μM Cd Research Articles

The role of the ABF1 gene in regulation of Cd-induced hormesis in Arabidopsis thaliana

Hormesis is important in plant performance in contaminated environments, but the underlying genetic mechanisms are poorly understood. This study aimed at mining key genes in regulating Cd-induced hormesis in Arabidopsis thaliana and verifying their biological function. Hormesis of fresh weight, dry weight, and root length occurred at concentrations of 0.003–2.4, 0.03–0.6, and 0.03–0.6 µM Cd, respectively. Superoxide dismutase and catalase activities, and chlorophyll content displayed inverted U-shaped curves, indicating that the antioxidant defense system and photosynthesis system played roles in hormesis. Based on KEGG pathway analysis with the trend chart of differentially expressed genes and weighted correlation network analysis, the key gene ABF1 in the metabolic pathway of abscisic acid was identified. Subsequently, genetic experiments with wild, overexpressing, and knockdown lines of A. thaliana were conducted to further verify the biological function of ABF1 involving Cd-induced hormesis in A. thaliana. The results revealed that the resistance capability of the overexpressing type to Cd stress was significantly enhanced and implicated that the ABF1 gene is essential for Cd-induced hormesis in A. thaliana. Mining key genes that regulate Cd-induced hormesis in plants and stimulate them could have a transformative impact on the phytoremediation of metal-contaminated environments.

Comparative transcriptome analysis reveals key genes and coordinated mechanisms in two rice cultivars differing in cadmium accumulation

Although Cd accumulation varies among rice varieties is recognized, the underlying mechanisms are not well clarified. In this study, comparative transcriptome analysis were performed by hydroponic culture system with two rice varieties, Y1540 (high Cd accumulator) and Y15 (low Cd accumulator) under 20 μM Cd stress. Results revealed 17,320 differentially expressed genes (DEGs) in roots of Y15 (7,655 upregulated and 9,665 downregulated) and 17,386 DEGs in roots of Y1540 (8,823 upregulated and 8,563 downregulated) expose to 20 μM Cd stress. Gene ontology (GO) analysis enriched 24 and 26 terms in Y15 and Y1540 respectively, including 23 common terms. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment showed 27 and 28 significant pathways in Y15 and Y1540 respectively, with 19 common pathways. Different responses to Cd stress between cultivars were not only reflected in differently enriched GO terms and KEGG pathways but also in different DEGs of 23 common GO terms and significant sequences represented by p-values of 19 common KEGG pathways. Both cultivars resist Cd through common processes with different weights; hence glutathione metabolism, mineral absorption, biosynthesis of secondary metabolites, and degradation of aromatic compounds could be playing a more important role in Y1540, whereas ribosome biogenesis in eukaryotes, mismatch repair, aminoacyl-tRNA biosynthesis, and the cell cycle maybe playing a more important role in Y15. Weighted gene co-expression network analysis (WGCNA) showed that five and three modules were clustered in Y15 and Y1540, respectively, with yellow and brown modules in Y15 and brown modules in Y1540 being significantly related to Cd stress. Further analysis showed that most of hub genes in Y15 were related to signal transduction or transcription factors, while most of hub genes in Y1540 were related to binding, metabolic, and secondary metabolic processes, which demonstrated their different response patterns at transcriptomic level to Cd stress.

Molybdenum and/or cadmium induce NLRP3 inflammasome production by causing mitochondria-associated endoplasmic reticulum membrane dysfunction in sheep hepatocytes

Accumulation of the heavy metals molybdenum (Mo) and cadmium (Cd) in the liver can induce organelle damage and inflammation, resulting in hepatotoxicity. The effect of Mo and/or Cd on sheep hepatocytes was investigated by determining the relationship between the mitochondria-associated endoplasmic reticulum membrane (MAM) and NLRP3 inflammasome. Sheep hepatocytes were divided into four groups: the control group, Mo group (600 μM Mo), Cd group (4 μM Cd) and Mo + Cd group (600 μM Mo+4 μM Cd). The results showed that Mo and/or Cd exposure increased the levels of lactate dehydrogenase (LDH) and nitric oxide (NO) in the cell culture supernatant, elevated the levels of intracellular Ca2+ and mitochondrial Ca2+, downregulated the expression of MAM-related factors (IP3R, GRP75, VDAC1, PERK, ERO1-α, Mfn1, Mfn2, ERP44), shortened the length of the MAM and reduced the formation of the MAM structure, eventually causing MAM dysfunction. Moreover, the expression levels of NLRP3 inflammasome-related factors (NLRP3, Caspase1, IL-1β, IL-6, TNF-α) were also dramatically increased after Mo and Cd exposure, triggering NLRP3 inflammasome production. However, an IP3R inhibitor, 2-APB treatment significantly alleviated these changes. Overall, the data indicate that Mo and Cd coexposure leads to structural disruption and dysfunction of MAM, disrupts cellular Ca2+ homeostasis, and increases NLRP3 inflammasome production in sheep hepatocytes. However, the inhibition of IP3R alleviates NLRP3 inflammasome production induced by Mo and Cd.

Induction of antioxidant defenses by a low-dose cadmium priming alleviates heat stress in pigeon pea

Global warming has a devastating effect on the growth and productivity of plants. Pigeon pea, the second most important legume crop with high nutritional value, is at high risk due to high temperature exposure. Priming is an innovative agronomical application that can be used as a strategy to minimize the detrimental effects of any kind of stresses. In this study, we investigated how low dose of cadmium priming alleviates heat stress (HS) in pigeon pea seedlings. The results demonstrated that low dose of cadmium priming induced the expression of antioxidant systems and maintain a redox homeostasis. An enhanced level of antioxidant glutathione, and antioxidative enzymes (SOD, APX, and GR) were observed in Cd+HS leaf (40 μM Cd priming followed by exposure to HS, 42°C) as compared to the HS leaf. Moreover, a reduction in hydrogen peroxide (H2O2) and oxidized glutathione (GSSG) content was also noticed in Cd+HS leaf. The GSH/GSSG ratio, which was indicative of the redox state in the plant system, was also high in Cd+HS leaf as compared to HS leaf. Thus, the priming of pigeon pea seeds with low dose Cd alleviates HS by elevating antioxidant defenses, ultimately protecting pigeon pea seedlings against HS.

Effects of Cd and Zn Treatments on Leaf Chemıcal Compounds of Japanese barberry (Berberis thunbergii), Boxwood (Buxus sempervirens var. rotundifolia), and Gold tassel (Euonymus japonica var. aurea) Species

In the present study, the effects of cadmium (25 μM and 50 μM) and zinc (200 μM and 400 μM) treatments on some bioactive compounds and mineral levels in leaves of japanese barberry, boxwood, and gold tassel genotypes were investigated. Given the results, it was determined that photosynthetic pigments were stimulated by 200 μM Zn and 400 μM Zn. Boxwood was found to be tolerant to the treatments in terms of chlorophyll and carotenoid. In contrast, japanese barberry was found to be tolerant in terms of chlorophyll b and total chlorophyll. The amount of anthocyanin was higher in the leaves of gold tassel, and boxwood and the total phenolic was higher level in gold tassel and japanese barberry in all treatments. Proline and nitrate levels were generally high in the treated groups of three plants, as well as RWC in japanese barberry and boxwood. Given the element results, japanese barberry had a higher accumulation capacity for P, S, Mn, Cl, Cd, Fe, Al, Si, Cu, Ba, Zn, Ti, and Cr, boxwood for K, Mn, Cl, Cd, Zn, Fe, Al, Si, and Cr, and Gold tassel for K, P, S, Mn, Cl, and Cd. As a result, boxwood showed a higher tolerance to 400 μM Zn, japanese barberry plant to 200 μM Zn, and 50 μM Cd. It can be said that boxwood and japanese barberry plants can be used in afforestation projects in urban parks, gardens, and roadside, as well as in areas with high soil pollution, to reduce the pollution damage.

Assessment of the capability of cadmium accumulation and translocation among 31 willows: four patterns of willow biomass variation response to cadmium.

Cadmium (Cd) pollution threatens food security and the environment. Willow species (Salix, Salicaceae) exhibit a remarkable potential to restore Cd-polluted sites due to their high biomass production and high Cd accumulation capacities. This study examined the Cd accumulation and tolerance in 31 genotypes of shrub willow in hydroponic conditions at varying Cd levels (0μM Cd, 5μM Cd, and 20μM Cd). The root, stem, and leaf biomass of 31 shrub willow genotypes showed significant differences to Cd exposure. Among 31 willow genotypes, four patterns of biomass variation response to Cd were identified: insensitive to Cd; growth inhibition due to excessive Cd supply (high Cd inhibition); low Cd causing inhibited growth, whereas high Cd leading to increased biomass (U-shape); and growth increment with excessive Cd exposure (high Cd induction). The genotypes belonging to the "insensitive to Cd" and/or "high Cd induction" were candidates for the utilization of phytoremediation. Based on the analysis of Cd accumulation of 31 shrub willow genotypes at high and low Cd levels, genotypes 2372, 51-3, and 1052 obtained from a cross between S. albertii and S. argyracea grew well and accumulated relatively more Cd levels than other genotypes. In addition, for Cd-treated seedlings, root Cd accumulation was positively correlated with shoot Cd accumulation and total Cd uptake, demonstrating that Cd accumulation in roots could serve as a biomarker for evaluating the Cd extraction capacity of willows, especially in hydroponics screening. The results of this study screened out willow genotypes with high Cd uptake and translocation capacities, which will provide valuable approaches for restoring Cd-contaminated soils with willows.

L-Cysteine functionalized coral-like Ag doped MnO2 nanostructures for the real-time electrochemical detection of lead and cadmium ions

In this report, L-Cysteine functionalized Ag@MnO2 nanocomposite was prepared for selective, rapid, and instantaneous electrochemical sensing of heavy metal ions (HMIs). Hydrothermal method was employed to synthesize L-Cysteine functionalized Ag@MnO2 nanocomposites. The composition and morphology of L-Cys/Ag@MnO2 were characterized by advanced techniques such as XRD, FTIR, UV-Vis and FESEM analysis. XRD spectra confirmed the synthesis of tetragonal L-Cys/Ag@MnO2, while FESEM confirmed the formation of coral like nanostructures. Coral like L-Cys/Ag@MnO2 with sufficient open pores provided high surface area and large number of active sites for sensing of HMIs. The electrochemical parameters were optimized i.e., pH effect, deposition potential, deposition time, and impact of interfering species to enhance HMIs detection. Under optimized conditions, the designed sensor exhibited high sensitivity towards the solution of both Cd+2 and Pb+2 ions over a wide range from 0.1 μM to 0.005 μM of Cd+2 and Pb+2, respectively with LOD = 0.052 nM for Pb+2 and 0.065 nM for Cd+2. The developed sensor's practical applicability was also tested in tap water. Due to the high conductivity, synergistic effect, and high electron transfer kinetics of the prepared material, as designed sensor can be utilized for sensing other toxic metal ions in real samples.

Seminal cadmium affects human sperm motility through stable binding to the cell membrane.

Environmental pollutants are claimed to be major factors involved in the progressive decline of the fertility rate worldwide. Exposure to the heavy metal Cadmium (Cd) has been associated with reproductive toxicity due to its ionic mimicry. However, the possible direct accumulation of Cd in human sperm cells has been poorly investigated. In this study, we aimed to clarify the possible direct effect of Cd exposure on sperm function through the analysis of its cell accumulation. Semen samples from 30 male subjects residing in high environmental impact areas and adhering to the "Exposoma e Plurifocalità nella Prevenzione Oncologica" campaign for testis cancer prevention were compared with semen samples from 15 males residing in low exposure areas. Semen levels and cell Cd content were quantified by inductively coupled plasma (ICP) spectroscopy. Cell Cd distribution was assessed by scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS). The impact of Cd on sperm function was evaluated by the in vitro exposure to the heavy metal, whilst possible scavenging approaches/agents were assessed. In addition to higher values of semen Cd, exposed subjects showed a reduction in total motile sperm fraction compared to not-exposed controls (59.6% ± 13.6% vs. 66.3% ± 7.3%, p = 0.037). Semen Cd levels were also significantly correlated with SEM-EDS signals of Cd detected on the head and neck of sperm (respectively p = 0.738, p < 0.001 and ρ = 0.465, p < 0.001). A total of 2h of in vitro exposure to 0.5μM Cd was associated with a significant reduction of sperm progressive motility. Scavenging approaches with either hypo-osmotic swelling or 10μM reduced glutathione were ineffective in blunting cell Cd and restoring motility. The reduction of exposure levels appears to be the main approach to reducing the reproductive issues associated with Cd.

Cadmium accelerates autophagy of osteocytes by inhibiting the PI3K/AKT/mTOR signaling pathway.

Cadmium (Cd) can damage bone cells and cause osteoporosis. Osteocytes are the most numerous bone cells and also important target cells for Cd-induced osteotoxic damage. Autophagy plays important role in the progression of osteoporosis. However, osteocyte autophagy in Cd-induced bone injury is not well characterized. Thus, we established a Cd-induced bone injury model in BALB/c mice and a cellular damage model in MLO-Y4 cells. Aqueous Cd exposure for 16 months showed an increase in plasma alkaline phosphatase (ALP) activity and increase in urine calcium (Ca) and phosphorus (P) concentrations in vivo. Moreover, expression level of autophagy-related microtubule-associated protein 1A/1B-light chain 3 II (LC3II) and autophagy-related 5 (ATG5) proteins were induced, and the expression of sequestosome-1 (p62) was reduced, along with Cd-induced trabecular bone damage. In addition, Cd inhibited the phosphorylation of mammalian target of rapamycin (mTOR), protein kinase B (AKT), and phosphatidylinositol 3-kinase (PI3K). In vitro, 80 μM Cd concentrations exposure upregulated LC3II protein expression, and downregulated of p62 protein expression. Similarly, we found that treatment with 80 μM Cd resulted in a reduction in the phosphorylation levels of mTOR, AKT, and PI3K. Further experiments revealed that addition of rapamycin, an autophagy inducer, enhanced autophagy and alleviated the Cd-induced damage to MLO-Y4 cells. The findings of our study reveal for the first time that Cd causes damage to both bone and osteocytes, as well as induces autophagy in osteocytes and inhibits PI3K/AKT/mTOR signaling, which could be a protective mechanism against Cd-induced bone injury.

Microbial extracellular polymeric substances alleviate cadmium toxicity in rice (Oryza sativa L.) by regulating cadmium uptake, subcellular distribution and triggering the expression of stress-related genes

Cadmium (Cd) accumulation in crops causes potential risks to human health. Microbial extracellular polymeric substances (EPS) are a complex mixture of biopolymers that can bind various heavy metals. The present work examined the alleviating effects of EPS on Cd toxicity in rice and its detoxification mechanism. The 100 μM Cd stress hampered the overall plant growth and development, damaged the ultrastructures of both leaf and root cells, and caused severe lipid peroxidation in rice plants. However, applying EPS at a concentration of 100 mg/L during Cd stress resulted in increased biomass, reduced Cd accumulation and transport, and minimized the oxidative damage. EPS application also enhanced Cd retention in the shoot cell walls and root vacuoles, and actively altered the expression of genes involved in cell wall formation, antioxidant defense systems, transcription factors, and hormone metabolism. These findings provide new insights into EPS-mediated mitigation of Cd stress in plants and help us to develop strategies to improve crop yield in Cd-contaminated soils in the future.

Cadmium tolerance in Elodea canadensis Michx: Subcellular distribution and metabolomic analysis

The aquatic plant Elodea canadensis is considered a good candidate for ecotoxicological investigations. Cadmium (Cd) is a widespread contaminant in aquatic systems. In this study, to better elucidate the underlying tolerance mechanism and molecular impact of environmentally relevant Cd concentration in aquatic plants, subcellular distribution, chemical forms, and gas chromatography–mass spectrometry-based non-targeted metabolomics profiles were comprehensively analyzed in E. canadensis subjected to 0 and 10 µM Cd treatment for 5 d. Subcellular fractionation analysis of Cd-containing leaves showed that 67% of Cd was compartmentalized in cell wall followed by the soluble fraction (24 %) and organelles (9 %). The majority of Cd (90 %) was found in the extraction using 1 M NaCl. Metabolomic analysis using unsupervised principal component analyses and a supervised partial least squares discriminant analysis revealed clear differences in metabolic profiles between the two groups, demonstrating the metabolic effects of Cd. The 155 identified compounds altered by Cd were mainly from primary metabolism, including sugars, amino acids, organic acids, and their derivatives. Secondary metabolites such as polyphenols and phenolamides were also detected. The massive up-regulation of metabolites, including trehalose, proline, sarcosine, nicotianamine, putrescine, α-ketoglutaric acid, citric acid, and phytol might represent a detoxification mechanism. These findings highlighted the mechanistic strategies that E. canadensis employs to defend against Cd toxicity.

Regulation of Wnt Signaling Pathway by Costic Acid Derivative, An Efficient Strategy for Treatment of Glucocorticoid‐Induced Osteoporosis in Rat Model

AbstractOsteoporosis leads to a decrease in bone mass, loss of mechanical strength, increase in fracture susceptibility and is a serious medical problem worldwide. The present study investigated the effect of costic acid derivative (CA) on dexamethasone (DXM)‐induced osteoporosis in vitro in osteoblasts and in vivo in rat a model. The results demonstrated that DXM‐mediated reduction in osteoblast viability was effectively prevented by CA treatment in dose‐dependent manner. The DXM‐induced loss of osteoblast viability was completely reversed by CA treatment at 4 μM dose. Treatment of the primary osteoblasts with 0. 5 and 4 μM CD for 72 h reversed DXM‐mediated reduction in ALP activity. The CA treatment significantly (P&gt;0.05) reversed DXM‐mediated lowering of osteoclacin, collagen type‐1 and osteonectin mRNA expression. The CA treatment at 1.5, 3 and 6 mg/kg doses significantly (P&gt;0.05) reversed DXM‐mediated decrease in BMD in rat femurs. Treatment of the rats with CA reversed DXM‐mediated changes in osteocalcin and CTX levels in serum samples. Administration of CA to the rats reversed DXM‐mediated decrease in Wnt, β‐catenin expression and increase in SOST and Dickkopf‐1 level. Docking studies showed that CA interacts with mammalian Wnt‐frizzled complex (6AHY) through conventional H‐bonding. Thus, CA inhibits DXM‐induced dysfunction of osteoblast differentiation in vitro and inhibits osteoporosis development in vivo in rat model. Therefore, CA may be developed as a potential therapeutic agent for treatment of bone damage induced by glucocorticoid (GC)‐mediated osteoporosis.

Reducing cadmium accumulation in shrimp using Escherichia coli with surface-displayed peptide

Cadmium (Cd) is a hazardous metal that can accumulate in aquatic organisms and endanger human health via the food chain. In this study, genetic engineering was used to display a peptide with Cd-binding potential on the surface of Escherichia coli cells. This whole-cell adsorbent exhibited high affinity for Cd ions (Cd2+) in the solution. The Cd2+ adsorption capacity of the whole-cell adsorbent was three-fold that of the control cells in a 20 μM Cd2+ solution, and 97.2% ± 2.38% of the Cd2+ was removed. The whole-cell adsorbent was fed to shrimp (Neocaridina denticulata), and the surface-engineered E. coli successfully colonized the shrimp intestine, which showed significantly less Cd accumulation than the group not fed surface-engineered E. coli. The whole-cell adsorbent evidently protected shrimp from the toxicity of Cd2+ by adsorbing it. Moreover, the whole-cell adsorbent mitigated the changes in microbial community structure in the shrimp gut caused by the exposure of Cd2+. These findings suggest that this strategy is effective for controlling the contamination of Cd2+ in shrimp.

The Changes of Tolerance, Accumulation and Oxidative Stress Response to Cadmium in Tobacco Caused by Introducing Datura stramonium L. Genes

Whether it is possible to create suitable plants for cadmium phytoremediation by introducing Datura stramonium L. genes into tobacco (Nicotiana tabacum L.) remains unclear. Hydroponic experiments were performed on N. tabacum L. var. MTLY, a newly developed hybrid variety, and the parents. Seedlings at the six-leaf stage were treated with 0 (control), 10 µM, 180 µM and 360 µM CdCl2 for 7 days, and their differences in Cd tolerance and accumulation and physiological and metabolic responses were evaluated. When subjected to 360 µM Cd, the growth of “MTLY”, in terms of the dry weight, plant height and root length, was obviously better than N. tabacum L. var. LY2 (female parent). In contrast to D. stramonium (male parent) and “LY2”, “MTLY” accumulated more Cd in shoots (127.6–3837.1 mg kg−1) and roots (121.6–1167.7 mg kg−1). Moreover, unlike “LY2”, “MTLY” could accumulate more Cd in its shoots than roots. Its bioconcentration factor (BCF) and translocation factor (TF) values reached 95.9–149.7 and 1.0–3.5, respectively, which were far greater than those of “LY2”. High-dose Cd stress significantly increased reactive oxygen species (ROS) and malondialdehyde (MDA) levels and decreased chlorophyll contents in tobacco seedlings, especially in “LY2”. Various enzymatic and non-enzymatic antioxidants in the three materials showed different responses to Cd stress. The change of the phenolic compounds and alkaloids in “MTLY” was basically similar to that in D. stramonium, but their levels were apparently higher than those in “LY2”. Results indicated that distant hybridization could be one of the effective methods for introducing metal-hyperaccumulator genes into a high biomass species, which contributed to enhancing the Cd tolerance, accumulation and detoxification in tobacco. This study has great significance in obtaining elite germplasm for phytoremediation. The exact mechanisms in molecules and genetics and the practical effectiveness in cadmium-contaminated soil remain to be further elucidated.

Copper, cadmium and nickel pollution inhibit growth and promote ascorbate catabolism in cell cultures of Arabidopsis thaliana and Zea mays

We established model systems for exploring the roles of symplastic and apoplastic ascorbate in heavy-metal-polluted dicot and monocot cells. Cell-suspension cultures of Arabidopsis and maize were treated with copper, cadmium or nickel; growth and ascorbate metabolism were measured. Growth was halved by ∼80 µM Cu2+, 90 µM Cd2+ or 1200 µM Ni2+ in Arabidopsis, and ∼90 µM Cu2+, 650 µM Cd2+ or 650 µM Ni2+ in maize. Cu2+ (128 µM) and Cd2+ (512 µM) caused partial loss of symplastic ascorbate, especially in Arabidopsis; Ni2+ (512 and 2048 µM) had moderate effects. Added apoplastic l-ascorbate (1 mM) was consumed by the cultures (half-life ∼23 and 44 min in Arabidopsis and maize, respectively), consumption rate being 3–6-fold increased by Cu2+, Cd2+ and Ni2+ in Arabidopsis, and by Cu2+ in maize; Cd2+ and Ni2+ had relatively little effect on apoplastic ascorbate consumption in maize. Radioactivity from exogenous 1 mM l-[1-14C]ascorbate remained extracellular; catabolites formed were dehydroascorbic acid, diketogulonate and oxalyl-threonates. In conclusion, suspension-cultured cells respond to heavy-metal stresses by maintaining symplastic ascorbate concentrations, which may beneficially scavenge symplastic reactive oxygen species (ROS). Apoplastic ascorbate is catabolised in metal-polluted cultures via several oxidative and non-oxidative reactions, the former potentially scavenging stress-related apoplastic ROS.

Methionine application at low phosphate level promotes root-to-shoot cadmium translocation by mobilizing weakly bound apoplastic cadmium in valerian (Valeriana officinalis L.)

Controlling the uptake and translocation of heavy metals in medicinal plants is crucial due to its strong impact on the safety and quality of derived medicinal plant products. This study investigated the effects of phosphate and methionine on the distribution and chemical forms of Cd in valerian (Valeriana officinalis L.) roots and shoots. Seedlings were grown for two weeks in a Cd-free nutrient solution containing either 400 or 1200 μM phosphate and then exposed for 10 days to 10 μM Cd either in combination with 400 μM or no methionine in the nutrient solution. Root Cd was partitioned into a symplastic and an apoplastic Cd fraction using a desorption procedure with EDTA. A sequential extraction method was applied to determine chemical forms in which Cd was retained in both roots and shoots. “Pectate- and protein-bound Cd” and HAc-soluble “Cd phosphates” were the dominant Cd forms in sequential extractions of both roots and shoots. Phosphate increased the HAc-soluble “Cd phosphate fraction” in the roots, but not in the shoots. Methionine did not affect this fraction, but strongly increased ethanol- and water-soluble Cd in roots and shoots. While it also increased the “pectate- and protein-bound Cd fraction” in the shoots, it decreased this fraction and the share of apoplastic Cd in the roots. The phosphate treatment reduced Zn accumulation in the roots but had no effect on Zn accumulation in the shoots, whereas Met increased shoot Zn. The results indicate that methionine induced root-to-shoot Cd translocation primarily by mobilizing weakly bound Cd to root cell walls at the low phosphate level. This could help limit Cd accumulation in valerian roots grown for medicinal use.

Integration of transcriptome and metabolome analyses reveals sorghum roots responding to cadmium stress through regulation of the flavonoid biosynthesis pathway.

Cadmium (Cd) pollution is a serious threat to plant growth and human health. Although the mechanisms controlling the Cd response have been elucidated in other species, they remain unknown in Sorghum (Sorghum bicolor (L.) Moench), an important C4 cereal crop. Here, one-week-old sorghum seedlings were exposed to different concentrations (0, 10, 20, 50, 100, and 150 μM) of CdCl2 and the effects of these different concentrations on morphological responses were evaluated. Cd stress significantly decreased the activities of the enzymes peroxidase (POD), superoxide dismutase (SOD), glutathione S-transferase (GST) and catalase (CAT), and increased malondialdehyde (MDA) levels, leading to inhibition of plant height, decreases in lateral root density and plant biomass production. Based on these results, 10 μM Cd concentration was chosen for further transcription and metabolic analyses. A total of 2683 genes and 160 metabolites were found to have significant differential abundances between the control and Cd-treated groups. Multi-omics integrative analysis revealed that the flavonoid biosynthesis pathway plays a critical role in regulating Cd stress responses in sorghum. These results provide new insights into the mechanism underlying the response of sorghum to Cd.

Highly sensitive detection of lead ions and cadmium ions based on ZIF-8-NH2 enhanced by carbon nanotubes and bismuth film

Heavy metal ions are common pollutants in the water environment, which have caused severe damage to the water environment, so it is necessary to monitor them. In this work, an electrochemical sensor based on aminated Zn (Ⅱ) metal-organic framework (ZIF-8-NH2) enhanced by carbon nanotubes (CNTs) and bismuth (Bi) film was prepared for simultaneous detection of lead ions (Pb2+) and cadmium ions (Cd2+) in water samples. The ZIF-8-NH2/CNTs was prepared by electrostatic assembly with ultrasonic assistance. The results show that the combination of ZIF-8-NH2 and CNTs not only can promote the three-dimensional distribution of CNTs, but also compensated for the poor electrical conductivity of ZIF-8-NH2. Furthermore, the deposition of Bi film in situ promoted the enrichment of Pb2+ and Cd2+ in the detection process, further enhancing the electrochemical signal. Based on this, the prepared sensor displayed good linear ranges of 0.050–1.000 μM (Pb2+) and 0.100–0.700 μM (Cd2+), lower detection limits of 8.00 nM (Pb2+) and 12.0 nM (Cd2+) under optimal experiment condition. At last, this sensor was successfully applied to simultaneously detect Pb2+ and Cd2+ in paddy water and lake water with recovery rates of 97.88 ∼ 104.06% and relative standard deviation (RSD) lower than 6.24%. Most importantly, there is no significant difference between the developed electrochemical method and certified method (P < 0.05). This work provides a new idea for the simultaneous detection of heavy metal ions in the water environment.

Integrated transcriptome and metabolome analysis reveals the mechanism of tolerance to manganese and cadmium toxicity in the Mn/Cd hyperaccumulator Celosia argentea Linn.

Understanding the molecular mechanism of tolerance to heavy metals in hyperaccumulators is important for improving the efficiency of phytoremediation and is interesting for evolutionary studies on plant adaption to abiotic stress. Celosia argentea Linn. was recently discovered to hyperaccumulate both manganese (Mn) and cadmium (Cd). However, the molecular mechanisms underlying Mn and Cd detoxification in C. argentea are poorly understood. Laboratory studies were conducted using C. argentea seedlings exposed to 360μM Mn and 8.9μMCd hydroponic solutions. Plant leaves were analyzed using transcriptional and metabolomic techniques. A total of 3960 differentially expressed genes (DEGs) in plants were identified under Cd stress, among which 17 were associated with metal transport, and 10 belonged to the ATP transporter families. Exposures to Mn or Cd led to the differential expression of three metal transport genes (HMA3, ABCC15, and ATPase 4). In addition, 33 and 77 differentially expressed metabolites (DEMs) were identified under Mn and Cd stresses, respectively. Metabolic pathway analysis showed that the ABC transporter pathway was the most affected in Mn/Cd exposed seedlings. Conjoint transcriptome and metabolome analysis showed that the glutathione (GSH) metabolic pathway was over-represented in the KEGG pathway of both DEGs and DEMs. Our results confirm that the ABC transporter and GSH metabolic pathways play important roles in Mn and Cd detoxification. These findings provide new insight into the molecular mechanisms of tolerance to Mn and Cd toxicity in plants.

Proteomic analysis reveals differential responsive mechanisms in Solanum nigrum exposed to low and high dose of cadmium

Cadmium (Cd) contamination is becoming a widespread environmental problem. However, the differential responsive mechanisms of Cd hyperaccumulator Solanum nigrum to low or high dose of Cd are not well documented. In this study, phenotypic and physiological analysis firstly suggested that the seedlings of S. nigrum showed slight leaf chlorosis symptoms under 25 μM Cd and severe inhibition on growth and photosynthesis under 100 μM Cd. Further proteomic analysis identified 105 differentially expressed proteins (DEPs) in the Cd-treated leaves. Under low dose of Cd stress, 47 DEPs are mainly involved in primary metabolic processes, while under high dose of Cd stress, 92 DEPs are mainly involved in photosynthesis, energy metabolism, production of phytochelatin and reactive oxygen species (ROS). Protein-protein interaction (PPI) network analysis of DEPs support above differential responses in the leaves of S. nigrum to low and high dose of Cd treatments. This work provides the differential responsive mechanisms in S. nigrum to low and high dose of Cd, and the theoretical foundation for the application of hyperaccumulating plants in the phytoremediation of Cd-contaminated soils.