Induction of oxidative stress biomarkers associated with heavy metal stress in Fontinalis antipyretica Hedw

Interaction between acid-tolerant alga Graesiella sp. MA1 and schwertmannite under long-term acidic condition

Schwertmannite (Sch), a typical Fe(III)-oxyhydroxysulphate mineral, is the precipitation reservoir of toxic elements in acid mine drainage (AMD). Acid-tolerant microbes in AMD can participate in the microbe-mediated transformation of Sch, while Sch affects the physiological characteristics of these acid-tolerant microbes. Based on our discovery of algae and Sch enrichment in a contaminated acid mine pit lake, we predicted the interaction between algae and Sch when incubated together. The acid-tolerant alga Graesiella sp. MA1 was isolated from the pit-lake surface water of an acidic mine and incubated with different contents of Sch. Sch was detected as the main product at the end of 81 d; however, there was a weak transformation. The presence of dissolved Fe(II) could be largely attributed to the photoreduction dissolution of Sch, which was promoted by Graesiella sp. MA1. The adaptation and growth phases of Graesiella sp. MA1 differed under Sch stress. The photosynthetic and metabolic activities increased and decreased at the adaptation and growth phases, respectively. The MDA contents and antioxidant activity of SOD, APX, and GSH in algal cells gradually enhanced as the Sch treatment content increased, indicating a defense strategy of Graesiella sp. MA1. Metabolomic analysis revealed that Sch affected the expression of significant differential metabolites in Graesiella sp. MA1. Organic carboxylic acid substances were essentially up-regulated in response to Sch stress. They were abundant in the medium-Sch system with the highest Fe(III) reduction, capable of complexing Fe(III), and underwent photochemical reactions via photo-induced charge transfer. The significant up-regulation of reducing sugars revealed the high energy requirement of Graesiella sp. MA1 under Sch stress. And first enriched KEGG pathway demonstrated the importance of sugar metabolism in Graesiella sp. MA1. Data acquired in this study provide novel insights into extreme acid stress adaptation of acid-tolerant algae and Sch, contributing to furthering understanding of AMD environments.

Microbial Sulfur and Arsenic Oxidation Facilitate the Establishment of Biocrusts during Reclamation of Degraded Mine Tailings

Degraded tailings generated by the mining of metal ores are major environmental threats to the surrounding ecosystems. Tailing reclamation, however, is often impeded due to adverse environmental conditions, with depleted key nutrients (i.e., nitrogen (N) and phosphorus (P)) and elevated sulfur and metal(loid) concentrations. Formation of biocrusts may significantly accelerate nutrient accumulation and is therefore an essential stage for tailing reclamation. Although suggested to play an important role, the microbial community composition and key metabolisms in biocrusts remain largely unknown and are therefore investigated in the current study. The results suggested that sulfur and arsenic oxidation are potential energy sources utilized by members of predominant biocrust bacterial families, including Beijerinckiaceae, Burkholderiaceae, Hyphomicrobiaceae, and Rhizobiaceae. Accordingly, the S and As oxidation potentials are elevated in biocrusts compared to those in their adjacent tailings. Biocrust growth, as proxied by chlorophyll concentrations, is enhanced in treatments supplemented with S and As. The elevated biocrust growth might benefit from nutrient acquisition services (i.e., nitrogen fixation and phosphorus solubilization) fueled by microbial sulfur and arsenic oxidation. The current study suggests that sulfur- and arsenic-oxidizing microorganisms may play important ecological roles in promoting biocrust formation and facilitating tailing reclamation.

Transcriptome analysis discloses antioxidant detoxification mechanism of Gracilaria bailinae under different cadmium concentrations and stress durations

To remedy Cd pollution in the ocean, macroalgae are used as a bioremediation tool because of their ability to absorb and accumulate Cd. Gracilaria bailinae has high economic and ecological value and can survive in Cd contaminated waters; however, the underlying molecular mechanisms remain unclear. In this study, physiological and biochemical indexes were analyzed after 1, 3, 5, or 7 days of Cd2+ exposure; further, the transcriptome of G. bailinae was examined after a 7-day exposure to a Cd2+ culture environment with Cd levels of 0 mg L-1 (cd1, control), 1 mg L-1 (cd2, low concentration), and 2.5 mg L-1 (cd3, high concentration). The results showed that in the cd2 group, G. bailinae maintained a stable RGR that did not differ significantly (P > 0.05) from that of the cd1 group. However, the soluble protein and MDA contents, as well as the activities of SOD, CAT and POD, were significantly increased (P< 0.05) compared to the cd1 group. No significant differences (P > 0.05) were found among the different Cd2+ stress durations. In contrast, compared with the cd1 group, the RGR, soluble protein content, SOD, CAT, and POD activities were significantly decreased (P< 0.05), while the MDA content was significantly increased (P< 0.05) in the cd3 group. Furthermore, significant differences (P< 0.05) were observed among the various tested Cd2+ stress durations within the cd3 group. Compared to the cd1 group, a total of 30,072 DEGs and 21,680 were identified in the cd2 and cd3 treatments, respectively. More up-regulated genes were found in cd2 group than in cd3 group. GO enrichment analysis showed that these genes were related to peptidase activity, endopeptidase activity, ion transport, peptide biosynthetic and metabolism. In addition, DEGs related to histidine metabolism and the stilbene, diarylheptane, and gingerol pathways were significantly up-regulated in the cd2 group compared to the cd3 group, which resulted in enhanced activities of antioxidant enzymes and promoted cell wall regeneration. The results of this study reveal the response mechanism of G. bailinae to Cd2+ stress, providing valuable insights for assessing the bioremediation potential of G. bailinae for Cd-contaminated waters.

Reactive oxygen species derived from NADPH oxidase as signaling molecules regulate fatty acids and astaxanthin accumulation in Chromochloris zofingiensis

Abiotic stresses can increase the total fatty acid (TFA) and astaxanthin accumulation in microalgae. However, it remains unknown whether a unified signal transduction mechanism exists under different stresses. This study explored the link between nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-derived reactive oxygen species (ROS) and the accumulation of fatty acids and astaxanthin in Chromochloris zofingiensis under three abiotic stresses. Results showed significant increases in fatty acid, astaxanthin, and ROS levels under nitrogen deficiency, phosphorus deficiency, and high-salinity stress. The introduction of the NADPH oxidase inhibitor diphenyleneiodonium (DPI) decreased the content of these components. This underscores the pivotal role of NADPH oxidase-derived ROS in the accumulation of fatty acid and astaxanthin under abiotic stress. Analysis of transcriptomes across three conditions following DPI addition revealed 1,445 shared differentially expressed genes (DEGs). Enrichment analysis revealed that biotin, betalain, thiamine, and glucosinolate may be important in stress responses. The heatmap demonstrated that DPI notably suppressed gene expression in the fatty acid and carotenoid biosynthesis pathways. Our findings underscore the pivotal role of NADPH oxidase-derived ROS in the accumulation of fatty acid and astaxanthin under abiotic stresses.

Embryo growth alteration and oxidative stress responses in germinating Cucurbita pepo seeds exposed to cadmium and copper toxicity

This study investigated the influence of cadmium (Cd) and copper (Cu) heavy metals on germination, metabolism, and growth of zucchini seedlings (Cucurbita pepo L.). Zucchini seeds were subjected to two concentrations (100 and 200 μM) of CdCl2 and CuCl2. Germination parameters, biochemical and phytochemical attributes of embryonic axes were assessed. Results revealed that germination rate remained unaffected by heavy metals (Cd, Cu). However, seed vigor index (SVI) notably decreased under Cd and Cu exposure. Embryonic axis length and dry weight exhibited significant reductions, with variations depending on the type of metal used. Malondialdehyde and H2O2 content, as well as catalase activity, did not show a significant increase at the tested Cd and Cu concentrations. Superoxide dismutase activity decreased in embryonic axis tissues. Glutathione S-transferase activity significantly rose with 200 μM CdCl2, while glutathione content declined with increasing Cd and Cu concentrations. Total phenol content and antioxidant activity increased at 200 μM CuCl2. In conclusion, Cd and Cu heavy metals impede zucchini seed germination efficiency and trigger metabolic shifts in embryonic tissue cells. Response to metal stress is metal-specific and concentration-dependent. These findings contribute to understanding the intricate interactions between heavy metals and plant physiology, aiding strategies for mitigating their detrimental effects on plants.

Distinctive physiological and molecular responses of foxtail millet and maize to nicosulfuron

Introduction

Nicosulfuron is the leading acetolactate synthase inhibitor herbicide product, and widely used to control gramineous weeds. Here, we investigated the metabolic process of nicosulfuron into foxtail millet and maize, in order to clarify the mechanism of the difference in sensitivity of foxtail millet and maize to nicosulfuron from the perspective of physiological metabolism and provide a theoretical basis for the breeding of nicosulfuron-resistant foxtail millet varieties.

Methods

We treated foxtail millet (Zhangzagu 10, Jingu 21) and maize (Nongda 108, Ditian 8) with various doses of nicosulfuron in both pot and field experiments. The malonaldehyde (MDA) content, target enzymes, detoxification enzymes, and antioxidant enzymes, as well as related gene expression levels in the leaf tissues of foxtail millet and maize were measured, and the yield was determined after maturity.

Results

The results showed that the recommended dose of nicosulfuron caused Zhangzagu 10 and Jingu 21 to fail to harvest; the yield of the sensitive maize variety (Ditian 8) decreased by 37.09%, whereas that of the resistant maize variety (Nongda 108) did not decrease. Nicosulfuron stress increased the CYP450 enzyme activity, MDA content, and antioxidant enzyme activity of foxtail millet and maize, reduced the acetolactate synthase (ALS) activity and ALS gene expression of foxtail millet and Ditian 8, and reduced the glutathione S-transferase (GST) activity and GST gene expression of foxtail millet. In conclusion, target enzymes, detoxification enzymes, and antioxidant enzymes were involved in the detoxification metabolism of nicosulfuron in plants. ALS and GST are the main factors responsible for the metabolic differences among foxtail millet, sensitive maize varieties, and resistant maize varieties.

Discussion

These findings offer valuable insights for exploring the target resistance (TSR) and non-target resistance (NTSR) mechanisms in foxtail millet under herbicide stress and provides theoretical basis for future research of develop foxtail millet germplasm with diverse herbicide resistance traits.

Metabolomic and physiological changes of acid-tolerant Graesiella sp. MA1 during long-term acid stress

Algae plays a significant role for the primary production in the oligotrophic ecosystems such as the acid mine pit lakes. Graesiella sp. MA1 was a new acid-tolerant photosynthetic protist isolated from an acid mine pit lake. To understand the acid responses of Graesiella sp. MA1, its physiological changes and metabolomics were studied during long-term acid stress. Photosynthetic pigments, soluble proteins, and antioxidant systems of Graesiella sp. MA1 cells displayed two phases, the adaptation phase and the growth phase. During the adaptation phase, both photosynthetic pigments and soluble proteins were inhibited, while antioxidant activity of SOD, APX, and GSH were promoted to response to the organism's damage. Metabolomics results revealed lipids and organic acids were abundant components in Graesiella sp. MA1 cells. In response to acid stress, the levels of acid-dependent resistant amino acids, including glutamate, aspartate, arginine, proline, lysine, and histidine, accumulated continuously to maintain orderly intracellular metabolic processes. In addition, fatty acids were mainly unsaturated, which could improve the fluidity of the cell membranes under acid stress. Metabolomic and physiological changes showed that Graesiella sp. MA1 had tolerance during long-term acid stress and the potential to be used as a bioremediation strain for the acidic wastewater.

Intestinal response of Rana chensinensis larvae exposed to Cr and Pb, alone and in combination

Although numerous investigations on the adverse impact of Cr and Pb have been performed, studies on intestinal homeostasis in amphibians are limited. Here, single and combined effects of Cr (104 μg/L) and Pb (50 μg/L) on morphological and histological features, bacterial community, digestive enzymes activities, as well as transcriptomic profile of intestines in Rana chensinensis tadpoles were assessed. Significant decrease in the relative intestine length (intestine length/snout-to-vent length, IL/SVL) was observed after exposure to Pb and Cr/Pb mixture. Intestinal histology and digestive enzymes activities were altered in metal treatment groups. In addition, treatment groups showed significantly increased bacterial richness and diversity. Tadpoles in treatment groups were observed to have differential gut bacterial composition from controls, especially for the abundance of phylum Proteobacteria, Firmicutes, Verrucomicrobia, Actinobacteria, and Fusobacteria as well as genus Citrobacter, Anaerotruncus, Akkermansia, and Alpinimonas. Moreover, transcriptomic analysis showed that the transcript expression profiles of GPx and SOD isoforms responded differently to Cr and/or Pb exposure. Besides, transcriptional activation of pro-apoptotic and glycolysis-related genes, such as Bax, Apaf 1, Caspase 3, PK, PGK, TPI, and GPI were detected in all treatment groups but downregulation of Bcl2 in Pb and Cr/Pb mixture groups. Collectively, these results suggested that Cr and Pb exposure at environmental relevant concentration, alone and in combination, could disrupt intestinal homeostasis of R. chensinensis tadpoles.

Non-Protein Thiol Compounds and Antioxidant Responses Involved in Bryophyte Heavy-Metal Tolerance

Heavy-metal pollution represents a problem which has been widely discussed in recent years. The biological effects of heavy metals have been studied in both animals and plants, ranging from oxidative stress to genotoxicity. Plants, above all metal-tolerant species, have evolved a wide spectrum of strategies to counteract exposure to toxic metal concentrations. Among these strategies, the chelation and vacuolar sequestration of heavy metals are, after cell-wall immobilization, the first line of defence that prevent heavy metals from interacting with cell components. Furthermore, bryophytes activate a series of antioxidant non-enzymatic and enzymatic responses to counteract the effects of heavy metal in the cellular compartments. In this review, the role of non-protein thiol compounds and antioxidant molecules in bryophytes will be discussed.

Toxicity analysis and biomarker response of Quinalphos Organophosphate Insecticide (QOI) on eco-friendly exotic Eudrilus eugeniae earthworm

An ever-increasing use of pesticides in agricultural fields has led to a catastrophic decline in crop quality and, ultimately soil fertility. To control various pests, quinalphos is commonly used in India's tea plantations. This study aims to investigate the effects of the Quinalphos organophosphate insecticide on the non-target beneficial organism Eudrilus eugeniae earthworms and the biomarkers that respond to its effects. Earthworm species, especially E. eugeniae, remains as the most trustworthy and well-suited model organism for conducting a wide variety of environmental studies. The median lethal concentration (LC₅₀) was identified as 3.561 µg cm^-2 (contact filter paper) and 1.054 mg kg^-2 (artificial soil toxicity). The 5% and 10% of LC₅₀ value 3.561 µg cm^-2 was exposed to earthworm to analyze the sublethal effects at pre-clitellum, clitellum, and post-clitellum segments. Specific enzymatic activities of neurotransmitter enzyme acetylcholinesterase; antioxidant enzymes such as lipid peroxidase, superoxide dismutase, and catalase; and detoxification enzymes including glutathione S transferase, reduced glutathione, carboxylesterase, and Cytochrome P450 were analyzed. Exposure of E. eugeniae earthworm to subacute exposures of pesticides caused significant alterations in these stress markers in a concentration-dependent manner. Morphological abnormalities like bulginess, coiling, and bleeding were observed after exposure of the insecticide treatments. Histological cellular disintegration, a reduced NRRT time, and an inhibited proteolytic zone were also identified in pesticide-exposed earthworms. Studies demonstrate that the organophosphate insecticide quinalphos causes acute toxicity in E. eugeniae; hence, it is suggested that non-target eco-friendly E. eugeniae earthworms may be at risk if exposed to the excessive concentrations of quinalphos organophosphate insecticide in soil.

The wild plant Gnaphalium lavandulifolium as a sentinel for biomonitoring the effects of environmental heavy metals in the metropolitan area of México Valley

Biomonitoring is a valuable tool for assessing the presence and effects of air pollutants such as heavy metals (HM); due to their toxicity and stability, these compounds can affect human health and the balance of ecosystems. To assess its potential as a sentinel organism of HM pollution, the wild plant Gnaphalium lavandulifolium was exposed to four sites in the metropolitan area of México Valley (MAMV): Altzomoni (ALT) Coyoacán (COY), Ecatepec (ECA), and Tlalnepantla (TLA) during 2, 4, and 8 weeks, between October and November 2019. Control plants remained under controlled conditions. The chemical analysis determined twelve HM (Al, As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, V, and Zn) in the leaves. Macroscopic damage to the leaves, later determined in semi-thin sections under light microscopy, lead to a finer analysis. Transmission electron microscope (TEM) showed major structural changes: chromatin condensation, protoplast shrinkage, cytoplasm vacuolization, cell wall thinning, decreased number and size of starch grains, and plastoglobules in chloroplasts. All these characteristics of stress-induced programed cell death (sPCD) were related to the significant increase of toxic HM in the leaves of the exposed plants compared to the control (p < 0.05). Immunohistochemistry revealed a significant amount of proteases with caspase 3-like activity in ECA and TLA samples during long exposure times. Ultrastructural changes and sPCD features detected confirmed the usefulness of G. lavandulifolium as a good biomonitor of HM contamination. They supported the possibility of considering subcellular changes as markers of abiotic stress conditions in plants.

Zero valent iron nanoparticles and organic fertilizer assisted phytoremediation in a mining soil: Arsenic and mercury accumulation and effects on the antioxidative system of Medicago sativa L

Zero valent iron nanoparticles (nZVI) attract interest given their effectiveness in soil remediation. However, little attention has been given to their impacts on plants. Likewise, although fertilizers are commonly used to enhance phytoremediation, their effects on As mobilization, resulting in potential toxic effects, require further study. In this context, we examined the impact of As and Hg accumulation on the antioxidative system of Medicago sativa grown in a soil amended with organic fertilizer and/or nZVI. The experiment consisted of 60 pots. Plants were pre-grown and transferred to pots, which were withdrawn along time for monitoring purposes. As and Hg were monitored in the soil-plant system, and parameters related to oxidative stress, photosynthetic pigments, and non-protein thiol compounds (NPTs) were measured. In general, the application of nZVI immobilized As in soil and increased Hg accumulation in the plant, although it surprisingly decreased oxidative stress. Plants in nZVI-treated soil also showed an increase in NPT content in roots. In contrast, the application of the fertilizer mobilized As, thereby improving bioaccumulation factors. However, when combining fertilizer with nZVI, the As accumulation is mitigated. This observation reveals that simultaneous amendments are a promising approach for soil stabilization and the phytomanagement of As/Hg-polluted soils.

Warming northward shifting southern limits of the iconic temperate seagrass (Zostera marina)

Global warming can shift the range edges of numerous species poleward. Here, eelgrass distribution was reinvestigated at its southern limits on the eastern coast of China, which indicated that there has been a northward shift in the southern limit of Z. marina. To determine if regional warming resulted in a northward shift in suitable eelgrass habitats, sixteen transplantations of adult eelgrass shoots and seeds at the historical southern distribution limit of eelgrass were conducted between 2016 and 2021. The results showed that high water temperatures in summer had negative effects on eelgrass growth, and directly triggered shoot mortality during 2016–2018. Under heat stress, antioxidant enzyme activity was initially increased, but then decreased under more stressful heat conditions; and the HSP70 protein and its molecular chaperone protein were highly expressed under heat stress. These results demonstrated that suitable eelgrass habitat was now located further north along the eastern coast of China.

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High temperatures trigger seagrass (Zostera marina L.) restoration failure

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None seedlings and adult shoots survived the first or second summer

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Over-summering shoots with lower density, height, and rhizome diameter

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Warming northward shifting eelgrass habitat range along the eastern coast of China

Growth and physiological response of Kandelia obovata and Bruguiera sexangula seedlings to aluminum stress

The role of mangroves as a biogeochemical buffer for heavy metal pollutants in coastal wetlands has been demonstrated, but knowledge gaps still exist on the tolerant capacity of mangroves to aluminum (Al). This study assessed the growth and physiological response of viviparous mangroves Kandelia obovata and Bruguiera sexangula to Al stress. The two mangrove seedlings were treated with AlCl₃ at concentrations of 0 (as control) to 100 mmol L^-1, and the impact of Al on their growth and antioxidant parameters were determined. Additionally, the accumulation and translocation of metal elements were estimated in B. sexangula seedlings under relative long-term Al stress. K. obovata appeared to survive with a tolerance potential of 10 mmol L^-1 AlCl₃, whereas B. sexangula had a higher tolerant ability of 50 mmol L^-1 AlCl₃. Both root elongation and seedling growth were inhibited by Al stress. The exposure to 25-100 mmol L^-1 AlCl₃ induced increases in membrane lipid peroxidation and osmoprotectant molecule (proline) in mangrove seedlings. Both mangrove seedlings revealed significant changes in antioxidant enzyme activities that were attributed to Al stress-induced oxidative damages. The activities of superoxide dismutase, catalase, peroxidase, and/or ascorbate peroxidase were differently impacted by the treatment time (7 days for short term versus 60 days for long term) and AlCl₃ concentrations in K. obovata and B. sexangula seedlings. For B. sexangula seedlings, Al accumulation was in an order root > leaf > stem, whereas the translocation of metal elements in the aboveground tissues (leaf and stem) was differently impacted by Al stress. In conclusion, this study provides insights into different Al-tolerant abilities operated in two mangrove species that are widespread in coastal wetlands of China.

Interest of a multispecies approach in active biomonitoring: Application in the Meuse watershed

A biomonitoring approach based on a single model species cannot be representative of the contaminations impacts on the ecosystem overall. As part of the Interreg DIADeM program ("Development of an integrated approach for the diagnosis of the water quality of the River Meuse"), a study was conducted to establish the proof of concept that the use of a multispecies active biomonitoring approach improves diagnostic of aquatic systems. The complementarity of the biomarker responses was tested in four model species belonging to various ecological compartments: the bryophyte Fontinalis antipyretica, the bivalve Dreissena polymorpha, the amphipod Gammarus fossarum and the fish Gasterosteus aculeatus. The species have been caged upstream and downstream from five wastewater treatment plants (WWTPs) in the Meuse watershed. After the exposure, a battery of biomarkers was measured and results were compiled in an Integrated Biomarker Response (IBR) for each species. A multispecies IBR value was then proposed to assess the quality of the receiving environment upstream the WWTPs. The effluent toxicity was variable according to the caged species and the WWTP. However, the calculated IBR were high for all species and upstream sites, suggesting that the water quality was already downgraded upstream the WWTP. This contamination of the receiving environment was confirmed by the multispecies IBR which has allowed to rank the rivers from the less to the most contaminated. This study has demonstrated the interest of the IBR in the assessment of biological impacts of a point-source contamination (WWTP effluent) but also of the receiving environment, thanks to the use of independent references. Moreover, this study has highlighted the complementarity between the different species and has emphasized the interest of this multispecies approach to consider the variability of the species exposition pathway and sensibility as well as the mechanism of contaminants toxicity in the final diagnosis.

Hepatic transcriptomic and histopathological responses of common carp, Cyprinus carpio, to copper and microplastic exposure

The combined effects of copper and polyvinyl chloride (PVC) microparticles were investigated on the metal accumulation, histopathological biomarkers, and targeted transcriptomics in Cyprinus carpio liver. The fish were exposed to 0.25 mg/L copper and/or 0.5 mg/L PVC microparticles over a 14-d period. The results showed that hepatic copper accumulation is facilitated by the PVC microparticles presence in water. All treatments induced significant hepatic stress and inflammation; however, the transcriptional responses involving in detoxification pathways and apoptotic mechanisms were mixed and often down-regulated in the fish exposed to copper and/or PVC microparticles. Exposure to copper and/or PVC microparticles induced hypermeia, leukocyte infiltration and increase in melanomacrophage centers number and area. Generally, the severity of the lesions was in the following order: PVC microparticles < copper < copper+ PVC microparticles. In conclusion, PVC MPs act as a copper vector, facilitating accumulation of copper in the fish liver and increasing the tissue damage.

Heavy metal accumulation characteristics and physiological response of Sabina chinensis and Platycladus orientalis to atmospheric pollution

Heavy metal (Cu, Mn, Zn, Pb, and Cd) concentrations were measured in the leaves of Sabina chinensis and Platycladus orientalis collected from urban, suburban, and rural sites in Tianjin, China. Photosynthetic pigment contents, reactive oxygen species content, malondialdehyde (MDA) content and antioxidant enzyme activity were investigated, providing physiological response parameters. Our comparison of the sites revealed that urbanization significantly influenced the heavy metal concentrations in both plant leaves. At the rural site, both plant leaves exhibited the lowest heavy metal accumulation. The highest Cu, Mn, and Zn concentrations were found in S. chinensis leaves from the urban site; the highest Pb and Cd concentrations were found in P. orientalis leaves from the urban site. These results indicate that the urban site contained larger heavy metal concentrations in the plant leaves that may reflect the anthropogenic emission gradient. It is also found that S. chinensis may be used to monitor airborne heavy metal pollution because it is highly quick response to heavy metals, while P. orientalis may be used for mitigation due to its high resistance. The results of this study can contribute to the development of monitoring and environmental management plans by providing information on sensitive and resistant tree species for city greening in North China.

Metal Detoxification in Land Plants: From Bryophytes to Vascular Plants. STATE of the Art and Opportunities

Potentially toxic elements are a widespread concern due to their increasing diffusion into the environment. To counteract this problem, the relationship between plants and metal(loid)s has been investigated in the last 30 years. In this field, research has mainly dealt with angiosperms, whereas plant clades that are lower in the evolutive scale have been somewhat overlooked. However, recent studies have revealed the potential of bryophytes, pteridophytes and gymnosperms in environmental sciences, either as suitable indicators of habitat health and elemental pollution or as efficient tools for the reclamation of degraded soils and waters. In this review, we summarize recent research on the interaction between plants and potentially toxic elements, considering all land plant clades. The focus is on plant applicability in the identification and restoration of polluted environments, as well as on the characterization of molecular mechanisms with a potential outlet in the engineering of element tolerance and accumulation.

Toxic effects of a mixture of five pharmaceutical drugs assessed using Fontinalis antipyretica Hedw

The potential health risks associated with the pharmaceuticals released into the environment through effluents from sewage treatment plants have become a major cause for concern. Owing to the lack of effective indicators, monitoring the concentration of these pollutants in the aquatic environment is challenging. The aim of this study was to assess the toxicity of a mixture of five pharmaceutical drugs (paracetamol, carbamazepine, diclofenac, irbesartan, and naproxen) using the aquatic moss Fontinalis antipyretica as a bioindicator and bioaccumulator. We examined the effects of the drug mixture on the cellular antioxidant system, chlorophyll content, and morphological traits of F. antipyretica. The plant was exposed for 5 months to three concentrations of the mixture, including the environmental concentration (MX1), and 10- (MX10) and 100-times (MX100) the environmental concentration. The results showed that only carbamazepine and irbesartan were accumulated by the species. The bioconcentration level increased with exposure time, with the maximum uptake at the 4th month of exposure. The increase in bioaccumulation with exposure time was more evident in plants exposed to MX100. Analysis of the activity of antioxidant enzymes showed that superoxide dismutase (SOD, EC 1.15.1.1.) and catalase (EC 1.11.1.6.) were highly sensitive to the drug mixture. The activity of the enzymes was significantly higher in plants exposed to MX100; however, the activity of guaiacol peroxidase (GPX, EC 1.11.1.7.) was not significantly affected. Plants exposed to MX10 and MX100 had significantly lower total chlorophyll content and chlorophyll a/b ratio compared with those of plants in the control group; however, photosynthetic activity was restored after 5 months of exposure. The morphological characteristics of F. antipyretica were less sensitive to the treatment conditions.

Chemical Elicitors-Induced Variation in Cellular Biomass, Biosynthesis of Secondary Cell Products, and Antioxidant System in Callus Cultures of Fagonia indica

Fagonia indica is a rich source of pharmacologically active compounds. The variation in the metabolites of interest is one of the major issues in wild plants due to different environmental factors. The addition of chemical elicitors is one of the effective strategies to trigger the biosynthetic pathways for the release of a higher quantity of bioactive compounds. Therefore, this study was designed to investigate the effects of chemical elicitors, aluminum chloride (AlCl₃) and cadmium chloride (CdCl₂), on the biosynthesis of secondary metabolites, biomass, and the antioxidant system in callus cultures of F. indica. Among various treatments applied, AlCl₃ (0.1 mM concentration) improved the highest in biomass accumulation (fresh weight (FW): 404.72 g/L) as compared to the control (FW: 269.85 g/L). The exposure of cultures to AlCl₃ (0.01 mM) enhanced the accumulation of secondary metabolites, and the total phenolic contents (TPCs: 7.74 mg/g DW) and total flavonoid contents (TFCs: 1.07 mg/g DW) were higher than those of cultures exposed to CdCl₂ (0.01 mM) with content levels (TPC: 5.60 and TFC: 0.97 mg/g) as compared to the control (TPC: 4.16 and TFC: 0.42 mg/g DW). Likewise, AlCl₃ and CdCl₂ also promoted the free radical scavenging activity (FRSA; 89.4% and 90%, respectively) at a concentration of 0.01 mM, as compared to the control (65.48%). For instance, the quantification of metabolites via high-performance liquid chromatography (HPLC) revealed an optimum production of myricetin (1.20 mg/g), apigenin (0.83 mg/g), isorhamnetin (0.70 mg/g), and kaempferol (0.64 mg/g). Cultures grown in the presence of AlCl₃ triggered higher quantities of secondary metabolites than those grown in the presence of CdCl₂ (0.79, 0.74, 0.57, and 0.67 mg/g). Moreover, AlCl₃ at 0.1 mM enhanced the biosynthesis of superoxide dismutase (SOD: 0.08 nM/min/mg-FW) and peroxidase enzymes (POD: 2.37 nM/min/mg-FW), while CdCl₂ resulted in an SOD activity up to 0.06 nM/min/mg-FW and POD: 2.72 nM/min/mg-FW. From these results, it is clear that AlCl₃ is a better elicitor in terms of a higher and uniform productivity of biomass, secondary cell products, and antioxidant enzymes compared to CdCl₂ and the control. It is possible to scale the current strategy to a bioreactor for a higher productivity of metabolites of interest for various pharmaceutical industries.

Responses of submerged macrophytes Vallisneria natans and epiphytic biofilm to floating plants Eichhornia crassipes in eutrophic water

The degeneration of submerged macrophytes and the invasion of Eichhornia crassipes (E. crassipes) destroyed the balance of aquatic ecosystems environments. In this study, responses of Vallisneria natans (V. natans) and the leaf-epiphytic biofilms to E. crassipes were analyzed to provide a technical scheme for V. natans restoration and E. crassipes control in eutrophic water. The results showed that a significant improvement of water quality achieved in 1100 ind·m^-2 E. crassipes density group and TN removal rate reached 63.53%. The presence of E. crassipes changed the morphological characteristics of V. natans, which stimulated the adaptive mechanisms via promotion of shoot height and root length. Concentrations of the antioxidant enzymes, peroxidase, superoxide dismutase, and catalase in the V. natans leaves remained stable. But E. crassipes greatly increased the microbial diversity on V. natans leave biofilms. Furthermore, the greatest richness in bacterial community diversity was observed at 700, 1100, and 1200 ind·m^-2 E. crassipes densities in heatmap, which was beneficial to the stability of the water ecological environment. These results showed that the combination of V. natans with E. crassipes of 1100 ind m^-2 providing more favorable conditions for the growth and restoration of submerged macrophytes and improve the water quality. PRACTITIONER POINTS: The responses of submerged macrophytes to floating plants were studied. The optimal density of Eichhornia crassipes was 1100 ind m^-2 . The biofilm microbial community changed in response to Eichhornia crassipes.

Genome-wide identification and function analysis of HMAD gene family in cotton (Gossypium spp.)

BACKGROUND

The abiotic stress such as soil salinization and heavy metal toxicity has posed a major threat to sustainable crop production worldwide. Previous studies revealed that halophytes were supposed to tolerate other stress including heavy metal toxicity. Though HMAD (heavy-metal-associated domain) was reported to play various important functions in Arabidopsis, little is known in Gossypium.

RESULTS

A total of 169 G. hirsutum genes were identified belonging to the HMAD gene family with the number of amino acids ranged from 56 to 1011. Additionally, 84, 76 and 159 HMAD genes were identified in each G. arboreum, G. raimondii and G. barbadense, respectively. The phylogenetic tree analysis showed that the HMAD gene family were divided into five classes, and 87 orthologs of HMAD genes were identified in four Gossypium species, such as genes Gh_D08G1950 and Gh_A08G2387 of G. hirsutum are orthologs of the Gorai.004G210800.1 and Cotton_A_25987 gene in G. raimondii and G. arboreum, respectively. In addition, 15 genes were lost during evolution. Furthermore, conserved sequence analysis found the conserved catalytic center containing an anion binding (CXXC) box. The HMAD gene family showed a differential expression levels among different tissues and developmental stages in G. hirsutum with the different cis-elements for abiotic stress.

CONCLUSIONS

Current study provided important information about HMAD family genes under salt-stress in Gossypium genome, which would be useful to understand its putative functions in different species of cotton.

Biochemical Responses of Medicinal Plant Tussilago farfara L. to Elevated Heavy Metal Concentrations in Soils of Urban Areas

This study was conducted in Tyumen (Russian Federation) to establish the effects of heavy metals' (Cu, Zn, Fe, Mn, Pb, and Cd) accumulation in soil and coltsfoot, as well as plants' biochemical responses to such an accumulation. The mobile and acid-soluble heavy metal fractions in soils, and the heavy metal contents in plants, were determined by atomic absorption spectrophotometry. The Cu, Zn, Fe, Mn, and Pb concentrations in soils exceeded background values. Pb content at the battery manufacturing plant was above the maximum permitted concentration. The percentages of the mobile heavy metal fractions decreased in the following order: Mn > Zn > Cu > Fe. The greatest heavy metal accumulation in soils and plants was found at the battery manufacturing and metallurgical plants examined in our study. Heavy metals' accumulation in the aboveground part of Tussilago farfara decreased in the following order: Fe > Zn > Cu > Mn > Pb > Cd. The accumulation of heavy metals stimulated the synthesis of photosynthetic pigments by 6-30%. Heavy metals provoked oxidative stress in cells, increasing the concentration of lipid peroxidation in products by up to 80%. Plant phenolics and flavonoids in the urban area of our study decreased compared to those in the control by 1.05, reaching up to 6.5 times. The change in coltsfoot catalase activity both increased and declined. Biochemical responses and heavy metal accumulation in coltsfoot from urban areas limit its use for medicinal purposes.

Zinc affects the physiology and medicinal components of Dendrobium nobile Lindl

The growth of Dendrobium nobile is often influenced by zinc. Here, D. nobile was regularly sprayed with different concentrations (0, 50, 100, 200, 400, 800, 1000, 2000 μmol L^-1) of zinc to study its effect on the growth and biosynthesis of medicinal components. Samples were taken at 0, 7, 14, and 21 days to detect physiological and medicinal components. The results showed that the net photosynthetic rate, transpiration rate, stomatal conductance, and Chl A and Chl B levels of leaves first increased and then decreased as the concentration of zinc increased. At 400 μmol L^-1 concentration, these parameters reached their maximum values. Thus, a certain dose of zinc could promote the photosynthesis of D. nobile. There was an obvious increase in the synthesis of superoxide dismutase (SOD), while the content of ascorbate peroxidase and ascorbic acid (AsA) were the highest after treatment with 400 μmol L^-1 zinc. Maximum levels of polysaccharides and polyphenols were observed on day 7 and 14, respectively, at a zinc concentration of 400 μmol L^-1. These results suggest that exogenous zinc may promote the accumulation of medicinal components in D. nobile. It was also found that polysaccharides could combine well with zinc to form a polysaccharide-zinc chelate and transform inorganic zinc into organic form, which is stored in the form of polysaccharide-Zn and is known to reduce the damage induced by Zn stress.

Synergistic effects of EDDS and ALA on phytoextraction of cadmium as revealed by biochemical and ultrastructural changes in sunflower (Helianthus annuus L.) tissues

This study explored the phytoremediation potential of sunflower on cadmium (Cd) contaminated soils. We also studied the mechanisms through which a plant growth regulator, 5-aminolevolinic acid (ALA) protected sunflower plants from Cd-induced cellular injury. Six-leaf old sunflower plants were exposed to 0.3 g kg^-1 Cd for one week and then treated with chelating agents i.e. trisodium (S,S)-ethylenediamine-N,N'-disuccinic acid (EDDS, 5 mmol kg^-1) and citric acid (CA,10 mmol kg^-1), and 10 mg L^-1 ALA. One week after chelators and ALA application, plants were harvested for further analyses. Results suggested that chelators EDDS/CA significantly increased Cd accumulation but inhibited plant growth of sunflower. In contrast, ALA promoted both Cd absorption and biomass accumulation, especially when applied in combination with EDDS. Bioaccumulation quantity and remove efficiency of Cd + EDDS + ALA treated plants was increased by 21.00% and 20.93% as compared with Cd + EDDS treatment. The qRT-PCR results revealed that increased Cd uptake by chelators EDDS/CA and ALA was associated with an increased expression of Cd transport genes e.g. OPT6, HMA3 and Nramp1 in sunflower leaves and roots. Our study suggested that ALA protects sunflower plants from Cd-induced cellular injury by immobilizing Cd ions, modulating activities of antioxidative enzymes and capturing reactive oxygen species.

Comparative Study of Cytotoxicity, DNA Damage and Oxidative Stress Induced by Heavy Metals Cd(II), Hg(II) and Cr(III) in Yeast

Wide range of applications of heavy metals and improperly discarded their castoffs possess serious threats to environment and human health. In this study, cytotoxicity, DNA damage and oxidative stress induced by Cd(II), Hg(II) and Cr(III) were comparatively studied in yeast Saccharomyces cerevisiae. Cd(II), Hg(II), and Cr(III) all produced strong cytotoxicity resulting in growth inhibition and cell mortality to varying degrees (Hg(II) > Cd(II) > Cr(III)). Hg(II) produced more oxidative stress. Cr(III) caused more serious DNA damage in vitro. Cd(II) also caused both obvious DNA damage and oxidative stress at higher concentration, but not as efficiently as Cd(II) and Hg(II). A further null mutation sensitivity assay showed that the relative sensitivity of rad1∆ to the metals was Cr(III) > Cd(II) > Hg(II), and that of trx1∆ to the metals was Hg(II) > Cd(II) > Cr(III). These data provide a clear evidence that the Cr(III) can cause significant DNA damage and potential genotoxicity; Hg(II) can strongly inhibit SOD activity, produce lipid peroxidation and cause serious membrane injury, suggesting these heavy metals can cause different toxic effects in different ways.

Analysis of physiological and metabolite response of Celosia argentea to copper stress

Copper-tolerant (Cu) plants with high ornamental value play an important role in the ecological restoration of the copper tail mining area. We first discovered Celosia argentea adaptability in a copper mine area in China; however, its resistance to Cu and the underlying mechanism are not clear. In this study, C. argentea was selected for pot culture experiments. Its heavy metal accumulation and translocation, physiological and metabolic products were analysed under different growth concentrations of Cu (0-2400 mg.kg^-1 ) stress. Our results indicated that roots strongly accumulated Cu²⁺ . Oxidative stress defence mechanisms were activated in leaves under Cu treatment. Higher Cu concentrations triggered higher electrolyte leakage (EL), Malondialdehyde (MDA), superoxide dismutase (SOD) and peroxidase (POD) activity, and consequently a higher capacity to scavenge oxygen radicals and maintain cellular membrane integrity. In the citrate cycle, some amino acids and sugars related to biological pathways were altered in C. argentea exposed to Cu stress. Metabolomics data revealed that C. argentea used elevated sugar content as an antioxidant to regulate reactive oxygen species (ROS). Some organic acids and amino acids were up-regulated compared with the control, indicating that these may chelate Cu in cells to remove excess Cu²⁺ . The up-regulation of polyamines and some organic acids may mitigate oxidative stress. These results indicate that C. argentea could be used as a Cu-tolerant plant in Cu mine restoration. Its Cu tolerance mechanism also provides a basis for future plant improvement or breeding for use in mine restoration.

Histopathological effects and biomarker response of earthworms, Eisenia fetida, after exposure to crude oil contaminated soils

Earthworms are the most abundant invertebrates in the soils and are permanently in close contact with soil particles. Therefore, they are significantly affected by the pollutants that reach the soil system. The study was aimed at evaluating the effect of exposure to crude oil contaminated soil on Eisenia fetida using cellular antioxidant enzymes and tissue organization as biomarkers. E. fetida were exposed to different concentrations of crude oil contamination of 1 mL, 2 mL. and 3 mL (0.25, 0.50 and 0.75%) for 14 days. The antioxidant/oxidant parameters were analysed in the muscle and liver tissues. The results showed that only the reduced glutathione (GSH) of earthworms exposed to 1 mL were not significant (p>0.05) from the control, while the other concentrations (2 mL – 0.50% and 3 mL – 0.75%) were significantly different (p<0.05) from the control. The activity of catalase (CAT) with respect to the total protein content was highest in the liver of earthworms exposed to 1 mL (0.25% conc.) on day 7 (51.84 μmol/mg pro) while the least CAT activity with respect to the total protein content was reported in the liver of control earthworms after 14 days (19.51 μmol/mL/min). A significant increase in the activity of superoxide dismutase at all the concentrations (0.25, 0.50 and 0.75%) after 14 days were also observed. Significant histopathological alterations were observed in E. fetida from the three concentrations. Severe disruptions in the arrangement of their body wall muscle layers, distorted internal viscera, as well as cellular degeneration, pigments, moderate to severe areas of lesion, and distortion of the shape of circular and longitudinal muscles, eroding of internal and external tissues leading to total destruction of body wall were observed. In conclusion, the study revealed that crude oil even at lower concentration induced biomarker responses in E. fetida such as higher levels of Malondialdehyde in E. fetida after exposure crude oil due its toxicity. Histopathological alterations such as cellular degeneration, moderate to severe areas of necrosis, areas of inflammation, inclusion bodies, pigments, and distortion of the shapes of circular and longitudinal muscles also showed the adverse impacts of crude oil pollution in the soils.

Can Biomarkers Respond Upon Freshwater Pollution?-A Moss-Bag Approach

Simple Summary

Pollution of the aquatic environment is a well-known problem with a long history. Monitoring water quality relies on biota in order to provide adequative assessment and management of the water bodies. Among the different biological indicators applied, aquatic macrophytes, and particularly mosses, are in direct relationship with the environment and their use as biomonitors is well documented. In the current study, we made an attempt to apply new fast, reliable and comprehensible methods for water pollution control. Three reservoirs were selected for the following reasons: (i) they were polluted with hazardous substances (heavy metals and organic material) and (ii) they are used for fish farming and irrigation and their water quality directly affects human health. Moss-bags with the selected biomonitor Fontinalis antipyretica were exposed in the reservoirs for a period of 30 days and molecular, chemical and micromorphological markers were studied. All biomarkers tested appeared to be sensitive to the pollution. This research provided a basis for further studies on selected biomarkers towards standardization.

Abstract

Moss-bags were applied to study the effect of contamination in three standing water bodies in Bulgaria (Kardzhali, Studen Kladenets and Zhrebchevo Reservoirs), the first two with old industrial contamination and the last polluted with short-chain chlorinated paraffins (SCCPs). Fontinalis antipyretica Hedw. collected from background (unpolluted) site was placed in cages for a period of 30 days. The present study examined whether inorganic and organic pollution detected with moss-bags resulted in corresponding differences in molecular, chemical and micromorphological markers. Suppressed large subunit of ribulose-1,5-bisphosphate carboxylase (rbcL) expression was assessed in moss-bags from two of the reservoirs, contaminated with heavy metals. There was a decrease of the total phenolic content (TPC) in the moss-bags, which provides a basis for further studies of the chemical content of aquatic mosses. Fontinalis antipyretica also showed a response through leaf micromorphological characteristics. In the all three reservoirs, an increase of the twig leaf cell number was recorded (p ≤ 0.01 for Kardzhali and p ≤ 0.001 for Studen Kladenets and Zhrebchevo reservoirs), as well as of the stem leaf cell number in Zhrebchevo Reservoir (p ≤ 0.001). On the contrary, the width of the cells decreased in the studied anthropogenically impacted reservoirs. All three studied groups of biomarkers (molecular, chemical and micromorphological) appeared to be sensitive to freshwater pollution. The results achieved indicated that rbcL gene expression, TPC, cell number and size are promising biomonitoring tools.

Physiological and genetic effects of cadmium and copper mixtures on carrot under greenhouse cultivation

The exposure to combinations of heavy metals can affect the genes of vegetables and heavy metals would accumulate in vegetables and thereby indirectly affecting human health. Exploring the links between genetic changes and phenotypic changes of carrot under the combined pollution of Cd and Cu is of great significance for studying the mechanism of heavy metal pollution. Therefore, this study examined the effects of mixtures of cadmium (Cd) and copper (Cu) on physiological measures (malondialdehyde (MDA), proline, and antioxidant enzyme) and expression of growth-related genes (gibberellin gene, carotene gene, and glycogene) in carrot under greenhouse cultivation. The results showed in the additions with mixtures of Cd and Cu at higher concentration, the MDA content increased significantly (p < 0.05), whereas the proline content was not significantly different from those in the control. In the mixed treatments with high Cd concentrations, the activity of superoxide dismutase (SOD) was significantly lower than that in the control (p < 0.05); whereas the activity of peroxidase (POD) increased to different degrees compared to the control. In the additions with mixtures of Cd and Cu, compared with the control, the expression of the gibberellin gene was downregulated from 1.97 to 20.35 times (not including the 0.2 mg kg^-1 Cd and 20 mg kg^-1 Cu mixture, the expression of gibberellin gene in this treatment was upregulated 1.29 times), which lead to decreases in the length and dry weight of carrots. The expression of the carotene gene in mixed treatments downregulated more than that in single treatments, which could reduce the ability of carrots to resist oxidative damage, as suggested by the significant increase in the MDA content. In the addition with mixtures of Cd and Cu, compared with the control, the expression of the glycogene was downregulated by 1.42-59.40 times, which can cause a significant reduction in the sugar content in carrots and possibly further reduce their ability to resist heavy metal damage. A cluster analysis showed that in the additions with mixtures of Cd and Cu, the plant phenotype was affected first, and then with increases in the added concentration, the expression of genes was also affected. In summary, in the additions with mixtures of Cd and Cu, plants were damaged as Cd and Cu concentrations increased.

Morphological and Physiological Changes of Broussonetia papyrifera Seedlings in Cadmium Contaminated Soil

Broussonetia papyrifera is a widely distributed economic tree species, and it is also a pioneer species in adverse environments. In order to investigate the growth and adaptation mechanism of B. papyrifera under cadmium (Cd) contaminated soil, potted experiments were used with six-month treatments to study Cd enrichment and the transportation, morphological and physiological characteristics of B. papyrifera tissues. The results showed that Cd mainly accumulated in the root when the Cd concentration was high (14.71 mg/kg), and the root biomass was significantly reduced by Cd stress although Cd promoted the growth of seedlings. The bioconcentration factors (BCF) increased with the increase in Cd concentration, and reached the maximum value of 0.21 at 14.71 mg/kg. On the contrary, translocation factor (TF) decreased significantly at 8.28–14.71 mg/kg Cd concentration. Cd not only led to the loose arrangement of the xylem vessels of leaves, but also changed the chlorophyll content. However, B. papyrifera could synthesize organic solutes such as soluble protein, soluble sugar and proline to reduce the intracellular osmotic potential. Our study proved that B. papyrifera has good tolerance to Cd stress and is a pioneer tree species for soil and ecological environment restoration.

Effect of Salicylic Acid Pre-Treatment after Long-Term Desiccation in the Moss Syntrichia ruralis (Hedw.) Web. and Mohr

The main objective of this research was to examine the effects of exogenous salicylic acid (SA) and to study the seasonal variation of the chlorophyll a fluorescence parameters and antioxidant enzymatic activities in desiccation-tolerant moss species Syntrichia ruralis (Hedw.) Web. and Mohr. Aqueous 0.001 M SA solution was sprayed on the moss cushions collected from semi-arid sandy grassland, Hungary in three seasons (spring, summer, autumn). These cushions were kept under the observation for 10 Days. Chlorophyll a fluorescence parameters, i.e., maximum photochemical quantum yield of PS II (Fv/Fm), effective photochemical quantum yield of PS II (ΦPSII), non-photochemical quenching (NPQ), and antioxidant enzymatic activities, i.e., ascorbate peroxidase (APX), catalase (CAT), guaiacol peroxidase (POD), and protein content were determined. The results showed the increase of Fv/Fm in spring and autumn season while ΦPSII was reduced significantly during spring and summer season after treatment with SA compared to control. SA-treated mosses showed higher values of non-photochemical quenching (NPQ) during the spring and autumn season than in summer. Activities of enzyme APX and CAT were found to increase in SA-treated except POD activity. In SA-treated moss cushions, lower protein content was found. It can be concluded that seasonal variation has been observed in chlorophyll fluorescence and antioxidant system after long term of desiccation in S. ruralis species that could be because of SA and might be due to fluctuations in conditions of their habitat, duration of light intensity, temperature and precipitation.

Effect of interactions between various humic acid fractions and iron nanoparticles on the toxicity to white rot fungus

Humic acid plays an important role in controlling the toxicity of nanoparticles to organisms. However, little is known about the influence of different fractions of dissolved humic acid (DHA) from soil on the toxicity of nanoparticles to organisms. The concentration of γ-Fe₂O₃ and the exposure time affected the malondialdehyde (MDA) content, reactive oxygen species (ROS) production and lactate dehydrogenase (LDH) activity in P. chrysosporium cells and were inversely proportional to the relative activities of the cells. P. chrysosporium was exposed to γ-Fe₂O₃ and DHA₁ for 3 h, 6 h and 12 h. Catalase (CAT) and peroxidase (POD) activities were generally higher than control. Particularly, under the influence of 50 mg/L DHA₁ and different concentrations of γ-Fe₂O₃ (10 and 50 mg/L), the CAT and POD activities were higher than those of cells exposed to γ-Fe₂O₃ alone. Conversely, both activities of P. chrysosporium exposed to DHA₄ combined with γ-Fe₂O₃ for 12 h were lower than those of cells exposed to γ-Fe₂O₃ alone and gradually decreased with increasing DHA₄ concentration (0, 10 and 50 mg/L). The μ-XAFS normalized spectrum indicated that Fe³⁺ entering the cells tended to transform into Fe²⁺ as the stress time prolonged. TEM analysis confirmed the toxicity of high concentrations of γ-Fe₂O₃ to P. chrysosporium. The comet assay showed that DHA₄ in soil enhanced the toxicity of γ-Fe₂O₃ to P. chrysosporium more than DHA₁ did. Namely, compared to DHA₁, DHA₄ made it easier for nano-Fe₂O₃ to enter P. chrysosporium cells, causing more toxicity of γ-Fe₂O₃ to P. chrysosporium.

A novel electrochemical sensor based on microporous polymeric nanospheres for measuring peroxynitrite anion released by living cells and studying the synergistic effect of antioxidants

Peroxynitrite anion (ONOO-) is a crucial reactive nitrogen species (RNS), which has aroused immense research interest in the biological and biomedical fields because aberrant expression levels of ONOO- are related to many diseases. In this work, a novel electrochemical sensor is described for the detection of peroxynitrite anion (ONOO-) released from living cells. It is constructed with a glassy carbon electrode (GCE) decorated with a nanocomposite (CTS-MPNS) synthesized from chitosan (CTS) functionalized microporous polymeric nanospheres (MPNS). The prepared CTS-MPNS/GCE sensor shows a supernormal manifestation in measuring ONOO- in a wide range of concentrations from 3.83 nM to 0.104 mM, and the detection limit is as low as 1.28 nM (S/N = 3), which makes it possible to detect trace amounts of ONOO- released from U87 cells. Significantly, the synergistic effect of different antioxidants on scavenging ONOO- in biological systems is further studied by an electrochemical method for the first time, which provides an efficient strategy for protecting cells against oxidative stress. The developed platform and the efficient strategy may pave the way for their future applications in the field of biomedicine and the treatment of cancer diseases.

Insight into the tolerance, biochemical and antioxidative response in three moss species on exposure to BDE-47 and BDE-209

Responses of Hypnum plumaeforme, Thuidium cymbifolium, and Plagiomnium cuspidatum to short-term (96 h) BDE-47 and BDE-209(0, 0.005, 0.05, 0.5, and 5 μM, respectively) stress were investigated. Both BDE-47 and BDE-209 increased the lipid peroxidation in the three moss species, malondialdehyde (MDA) content increased with the elevated concentration of contaminants, and followed the order: P. cuspidatum > H. plumaeforme > T. cymbifolium on exposure to different concentrations. BDE-47 and BDE-209 stimulated the superoxide dismutase (SOD) and peroxidase (POD) activity of the three moss species, indicating that they played an important role in preventing oxidative stress. Reactive oxygen species (ROS) accumulation was positively correlated with the level of contaminants. The response of anti-oxidative enzymes to BDE-47 and BDE-209 stress differed among the three species. At 5  μM BDE-47 and BDE-209 treatment, the chlorophyll content of T. cymbifolium was even a little higher than the control group. Proline played an important role for the scavenging of ROS in P. cuspidatum and T. cymbifolium. In summary, BDE-47 was more toxic to the three moss species than BDE-209. P. cuspidatum was the most sensitive and T. cymbifolium was the most tolerant species to BDE-47 and BDE-209 stress. The strong resistance and tolerance of T. cymbifolium, combined with sensitive/moderate anti-oxidative response could elucidate its potential use as bio-indicator in the ecological risk assessment of BDE-47 and BDE-209 contamination.

Physiological and enzymatic responses of Chlorella vulgaris exposed to produced water and its potential for bioremediation

In South America, Colombia is known as an important oil-producing country. However, the environmental impact of crude oil industry has not been studied deeply and few studies have been carried out for evaluating responses of algae and its adaptation under specific conditions. Enzymatic and physiological effects in Chlorella vulgaris and its potential for bioremediation after exposure to produced water (PW) were assessed using different PW concentrations (0, 25, 50, 75 and 100%) and crude oil. Variables such as cell density, growth rate (μ), percentage of growth inhibition (% I), chlorophyll a and b and cell diameter were evaluated during 5 days. Furthermore, enzymatic biomarkers such as superoxide dismutase (SOD) and catalase (CAT) were also measured. Results showed that the treatment with 100% PW had the highest cell density and μ; similarly, 25% PW treatment had a similar behaviour, being these two treatments with the highest growth. A dose-dependent response was seen for chlorophyll a and b and cell diameter, showing significant differences between treatments and the control. Different levels of SOD and CAT were observed in algae exposed to PW. At 24 h, an increase in SOD and CAT activity was observed, probably due to effects caused by xenobiotics. After 72 h, a decrease in the activity of both enzymes was observed. The results evidenced that C. vulgaris can adapt easily to PW, showing an increase on its growth and stabilisation in its antioxidant activity. Additionally, cell diameter results and decrease of hydrocarbons and phenols show the potential of these algae to degrade xenobiotics from PW.

Synergistic effects of chromium and copper on photosynthetic inhibition, subcellular distribution, and related gene expression in Brassica napus cultivars

Nowadays, modern plant physiology focuses on complex behavior of metal co-contaminants in agrosystems. Keeping this in view, the current study was conducted to investigate the response of two Brassica napus cultivars (Zheda 622 and ZS 758) under co-contamination of copper (Cu²⁺) and chromium (Cr⁶⁺) to observe their effects on plant growth, photosynthetic parameters, and subcellular distribution of these metals in leaves and roots. The results showed that exposure to Cu and Cr causes decline in plant growth, including biomass and plant height. Significant decrease in pigment concentration and the photosynthetic activity [photosynthetic rate (Pn), stomatal conductance (Gs), and transpiration rate (E), maximal quantum yield of photosystem II (Fv/Fm)] in leaves was also observed. Results of subcellular distribution of metals showed that Cu and Cr were predominantly distributed in cell wall and soluble fraction of roots and leaves. Moreover, Cu and Cr in cellular fractions showed a synergistic accumulation pattern under combined metal stress treatment. Both cultivars showed increased levels of reactive oxygen species (ROS), i.e., hydrogen peroxide (H₂O₂) and superoxide radical (O₂^•-), and significant modulation in the activities of antioxidant enzymes [superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), ascorbate peroxidase (APX)] under Cu/Cr alone or their combined treatments. Similarly, expression levels of defense-related genes, such as BnCat, BnApx, BnPrx, and BnSod, were also generally up-regulated compared with control. Electron micrographs (TEM) of the mesophyll and root tip cells indicated prominent alterations both in cellular and organelle levels. Additionally, Cr was found to be more toxic than Cu but less than their combined effect, as revealed by enhanced production of oxidative stress and a reduction in biomass production and photosynthetic activity. The present results also suggest that cultivar ZS 758 is more resistant to Cu/Cr than Zheda 622, due to better adapted metabolism and maintenance of structural integrity under metal stress.

Parameters of oxidative stress, cholinesterase activity, Cd bioaccumulation in the brain and midgut of Lymantria dispar (Lepidoptera: Lymantriidae) caterpillars from unpolluted and polluted forests

Cadmium (Cd) can display a variety of different effects on living organisms. The objectives of the present study were to investigate Cd bioaccumulation and differences in parameters of oxidative stress (activities of the enzymes: superoxide dismutase, catalase, glutathione reductase, ascorbate peroxidase, glutathione S-transferase, and amounts of non-enzymatic free sulfhydryl groups and total glutathione) and cholinesterase activity in larval brain and midgut tissues of the polyphagous forest insect Lymantria dispar collected from unpolluted and polluted oak forests. Fourth instar L. dispar caterpillars from the unpolluted forest had higher body mass but accumulated more Cd in comparison to caterpillars from the polluted forest. In both populations the midgut was more sensitive than the brain to the prooxidative effects of Cd. Enzyme activities and amounts of non-enzymatic parameters tended to be greater in midgut tissues than in the brain, except for cholinesterase activity. Parameters of oxidative stress had higher values in caterpillar tissues from the polluted than from the unpolluted oak forest. The observed differences between the two natural populations point to the importance of knowing the history of population exposure to environmental pollution when monitoring forest ecosystems.

Effects of silver nanoparticles with different dosing regimens and exposure media on artificial ecosystem

Due to the wide use of silver nanoparticles (AgNPs) in various fields, it is crucial to explore the potential negative impacts on the aquatic environment of AgNPs entering into the environment in different ways. In this study, comparative experiments were conducted to investigate the toxicological impacts of polyvinylpyrrolidone-coated silver nanoparticles (PVP-AgNPs) with two kinds of dosing regimens, continuous and one-time pulsed dosing, in different exposure media (deionized water and XiangJiang River water). There were a number of quite different experimental results (including 100% mortality of zebrafish, decline in the activity of enzymes, and lowest number and length of adventitious roots) in the one-time pulsed dosing regimen at high PVP-AgNP concentration exposure (HOE) compared to the three other treatments. Meanwhile, we determined that the concentration of leached silver ions from PVP-AgNPs was too low to play a role in zebrafish death. Those results showed that HOE led to a range of dramatic ecosystem impacts which were more destructive than those of other treatments. Moreover, compared with the continuous dosing regimen, despite the fact that higher toxicity was observed for HOE, there was little difference in the removal of total silver from the aquatic environment for the different dosing regimens. No obvious differences in ecological impacts were observed between different water columns under low concentration exposure. Overall, this work highlighted the fact that the toxicity of AgNPs was impacted by different dosing regimens in different exposure media, which may be helpful for assessments of ecological impacts on aquatic environments.

Molecular cloning, characterization, expression and enzyme activity of catalase from planarian Dugesia japonica in response to environmental pollutants

Catalase (CAT) is an important antioxidant enzyme that protects aerobic organisms against oxidative damage by degrading hydrogen peroxide to oxygen and water. CAT mRNAs have been cloned from many species and employed as useful biomarkers of oxidative stress. In the present study, we cloned the cDNA sequence of CAT gene from freshwater planarian Dugesia japonica (designated as DjCAT) by means of RACE method. Sequence analysis and multiple alignment jointly showed that the full-length cDNA sequence consists of 1734 nucleotides, encoding 506 amino acids. Three catalytic amino acid residues of His71, Asn144 and Tyr354, two CAT family signature sequences of a proximal active site signature (60FDRERIPERVVHAKGGGA77) and a heme-ligand signature motif (350RLFSYRDTQ358) are highly conserved, suggesting that the DjCAT belongs to the NADPH and heme-binding CAT family and has similar functions. In addition, the transcriptional level of CAT gene and activity of CAT enzyme upon acute exposure of environmental pollutants glyphosate and 1-decyl-3-methylimidazolium bromide ([C10mim]Br) were investigated systematically. The variation of CAT mRNA expression in D. japonica was quantified by real-time PCR and the results indicated that it was up-regulated after exposure to glyphosate or [C10mim]Br with a dose-dependent manner but not linearly. Even though the variation trend of CAT activity upon glyphosate stress was not monotonously increased and inconsistent with that after [C10mim]Br exposure on day 1 and 3 sampling time, with the duration prolonged to day 5 they both presented a dose-dependent increase and the differences achieved extreme significance in all treated groups compared to the control. These findings suggested that DjCAT plays an important role in antioxidant defense in D. japonica, and the mRNA expression of CAT would also be used as an effective biomarker to monitor the pollution in aquatic environment just like its corresponding enzyme.

Combined effect of Cr-toxicity and temperature rise on physiological and biochemical responses of Atriplex halimus L

An experiment was conducted to evaluate the combined effect of temperature (26 and 30 °C) and Cr toxicity (0, 100 and 1000 μM Cr) on growth, photosynthesis, water content, Cr and nutrients uptake and translocation. The role of antioxidative enzyme towards stresses tolerance was also investigated. Results showed that the maximum relative growth rate and leaf area per plant of Atriplex halimus L. were recorded at 100 μM Cr and 26 °C. However, presence of Cr reduced net photosynthetic and stomatal conductance rates. Overall, temperature rise enhanced the toxic effect of Cr by reducing growth and photosynthesis and inducing antioxidant enzymes activities. Furthermore, temperature rise increased nutrient uptake, as well as nutrient translocation to aboveground tissues; while it diminished Cr translocation. Finally, roots were the main sink for Cr accumulation in A. halimus. At 1000 μM Cr, root Cr concentrations reached 7.2 and 9.1 mg g^-1 at 26 and 30 °C, respectively; while shoot Cr concentrations were 0.45 and 0.44 mg g^-1 (26 and 30 °C, respectively). The high Cr-accumulation in roots suggests that A. halimus presents a great potential for phytoremediation, especially phytostabilisation of Cr contaminated soils.

Joint toxicity on hepatic detoxication enzymes in goldfish (Carassius auratus) exposed to binary mixtures of lead and paraquat

Compared to single exposure, chemical mixtures might induce joint toxicity including additive, synergistic and antagonistic effects on both organisms and environment. Owing to the specific toxicity of oxidative stress and binding to proteins, lead (Pb) is generally recognized a non-essential and threatening heavy metal to animals and human. Paraquat (PQ) is a widely used herbicide in agriculture and can trigger oxidative stress as well as Pb. Little information was available about joint effects of the two chemicals on toxicological responses in organisms, especially in fish. In our present study, goldfish (Carassius auratus) were randomly exposed to single and combined experiments with different concentrations of Pb and PQ for 28 days. Activities of four enzyme biomarkers in liver, ethoxyresorufin-O-deethylase (EROD), 7-benzyloxy-4-trifluoromethyl-coumarin-O-debenzyloxylase (BFCOD), glutathione-S-transferase (GST) and UDP-glucuronosyltransferase (UGT) were evaluated in each experimental group on day 14 and 28. The results showed four enzyme levels were markedly reduced with the increase of concentrations in mixtures and prolonged exposure. The inhibitory EROD and BFCOD activities were not significantly changed in goldfish following PQ-treated groups with or without 0.5 mg/L Pb, which indicated PQ has more inhibitory toxicity on CYP450 enzymes than Pb in co-exposure groups. However, the reduced values of GST were observed only in the combinations containing high doses of Pb or PQ during experimental periods. Although the responses of UGT activity were similar to GST on 14th day, all combinations of Pb and PQ generated stronger inhibitions on UGT activities compared to individual Pb and PQ-treated group. These results suggested that combined exposure of Pb and PQ have more inhibitory toxicity on phase I enzymes than phase II enzymes.

Physiological and anthocyanin biosynthesis genes response induced by vanadium stress in mustard genotypes with distinct photosynthetic activity

The present study aimed to elucidate the photosynthetic performance, antioxidant enzyme activities, anthocyanin contents, anthocyanin biosynthetic gene expression, and vanadium uptake in mustard genotypes (purple and green) that differ in photosynthetic capacity under vanadium stress. The results indicated that vanadium significantly reduced photosynthetic activity in both genotypes. The activities of the antioxidant enzymes were increased significantly in response to vanadium in both genotypes, although the purple exhibited higher. The anthocyanin contents were also reduced under vanadium stress. The anthocyanin biosynthetic genes were highly expressed in the purple genotype, notably the genes TT8, F3H, and MYBL2 under vanadium stress. The results indicate that induction of TT8, F3H, and MYBL2 genes was associated with upregulation of the biosynthetic genes required for higher anthocyanin biosynthesis in purple compared with the green mustard. The roots accumulated higher vanadium than shoots in both mustard genotypes. The results indicate that the purple mustard had higher vanadium tolerance.

In-field and in-vitro study of the moss Leptodictyum riparium as bioindicator of toxic metal pollution in the aquatic environment: Ultrastructural damage, oxidative stress and HSP70 induction

This study evaluates the effects of toxic metal pollution in the highly contaminated Sarno River (South Italy), by using the aquatic moss Leptodictyum riparium in bags at 3 representative sites of the river. Biological effects were assessed by metal bioaccumulation, ultrastructural changes, oxidative stress, as Reactive Oxygen Species (ROS) production and Glutathione S-transferase (GST) activity, as well as Heat Shock Proteins 70 (HSP70s) induction. The results showed that L. riparium is a valuable bioindicator for toxic metal pollution of water ecosystem, accumulating different amounts of toxic metals from the aquatic environment. Toxic metal pollution caused severe ultrastructural damage, as well as increased ROS production and induction of GST and HSP70s, in the samples exposed at the polluted sites. To assess the role and the effect of toxic metals on L. riparium, were also cultured in vitro with Cd, Cr, Cu, Fe, Ni, Pb, Zn at the same concentrations as measured at the 3 sites. Ultrastructure, ROS, GST, and HSP70s resulted severely affected by toxic metals. Based on our findings, we confirm L. riparium as a model organism in freshwater biomonitoring surveys, and GST and HSP70s as promising biomarkers of metal toxicity.

Eco-physiological response of Hypnum cupressiforme Hedw. to increased atmospheric ammonia concentrations in a forest agrosystem

Ammonia (NH₃) emissions are linked to eutrophication, plant toxicity and ecosystem shifts from N to P limitation. Bryophytes are key components of terrestrial ecosystems, yet highly sensitive to N deposition. Hence, physiological responses of mosses may be indicative of NH₃-related impacts, and thus useful to foresee future ecosystem damages and establish atmospheric Critical Levels (CLEs). In this work, samples of Hypnum cupressiforme Hedw. were seasonally collected along a well-defined NH₃ concentration gradient in an oak woodland during a one-year period. We performed a comprehensive evaluation of tissue chemistry, stoichiometry, metabolic enzymes, antioxidant response, membrane damages, photosynthetic pigments, soluble protein content and N and C isotopic fractionation. Our results showed that all the physiological parameters studied (except P, K, Ca and C) responded to the NH₃ gradient in predictable ways, although the magnitude and significance of the response were dependent on the sampling season, especially for enzymatic activities and pigments content. Nutritional imbalances, membrane damages and disturbance of cellular C and N metabolism were found as a consequence to NH₃ exposure, being more affected the mosses more exposed to the barn atmosphere. These findings suggested significant implications of intensive farming for the correct functioning of oak woodlands and highlighted the importance of seasonal dynamics in the study of key physiological processes related to photosynthesis, mosses nutrition and responses to oxidative stress. Finally, tissue N showed the greatest potential for the identification of NH₃-related ecological end points (estimated CLE=3.5μgm^-3), whereas highly scattered physiological responses, although highly sensitive, were not suitable to that end.