking a 128.38 % increase over the control. Furthermore, the fatty acid analysis results revealed an 18.85 % increase in the saturated fatty acid content, indicating enhanced combustion performance of microalgae cultivated under the dual stress of red light and 0.5 mg·L-1 Cu2+. This study offers insights into the potential application of Tetradesmus obliquus in biofuel production.

Oenothera biennis with strong copper toxicity resistance enriches trace copper in seeds under copper pollution soil

Excess copper (Cu) imparts negative effects on plant growth and productivity in soil. To develop the ability of O. biennis to govern pollution soil containing excessive Cu, we investigated seed germination, seedling growth, and seed yield. Furthermore, Cu content and the expression levels of Cu transport related genes in different tissues were measured under exogenous high concentration Cu. O. biennis seeds were sensitive to excess Cu, with an observed reduction in the germination rate, primary root length, fresh weight, and number of seeds germinated daily. Consecutive Cu stress did not cause fatal damage to evening primrose, yet it slowed down plant growth slightly by reducing the leaf water, chlorophyll, plant yield, and seed oil contents while increasing the soluble sugar, proline, malondialdehyde, and H2O2 contents. The Cu content in different organs of O. biennis was disrupted by excess Cu. In particular, the Cu content in O. biennis seeds and seed oil increased and subsequently decreased with the increase of exogenous Cu, reaching a peak under 600 mg·kg-1 consecutive Cu. Furthermore, the 4-month 900 mg·kg-1 Cu treatment did not induce the excessive accumulation of Cu in peels, seeds, and seed oil, maintaining the Cu content within the range required by the Chinese National Food Safety Standards. The treatment also resulted in an upregulation of Cu-uptake (ObCOPT5, ObZIP4, and ObYSL2) and vigorous efflux (ObHMA1) of transport genes, of which expression levels were significant positive correlation (p < 0.05) with the Cu content. Among all organs, the stem replaced the root as the organ exhibited the greatest ability to absorb and store Cu, and even the Cu transport genes could still function continuously in stem under excess Cu. This work identified a species that can tolerate high Cu content in soil while maintaining a high yield. Furthermore, the results revealed the enrichment of Cu to occur primarily in the O. biennis stem rather than the seeds and peel under excess Cu.

Bioinformatics and Functional Analysis of OsASMT1 Gene in Response to Abiotic Stress

The study aimed to elucidate the functional characteristics of OsASMT1 gene under copper (Cu) or sodium chloride (NaCl) stress. Bioinformatics scrutiny unveiled that OsASMT1 is situated on chromosome 9. Its protein architecture, comprising dimerization and methyltransferase domains, showed significant similarities to OsASMT2 and OsASMT3. High expression in roots and panicles, along with abiotic stress putative cis-regulatory elements in the promoter, indicated potential stress responsiveness. Real-time quantitative PCR confirmed OsASMT1 induction under Cu and NaCl stress in rice. Surprisingly, yeast expressing OsASMT1 did not exhibit enhanced resistance to abiotic stresses. The results of subcellular localization analysis indicated that OsASMT1 plays a role in the cytoplasm. While OsASMT1 responded to Cu and NaCl stress in rice, its heterologous expression in yeast failed to confer abiotic stress resistance, highlighting the need for further investigation of its functional implications.

Copper Stimulation of Tetrahydrocannabinol and Cannabidiol Production in Hemp (Cannabis sativa L.) Is Copper-Type, Dose, and Cultivar Dependent

Copper (Cu) is an element widely used as a pesticide for the control of plant diseases. Cu is also known to influence a range of plant secondary metabolisms. However, it is not known whether Cu influences the levels of the major metabolites in hemp (Cannabis sativa L.), tetrahydrocannabinol (THC) and cannabidiol (CBD). This study investigated the impact of Cu on the levels of these cannabinoids in two hemp cultivars, Wife and Merlot, under field conditions, as a function of harvest time (August-September), Cu type (nano, bulk, or ionic), and dose (50, 100, and 500 ppm). In Wife, Cu caused significant temporal increases in THC and CBD production during plant growth, reaching increases of 33% and 31% for THC and 51% and 16.5% for CBD by harvests 3 and 4, respectively. CuO nanoparticles at 50 and 100 ppm significantly increased THC and CBD levels, compared to the control, respectively, by 18% and 27% for THC and 19.9% and 33.6% for CBD. These nanospecific increases coincided with significantly more Cu in the inflorescences (buds) than in the control and bulk CuO treatments. Contrarily, no temporal induction of the cannabinoids by Cu was noticed in Merlot, suggesting a cultivar-specific response to Cu. However, overall, in Merlot, Cu ions, but not particulate Cu, induced THC and CBD levels by 27% and 36%, respectively, compared to the control. Collectively, our findings provide information with contrasting implications in the production of these cannabinoids, where, dependent on the cultivar, metabolite levels may rise above the 0.3% regulatory threshold for THC but to a more profitable level for CBD. Further investigations with a wider range of hemp cultivars, CuO nanoparticle (NP) doses, and harvest times would clarify the significance and broader implications of the findings.

Microbial strategies for copper pollution remediation: Mechanistic insights and recent advances

Environmental contamination is aninsistent concern affecting human health and the ecosystem. Wastewater, containing heavy metals from industrial activities, significantly contributes to escalating water pollution. These metals can bioaccumulate in food chains, posing health risks even at low concentrations. Copper (Cu), an essential micronutrient, becomes toxic at high levels. Activities like mining and fungicide use have led to Copper contamination in soil, water, and sediment beyond safe levels. Copper widely used in industries, demands restraint of heavy metal ion release into wastewater for ecosystem ultrafiltration, membrane filtration, nanofiltration, and reverse osmosis, combat heavy metal pollution, with emphasis on copper.Physical and chemical approaches are efficient, large-scale feasibility may have drawbackssuch as they are costly, result in the production of sludge. In contrast, bioremediation, microbial intervention offers eco-friendly solutions for copper-contaminated soil. Bacteria and fungi facilitate these bioremediation avenues as cost-effective alternatives. This review article emphasizes on physical, chemical, and biological methods for removal of copper from the wastewater as well asdetailing microorganism's mechanisms to mobilize or immobilize copper in wastewater and soil.

Species-specific effects of mycorrhizal symbiosis on Populus trichocarpa after a lethal dose of copper

Poplars have been identified as heavy metals hyperaccumulators and can be used for phytoremediation. We have previously established that their symbiosis with arbuscular mycorrhizal fungi (AMF) may alter their uptake, tolerance and distribution to excess concentrations of heavy metals in soils. In this study we hypothesised that mycorrhizal symbiosis improves the tolerance of poplars to lethal copper (Cu) concentrations, but this influence may vary among different AMF species. We conducted an experiment in a growth chamber with three Cu application levels of control (0 mg kg-1), threshold-lethal (729 mg kg-1) and supra-lethal (6561 mg kg-1), and three mycorrhizal treatments (non-mycorrhizal, Rhizophagus irregularis, and Paraglomus laccatum) in a completely randomized design with six replications. The poplars did not grow after application of 729 mg Cu kg-1 substrate, and mycorrhizal symbiosis did not help plants to tolerate this level of Cu. This can be explained by the toxicity suffered by mycorrhizal fungi. Translocation of Cu from roots to shoots increased when plants were colonised with R. irregularis and P. laccatum under threshold-lethal and supra-lethal applications of Cu, respectively. This result shows that mycorrhizal mediation of Cu partitioning in poplars depends on the fungal species and substrate Cu concentration. Multi-model inference analysis within each mycorrhizal treatment showed that in plants colonised with R. irregularis, a higher level of mycorrhizal colonisation may prevent Cu transfer to the shoots. We did not observe this effect in P. laccatum plants probably due to the relatively low colonisation rate (14%). Nutrient concentrations in roots and shoots were impacted by applied substrate Cu levels, but not by mycorrhizas. Magnesium (Mg), potassium (K), and manganese (Mn) concentrations in roots reduced with enhancing applied substrate Cu due to their similar ionic radii with Cu and having common transport mechanism. Synergistic effect on shoot concentration between applied substrate Cu levels and Mg, K, calcium, iron (Fe), and zinc was observed. Root Cu concentration was inversely related with root K and Mn concentrations, and shoot Cu concentration had a positive correlation with shoot Fe and K concentrations. Overall, mycorrhizal symbiosis has the potential to enhance plant health and their resilience to Cu toxicity in contamination events. However, it is important to note that the effectiveness of this symbiotic relationship varies among different mycorrhizal species and is influenced by the level of contamination.

Copper removal from aqueous solutions by white rot fungus Pleurotus ostreatus GEMB-PO1 and its potential in co-remediation of copper and organic pollutants

Addressing the environmental contamination from heavy metals and organic pollutants remains a critical challenge. This study explored the resilience and removal potential of Pleurotus ostreatus GEMB-PO1 for copper. P. ostreatus GEMB-PO1 showed significant tolerance, withstanding copper concentrations up to 2 mM. Its copper removal efficiency ranged from 64.56 % at 0.5 mM to 22.90 % at 8 mM. Transcriptomic insights into its response to copper revealed a marked upregulation in xenobiotic degradation-related enzymes, such as laccase and type II peroxidases. Building on these findings, a co-remediation system using P. ostreatus GEMB-PO1 was developed to remove both copper and organic pollutants. While this approach significantly enhanced the degradation efficiency of organic contaminants, it concurrently exhibited a diminished efficacy in copper removal within the composite system. This study underscores the potential of P. ostreatus GEMB-PO1 in environmental remediation. Nevertheless, further investigation is required to optimize the simultaneous removal of organic pollutants and copper.

HY5: a key regulator for light-mediated nutrient uptake and utilization by plants

ELONGATED HYPOCOTYL 5 (HY5), a bZIP-type transcription factor, is a master regulator of light-mediated responses. ELONGATED HYPOCOTYL 5 binds to the promoter of c. 3000 genes, thereby regulating various physiological and biological processes, including photomorphogenesis, flavonoid biosynthesis, root development, response to abiotic stress and nutrient homeostasis. In recent decades, it has become clear that light signaling plays a crucial role in promoting nutrient uptake and assimilation. Recent studies have revealed the molecular mechanisms underlying such encouraging effects and the crucial function of the transcription factor HY5, whose activity is regulated by many photoreceptors. The discovery that HY5 directly activates the expression of genes involved in nutrient uptake and utilization, including several nitrogen, iron, sulphur, phosphorus and copper uptake and assimilation-related genes, enhances our understanding of how light signaling regulates uptake and utilisation of multiple nutrients in plants. Here, we review recent advances in the role of HY5 in light-dependent nutrient uptake and utilization.

Copper oxide nanoparticles: an effective suppression tool against bacterial leaf blight of rice and its impacts on plants

BACKGROUND

To address the challenges of food security for the ever-increasing population, the emergence of nanotechnology provides an alternate technology of choice for the production of safer pesticides which serves as a substitute for conventional fertilizer. The antidrug resistance of Xanthomonas oryzae pv. oryzae (Xoo) and build-up of chemicals in the environment has made it necessary to find alternative safe techniques for effective disease management. Hence, in this study, copper oxide nanoparticles (CuONPs) were produced by green synthesis using a Hibiscus rosa-sinensis L. flower extract.

RESULTS

The characterization of CuONPs using ultraviolet-visible spectrophotometry, scanning electron microscopy with an energy-dispersive spectrum profile, Fourier transform infrared spectroscopy, and X-ray diffraction ascertained the presence of CuONPs, which were nanorods of 28.1 nm. CuONPs significantly obstructed the growth and biofilm development of Xoo by 79.65% and 79.17% respectively. The antibacterial mechanism of CuONPs was found to result from wounding the cell membrane, giving rise to an exodus of intracellular content and generation of oxidative reactive oxygen species that invariably inhibited Xoo respiration and growth. A toxicity study under greenhouse conditions revealed that CuONPs significantly increased growth variables and the biomass of rice, and reduced bacterial leaf blight. Application of CuONPs on Arabidopsis improved the chlorophyll fluorescence parameters; the ΦPSII was significantly increased by 152.05% in comparison to the control.

CONCLUSION

Altogether, these results suggest that CuONPs in low concentration (200.0 μg mL-1 ) are not toxic to plants and can serve as nano-fertilizers and nano-pesticides. © 2023 Society of Chemical Industry.

Grass lignin: biosynthesis, biological roles, and industrial applications

Lignin is a phenolic heteropolymer found in most terrestrial plants that contributes an essential role in plant growth, abiotic stress tolerance, and biotic stress resistance. Recent research in grass lignin biosynthesis has found differences compared to dicots such as Arabidopsis thaliana. For example, the prolific incorporation of hydroxycinnamic acids into grass secondary cell walls improve the structural integrity of vascular and structural elements via covalent crosslinking. Conversely, fundamental monolignol chemistry conserves the mechanisms of monolignol translocation and polymerization across the plant phylum. Emerging evidence suggests grass lignin compositions contribute to abiotic stress tolerance, and periods of biotic stress often alter cereal lignin compositions to hinder pathogenesis. This same recalcitrance also inhibits industrial valorization of plant biomass, making lignin alterations and reductions a prolific field of research. This review presents an update of grass lignin biosynthesis, translocation, and polymerization, highlights how lignified grass cell walls contribute to plant development and stress responses, and briefly addresses genetic engineering strategies that may benefit industrial applications.

Nutritional status of Zombi pea (Vigna vexillata) as influenced by plant density and deblossoming

Feeding billions, a healthy and nutritious diet in the era of climate change is a major challenge before plant breeders, geneticists and agronomist. In this context, the continuous search for adaptive and nutritious crops could be a better alternative to combat the problems of hunger and malnutrition. The zombi pea, a nutritious and underutilized leguminous vegetable, is one of such better alternatives to feed billions a nutritious food besides being a potential gene source for breeding abiotic stress resistant varieties. To evaluate its potential as a wonder crop in the tropical and subtropical regions of India, the nutritional status of tubers, pods and pericarp were investigated under different treatments of plant spacings and deblossoming. The experiment was conducted in split plot design with three replications and eight treatments during 2021-2022 in the coastal regions of India. The nutrient profiling in tubers and pericarp of pods in zombi pea revealed higher accumulation of nutrients viz. potassium (K), magnesium (Mg), iron (Fe), manganese (Mn) and zinc (Zn) with blossom retention. The zombi pea tubers reflected significantly high protein accumulation with the increase in plant spacing. The results pertaining to nutrient profiling in the pods of zombi pea indicated that the plant spacing has no significant effect on the accumulation of majority of nutrients under study. The above-mentioned findings are conspicuously novel and valuable. The present study would pave the way for understanding nutritional importance and breeding potential of this orphan crop. The blossom retention renders higher nutrient accumulation in tubers, pods and pericarp of zombi pea. Deblossoming has no significant influence on nutritional profile of this wonder crop but, wider spacing is effective in producing tubers with high protein content.

The use of copper as plant protection product contributes to environmental contamination and resulting impacts on terrestrial and aquatic biodiversity and ecosystem functions

Copper-based plant protection products (PPPs) are widely used in both conventional and organic farming, and to a lesser extent for non-agricultural maintenance of gardens, greenspaces, and infrastructures. The use of copper PPPs adds to environmental contamination by this trace element. This paper aims to review the contribution of these PPPs to the contamination of soils and waters by copper in the context of France (which can be extrapolated to most of the European countries), and the resulting impacts on terrestrial and aquatic biodiversity, as well as on ecosystem functions. It was produced in the framework of a collective scientific assessment on the impacts of PPPs on biodiversity and ecosystem services in France. Current science shows that copper, which persists in soils, can partially transfer to adjacent aquatic environments (surface water and sediment) and ultimately to the marine environment. This widespread contamination impacts biodiversity and ecosystem functions, chiefly through its effects on phototrophic and heterotrophic microbial communities, and terrestrial and aquatic invertebrates. Its effects on other biological groups and biotic interactions remain relatively under-documented.

A voltammetric peptide biosensor for Cu2+ metal ion quantification in coffee seeds

A prion-derived copper(II)-binding peptide was assembled onto a gold electrode for the building of a voltammetric biosensor for measuring the Cu2+ metal ion in biological samples. The chosen sequence was H-CVNITKQHTVTTTT-NH2, with an appended cysteine residue for binding to the gold surface as a self-assembled monolayer and a histidine residue as the anchorage point for copper(II) complexation. The biosensor showed a linear range of 10-7 to 10-6 M with an 8.0 × 10-8 M detection limit and a 1.0 × 10-7 M quantification limit, with good precision, trueness, and absence of matrix effect. The quantification of Cu2+ was performed in the presence of other transition metal ions, such as Zn2+, Cd2+, Fe2+, or Ni2+, which indicates the excellent selectivity of the biosensor. When the modified electrode was applied for measuring copper(II) in calcined coffee seeds, a difference in copper amount was observed between two Coffea arabica cultivars that were submitted to a treatment with a copper-based antifungal, showing the applicability of the biosensor in the agricultural field.

All-in-One Zinc-Doped Prussian Blue Nanozyme for Efficient Capture, Separation, and Detection of Copper Ion (Cu2+ ) in Complicated Matrixes

Copper is a vital micronutrient for lives and an important ingredient for bactericides and fungicides. Given its indispensable biological and agricultural roles, there is an urgent need to develop simple, affordable, and reliable methods for detecting copper in complicated matrixes, particularly in underdeveloped regions where costly standardized instruments and sample dilution procedures hinder progress. The findings that zinc-doped Prussian blue nanoparticle (ZnPB NP) exhibits exceptional efficiency in capturing and isolating copper ions, and accelerates the generation of dissolved oxygen in a solution of H2 O2 with remarkable sensitivity and selectivity, the signal of which displays a positive correlation with the copper level due to the copper-enhanced catalase-like activity of ZnPB NP, are presented. Consequently, the ZnPB NP serves as an all-in-one sensor for copper ion. The credibility of the method for copper assays in human urine and farmland soil is shown by comparing it to the standard instrumentation, yielding a coefficient of correlation (R2 = 0.9890), but the cost is dramatically reduced. This ZnPB nanozyme represents a first-generation probe for copper ion in complicated matrixes, laying the groundwork for the future development of a practical copper sensor that can be applied in resource-constrained environments.

Transcriptomic and Proteomic Analyses Unveil the Role of Nitrogen Metabolism in the Formation of Chinese Cabbage Petiole Spot

Chinese cabbage is the most widely consumed vegetable crop due to its high nutritional value and rock-bottom price. Notably, the presence of the physiological disease petiole spot significantly impacts the appearance quality and marketability of Chinese cabbage. It is well known that excessive nitrogen fertilizer is a crucial factor in the occurrence of petiole spots; however, the mechanism by which excessive nitrogen triggers the formation of petiole spots is not yet clear. In this study, we found that petiole spots initially gather in the intercellular or extracellular regions, then gradually extend into intracellular regions, and finally affect adjacent cells, accompanied by cell death. Transcriptomic and proteomic as well as physiology analyses revealed that the genes/proteins involved in nitrogen metabolism exhibited different expression patterns in resistant and susceptible Chinese cabbage lines. The resistant Chinese cabbage line has high assimilation ability of NH4+, whereas the susceptible one accumulates excessive NH4+, thus inducing a burst of reactive oxygen species (ROS). These results introduce a novel perspective to the investigation of petiole spot induced by the nitrogen metabolism pathway, offering a theoretical foundation for the development of resistant strains in the control of petiole spot.

MitomiR-1736-3p regulates copper-induced mitochondrial pathway apoptosis by inhibiting AATF in chicken hepatocytes

Copper (Cu) is a toxic heavy metal pollutant. The hepatic toxicity of Cu has attracted widespread attention from researchers. However, its underlying mechanism remains elusive. Mitochondrial microRNAs (mitomiRs) are considered important factors in regulating mitochondrial and cellular functions, and their roles have been implicated in the mechanisms of metal toxicity. Therefore, this research revealed the changes in the mitomiRs expression profile of chicken liver after Cu exposure. It was ultimately determined that mitomiR-1736-3p can be involved in Cu-induced chicken liver damage by targeting AATF. In particular, our investigations have uncovered that exposure to Cu can trigger heightened levels of apoptosis in the hepatic tissue of chickens and primary chicken embryo hepatocytes (CEHs). It is noteworthy that we found upregulation of miR-1736-3p expression can exacerbate Cu-induced cell apoptosis, while inhibition of miR-1736-3p can effectively reduce apoptosis occurrence. Subsequently, we found that Cu-induced cell apoptosis could be restored by overexpressing AATF, while silencing AATF exacerbated the level of apoptosis. Fascinatingly, this change in apoptotic level is directly influenced by AATF on Bax and Bak1, rather than on p53 and Bcl-2. Overall, these findings suggest that the mitomiR-1736-3p/AATF axis mediates the mitochondrial pathway of cell apoptosis potentially involved in Cu-induced chicken liver toxicity.

Circulating copper levels and the risk of cardio-cerebrovascular diseases and cardiovascular and all-cause mortality: A systematic review and meta-analysis of longitudinal studies

BACKGROUND

Copper is an essential trace element in the human body; its relationship with cardio-cerebrovascular diseases (CCVDs) remains unclear. This study aimed to comprehensively investigate the association between circulating copper concentrations and CCVD risk and mortality.

METHODS

We searched the PubMed, Cochrane Library, Embase, Scopus, and Web of Knowledge databases for cohort studies reporting associations between circulating copper concentrations and cardiovascular diseases and mortality published up to August 23, 2023. Effect sizes were pooled using random-effects models. We graded the certainty of the evidence by the GRADE (Grading of Recommendations Assessment, Development, and Evaluation) framework.

RESULTS

Our analysis included 47,813 patients across 17 cohort studies. Elevated circulating copper levels were linked to the risk of stroke (OR = 1.52; 95% CI 1.30-1.78), coronary artery disease mortality (RR = 2.77; 95% CI 1.82-4.19), cardiovascular mortality (RR = 1.79; 95% CI 1.52-2.11), and all-cause mortality (RR = 1.56; 95% CI 1.35-1.79) but not the risk of acute myocardial infarction (RR = 2.01; 95% CI 0.63-6.47). Continuous analysis (per 20 μg/dl increase) showed consistent results regarding the association between copper levels and stroke incidence (OR = 1.23; 95% CI 1.14-1.33), cardiovascular mortality (HR = 1.28; 95% CI 1.07-1.53) and all-cause mortality (HR = 1.22; 95% CI 1.04-1.44). Except for the low certainty of evidence of acute myocardial infarction incidence, all outcomes had moderate certainty of evidence.

CONCLUSION

Excessive circulating copper levels are associated with stroke, coronary artery disease mortality, cardiovascular mortality, and all-cause mortality with moderate certainty.

Effect of copper oxide and zinc oxide nanoparticles on photosynthesis and physiology of Raphanus sativus L. under salinity stress

The study evaluates the impact of two metal oxide nanoparticles: copper oxide (CuO) and zinc oxide (ZnO) on the growth and physiology of Raphanus sativus L. (radish) under salinity stress. Fifteen days old seedlings of R. sativus were subjected to different concentrations of salt stress (0 mM, 150 mM, and 300 mM NaCl) alone and in interaction with 100 mgL-1 metal oxide nanoparticle treatments (CuO and ZnO NPs via foliar spray) for 15 days. The results confirmed the severe effects of salinity stress on the growth and physiology of radish plants by decreasing nutrient uptake, leaf area, and photosystems photochemistry and by increasing proline accumulation, anthocyanin, flavonoids content, and antioxidant enzyme activities which is directly linked to increased oxidative stress. The foliar application of CuO and ZnO NPs alleviated the adverse effects of salt stress on radish plants, as indicated by improving these attributes. Foliar spray of ZnO NPs was found efficient in improving the leaf area, photosynthetic electron transport rate, the PSII quantum yield, proton conductance and mineral content in radish plants under NaCl stress. Besides, ZnO NPs decreased the NaCl-induced oxidative stress by declining proline, anthocyanin, and flavonoids contents and enzymatic activities such as superoxide dismutase (SOD), ascorbate peroxidase (APX) and guaiacol peroxidase (GOPX). Thus, our study revealed that ZnO NPs are more effective and have beneficial effects over CuO NPs in promoting growth and reducing the adverse effects of NaCl stress in radish plants.

Potential of herbaceous plant species for copper (Cu) accumulation

The removal of copper (Cu) in soils by green technology is less treated with urgency, as it is a plant micronutrient. We examined the efficiency of Cu shoot accumulation by herbaceous plants in Cu-contaminated and non-contaminated soils in Trhové Dusniky and Podles, respectively, in the Czech Republic. The total soil Cu content of 81 mg kg-1 in Trhové Dusniky indicated a slight contamination level compared to 50 mg kg-1, the permissible value by WHO, and < 35 in Podlesí, representing a clean environment. The Cu content was above the permissible value in plants (10 mg kg-1 by WHO) in herbaceous speciesat the control site without trees: Stachys palustris L. (10.8 mg kg-1), Cirsium arvense L. (11.3 mg kg-1), Achillea millefolium L. (12.1 mg kg-1), Anthemis arvense L. (13.2 mg kg-1), and Calamagrostis epigejos L. (13.7 mg kg-1). In addition, Hypericum maculatum Crantz (10.6 mg kg-1), Campanula patula L. (11.3 mg kg-1), C. arvense (15 mg kg-1), and the highest accumulation in shoot of Equisetum arvense L. (37.1 mg kg-1), all under the canopy of trees at the uncontaminated site, were above the WHO value. Leucanthemum Vulgare (Lam.) and Plantago lanceolata L. recorded 11.2 mg kg-1 and 11.5 mg kg-1, respectively, in the soil of the Cu-contaminated site. These herbaceous species can support the phyto-management of Cu-contaminated soils, especially E. arvense. Critical attention is well-required in the medicinal application of herbaceous plants in treating human ailments due to their Cu accumulation potentials above the threshold. Spontaneous surveys and analysis of Cu speciation in herbaceous species can reveal suitable plants to decontaminate soils and provide caution on consumable products, especially bioactive compounds.

Crinum bulbispermum, a Medicinal Geophyte with Phytostabilization Properties in Metal-Enriched Mine Tailings

Ancient grasslands are lost through transformation to agriculture, mining, and urban expansion. Land-use change leads to ecosystem degradation and a subsequent loss of biodiversity. Globally, degraded grasslands have become a priority for restoration efforts to recover lost ecosystem services. Although the ecological and social benefits of woody species and grasses are well documented, limited research has considered the use of forbs for restoration purposes despite their benefits (e.g., C sequestration and medicinal uses). The aim of this study was to determine if Crinum bulbispermum (Burm.f.) Milne-Redh. & Schweick., a medicinal geophyte, could form part of restoration initiatives to restore mine soils in grasslands of the South African Highveld. A pot experiment was conducted to assess the performance of C. bulbispermum in a random design, with three soil treatments varying in level of degradation and metal contamination. The plants were monitored for 12 months, and the morphological characters were measured monthly to assess performance and survival. Inductively coupled plasma mass spectrometry (ICP-MS) was used to determine the soil and plant tissue concentration of potentially toxic metals. The results indicated that mine tailings negatively affected the growth and development of C. bulbispermum. Although the survival rates indicated that it could survive on tailings, its below-par productivity indicated that the species is not ideal for restoration purposes unless the tailings are ameliorated with topsoil. Although there was root accumulation of metals (Co, Cd, Cu, Mo, and Zn), there was no translocation to the bulbs and leaves, which makes C. bulbispermum suitable for medicinal use even when grown on metal-enriched soil. This species may not be viable for phytoremediation but is a contender to be used in phytostabilization due to its ecological advantages and the fact that it does not accumulate or store metals. These findings underscore the importance of considering geophytes in grassland restoration strategies, expanding their ecological and societal benefits beyond conventional approaches.

Mitochondrial DNA release mediated by TFAM deficiency promotes copper-induced mitochondrial innate immune response via cGAS-STING signalling in chicken hepatocytes

Copper (Cu) is pollution metal that is a global concern due to its toxic effects. A recent study found that the release of mitochondrial DNA (mtDNA) into the cytoplasm can activate the innate immune response, but the exact mechanisms underlying the effect of Cu exposure remains unknown. In this study, we identified that the reduction in transcription Factor A (TFAM) led to mtDNA leakage into the cytoplasm under Cu exposure in hepatocytes, accompanied by the activation of the cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway-mediated innate immunity (increased expression of cGAS, STING, TANK-binding kinase-1 (TBK1), and interferon regulatory factor-3 (IRF3)) genes and proteins, and enhanced phosphorylation levels of TBK1 and IRF3). Subsequently, silencing TFAM (siTFAM) significantly aggravated mtDNA release and the innate immune response under Cu treatment. Mitochondrial DNA depletion alleviated Cu-induced innate immunity in hepatocytes, while mtDNA transfection further enhanced the innate immune response. Notably, the inhibition of STING effectively alleviated the phosphorylation levels of the TBK1 and IRF3 proteins induced by Cu, while the upregulation of STING aggravated the Cu-induced innate immunity. Furthermore, EtBr and H-151(a STING inhibitor) treatment dramatically reversed the effect of TFAM depletion on the sharpened innate immune response induced by Cu via the cGAS-STING pathway. In general, these findings demonstrated the TFAM deficiency promotes innate immunity by activating the mtDNA-cGAS-STING signalling pathway under Cu exposure in hepatocytes, providing new insight into Cu toxicology.

Silicon dioxide nanoparticles suppress copper toxicity in Mentha arvensis L. by adjusting ROS homeostasis and antioxidant defense system and improving essential oil production

Copper (Cu) is an essential micronutrient for plants; however, the excessive accumulation of Cu due to various anthropogenic activities generates progressive pollution of agricultural land and that causes a major constraint for crop production. Excess Cu (80 mg kg-1) in the soil diminished growth and biomass, photosynthetic efficiency and essential oil (EO) content in Mentha arvensis L., while amplifying the antioxidant enzyme's function and reactive oxygen species (ROS) production. Therefore, there is a pressing need to explore effective approaches to overcome Cu toxicity in M. arvensis plants. Thus, the present study unveils the potential of foliar supplementation of two distinct forms of silicon dioxide nanoparticles (SiO2 NPs) i.e., Aerosil 200F and Aerosil 300 to confer Cu stress tolerance attributes to M. arvensis. The experiment demonstrated that applied forms of SiO2 NPs (120 mg L-1), enhanced plants' growth and augmented the photosynthetic efficiency along with the activities of CA (carbonic anhydrase) and NR (nitrate reductase), however, the effects were more accentuated by Aerosil 200F application. Supplementation of SiO2 NPs also exhibited a beneficial effect on the antioxidant machinery of Cu-disturbed plants by raising the level of proline and total phenol as well as the activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), ascorbate peroxidase (APX) and glutathione reductase (GR), thereby lowering ROS and electrolytic leakage (EL). Interestingly, SiO2 NPs supplementation upscaled EO production in Cu-stressed plants with more pronounced effects received in the case of Aerosil 200F over Aerosil 300. We concluded that the nano form (Aerosil 200F) of SiO2 proved to be the best in improving the Cu-stress tolerance in plants.

Field study of irrigation strategies with treated wastewater and saline water on heavy metal accumulation in barley grain

This study examines the effects of three irrigation regimes with a combination of saline water and treated wastewater on the accumulation of heavy metals in barley grains. A field experiment was designed as a split-split plot arrangement in a randomized complete block design, in which treatments were different irrigation regimes (50%, 70%, and 100% full irrigation) and irrigation water types (saline water [SW], treated wastewater [TW], mixed water resources [MWR], and alternative irrigation [AI]). After cultivation and harvesting of the barley crop, the grain yield, 1000-grain weight, and contents of heavy metals in the grains were measured. The grain yield was enhanced by TW alone, MWR, and AI to 12.8%, 5%, and 9.5% under 70%-deficit irrigation; and 58.3%, 21.7%, and 8.7% under full irrigation, respectively. Based on the guidelines for safe limits of heavy metals in edible plants and livestock feed, the barley grains were safe for livestock and toxic for humans. The trend of heavy metal contents in the grains was Fe > Zn > Pb > Cu ≥ Cr > Cd. Irrigation with SW compared with TW increased Fe, Cu, Zn, Pb, Cd, and Cr contents in the grains to 11.75%, 10.97%, 5.22%, 19.15%, 3.45%, and 9.21%, respectively. The amounts of toxic elements of Cd and Pb were maximized by using MWR, whereas the Cr content in the grain was maximized by using AI. There were no significant difference in the metal uptake by the grains among all irrigation regimes in any irrigation water resource. However, compared with the other irrigation regimes, the full irrigation resulted in lower Zn, Cu, and Cd contents, whereas the 50%-deficit irrigation led to lower Pb and Cr contents in the grains. Therefore, irrigation with TW is recommended based on the grain yield, whereas AI is suggested due to lower Cu, Pb, and Cd contents in the grain, and MWR is recommended due to lower Cr content. Furthermore, full and 50%-deficit irrigation regimes are recommended to, respectively, maximize grain yield and minimize the toxic metal contents in the grain. PRACTITIONER POINTS: Mixed saline water and treated wastewater and alternative irrigation enhanced grain yield. Saline water versus treated wastewater increased the grain heavy metal contents. Alternative irrigation decreased Fe, Cu, Pb, and Cd amounts in the grain. Grain Cu content had strong relationship with irrigation regime. 50%-deficit irrigation minimized Pb and Cr contents in the grain.

The adaptation of root cell wall pectin to copper toxicity in two citrus species differing in copper tolerance: remodeling and responding

Citrus species are prone to suffer from copper (Cu) toxicity because of improper application of Cu-based agrochemicals. Copper immobilization mediated by pectin methylesterase (PME) in the root cell wall (CW) is effective for Cu detoxification. However, the underlying mechanisms of the structural modification and stress responses of citrus root CW pectin to Cu toxicity have been less discussed. In the present study, seedlings of 'Shatian pummelo' (Citrus grandis L. Osbeck) and 'Xuegan' (Citrus sinensis L. Osbeck), which differ in Cu tolerance, were irrigated with nutrient solution containing 0.5 (as control), 100, 300 or 500 μM Cu for 18 weeks in sandy culture or 24 h in hydroponics. At the end of treatments in the 18-week sandy culture, Cu toxicity on CW pectin content, Cu distribution, degree of pectin methylesterification (DPM) and the PME enzyme activity were discussed. At the genome-wide level, PME gene family was identified from the two citrus species, and qRT-PCR array of citrus PMEs under control and 300 μM Cu stress for 18 weeks were performed to screen the Cu-responsive PME genes. Moreover, the candidate genes that responded to Cu toxicity were further examined within 24 h. The results showed that Cu toxicity increased the root CW pectin content. The root CW pectin under Cu toxicity was remodeled by upregulation of the expression of the Cu-responsive PME genes followed by increasing PME activity, which mainly promoted low methylesterased pectin level and the Cu content on root CW pectin. Compared with C. sinensis, C. grandis root CW had a lower DPM and higher Cu content on the Cu-stressed root CW pectin, contributing to its higher Cu tolerance. Our present study provided theoretical evidence for root CW pectin remodeling in response to Cu toxicity of citrus species.

Human Health Risk Assessment of Arsenic and Other Metals in Herbal Products Containing St. John's Wort in the Metropolitan Area of Mexico City

Consumption of St. John's wort plant is high worldwide due to its various medicinal properties. However, herbal products containing St. John's wort may be contaminated with toxic metals. This is often related to contamination of both water and the atmosphere, lack of proper cultivation methods, and inadequate plant storage conditions, as well as a lack of stricter sanitary supervision. A safety assessment of copper (Cu), lead (Pb), cadmium (Cd) and arsenic (As) content in 23 products containing St. John's wort (pharmaceutical herbal products, food supplements and traditional herbal remedies) sold in the metropolitan area of Mexico City was conducted. The analysis of metals was determined using a graphite-furnace atomic absorption spectrometer. All herbal products were contaminated with Cu, Pb, Cd and As. The pharmaceutical herbal items showed less contamination by metals. The daily human intake (DHI) values for Pb exceeded the permissible limits in the group of traditional herbal remedies. The DHI calculation for As exceeded the permitted intake values for all items in the group of traditional herbal remedies, five food supplements and one pharmaceutical herbal product. The hazard indicator calculation of the non-carcinogenic cumulative risk values for traditional herbal remedies was greater than 1, suggesting a risk to human health.

Farmyard manure, a potential organic additive to reclaim copper and Macrophomina phaseolina stress responses in mash bean plants

In the era of global warming, stress combinations instead of individual stress are realistic threats faced by plants that can alter or trigger a wide range of plant responses. In the current study, the cumulative effect of charcoal rot disease caused by notorious fungal pathogen viz., Macrophomina phaseolina was investigated under toxic levels of copper (Cu) in mash bean, and farmyard manure (FYM) was employed to manage stress. Therefore, Cu-spiked soil (50 and 100 mg/kg) was inoculated with the pathogen, and amended with 2% FYM, to assess the effect of intricate interactions on mash bean plants through pot experiments. Results demonstrated that the individual stress of the pathogen or Cu was more severe for morpho-growth, physio-biochemical, and expression profiles of stress-related genes and total protein in mash bean plants as compared to stress combinations. Under single Cu stress, a significant amount of Cu accumulated in plant tissues, particularly in roots than in upper ground tissues, while, under stress combination less Cu accumulated in the plants. Nonetheless, 2% FYM in soil encountered the negative effect of stress responses provoked by the pathogen, Cu, or both by improving health markers (photosynthetic pigments, reducing sugar, total phenolics) and oxidative stress markers (catalase, peroxidase, and polyphenol oxidase), together with regulating the expression of stress-related genes (catalase, ascorbate peroxidase, and cytokinin-resistant genes), and proteins, besides decreasing Cu uptake in the plants. FYM worked better at lower concentrations (50 mg/kg) of Cu than at higher ones (100 mg/kg), hence could be used as a suitable option for better growth, yield, and crop performance under charcoal rot disease stress in Cu-contaminated soils.

Recent Advances in Microbial-Assisted Remediation of Cadmium-Contaminated Soil

Soil contamination with cadmium (Cd) is a severe concern for the developing world due to its non-biodegradability and significant potential to damage the ecosystem and associated services. Industries such as mining, manufacturing, building, etc., rapidly produce a substantial amount of Cd, posing environmental risks. Cd toxicity in crop plants decreases nutrient and water uptake and translocation, increases oxidative damage, interferes with plant metabolism and inhibits plant morphology and physiology. However, various conventional physicochemical approaches are available to remove Cd from the soil, including chemical reduction, immobilization, stabilization and electro-remediation. Nevertheless, these processes are costly and unfriendly to the environment because they require much energy, skilled labor and hazardous chemicals. In contrasting, contaminated soils can be restored by using bioremediation techniques, which use plants alone and in association with different beneficial microbes as cutting-edge approaches. This review covers the bioremediation of soils contaminated with Cd in various new ways. The bioremediation capability of bacteria and fungi alone and in combination with plants are studied and analyzed. Microbes, including bacteria, fungi and algae, are reported to have a high tolerance for metals, having a 98% bioremediation capability. The internal structure of microorganisms, their cell surface characteristics and the surrounding environmental circumstances are all discussed concerning how microbes detoxify metals. Moreover, issues affecting the effectiveness of bioremediation are explored, along with potential difficulties, solutions and prospects.

Copper boosts the biostimulant activity of a vegetal-derived protein hydrolysate in basil: morpho-physiological and metabolomics insights

In addition to be used as a plant protection agent, copper (Cu) is also an essential micronutrient for plant growth and development. The bioavailability of Cu in agricultural systems can be limited due to its specific physical-chemical characteristics, leading to imbalances in plant production. To address this issue, an experimental trial was conducted on Genovese basil (Ocimum basilicum L.) in protected conditions to comparatively evaluate the effects of a vegetable protein hydrolysate (VPH), free Cu and Cu complexed with peptides and amino acids of vegetal origin (Cu and Cu-VPH, respectively), and a combination of VPH and Cu-VPH (VPH+Cu-VPH). The study showed that the combined application of VPH+Cu-VPH led to a significant average increase of 16.3% in fresh yield compared to the untreated Control and Cu treatment. This finding was supported by an improved photosynthetic performance in ACO2 (+29%) and Fv/Fm (+7%). Furthermore, mineral analysis using ICP OES demonstrated that Cu and Cu-VPH treatments determined, on average, a 15.1-, 16.9-, and 1.9-fold increase in Cu in plant tissues compared to control, VPH, and VPH+Cu-VPH treatments, respectively. However, the VPH+Cu-VPH treatment induced the highest contents of the other analyzed ions, except for P. In particular, Mg, Mn, Ca, and Fe, which take part in the constitution of chlorophylls, water splitting system, and photosynthetic electron transport chain, increased by 23%, 21%, 25%, and 32% compared to respective controls. Indeed, this improved the photosynthetic efficiency and the carboxylation capacity of the plants, and consequently, the physiological and productive performance of Genovese basil, compared to all other treatments and control. Consistently, the untargeted metabolomics also pointed out a distinctive modulation of phytochemical signatures as a function of the treatment. An accumulation of alkaloids, terpenoids, and phenylpropanoids was observed following Cu treatment, suggesting an oxidative imbalance upon metal exposure. In contrast, a mitigation of oxidative stress was highlighted in Cu-VPH and VPH+Cu-VPH, where the treatments reduced stress-related metabolites. Overall, these results highlight an interaction between Cu and VPH, hence paving the way towards the combined use of Cu and biostimulants to optimize agronomic interventions.

Biochar-biofertilizer combinations enhance growth and nutrient uptake in silver maple grown in an urban soil

Declining tree health status due to pollutant impacts and nutrient imbalance is widespread in urban forests; however, chemical fertilizer use is increasingly avoided to reduce eutrophication impacts. Biochar (pyrolyzed organic waste) has been advocated as an alternative soil amendment, but biochar alone generally reduces plant N availability. The combination of biochar and either organic forms of N or Plant Growth Promoting Microbes (PGPMs) as biofertilizers may address these challenges. We examined the effects of two wood biochar types with Bacillus velezensis and an inactivated yeast (IY) biofertilizer in a three-month factorial greenhouse experiment with Acer saccharinum L. (silver maple) saplings grown in a representative urban soil. All treatments combining biochars with biofertilizers significantly increased sapling growth, with up to a 91% increase in biomass relative to controls. Growth and physiological responses were closely related to nutrient uptake patterns, with nutrient vector analyses indicating that combined biochar and biofertilizer treatments effectively addressed nutrient limitations of both macronutrients (N, P, K, Mg, Ca), and micronutrients (B, Fe, Mn, Mo, Na, S, and Zn). Biochar-biofertilizer treatments also reduced foliar concentrations of Cu, suggesting potential to mitigate toxic metal impacts common in urban forestry. We conclude that selected combinations of biochar and biofertilizers have substantial promise to address common soil limitations to tree performance in urban settings.

Essential oil-grafted copper nanoparticles as a potential next-generation fungicide for holistic disease management in maize

Sustainable food production is necessary to meet the demand of the incessantly growing human population. Phytopathogens pose a major constraint in food production, and the use of conventional fungicides to manage them is under the purview of criticism due to their numerous setbacks. In the present study, essential oil-grafted copper nanoparticles (EGC) were generated, characterized, and evaluated against the maize fungal pathogens, viz., Bipolaris maydis, Rhizoctonia solani f. sp. sasakii, Macrophomina phaseolina, Fusarium verticillioides, and Sclerotium rolfsii. The ED₅₀ for the fungi under study ranged from 43 to 56 μg ml^-1, and a significant inhibition was observed at a low dose of 20 μg ml^-1 under in vitro conditions. Under net house conditions, seed treatment + foliar spray at 250 and 500 mg L^-1 of EGC performed remarkably against maydis leaf blight (MLB), with reduced percent disease index (PDI) by 27.116 and 25.292%, respectively, in two Kharif seasons (May-Sep, 2021, 2022). The activity of enzymatic antioxidants, viz., β-1, 3-glucanase, PAL, POX, and PPO, and a non-enzymatic antioxidant (total phenolics) was increased in treated maize plants, indicating host defense was triggered. The optimum concentrations of EGC (250 mg L^-1 and 500 mg L^-1) exhibited improved physiological characteristics such as photosynthetic activity, shoot biomass, plant height, germination percentage, vigor index, and root system traits. However, higher concentrations of 1,000 mg L^-1 rendered phytotoxicity, reducing growth, biomass, and copper bioaccumulation to high toxic levels, mainly in the foliar-sprayed maize leaves. In addition, EGC and copper nanoparticles (CuNPs) at 1,000 mg L^-1 reduced the absorption and concentration of manganese and zinc indicating a negative correlation between Cu and Mn/Zn. Our study proposes that the CuNPs combined with EO (Clove oil) exhibit astounding synergistic efficacy against maize fungal pathogens and optimized concentrations can be used as an alternative to commercial fungicides without any serious impact on environmental health.