μM Cd Research Articles

Involvement of Ca2+ Channels in Abnormal Excitability of Hippocampal CA3 Pyramidal Cells in Noda Epileptic Rats

Noda epileptic rat (NER) is a mutant rat, which spontaneously exhibits a tonic-clonic convulsion from 14 weeks of age. An intracellular recording study was performed to elucidate the abnormal excitability of NER hippocampal CA3 neurons. The recorded neurons were classified into two groups, group A and B neurons, according to the responses to a single stimulation of mossy fibers. In group A neurons, a stimulus elicited a long-lasting depolarization shift accompanying repetitive firings followed by after-hyperpolarization. In group B neurons, the same stimulus elicited a single spike without a long-lasting depolarization shift. Bath application of 1 mM Cd2+, a nonselective Ca2+ channel blocker, completely inhibited the abnormal excitation in group A neurons. We further examined the character of Ca2+ spikes in NER CA3 neurons. Ca2+ spikes were completely blocked by 10 μM Cd2+ in group A neurons, but not in either group B or control neurons, suggesting that Ca2+ channels in NER group A neurons have the hypersensitivity to Cd2+. Analysis using subtype specific blockers of Ca2+ channel raised the possible involvement of T-type Ca2+ channels. These results suggest that Ca2+ channel dysfunction is involved in the abnormal excitability of CA3 pyramidal neurons and pathogenesis of epilepsy in NER.

Examining the relationship between metal exposure (Cd and Hg), subcellular accumulation, and physiology of juvenile Crassostrea virginica.

To assess the toxicity and accumulation (total and subcellular partitioning) of cadmium (Cd) and mercury (Hg), juvenile eastern oysters, Crassostrea virginica, were exposed for 4 weeks to a range of concentrations (Control, Low (1×), and High (4×)). Despite the 4-fold increase in metal concentrations, oysters from the High-Cd treatment (2.4 μM Cd) attained a body burden that was only 2.4-fold greater than that of the Low-Cd treatment (0.6 μM Cd), while oysters from the High-Hg treatment (0.056 μM Hg) accumulated 8.9-fold more Hg than those from the Low-Hg treatment (0.014 μM Hg). This fold difference in total Cd burdens was, in general, mirrored at the subcellular level, though binding to heat-denatured proteins in the High-Cd treatment was depressed (only 1.6-fold higher than the Low-Cd treatment). Mercury did not appear to appreciably partition to the subcellular fractions examined in this study, with the fold difference in accumulation between the Low- and High-Hg treatments ranging from 1.5-fold (heat-stable proteins) to 4.6-fold (organelles). Differences in toxicological impairments (reductions in condition index, protein content, and ETS activity) exhibited by oysters from the High-Cd treatment may be partially due to the nature of how different metals partition to subcellular components in the oysters, though exact mechanisms will require further examination.

Modulation of the defence responses against Cd in willow species through a multifaceted analysis

Willow, due to the extensive root system, high transpiration rates and ability to accumulate large amounts of cadmium, is considered particularly useful for green remediation practices. In this study two different willow species, Salix viminalis and Salix alba, were used to assess possible differences in their ability of cadmium accumulation and to analyse in detail the physiology of their response to treatments with this metal using a multidisciplinary approach. Plants were grown in hydroponics and treated with 0, 50 and 100 μM Cd2+ (CdCl2) for 7 and 14 days. Cadmium content, oxidative stress, both evaluated by biochemical and histochemical techniques, antioxidant response, leaf stomatal conductance and photosynthetic efficiency were measured in control and treated roots and/or leaves. The two willow species removed cadmium with a high efficiency from the growth solution; however, the highest contents of Cd recorded in plants grown in the presence of the lower Cd concentrations suggest a limited capacity of metal accumulation. No photochemical limitation characterised treated plants, probably due to the ability to store large amounts of Cd in the root compartment, with reduction of damage to the photosynthetic machinery. S. viminalis, able to uptake cadmium also in the root apical region, seemed to be a more efficient accumulator than S. alba and, thanks to a relatively higher antioxidant response, did not show a higher level of oxidative stress. On the basis of the above, the two plant species, in particular S. viminalis, are confirmed as useful for cadmium phytostabilisation/phytoextraction.

Inoculation of plant growth promoting bacteria from hyperaccumulator facilitated non-host root development and provided promising agents for elevated phytoremediation efficiency

Plant growth promoting bacteria (PGPB) have been reported to have the ability to promote plant growth, development and increase heavy metals (HMs) uptake. Therefore, PGPB inoculation as soil remediation agents into plants with larger biomass and potential of phytoextraction is of great importance to increase bioremediation efficiency. In this study, 12 PGPB strains isolated from a cadmium (Cd)/zinc hyperaccumulator Sedum alfredii Hance were inoculated into non-host plant Brassica juncea and their effects on plant growth and Cd uptake were determined. The results showed that inoculation of most PGPB strains promoted plant growth, boosted root development and improved chlorophyll content in the absence of Cd. Inoculation of PGPB strains promoted plant growth up to 111% in shoot and 358% in root when treated with 2 μM Cd. In addition, PGPB inoculation not only ameliorated plant root morphology including the total root length (RL), total surface area (SA), total root volume (RV) and number of root tips (RT), but also facilitated Cd uptake up to 126%. Furthermore, inoculation of PGPB strains promoted plant Cd accumulation up to 261% in shoot and up to 8.93-fold increase in root. Among all the 12 PGPB strains, Burkholdria SaMR10 and Sphingomonas SaMR12 were identified as the promising microbes for improving phytoremediation efficiency of Cd contaminated soils. These results not only provided useful findings for further investigation of interacting mechanisms between different bacterial strains and plants, but also facilitated the development of microbe-assisted phytoremediation application for HM contaminated soil.

Cellular distribution of cadmium in two amaranth (Amaranthus mangostanus L.) cultivars differing in cadmium accumulation.

Differences in cellular cadmium (Cd) distribution between Cd-tolerant and Cd-sensitive lines of amaranth (Amaranthus mangostanus L.) may reveal mechanisms involved in Cd tolerance and hyperaccumulation. We compared the cellular distribution and accumulation of Cd in roots, stems, and leaves between a low-Cd accumulating cultivar (Zibeixian, L-Cd) and a high-Cd accumulating cultivar (Tianxingmi, H-Cd) in a hydroponic experimental system. In all treatments, H-Cd grew better than L-Cd and accumulated more Cd. As the Cd concentration increased, the H-Cd plants grew normally and their biomass increased, except in the 60 μM Cd treatment. The biomass of L-Cd decreased with increasing Cd concentrations. The highest Cd concentration in the roots, stems, and leaves of H-Cd was 950 mg/kg, 305 mg/kg, and 205 mg/kg, respectively, compared with 269 mg/kg, 62.9 mg/kg, and 74.8 mg/kg, respectively, in L-Cd. The Cd distribution differed between the two cultivars. Scanning and transmission electron microscopy and energy-dispersive spectrometry analyses showed that Cd was distributed across the entire cross section of H-Cd roots but largely restricted to the epidermal cells and the exodermis of L-Cd roots. The main Cd storage sites were the root apoplast, cell walls, and intercellular spaces in H-Cd and the root epidermal cells and the exodermis in L-Cd. In H-Cd leaves, Cd accumulated mainly in vacuoles of epidermal cells and, at high external Cd concentrations, in the vacuoles of mesophyll cells.

Enhanced nitric oxide generation mitigates cadmium toxicity via superoxide scavenging leading to the formation of peroxynitrite in barley root tip

The aim of this study was to observe the possible function of increased superoxide and NO production in the response of barley root tip to the harmful level of Cd. While superoxide generation was detected only in the transition zone, the formation of NO was observed in the apical elongation zones of the control root tips. However, the root region with the superoxide generation was also associated with peroxynitrite specific fluorescence signal. Superoxide, H2O2 and peroxynitrite generation increased with Cd treatment in a dose-dependent manner. In turn, NO level increased at low 10–20 μM but decreased at high 50–60 μM Cd concentrations in comparison with the control. While co-treatment of roots with rotenone markedly attenuated the Cd-induced superoxide generation and lipid peroxidation, it increased the level of NO in the root tips. Although rotenone did not influence the Cd-induced increase of GPX activity at 10–30 μM Cd concentrations, it markedly reversed the high 40–60 μM Cd concentrations-induced decline of GPX activity. Cd-induced cell death was associated with robust superoxide generation, but not with a high level of peroxynitrite. The Cd-evoked inhibition of root growth was significantly reversed by a strong antioxidant N-acetyl cysteine but not by a peroxynitrite scavenger uric acid, suggesting that similarly to Cd-induced cell death, an imbalance in the ROS homeostasis and not an enhanced level of peroxynitrite is responsible for the Cd-induced root growth inhibition. Based on these findings, it can be assumed that NO acts mainly in the regulation of superoxide level in the tips of root. Under Cd stress, the enhanced NO level is involved in the scavenging of highly toxic superoxide through the formation of peroxynitrite, thus reducing the superoxide-mediated cell death in barley root.

Seed priming with calcium chloride improves the photosynthesis performance of faba bean plants subjected to cadmium stress

Faba bean (Vicia faba L.) seeds were treated with H2O [nonprimed (NP)] or 2% CaCl2 [primed (P)] before germination for 6 h. After seven days, seedlings were exposed to 0 or 50 µM CdCl2 concentrations for three weeks. Under Cd treatment, P plants showed an improvement of gas-exchange characteristics, chlorophyll (Chl) and carotenoids contents as compared to NP plants subjected to Cd stress. Additionally, the values of Chl fluorescence were relatively similar to those of control, implying that no photodamage occurred. Moreover, under 50 µM Cd, the P plants exhibited lesser accumulation of hydrogen peroxide and superoxide radicals in leaves as compared to NP plants. Likewise, results showed that CaCl2-seed pretreatment alleviated adverse effects of Cd on electrolyte leakage. In conclusion, CaCl2 improved photosynthesis attributes of faba bean plants subjected to Cd stress by mitigating the adverse effects of Cd toxicity through a reduced generation of reactive oxygen species.

Assessing interactions between environmental factors and aquatic toxicity: Influences of dissolved CO2 and light on Cd toxicity in the aquatic macrophyte Potamogeton crispus

The objective of this study was to investigate the combined effects of varying dissolved CO2 concentration (ambient CO2, 3˜17 μmol L−1, elevated CO2, 48˜81 μmol L−1) and light intensity (high light, c. 150 μmol photon m−2 s−1, low light, c. 25 μmol photon m−2 s−1) on the bioaccumulation and phytotoxicity of cadmium (Cd) in a macrophyte Potamogeton crispus, under constant Cd exposure. The data confirmed that 100 μM Cd led to adverse changes in morphology, ultrastructure and biochemistry in P. crispus. The toxic effects depended strongly on CO2 concentration and light intensity: elevated CO2 and high light both increased Cd concentrations in P. crispus, and there was a significant interaction between the two factors. Compared to high light grown plants, the photochemical efficiency and chlorophyll content of low light grown P. crispus were much less affected and the MDA content was lower, when exposed to 100 μM Cd. In addition, an antioxidative response was observed with a significant increase in SOD, POD and GST activities, indicating that low light grown P. crispus are more protected against Cd toxicity. When compared with ambient CO2 concentrations, chlorophyll content, chlorophyll fluorescence, photosynthetic rate and starch content, as well as the activity of SOD and GST, were significantly enhanced in Cd treated P. crispus under elevated CO2. This suggests that elevated CO2 reduced Cd toxicity in P. crispus by increasing photosynthesis and enhancing the antioxidant system. Moreover, the statistical results showed that dissolved CO2 and light had additive effects on Cd toxicity in P. crispus, reflected by the physiological parameters of total chlorophyll content, SOD activity and MDA content, indicating that the combination of high CO2 and low light produced more protection against Cd toxicity than did the factors alone. Based on the results of this study, it appears clear that referring to a specific site in aquatic ecosystem, dissolved CO2 concentration and light availability should be considered when assessing and managing Cd impacts on aquatic plants.

Gadolinium inhibits cadmium transport by blocking non-selective cation channels in rice seedlings

Non-selective cation channels (NSCCs) play important roles in uptake of heavy metals in plants. However, little information is available concerning the contribution of NSCCs to cadmium (Cd) transport in rice seedlings. Results from the hydroponic experiment showed that the inhibition of 2.7 μM Cd on the development of rice roots was alleviated by adding 0.1 mM gadolinium (Gd) in nutrient solution, companied by reduction of Cd content by 55.3% in roots and by 45.0% in shoots. Inhibition of Gd on Cd accumulation in cytoplasm fraction (F3) was much greater than that in cell walls (F1) and organelles (F2) in roots. After increasing concentrations of Mn and Zn in nutrient solution, adding 0.1 mM Gd resulted in reductions in Cd content by 89.1%, in micronutrients by 54.9% and in macronutrients by 5.4% in roots, respectively. Cd stress resulted in significant increase of PC2∼4 and free amino acids, but decrease of V-ATPase activity by 32.3% in roots. These results indicate that NSCCs make a great contribution to uptake of Cd in rice seedlings and opportunities for Cd to be transported by NSCCs can be efficiently reduced by blocking NSCCs and/or increasing essential microelements like Mn and Zn.

Zn Supplement-Antagonized Cadmium-Induced Cytotoxicity in Macrophages In Vitro: Involvement of Cadmium Bioaccumulation and Metallothioneins Regulation.

Cadmium (Cd) is a toxic metal leading to multiple forms of organ damage. Zinc (Zn) was reported as a potential antagonist against Cd toxicity. The present study investigates the antagonistic effect of Zn (20 μM) on Cd (20 or 50 μM) cytotoxicity in macrophages in vitro. The results shows that Cd exposure caused dose-dependent morphologic and ultrastructural alterations in RAW 264.7 macrophages. Zn supplement significantly inhibited Cd cytotoxicity in RAW 264.7 or HD-11 macrophages by mitigating cell apoptosis, excessive ROS output, and mitochondrial membrane depolarization. Notably, Zn supplement for 12 h remarkably prevented intracellular Cd2+ accumulation in 20 μM (95.99 ± 9.93 vs 29.64 ± 5.08 ng/106 cells; P = 0.0008) or 50 μM Cd (179.78 ± 28.66 vs 141.62 ± 22.15 ng/106 cells; P = 0.003) exposed RAW 264.7 cells. Further investigation found that Cd promoted metallothioneins (MTs) and metal regulatory transcription factor 1 (MTF-1) expression in RAW 264.7 macrophages. Twenty μM Zn supplement dramatically enhanced MTs and MTF-1 levels in Cd-exposed RAW 264.7 macrophages. Intracellular Zn2+ chelation or MTF-1 gene silencing inhibited MTs synthesis in Cd-exposed RAW 264.7 macrophages, which was accompanied by the declined expression of MTF-1, indicating that regulation of Zn on MTs was partially achieved by MTF-1 mobilization. In conclusion, this study demonstrates the antagonism of Zn against Cd cytotoxicity in macrophages and reveals its antagonistic mechanism by preventing Cd2+ bioaccumulation and promoting MTs expression.

Exogenous Glycinebetaine Reduces Cadmium Uptake and Mitigates Cadmium Toxicity in Two Tobacco Genotypes Differing in Cadmium Tolerance.

Greenhouse hydroponic experiments were conducted using Cd-sensitive (cv. Guiyan1) and Cd-tolerant (cv. Yunyan2) tobacco cultivars to study the ameliorative effects of exogenous glycinebetaine (GB) upon 5 μM Cd stress. The foliar spray of GB markedly reduced Cd concentrations in plants and alleviated Cd-induced soil plant analysis development (SPAD) value, plant height and root length inhibition, with the mitigation effect being more obvious in Yunyan2. External GB markedly reduced Cd-induced malondialdehyde (MDA) accumulation, induced stomatal closure, ameliorated Cd-induced damages on leaf/root ultrastructure, and increased the chlorophyll content and fluorescence parameters of Fo, Fm, and Fv/Fm in both cultivars and Pn in Yunyan2. Exogenous GB counteracted Cd-induced alterations of certain antioxidant enzymes and nutrients uptake, e.g., the depressed Cd-induced increase of superoxide dismutase (SOD) and peroxidase (POD) activities, but significantly elevated the depressed catalase (CAT) and ascorbate peroxidase (APX) activities. The results indicate that alleviated Cd toxicity by GB application is related to the reduced Cd uptake and MDA accumulation, balanced nutrients and antioxidant enzyme activities, improved PSII, and integrated ultrastructure in tobacco plants.

Influence of cadmium stress on the lipid production and cadmium bioresorption by Monoraphidium sp. QLY-1

Cadmium (Cd) stress is a cost-effective, clean, and environmentally friendly approach for microalgal lipid production and wastewater treatment. To study the regulatory networks involved in the growth and development of microalgae, the relationship between calcium and reactive oxygen species (ROS) signalling in the regulation of cell growth and lipid biosynthesis and Cd biosorption after Cd treatment were analysed. The highest lipid content (52.78%) and productivity (96.75 mg L−1 d−1) were enhanced by 1.59- and 1.39-fold in algal cells treated with 80 μM and 40 μM Cd, respectively, compared to the control. The protein content, ROS, antioxidases, Ca2+ and lipid biosynthetic gene transcription levels were upregulated by Cd induction. Additionally, the results indicated that increased endogenous Ca2+ could alleviate oxidative stress by activating antioxidases and mediating Cd biosorption, resulting in cell growth modulation and lipid accumulation. These results demonstrated that Cd stress is a useful strategy for lipid production and Cd bioaccumulation in microalgae and that there is vital interaction between ROS and Ca2+ levels in the regulation of lipid accumulation under Cd stress.

Variations in pH significantly affect cadmium uptake in grafted muskmelon (Cucumis melo L.) plants and drive the diversity of bacterial communities in a seedling substrate

Substrates are fundamental prerequisites for growing grafted seedlings. In this study, substrates with different pH levels (5.0, 5.5, 6.0, 6.5, 7.0, and 8.0) were set up to elucidate the effect of pH on cadmium (Cd) uptake in grafted muskmelon (Cucumis melo L.) plants. Bacterial diversity was also investigated. Results showed that pH and high Cd concentration greatly affected the growth of grafted plants. The chlorophyll content of the muskmelon leaves decreased at 100 μM Cd. The majority of the Cd ions accumulated in the rootstock rather than in the shoot tissue in all of the treatments. The shoots and roots showed the highest Cd content at pH 5.5 and the lowest Cd content at pH 8.0 regardless of the Cd concentration. The operational taxonomic units belonging to Proteobacteria and Bacteroidetes were significantly (p < 0.05) enriched at different substrate pH levels compared with those at pH 5.0. The operational taxonomic units belonging to the phyla Firmicutes, Acidobacteria, and Chloroflexi were significantly decreased. The available nitrogen, phosphorus, Cd, and pH were strongly linked to bacterial community compositions. On the contrary, the available potassium was weakly correlated with the bacterial structure. This study demonstrates that pH greatly affects Cd uptake in grafted muskmelon plants and predicts microbial community structures in breeding substrates with different pH levels. Our results suggest that Cd accumulation in grafted plants can be reduced by setting the appropriate substrate pH. This work can serve as a reference for growing high-quality grafted plants and ensuring food safety in the presence of Cd contamination.

Characteristics of membrane-bound fatty acid desaturase (FAD) genes in Brassica napus L. and their expressions under different cadmium and salinity stresses

The membrane-bound fatty acid desaturases (FADs) play vital roles in regulating plant fatty acid (FA) compositions which directly affect oil quality in rapeseed (Brassica napus L.). In the present study, a total of 68 putative FAD genes were identified in the crop and were phylogenetically clustered into four subfamilies. Genomic localization revealed that the genes were distributed across 21 chromosomes at various densities. The structures of paralogous genes were considerably conserved in the number of exons and in the length of introns. It was found that the expansion of the B. napus FAD family was mainly attributable to whole genome duplication and segmental duplication. Rapeseed seedlings were grown hydroponically under three levels (0, 250, and 500 μM) of cadmium (Cd) and three levels (0, 50, and 100 mM) of salinity. After one week of treatment, the roots and leaves of seedlings were harvested to study the expression patterns of 68 selected BnFADs in response to the different stresses. The results from qRT-PCR analyses suggested that the FAD genes in rapeseed were differentially expressed under various abiotic stresses. The transcript levels of the FAD genes ADS4.8, ADS4.9, ADS4.10, ADS9.1 and SLD8 in the leaves of Cd-tolerant cultivar ZD619 were significantly higher than those in the leaves of sensitive cultivar ZD622 under the 250 μM Cd stress condition. Moreover, the expression levels of 8FAD genes (ADS4.1, ADS4.4, ADS4.9, ADS9.1, ADS9.2, SLD8, FAD7.4 and FAD7.5) in ZD619 roots were obviously enhanced with the increase of salinity concentrations. These results indicate the likelihood of FAD genes involved in Cd and salinity tolerance. This study provides insight on membrane-bound FAD genes involvement in tolerance to abiotic stresses and would provide some more candidate genes for the crop improvement.

Subcellular distribution of cadmium in a novel potential aquatic hyperaccumulator – Microsorum pteropus

Microsorum pteropus is a novel potential Cd (cadmium) aquatic hyperaccumulator. In the present study, hydroponic experiments were conducted to assess the accumulation and subcellular distribution of Cd in the root, stem and leaf of M. pteropus. SEM (scanning electron microscopy) – EDX (energy dispersive X-ray fluorescence spectrometer) and TEM (transmission electron microscopy) were used to observe the ultrastructure of different tissues under 500 μM Cd exposure. After exposure to 500 μM Cd for 7 days, the root, stem and leaf of M. pteropus can accumulate to be > 400 mg/kg Cd in dry mass with no significant influence on the growth. In the root and leaf of M. pteropus, the Cd was more likely to store in the cell wall fraction. However, Cd in the stem was mainly stored in both the cell wall fraction and the cytoplasm fraction. Under SEM observation and EDX detection, 1) Cd was found to be sequestrated in the epidermis or chelated in the root cells, 2) no significant deposit spots were observed in the stem, 3) Cd was found in the trichome of the leaf, and the sporangium was not damaged. TEM observations revealed 1) possible Cd precipitations in the root cell and 2) no significant ultrastructure variation in the stem, and 3) the chloroplast retained its structure and was not affected by the Cd. M. pteropus showed great capacity for Cd accumulation without influencing growth. In addition, the ultrastructure of all the tissues was not damaged by the Cd. M. pteropus showed a great potential in phytoremediation in heavy metal polluted water solutions, and may provide new directions for the study of resistance mechanisms of aquatic hyperaccumulators.

Hydrothermal synthesis of carbon dots codoped withnitrogen and phosphorusas a turn-on fluorescent probe for cadmium(II).

Nitrogen and phosphorus co-doped carbon dots (N,P-CDs) have been synthesized via hydrothermal method starting from o-phosphorylethanolamine and citric acid. The blue-green fluorescence of the N,P-CDs (with excitation/emission peaks at 325/435nm) isgradually enhanced on sequential addition of Cd(II) ions. This fluorometric assay works in the 0.5μM to 12.5μM Cd(II) concentration range and has a 0.16μM detection limit. The phenomenon may be attributed to chelation enhanced fluorescence that is induced by the formation of Cd(II)-N,P-CDs complex with functional groups present on the surface. The method has applied to the detection of Cd(II) in spiked serum and urine samples and gave satisfying results. Graphical abstract Schematic presentation of the synthesis of nitrogen and phosphorus co-doped carbon dots (N,P-CDs) and their application as a turn-on fluorescence probe for Cd(II) detection.

Foliar application of salicylic acid alleviate the cadmium toxicity by modulation the reactive oxygen species in potato

Heavy metal toxicity is one of the main factors that limit crop growth and yield in the world. Salicylic acid (SA) is thought to be a plant hormone that plays an important role in plant growth, development, and resistance to abiotic stresses. To uncover the toxic alleviation effects of SA on potato plants to cadmium (Cd) stress, the morphological, physiological, and biochemical indexes including antioxidant defense system were assayed in potato plants under 200 μM Cd stress in 1/2 Hoagland solution with foliar application of 600 μM SA concentration (10 ml/plant). Interestingly, exogenous SA treatment mitigated Cd toxicity by increasing the relative water content (RWC), chlorophyll, proline, and endogenous SA contents along with decline in malondialdehyde (MDA), hydrogen peroxide (H2O2), and superoxide anion radicals (O2-). Correspondingly, our study also proved that SA may stimulate the antioxidant enzymatic mechanism pathway including superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6), ascorbate peroxidase (APX, EC 1.11.1.11), and glutathione reductase (GR, EC 1.6.4.2) in potato plants subjected to Cd stress. Moreover, the expression level of selected genes relate to SA and reactive oxygen species (ROS) metabolism (StSABP2, StSOD and StAPX) were enhanced in SA-treated potato plants under Cd stress, indicating that SA treatment regulated the expression of these genes, which in turn enhanced potato tolerance to Cd stress. Taken together, our results indicated that exogenous SA can play a positive regulatory role in alleviating Cd toxicity in potato plants.

Enhanced stripping voltammetric response of Hg2+, Cu2+, Pb2+ and Cd2+ by ZIF-8 and its electrochemical analytical application

The zeolitic imidazolate framework ZIF-8 was synthesized and mixed with chitosan (CS) solution to obtain a homogeneous dispersion. Then the dispersion of ZIF-8 and CS (ZIF-8-CS) modified glassy carbon electrode is fabricated and utilized for stripping voltammetric analysis of Hg2+, Cu2+, Pb2+ and Cd2+ for the first time. The large surface area effect and strong enriching effect of the nanosized ZIF-8 to the four heavy metal ions contribute to significantly enhance analytical signals. Under the optimum conditions, the stripping peak current densities linearly increased with Hg2+ concentration in the range from 1.0μM to 80.0μM, and with Cu2+, Pb2+ and Cd2+ concentrations in the range from 1.0μM to 100.0μM. The analytical sensitivity for the four ions are estimated to be 14.20μA·μM−1·cm−2 (Hg2+), 2.797μA·μM−1·cm−2 (Cu2+), 5.203μA·μM−1·cm−2 (Pb2+) and 1.390μA·μM−1·cm−2 (Cd2+), respectively. The limits of detection for the four ions were estimated to be 0.0293μM (Hg2+), 0.108μM (Cu2+), 0.0619μM (Pb2+) and 0.135μM (Cd2+), respectively. The ZIF-8 based modified electrode also presented excellent anti-interference ability, and good reliability for monitoring the four ions in real water samples.

Multi-metal tolerance of von Willebrand factor type D domain isolated from metal contaminated site by metatranscriptomics approach

Environmental pollution through heavy metals is an upcoming universal problem that relentlessly endangers human health, biodiversity and ecosystems. Hence remediating these heavy metal pollutants from the environment by engineering soil microbiome through metatranscriptomics is befitting reply. In the present investigation, we have constructed size fractionated cDNA libraries from eukaryotic mRNA of cadmium (Cd) contaminated soil and screened for Cd tolerant genes by yeast complementation system by using Cd sensitive ycf1Δ mutant. We are reporting one of the transformants PLCe10 (from library C, 1–4 kb) with potential tolerance towards Cd toxicity (40 μM–80 μM). Sequence analysis of PLCe10 transcript showed homology to von Willebrand factor type D domain (VWD) of vitellogenin-6 of Ascaris suum encoding 338 amino acids peptide. qPCR analysis revealed that PLCe10 induced in presence of Cd (32 fold) and also accumulated maximum amount of Cd at 60 μM Cd. This cDNA was further tested for its tolerance against other heavy metals like copper (Cu), zinc (Zn) and cobalt (Co). Heterologous complementation assays of cDNA PLCe10 showed a range of tolerance to Cu (150 μM–500 μM), Zn (10 mM–12 mM) and Co (2–4 mM). Results of the present study suggest that cDNA PLCe10 is one of the functional eukaryotic heavy metal tolerant genes present among the soil microbial community and could be exploited to rehabilitate metal contaminated sites.

Glassy Carbon Electrodes Modified with Ordered Mesoporous Silica for the Electrochemical Detection of Cadmium Ions.

Four different samples of ordered mesoporous silica powders (MCM-41 and SBA-15) and amino-functionalized mesoporous silica (MCM-41-NH2 and SBA-15-NH2) were used to prepare modified glassy carbon electrodes coated with ion-exchange polymer Nafion to be used for the electrochemical detection of Cd(II). The mesoporous silica samples were characterized through transmission electron microscopy, small-angle X-ray scattering, and N2-adsorption/desorption isotherms. The electrodes were characterized by using square wave anodic stripping voltammetry. The effect of pH and of the silica type on the electrodes’ response was investigated. The influence of amino functional groups grafted on the silica surface toward Cd(II) ion detection was also examined. The detection limits determined with the new silica-modified electrodes [between 0.36 and 1.68 μM Cd(II)] are slightly higher than those reported in the literature, but they are lower than those stipulated in the European legislation [45 μM Cd(II)] and, consequently, the electrodes could be successfully used to detect Cd(II) in aqueous solutions.