Cadmium Pollution Research Articles

Mapping and Identifying Candidate Genes Enabling Cadmium Accumulation in Brassica napus Revealed by Combined BSA-Seq and RNA-Seq Analysis.

Rapeseed has the ability to absorb cadmium in the roots and transfer it to aboveground organs, making it a potential species for remediating soil cadmium (Cd) pollution. However, the genetic and molecular mechanisms underlying this phenomenon in rapeseed are still unclear. In this study, a 'cadmium-enriched' parent, 'P1', with high cadmium transport and accumulation in the shoot (cadmium root: shoot transfer ratio of 153.75%), and a low-cadmium-accumulation parent, 'P2', (with a cadmium transfer ratio of 48.72%) were assessed for Cd concentration using inductively coupled plasma mass spectrometry (ICP-MS). An F2 genetic population was constructed by crossing 'P1' with 'P2' to map QTL intervals and underlying genes associated with cadmium enrichment. Fifty extremely cadmium-enriched F2 individuals and fifty extremely low-accumulation F2 individuals were selected based on cadmium content and cadmium transfer ratio and used for bulk segregant analysis (BSA) in combination with whole genome resequencing. This generated a total of 3,660,999 SNPs and 787,034 InDels between these two segregated phenotypic groups. Based on the delta SNP index (the difference in SNP frequency between the two bulked pools), nine candidate Quantitative trait loci (QTLs) from five chromosomes were identified, and four intervals were validated. RNA sequencing of 'P1' and 'P2' in response to cadmium was also performed and identified 3502 differentially expressed genes (DEGs) between 'P1' and 'P2' under Cd treatment. Finally, 32 candidate DEGs were identified within 9 significant mapping intervals, including genes encoding a glutathione S-transferase (GST), a molecular chaperone (DnaJ), and a phosphoglycerate kinase (PGK), among others. These genes are strong candidates for playing an active role in helping rapeseed cope with cadmium stress. Therefore, this study not only sheds new light on the molecular mechanisms of Cd accumulation in rapeseed but could also be useful for rapeseed breeding programs targeting this trait.

Abscisic acid (ABA) alleviates cadmium toxicity by enhancing the adsorption of cadmium to root cell walls and inducing antioxidant defense system of Cosmos bipinnatus

Cadmium (Cd) pollution is a global problem affecting soil ecology and plant growth. Abscisic acid (ABA) acts as a growth and stress hormone, regulates cell wall synthesis, and plays an important role in plant responses to stress. There are few studies on the mechanisms behind abscisic acid alleviation of cadmium stress in Cosmos bipinnatus, especially in regards to regulation of the root cell wall. This study examined the effects of different concentrations of abscisic acid at different concentrations of cadmium stress. Through adding 5 μmol/L and 30 μmol/L cadmium, followed by spraying 10 μmol/L and 40 μmol/L ABA in a hydroponic experiment, it was found that under two concentrations of cadmium stress, low concentration of ABA improved root cell wall polysaccharide, Cd, and uronic acid content. Especially in pectin, after the application of low concentration ABA, the cadmium concentration was significantly increased by 1.5 times and 1.2 times compared with the Cd concentration under Cd5 and Cd30 treatment alone, respectively. Fourier-Transform Infrared spectroscopy (FTIR) demonstrated that cell wall functional groups such as -OH and -COOH were increased with exposure to ABA. Additionally, the exogenous ABA also increased expression of three kinds of antioxidant enzymes and plant antioxidants. The results of this study suggest that ABA could reduce Cd stress by increasing Cd accumulation, promoting Cd adsorption on the root cell wall, and activating protective mechanisms. This result could help promote application of C. bipinnatus for phytostabilization of cadmium-contaminated soil.

Adaptive pattern of mangrove species and the mangrove landscaping in the heavy metal polluted area of Eastern Segara Anakan Lagoon, Indonesia

Abstract. Hilmi E, Prayogo NA, Junaidi T, Mahdiana A, Fikriyya N. 2023. Adaptive pattern of mangrove species and the mangrove landscaping in the heavy metal polluted area of Eastern Segara Anakan Lagoon, Indonesia. Biodiversitas 24: 2927-2937. The mangrove species have specific adaptations to exclude, accumulate, translocate, and exert heavy metal contaminants. Mangrove species' adaptation to Cadmium (Cd) and Zinc (Zn) pollution are shown by their ability to reduce the negative impact of Cd and Zn pollution. This research aimed to analyze the adaptive pattern and mangrove landscaping in Cd and Zn contaminant areas of Eastern Segara Anakan (E-SAL), Indonesia. Cd and Zn content in different tissues (stem, leaves, and root) of 15 mangrove species were analyzed using Atomic Absorption Spectrometric method. Adaptive pattern and mangrove landscaping were assessed using bioaccumulation factor (BAF) and translocation factor (TF). The results showed that the Cd accumulation varied between 0.0610-0.2300 ppm in the stem, 0.0140-0.0480 ppm in leaves, 0.1501-0.3100 ppm in roots, whereas Zn accumulation varied between 5.7781-37.3409 ppm in the stem, 2.3973-32.2859 ppm in leaves, 10.8380-35.842 ppm in roots. Relatively Cd and Zn accumulation was highest in root than other parts. BAF scores of Cd and Zn varied between 0.0111-0.1760 and 0.1936-0.9017, respectively. TF score of Cd and Zn varied between 0.0642-0.9414 and 0.3419-1.3057, respectively. Based on the adaptation pattern, the mangrove landscape showed that Avicennia marina (Forssk.) Vierh., Rhizophora mucronata Lam., and Rhizophora apiculata Blume were the best accumulator of Cd contaminants. At the same time, A. marina, R. apiculata, and X. granatum were the best accumulator of Zn contaminant. The conclusion explains that mangrove species significantly adapt to life and grow in Zn and Cd-polluted areas. Therefore, mangrove landscaping can be developed to reduce the impact of Zn and Cd pollution.

Alleviation of cadmium-induced photoinhibition and oxidative stress by melatonin in Chlamydomonas reinhardtii.

As one of the most threatening challenges to the natural environment and human health, cadmium (Cd) pollution has seriously impacted natural organisms. Green algae, such as Chlamydomonas reinhardtii (C. reinhardtii), can provide a safer, lower cost, and more effective ecological approach to the treatment of heavy metal ions in wastewater due to their sorption properties. However, heavy metal ions affect C. reinhardtii when adsorbed. Melatonin is able to protect the plant body from damage when the plant is under biotic/abiotic stress. Therefore, we investigated the effects of melatonin on the cell morphology, chlorophyll content, chlorophyll fluorescence parameters, enzymatic activity of the antioxidant system, gene expression, and the ascorbic acid (AsA)-glutathione (GSH) cycle of C. reinhardtii under the stress of Cd (13mg/L). Our results indicated that Cd significantly induced photoinhibition and overaccumulation of reactive oxygen species (ROS). By application with the concentration of 1.0μM melatonin, the algal solute of C. reinhardtii under the Cd stress gradually regained its green color, the cell morphology became intact, and the photosynthetic electron transport function was retained. However, in the melatonin-silenced strain, there was a significant decrease in all of the above indicators. In addition, the use of exogenous melatonin or the expression of endogenous melatonin genes could enhance the intracellular enzyme activities of catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), ascorbate peroxidase (APX), and glutathione reductase (GR). It also upregulated the expression of active enzyme genes such as SOD1, CAT1, FSD1, GSH1, GPX5, and GSHR1. These results indicate that the presence of melatonin effectively protects the activity of photosynthetic system II in C. reinhardtii, enhances antioxidant activity, upregulates gene expression in the AsA-GSH cycle, and reduces the level of ROS, thereby alleviating the damage caused by Cd toxicity.

Water Quality and Microbiological Assessment of Burullus Lake and Its Surrounding Drains

Burullus Lake, which is the second-largest coastal lagoon in Egypt, is deteriorating due to nutrient enrichment and pollutant loading. The study aims to assess the lake’s water quality using water quality indices and microbiological assessment. Surface water samples were collected from Burullus Lake in winter and summer, as well as samples from drains that discharge waste into the lake. Most lake stations are classified in the marginal category based on the water quality index (WQI). Dissolved oxygen, ammonia, copper, and cadmium have the greatest impact on WQI, reflecting pollution loads. Based on the contamination index, heavy metal classification results ranged from “lowly polluted” to “highly polluted.” According to the Nemerow Index, human activity has significantly impaired the ecology of the lake and surrounding drains through copper and cadmium pollution. The fecal coliform/fecal streptococci ratio was less than 0.6 in lake water samples, suggesting fecal contamination from domesticated animal wastes. Drain water contaminated with fecal streptococci indicated frequent contamination. Several drains allow a significant amount of effluent, including high amounts of pesticides and fertilizers, to enter the lake, causing serious metal and microbiological pollution Dredging and deepening the inlet link between the lake and Mediterranean Sea have had a positive impact on water quality. However, there are still other options for improving the lake’s health. Therefore, it is recommended to routinely check Burullus Lake’s water quality and its surrounding drains to keep track of its condition and assess any improvement efforts’ effectiveness.

Uptake and translocation of lead and cadmium in wild-found plant species from Bekasi and Karawang, West Java, for phytoremediation

Environmental degradation due to lead (Pb) and cadmium (Cd) pollution has been increasing. One of the alternative cost-effective green technologies to clean up heavy metal contamination is phytoremediation. This research aims to determine the potential of wild-found plants that could be used as Pb and Cd bioaccumulators. Plant species in this study were collected from heavy metal-contaminated soil in Bekasi and Karawang, West Java. Five species, namely Saccharum spontaneum, Acorus calamus, Ipomoea fistulosa, Ludwigia hyssopifolia, and Eichhornia crassipes, were studied for Pb accumulation capacity. Furthermore, five plant species, namely Limnocharis flava, Colocasia esculenta, Ipomoea fistulosa, Commelina benghalensis, and Eichhornia crassipes, were studied for their Cd accumulation capacity. The experiment was done in a greenhouse for eight weeks. Pb and Cd concentration were analyzed using atomic absorption spectrometry (AAS) to determine the uptake and translocation of Pb or Cd. I. fistulosa accumulated the highest amount of Pb, with a growth rate of up to 27.07 g week−1, a bioconcentration factor (BCF) of 1.46, and a translocation factor (TF) of 0.87 upon 300 mg kg−1 Pb treatment. C. esculenta showed considerable Cd bioaccumulation, as indicated by a BCF of 0.95 and a TF of 0.65, accompanied by sustained relative biomass increase (124.9%) and the highest growth rate (36.96 g week−1) among tested plant species upon 75 mg kg−1 Cd treatment. With their capacities for bioaccumulating Pb and Cd, respectively, I. fistulosa and C. esculenta were identified as potential accumulator species for phytoremediation in heavy metal-contaminated sites such as former mining lands, landfills, and highly polluted agricultural lands.

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.

Trophodynamics features and potential human health risk of arsenic and cadmium in marine fauna from the Yellow River Estuary, China

Toxic arsenic (As) and cadmium (Cd) pollution threatens organisms and humans in coastal ecosystems, but their biomagnification in marine systems remains under debate. This study investigated the levels and trophodynamic features of As and Cd, and potential human health risks of marine fauna within continuous trophic levels (TLs) from the Yellow River Estuary, China, and adjacent sea (YRE), as indicated by nitrogen stable isotope analyses. Individual faunal samples were grouped into continuous TL ranges and analyzed separately in fish and invertebrates. As and Cd concentrations varied significantly between fish and invertebrates within different TL ranges. Trophic magnification factors (TMFs) also revealed different bioaccumulation features of As and Cd with increasing TL via trophic transfer in the food chain. Although As and Cd were biodiluted in marine organisms overall from the YRE, they were biomagnified in invertebrates through trophic transfer, with TMFs of 1.91 and 1.70, respectively. As and Cd biomagnification in invertebrates was hidden by overall evaluation of toxic element bioaccumulation in marine fauna. Crustacea accounted for 55% of the invertebrate taxa in the study, which could have an important role in the biomagnification of these two elements in invertebrates as a whole. Given that marine organisms occupying higher trophic positions at higher risk of As and Cd biomagnification might be underestimated in the analyses of mean values at the species level, the target hazard quotient through fish and invertebrate consumption was calculated separately based on individuals distributed within continuous TL ranges corresponding to element concentrations, and the health risks to adults and children were evaluated. Results indicated that, in the study area, the non-carcinogenic health risk associated with As and Cd from consuming invertebrates was higher than that from fish, especially for children. In addition, estimation of As carcinogenic risk (>10–4 in both invertebrates and fish) also indicated that ingestion of seafood from the YRE with suggested meal size would cause cancer risk with long-term consumption, especially of invertebrates. Therefore, it is necessary to monitor toxic metal concentrations in aquatic organisms to devise regulations around seafood consumption by humans.

Spatial patterns and the associated factors for breast cancer hospitalization in the rural population of Fujian Province, China

BackgroundDespite the known increasing incidence of breast cancer in China, evidence on the spatial pattern of hospitalization for breast cancer is scarce. This study aimed to describe the disparity of breast cancer hospitalization in the rural population of Southeast China and to explore the impacts of socioeconomic factors and heavy metal pollution in soil.MethodsThis study was conducted using the New Rural Cooperative Medical Scheme (NRCMS) claims data covering 20.9 million rural residents from 73 counties in Southeast China during 2015–2016. The associations between breast cancer hospitalization and socioeconomic factors and soil heavy metal pollutants were evaluated with quasi-Poisson regression models and geographically weighted Poisson regressions (GWPR).ResultsThe annual hospitalization rate for breast cancer was 101.40/100,000 in the studied area and the rate varied across different counties. Overall, hospitalization for breast cancer was associated with road density (β = 0.43, P = 0.02), urbanization (β = 0.02, P = 0.002) and soil cadmium (Cd) pollution (β = 0.01, P = 0.02). In the GWPR model, a stronger spatial association of Cd, road density and breast cancer hospitalization was found in the northeast regions of the study area while breast cancer hospitalization was mainly related to urbanization in the western regions.ConclusionsSoil Cd pollution, road density, and urbanization were associated with breast cancer hospitalization in different regions. Findings in this study might provide valuable information for healthcare policies and intervention strategies for breast cancer.

Comparative Metabolomics Combined with Physiological Analysis Revealed Cadmium Tolerance Mechanism in Indica Rice (Oryza sativa L.).

Cadmium (Cd) pollution reduces rice production and quality, putting food security and human health at risk. We conducted comparative physiology and metabolomic analyses in two indica rice ('NH199' and 'NH224') to elucidate the Cd-tolerance mechanism. Cd hampered rice growth, induced oxidative stress, and changed the metabolomics profiling of the root. The biochemical and physiological analysis demonstrated that NH224 exhibited a more potent Cd-tolerance ability than NH199. Cd was primarily distributed in root, and NH224 had a lower Cd translocation factor than NH199 by about 24%. The metabolomic analysis revealed 180 and 177 differentially accumulated metabolites between Cd-stressed seedlings and the controls in NH224 and NH199, respectively. In NH224, amino acids biosynthesis, hormone metabolism, lipids-related metabolism, phenylalanine metabolism, and phenylpropanoid biosynthesis pathways were more active and highly associated with antioxidant defense system, biosynthesis of the cell wall and phytochelatins, and maintenance of plasma membrane stability. These findings provide insights into the metabolic profiles of rice following Cd stress and the screening and breeding of Cd-tolerant rice varieties.

Potential of Arthrobacter nicotiniae to Preferentially Remove Lead, Cadmium, Silver and Zinc from Contaminated Soil from Amaonye-Ishiagu Agricultural Forest, Ebonyi State, Nigeria

This study evaluates the potential of Arthrobacter nicotiniae to preferentially remove lead, cadmium, silver and zinc from contaminated soil from Amaonye-ishiagu Agricultural Forest, Ebonyi State, Nigeria using standard methods. The study revealed optimum values of factor as 8ml of nutrient volume, 5g of the organism, 30oC of temperature, pH of 8 and stirring frequency of 4pw. The study showed 79.78% removal of lead, 61.50% removal of cadmium, 48.59% removal of arsenic and 7.04% removal of zinc on the 35th day. The organism is thus good for lead and cadmium pollution control, arsenic pollution abatement but it is neither good for zinc pollution control, nor abatement.

Cadmium Absorption in Various Genotypes of Rice under Cadmium Stress.

Cadmium (Cd) is a kind of heavy metal. Cadmium pollution in paddy fields will accumulate a large amount of cadmium in rice, which will affect the growth and development of rice. In addition, long-term consumption of rice contaminated with Cd can harm human health. In this study, four rice varieties with high Cd accumulation (S4699, TLY619, JHY1586, QLY155) and four varieties with low Cd accumulation (YY4949, CYJ-7, G8YXSM, MXZ-2) were screened through field experiments for two consecutive years (2021 and 2022) and differences in antioxidant enzyme systems and expression of genes in their organs were analyzed. The total Cd content showed as follows: indica rice > japonica rice, high-Cd-accumulation variety > low-Cd-accumulation variety, and the total Cd content of each organ of rice showed root > stem > leaf > grain. The results of the antioxidant enzyme system showed that the contents of malondialdehyde (MAD), reduced glutathione (GSH), oxidized glutathione (GSSH), and peroxidase (POD) were positively correlated with the total Cd content in rice, and superoxide dismutase (SOD) showed the opposite performance in the leaves. There was no correlation between catalase (CAT) and Cd content, but CAT content decreased in leaves and grains and increased in roots and stems with increasing fertility. Based on this study, RT-qPCR was used to further validate the expression of Cd-uptake-related genes in different rice varieties. It was found that high expression of OsHMA3, OsCCX2, OsNRAMP5, and OsHMA9 genes promoted Cd uptake and translocation in rice, especially in rice varieties with high Cd accumulation. The high expression of OslRT1, OsPCR1, and OsMTP1 genes hindered Cd uptake by rice plants, which was especially evident in low-accumulating Cd rice varieties. These results provide an important theoretical reference and scientific basis for our in-depth study and understanding of the mechanism of cadmium stress tolerance in rice.

Cadmium accumulation and isotope fractionation in typical protozoa Tetrahymena: A new perspective on remediation of Cd pollution in wastewater

Cadmium (Cd) pollution threatens water safety and human health, which has raised serious public concern. Tetrahymena is a model protozoan, possessing the potential to remediate Cd contaminated water given the rapid expression of thiols. However, the mechanism of Cd accumulation in Tetrahymena has not been well understood, which hinders its application in environmental remediation. This study elucidated the pathway of Cd accumulation in Tetrahymena using Cd isotope fractionation. Our results showed that Tetrahymena preferentially absorb light Cd isotopes, with Δ114/110CdTetrahymena−solution = −0.20 ± 0.02‰ ∼ − 0.29 ± 0.02‰, which implies that the intracellular Cd is probably in the form of Cd−S. The fractionation generated by Cd complexation with thiols is constant (Δ114/110CdTetrahymena−remaining solution ∼ −0.28 ± 0.02‰), which is not affected by the concentrations of Cd in intracellular and culture medium, nor by the physiological changes in cells. Furthermore, the detoxification process of Tetrahymena results in an increase in cellular Cd accumulation from 11.7% to 23.3% with the elevated Cd concentrations in batch Cd stress culture experiments. This study highlights the promising application of Cd isotope fractionation in Tetrahymena for the remediation of heavy metal pollution in water.

Effects of α-Fe2O3 nanoparticles and biochar on plant growth and fruit quality of muskmelon under cadmium stress.

Cadmium pollution in farmland has become a global environmental problem, threatening ecological security and human health. Biochar is effective in remediation of soil pollution. However, high concentrations of biochar can inhibit plant growth, and low concentrations of biochar have limited mitigation effect on cadmium toxicity. Therefore, the combination of low-concentration biochar and other amendments is a promising approach to alleviate cadmium toxicity in plants and improve the safety of edible parts. In this study, muskmelon was selected as the research object, and different concentrations of α-Fe2O3 nanoparticles were used alone or combined with biochar to explore the effects of different treatments on muskmelon plants in cadmium-contaminated soil. The results showed that the combined application of 250mg/kg α-Fe2O3 nanoparticles and biochar had a good effect on the repair of cadmium toxicity in muskmelon plants. Compared with cadmium treatment, its application increased plant height by 32.53%, cadmium transport factor from root to stem decreased by 32.95%, chlorophyll content of muskmelon plants increased by 14.27%, and cadmium content in muskmelon flesh decreased by 18.83%. Moreover, after plant harvest, soil available cadmium content in 250mg/kg α-Fe2O3 nanoparticles and biochar combined treatment decreased by 31.18% compared with cadmium treatment. The results of this study provide an effective reference for the composite application of different exogenous amendments and a feasible idea for soil heavy metal remediation and mitigation of cadmium pollution in farmland.

Foliar cadmium uptake, transfer, and redistribution in Chili: A comparison of foliar and root uptake, metabolomic, and contribution

Atmospheric deposition is an essential cadmium (Cd) pollution source in agricultural ecosystems, entering crops via roots and leaves. In this study, atmospherically deposited Cd was simulated using cadmium sulfide nanoparticles (CdSN), and chili (Capsicum frutescens L.) was used to conduct a comparative foliar and root experiment. Root and foliar uptake significantly increased the Cd content of chili tissues as well as the subcellular Cd content. Scanning electron microscopy and high-resolution secondary ion mass spectrometry showed that Cd that entered the leaves via stomata was fixed in leaf cells, and the rest was mainly through phloem transport to the other organs. In leaf, stem, and root cell walls, Cd signal intensities were 47.4%, 72.2%, and 90.0%, respectively. Foliar Cd uptake significantly downregulated purine metabolism in leaves, whereas root Cd uptake inhibited stilbenoid, diarylheptanoid, and gingerol biosynthesis in roots. Root uptake contributed 90.4% Cd in fruits under simultaneous root and foliar uptake conditions attributed to xylem and phloem involvement in Cd translocation. Moreover, root uptake had a more significant effect on fruit metabolic pathways than foliar uptake. These findings are critical for choosing pollution control technologies and ensuring food security.

Effects of cadmium stress on fruits germination and growth of two herbage species.

Cadmium (Cd) pollution is a global environmental problem. It is of great significance to find a kind of pasture that can grow normally in a cadmium environment, especially in the Tibetan Plateau. We studied the fruit germination and fruit growth of Elymus sinsubmuticus S.L. Chen and Elymus tangutorum (Nevski), native plants of the Tibetan Plateau, in different cadmium environments. The results showed that with increased cadmium stress, the fruit germination rate, final germination rate, fruit-vigor, average germination time, and germination-speed index for the two grass species gradually decreased, and the 50% germination time for the seed gradually increased. Root length, biomass, and the number of leaves decreased in both species. We quantified the fruit germination and growth of plants in the cadmium environment and found that E. sinosubmuticus S.L. Chen had better fruit germination and fruit growth, and it had the development potential of cadmium pollution control.

Influencing Factors of Cadmium Content in Wheat Grain: A Meta-analysis and Decision Tree Analysis

Rapid urbanization, industrialization, and agricultural intensification have resulted in serious soil problems, such as soil acidification and cadmium pollution, affecting food security and human health. Wheat is the second largest food crop in China and has a strong accumulation capacity for cadmium. Understanding the influencing factors of cadmium content in wheat grain is crucial to realize the safe production of wheat. However, a comprehensive and quantitative analysis of how soil physicochemical properties and cultivars affect wheat cadmium accumulation is lacking. The Meta-analysis and decision tree analysis of 56 related studies published in the past 10 years showed that the proportion of cadmium content in soil and wheat grain exceeding the national standard was 52.6% and 64.1%, respectively. Among soil physical and chemical properties, pH, organic matter, available phosphorus, and total soil cadmium content were the important factors affecting the cadmium content in wheat grains. When soil pH ≤ 5.5 and 5.5<pH ≤ 6.5, the proportion of cadmium content in wheat grain exceeding the national standard was 99.4% and 76.2%, respectively. When 20 g·kg-1<soil organic matter content ≤ 30 g·kg-1, the proportion of cadmium content in wheat grain exceeding the national standard was the highest (61.0%). Soil pH ≥ 7.1 and total cadmium content <1.60 mg·kg-1 was suitable for wheat safety production. There were significant differences in grain cadmium content and cadmium enrichment factors among different wheat cultivars. Planting wheat cultivars with low cadmium accumulation is an economical and effective measure to decrease cadmium content in wheat grains. The current study can provide guidance for the safe production of wheat in cadmium-contaminated farmland.

Regulation of gut bacteria in silkworm (Bombyx mori) after exposure to endogenous cadmium-polluted mulberry leaves

Soil cadmium (Cd) pollution presents a severe pollution burden to flora and fauna due to its non-degradability and transferability. The Cd in the soil is stressing the silkworm (Bombyx mori) out through a soil-mulberry-silkworm system. The gut microbiota of B.mori are reported to shape host health. However, earlier research had not reported the effect of endogenous Cd-polluted mulberry leaves on the gut microbiota of B.mori. In the current research, we compared the phyllosphere bacteria of endogenous Cd-polluted mulberry leaves at different concentrations. The investigation of the gut bacteria of B.mori fed with the mulberry leaves was done to evaluate the impact of endogenous Cd- polluted mulberry leaves on the gut bacteria of the silkworm. The results revealed a dramatic change in the gut bacteria of B.mori whereas, the changes in the phyllosphere bacteria of mulberry leaves in response to an increased Cd concentration were insignificant. It also increased the α-diversity and altered the gut bacterial community structure of B. mori. A significant change in the abundance of dominant phyla of gut bacteria of B.mori was recorded. At the genus level, the abundance of Enterococcus, Brachybacterium and Brevibacterium group related to disease resistance, and the abundance of Sphingomonas, Glutamicibacter and Thermus related to metal detoxification was significantly increased after Cd exposure. Meanwhile, there was a significant decrease in the abundance of the pathogenic bacteria Serratia and Enterobacter. The results demonstrated that endogenous Cd-polluted mulberry leaves caused perturbations in the gut bacterial composition of B.mori, which may driven by Cd content rather than phyllosphere bacteria. A significant variation in the specific bacterial community indicated the adaptation of B. mori gut for its role in heavy metal detoxification and immune function regulation. The results of this study help to understand the bacterial community associated with endogenous Cd-polluted resistance in the gut of B.mori, which proves to be a novel addition in describing its response in activating the detoxification mechanism and promoting its growth and development. This research work will help to explore the other mechanisms and microbiota associated with the adaptations to mitigate the Cd pollution problems.

Cadmium pollution leads to selectivity loss of glutamate receptor channels for permeation of Ca2+/Mn2+/Fe2+/Zn2+ over Cd2+ in rice plant

The selective permeation of glutamate receptor channels (GLRs) for essential and toxic elements in plant cells is poorly understood. The present study found that the ratios between cadmium (Cd) and 7 essential elements (i.e., K, Mg, Ca, Mn, Fe, Zn and Cu) in grains and vegetative organs increased significantly with the increase of soil Cd levels. Accumulation of Cd resulted in the significant increase of Ca, Mn, Fe and Zn content and the expression levels of Ca channel genes (OsCNGC1,2 and OsOSCA1.1,2.4), while remarkable reduction of glutamate content and expression levels of GLR3.1–3.4 in rice. When planted in the same Cd-polluted soil, mutant fc8 displayed significantly higher content of Ca, Fe, Zn and expression levels of GLR3.1–3.4 than its wild type NPB. On the contrary, the ratios between Cd and essential elements in fc8 were significantly lower than that in NPB. These results indicate that Cd pollution may damage the structural integrity of GLRs by inhibiting glutamate synthesis and expression levels of GLR3.1–3.4, which leads to the increase of ion influx but the decrease of preferential selectivity for Ca2+/ Mn2+/ Fe2+/ Zn2+ over Cd2+ through GLRs in rice cells.

Byssus of Green-Lipped Mussel Perna viridis as a Biomonitoring Biopolymer for Zinc Pollution in Coastal Waters.

The present study aimed to confirm the use of the byssus (BYS) of the green-lipped mussel Perna viridis as a biomonitoring biopolymer for zinc (Zn) by comparing it to copper (Cu) and cadmium (Cd) pollution in coastal waters under experimental field conditions, based on the transplantation of caged mussels between polluted and unpolluted sites in the Straits of Johore (SOJ). Four important evidential points were found in the present study. First, the 34 field-collected populations with BYS/total soft tissue (TST) ratios > 1 indicated that the BYS was a more sensitive, concentrative, and accumulative biopolymer for the three metals than TST. Significant (p < 0.05) and positive correlations between BYS and TST in terms of the levels of the three metals were observed. Second, the data obtained in the present study were well-supported by the interspecific comparison, which indicated that the BYS of P. viridis was a significantly better biomonitoring biopolymer for the identification of coastal areas exposed to Zn, Cd, and Cu pollution and played the role of an excretion route of metal wastes. Third, the higher positive correlation coefficients for the metals between the BYS sedimentary geochemical fractions than the TST sedimentary geochemical fractions indicated that the BYS was more reflective of metal bioavailability and contamination in coastal waters. Fourth, and most importantly, the field-based cage transplantation study clearly indicated the accumulation and elimination of the three metals by the BYS in both polluted and unpolluted sites in the Straits of Johore. In sum, the BYS of P. viridis was confirmed as a better biopolymer than TST for Zn, as well as Cd and Cu, bioavailability and contamination in tropical coastal waters.