Levels Of Cd Accumulation Research Articles

Deciphering the mechanism of rhizosphere microecosystem in modulating rice cadmium accumulation via integrating metabolomics and metagenomics.

Cadmium (Cd) accumulation in rice poses significant risks to human health. The Cd accumulation levels vary widely among cultivars and are strongly associated with the rhizosphere microecosystem. However, the underlying mechanisms remain poorly understood. Here, we conducted a field experiment in Cd-contaminated areas with 24 popular regional cultivars. These cultivars were categorized into high Cd accumulation (HA) and low Cd accumulation (LA) groups based on their grain Cd content. Rhizosphere soil physicochemical properties were monitored, and key metabolites, microbiomes, and their interaction contributing to Cd accumulation were analyzed using omics-sequencing technologies and bioinformatics analysis. Metabolomic analysis identified distinct rhizosphere metabolite profiles between the HA and LA groups, with key metabolites showing strong correlations with Cd accumulation. Key metabolites in the LA group were linked to reduced Cd uptake and enhanced antioxidant defense mechanisms, while those in the HA group were associated with increased Cd mobility and uptake. Metagenomic analysis of the rhizosphere soil showed that the LA group harbored a more diverse and interconnected microbial community, with tax such as Syntrophaceae, Anaerolineae, Thermoflexales, and Syntrophales, along with metabolite such as disopyramide, playing central roles in Cd immobilization and detoxification. Additionally, the enhanced carbon, nitrogen, and phosphorus cycling in the LA group suggests a more robust nutrient assimilation process that supports plant growth and reduces Cd uptake. This study highlights the critical role of the rhizosphere microecosystem in regulating Cd accumulation and underscores the potential of selecting rice cultivars with favorable rhizosphere traits as a strategy for reducing Cd uptake.

Genome-wide association study of novel genetic loci for cadmium accumulation and germplasm screening for low-cadmium accumulation in common wheat (Triticumaestivum L.)

Cadmium (Cd) contamination in wheat farmland is increasing at an alarming rate, posing threats to food security and public health. Breeding and utilizing wheat varieties characterized by low Cd accumulation levels constitute an effective strategy in the battle against wheat Cd contamination. The adoption of molecular marker-assisted approaches can greatly expedite the selection and enhancement of wheat varieties with low Cd accumulation. Nonetheless, research concerning genes associated with wheat cadmium accumulation remains scarce. In this study, a high-density 660K SNP array was employed for conducting genome-wide association studies (GWASs) on the grain Cd concentration (GCdC), bioconcentration factor (BCF) and translocation factor (TF) in 175 wheat germplasms. The findings revealed 401 significant SNPs identified across three diverse environments. Linkage disequilibrium analysis revealed 30 core quantitative trait locus (QTLs)capable of reliably modulating wheat Cd accumulation phenotypes. Through gene annotation, transcriptomics, and gene molecular features, four candidate genes (TraesCS7B02G000200, TraesCS4A02G035900, TraesCS4A02G040900, TraesCS5D02G564000) were identified as potential constituents of the biological process of wheat Cd accumulation. Furthermore, in this study 6 wheat germplasms exhibiting low grain Cd accumulation were isolated, and two Kompetitive Allele Specific PCR (KASP) markers conducive to breeding selection were developed. These findings provide valuable genetic resources for cultivating wheat with low Cd accumulation and establish a foundation for understanding the molecular mechanisms underlying low Cd accumulation in wheat. The candidate genes and KASP markers elucidated in this research have potential for effective employmentuse in genetic enhancement and marker-assisted selection in the breeding of wheat with low Cd accumulation.

Endoplasmic reticulum stress response modulator OsbZIP39 regulates cadmium accumulation via activating the expression of defensin-like gene OsCAL2 in rice

Accumulation of cadmium (Cd) in rice is not only harmful to the growth of plants but also poses a threat to human health. Exposure to Cd triggers unfolded protein response (UPR) within cells, a process that is still not completely understood. The study demonstrated that the lack of OsbZIP39, an essential endoplasmic reticulum (ER)-resident regulator of the UPR, resulted in decreased Cd intake and reduced Cd levels in the roots, stems, and grains of rice. Upon exposure to Cd stress, GFP-OsbZIP39 translocated from ER to nucleus, initiating UPR. Further investigation revealed that Cd treatment caused changes in sphingolipid levels in the membrane, influencing the localization and activation of OsbZIP39. Yeast one-hybrid and dual-LUC assays were conducted to validate the interaction between activated OsbZIP39 and the promoter of the defensin-like gene OsCAL2, resulting in an increase in its expression. Different variations were identified in the coding region of OsbZIP39, which may explain the varying levels of Cd accumulation observed in the indica and japonica subspecies. Under Cd treatment, OsbZIP39ind exhibited a more significant enhancement in the transcription of OsCAL2 compared to OsbZIP39jap. Our data suggest that OsbZIP39 positively regulates Cd uptake in rice, offering an encouraging objective for the cultivation of low-Cd rice.

The role of Zip1 and Zip3 in cadmium accumulation in Fujian oyster (Crassostrea angulata)

Oysters are notably susceptible to accumulating substantial amounts of cadmium (Cd), leading to food safety concerns, yet the molecular mechanisms are not fully understood. Previous study identified a significant correlation between polymorphisms in the Zip1 and Zip3 of Fujian oyster (Crassostrea angulata) and the levels of Cd accumulation. Zip1 and Zip3, belonging to the Zip family, are primarily responsible for the cellular transport of zinc and other metal ions. To delve deeper into their roles in Cd transport within oysters, this research cloned and analyzed the sequences of Fujian oyster Zip1 and Zip3. The open reading frames for Zip1 and Zip3 were 960 and 978 bp, respectively, encoding proteins of 319 and 325 amino acids. Following Cd exposure, the expression levels of these genes in the mantle, gills, and other tissues initially increased significantly before decreasing, demonstrating a dose-dependent response. The lowest expression levels were observed in the adductor muscle, with Zip1 reaching its highest expression in the mantle and Zip3 in the visceral mass. In vitro RNAi experiments revealed that silencing Zip1 led to a 1.26-fold decrease in new 113Cd accumulation in the mantle, whereas silencing Zip3 resulted in a 1.29-fold increase. Immunohistochemistry showed weak expression of Zip1 and Zip3 proteins in the connective tissue of the mantle. In summary, Zip1 and Zip3 in Fujian oyster can transport Cd as a substrate, and played different roles in the absorption and efflux of Cd.

The effect of different types of microplastic and acute cadmium exposure on the Mytilus galloprovincialis (Lamarck, 1819)

Microplastic (MP) pollution is a pressing issue for both environmental health and the safety of human food sources. This study provides a comprehensive analysis of the effects of MPs on Mediterranean mussels (Mytilus galloprovincialis, Lamarck 1819), focusing on the food safety risks associated with MP and cadmium (Cd) exposure in these organisms intended for consumption. The retention of different polymer types of MPs in mussels was specifically evaluated, and the influence of Cd on MP retention across these polymers was investigated. Mussels were exposed to polystyrene (PS), polypropylene (PP), and polyethylene terephthalate (PET) MPs individually and in combination with the toxic metal Cd for a duration of 7 days. Antioxidant enzymes, oxidative stress parameters, and digestive system enzyme activities, selected as biomarkers for Cd and MPs pollution, were assessed. Furthermore, human consumption risk evaluations and limits regarding mussel intake were analysed in terms of food safety. The results suggest that exposure to Cd, MPs, or their combination induces oxidative stress, tissue damage, and neurotoxicity. Alterations in digestive enzyme activities could impact the mussels' energy acquisition from food and their capacity to conserve energy reserves. The estimated daily intake (EDI), provisional tolerable weekly intake (PTWI), target hazard quotient (THQ), and target cancer risk (TCR) levels for all groups surpassed established limits, implying a significant health risk for humans consuming these products. These results underscore the potential health risks for humans associated with consuming mussels exposed to Cd and/or MPs and provide valuable data for monitoring pollution levels and ecological risks in aquatic organisms. Additionally, our findings reveal that the retention of Cd in mussel tissues varies significantly after exposure, with combinations of PET and Cd showing lower levels of Cd accumulation compared to other groups, suggesting a differential interaction that influences Cd retention.

The impact on Cd bioavailability and accumulation in rice (Oryza sativa L.) induced by dry direct-seeding cultivation method in field-scale experiments

Dry direct-seeded rice cultivation has gained popularity and expanded its cultivated area due to reduced labor requirements and water consumption. However, the impact of this cultivation method on cadmium (Cd) bioavailability in soil and the accumulation levels in grains remains uncertain. Field experiments were conducted in acidic soils at two locations in southern China to compare rice varieties and evaluate the dry direct-seeding method alongside the wet direct-seeding and traditional transplanting methods. Dry direct-seeded rice reached significantly higher Cd concentrations in its tissues starting from the heading stage than transplanted rice. Cd accumulation levels by the maturation stage in the brown rice of dry direct-seeded rice were 18.33 %–150.69 % higher than those of wet direct-seeded and transplanted rice, with a considerable ability to translocate Cd into brown rice. Furthermore, dry direct seeding decreased iron plaque formation, particularly in the amorphous Fe form; it resulted in high soil temperature and low moisture content during tillering, elevating Cd availability in the soil. Additionally, the proportion of ions and more labile forms of Cd in the soil solution was high. Moreover, the soil under dry direct seeding had high urease and acid phosphatase enzyme activities. However, low richness and diversity in the bacterial community were characterized by a significant increase in the relative abundance of Actinobacteria and Gammaproteobacteria at the class level, while exhibiting decreased relative abundances of Alphaproteobacteria, Bacilli, and KD4-96, along with fewer biomarkers. Nonetheless, these differences are gradually reduced during the maturation stage. Overall, although dry direct seeding offers several advantages, it is crucial to implement additional measures to mitigate the increased health risks linked to rice cultivation through this approach in Cd-contaminated areas.

Influence of different diets and sorbents on the accumulation of Cd in the muscle tissue of young cattle and pigs

The article, based on scientific research, examines an important problematic issue regarding the quality and safety of beef and pork during their production in the Polissia zone of Ukraine, affected by the Chornobyl accident. The purpose of the research was to evaluate the effect of different diets and saponite sorbent on the level of Cd accumulation in the muscle tissue of young bulls and pigs kept in the territory belonging to the third zone of radioactive contamination. Two scientific and economic experiments were conducted. When growing Ukrainian black and white dairy young bulls, the influence of different silages (4-component cereal-bean mixture and Echinоchloa frumentаcea silage) on the content of Cd in the longest back muscle was studied (experiment 1), and optimization of the protein nutrition of animals was carried out at the expense of various feeds with a high protein content (narrow-leaved lupine and fodder beans) (experiment 2). In the third experiment, young pigs were fed various amounts of the natural mineral saponite as part of their diet, and its influence on the ecological quality of products was studied. Since different types and amounts of feed components were used when feeding the animals of the studied groups, it was necessary to balance the rations according to the content of nutrients for each of the presented groups. Regulation and verification of the nutritional value of the rationed feed was carried out monthly. When changing rations for animals, their growth, live weight, zootechnical analysis of feed, their nutritional value and feeding rates were taken into account. Sample preparation of fodder and muscles was carried out according to GSTU 7670:2014 with the help of dry mineralization, the concentration of the toxicant was determined by the atomic absorption method. The transition coefficient of Cd in the chain «diet – muscle tissue» in this study is within the established standards. At the same time, feeding by Echinоchloa frumentаcea silage contributed to a decrease in the coefficient of transition of Cd into the muscle tissue of young bulls by 0.68 % (absolute). The introduction of 30 % (by mass) of fodder beans into the grain mixture instead of a similar amount of lupine for young cattle (cattle) for fattening in the territory of radioactive contamination (the third zone) contributed to a significantly lower accumulation and transition of Cd into the muscle tissue of animals – on 25.0 % and 0.71 % (absolute), respectively. The inclusion of the natural sorbent mineral saponite in the amount of 3–7 % by mass of concentrated feed in the diet of growing and fattening pigs contributed to a reduction of Cd in the longest muscle of the back by 21.8– 37.9%, while at the same time it was better in terms of the sorption efficiency for excretion of Cd, which turned out to be a saponite dose of 7 %. Key words: young bulls, pigs, nutrition, different diets, saponite, accumulation of Cd.

Cadmium affects the growth, antioxidant capacity, chlorophyll content, and homeostasis of essential elements in soybean plants

Soybean (Glycine max L.), as an oil and protein crop, has attracted interest for its potential in the reclamation/restoration of barren and contaminated habitats due to its ability to tolerate adverse environments. To investigate the effects of the growth (biomass and plant height), chlorophyll content, antioxidative capacity (peroxidase and superoxide dismutase activities), and homeostasis of essential elements in soybean plants induced by cadmium (Cd), a pot experiment was performed. Soybean seeds were cultivated in six different levels of Cd-contaminated soil (0, 0.25, 0.50, 1.00, 2.50, 5.00, and 10.00 mg kg−1) for 27 days at 60 % humidity and 25–35 °C in a greenhouse with natural light. Soybean seedling growth was stimulated and inhibited at low (≤1.00 mg kg−1) and high (≥2.50 mg kg−1) Cd concentrations, respectively. Essential metal elements (Mg, Fe, and Zn) and chlorophyll contents of leaves were increased and decreased at low and high Cd concentrations, respectively. Exposure to high Cd concentrations interfered with the homeostasis of essential elements in soybean plants. High Cd concentrations reduced antioxidant capacity and chlorophyll content, which inhibited soybean growth. The Cd accumulation level (>100 mg kg−1) in soybean plant organs was unsafe for producing soybean products. However, soybean seedlings appear to tolerate moderate Cd contamination.

Characteristics of cadmium accumulation and tolerance in apple plants grown in different soils.

Cadmium (Cd) is a nonessential element and highly toxic to apple tree. However, Cd accumulation, translocation and tolerance in apple trees planted in different soils remain unknown. To investigate soil Cd bioavailability, plant Cd accumulation, physiological changes as well as gene expression patterns in apple trees grown in five different soils, 'Hanfu' apple seedlings were planted in orchard soils collected from Maliangou village (ML), Desheng village (DS), Xishan village (XS), Kaoshantun village (KS) and Qianertaizi village (QT), and subjected to 500 μM CdCl2 for 70d. Results showed that soils of ML and XS had higher content of organic matter (OM), clay and silt, and cation exchange capacity (CEC) but lower sand content than the other soils, thereby reduced Cd bioavailability, which could be reflected by lower concentrations and proportions of acid-soluble Cd but higher concentrations and proportions of reducible and oxidizable Cd. The plants grown in soils of ML and XS had relatively lower Cd accumulation levels and bio-concentration factors than those grown in the other soils. Excess Cd reduced plant biomass, root architecture, and chlorophyll content in all plants but to relatively lesser degree in those grown in soils of ML and XS. The plants grown in soils of ML, XS and QT had comparatively lower reactive oxygen species (ROS) content, less membrane lipid peroxidation, and higher antioxidant content and enzyme activity than those grown in soils of DS and KS. Transcript levels of genes regulating Cd uptake, transport and detoxification such as HA11, VHA4, ZIP6, IRT1, NAS1, MT2, MHX, MTP1, ABCC1, HMA4 and PCR2 displayed significant differences in roots of plants grown in different soils. These results indicate that soil types affect Cd accumulation and tolerance in apple plants, and plants grown in soils with higher OM content, CEC, clay and silt content and lower sand content suffer less Cd toxicity.

The Expression of the StNRAMP2 Gene Determined the Accumulation of Cadmium in Different Tissues of Potato.

Cadmium (Cd) is a toxic metal that threatens human health when enriched in crops. NRAMPs are a family of natural macrophage proteins reported to play a key role in Cd transport in plants. In order to explore the gene regulation mechanism of potato under Cd stress and the role of NRAMPs family in it, this study analyzed the gene expression differences of two different Cd accumulation levels in potato after 7 days of 50 mg/kg Cd stress and screened out the key genes that may play a major role in the differential accumulation of Cd in different varieties. Additionally, StNRAMP2 was selected for verification. Further verification showed that the StNRAMP2 gene plays an important role in the accumulation of Cd in potato. Interestingly, silencing StNRAMP2 increased Cd accumulation in tubers but significantly decreased Cd accumulation in other sites, suggesting a critical role of StNRAMP2 in Cd uptake and transport in potatoes. To further confirm this conclusion, we performed heterologous expression experiments in which overexpression of StNRAMP2 gene in tomato resulted in a threefold increase in Cd content, which further confirmed the important role of StNRAMP2 in the process of Cd accumulation compared with wild-type plants. In addition, we found that the addition of Cd to the soil increased the activity of the plant antioxidant enzyme system, and silencing StNRAMP2 partially reversed this effect. This suggests that the StNRAMP2 gene plays an important role in plant stress tolerance, and future studies could further explore the role of this gene in other environmental stresses. In conclusion, the results of this study improve the understanding of the mechanism of Cd accumulation in potato and provide experimental basis for remediation of Cd pollution.

The Relationship between Cadmium-Related Gene Sequence Variations in Rice and Cadmium Accumulation

Cadmium (Cd) pollution and uptake into the grains of developing rice plants represent a major threat to human health. Studies of specific genes can offer new insights into the functional roles of particular genes, highlighting candidate alleles that can be leveraged as DNA markers. Accordingly, the identification of novel Cd-related traits and sequence variants can provide new molecular markers for Cd resistance in rice. In the present study, a genetic diversity analysis was carried out on 85 rice varieties exhibiting varied Cd accumulation, and 436 single polymorphic sites (SNP) corresponding to 43 haplotypes were detected across 12 Cd-associated genes (CAL1, OsCADT1, Oscd1, OsHMA4, OsHMA9, OsNRAMP1, OsNRAMP2, OsNRAMP5, OsHMA2, OsHSMA3, OsPCR1, and OsABCG43). By utilizing the information of the SNPs, 85 rice varieties was classified the into 2 clusters with different source categories and Cd contents. Among the variants, 45 sites in 5 genes were significantly associated with the Cd content in rice grains, of which 8 alleles in OsPCR1, CAL1, and Oscd1 were negatively correlated with Cd accumulation. The results of haplotype aggregation analysis for OsPCR1, Oscd1, and CAL1 showed that 85 rice varieties were divided into 5 clusters. Interestingly, most of the varieties in Cluster A belonged to tropical type, which contained the aggregation of three favorable alleles, whereas the temperate varieties constituted the majority of Cluster B lacking favorable alleles. This observation suggests that the allelic combination found in tropical rice varieties may hold promise for reducing Cd accumulation levels in rice grains. The Cd-associated alleles identified in the present study can not only be used to check the Cd tolerance of rice varieties, but also serve as functional molecular markers to differentiate the source of the rice varieties, which provides a better understanding of the relationship between the sequence variation in Cd-related genes and Cd accumulation in rice.

Characterization of cadmium accumulation mechanism between eggplant (Solanum melongena L.) cultivars.

Excessive cadmium (Cd) accumulation in vegetables due to farmland pollution constitutes a serious threat to human health. Eggplant has a tendency to accumulate Cd. To investigate the mechanism of the differences in Cd accumulation levels between high-Cd (BXGZ) and low-Cd (MYQZ) eggplant cultivar, physiological and biochemical indicators and mRNA expression of eggplant were examined using photosynthetic apparatus, biochemical test kits, Fourier transform infrared (FTIR) spectroscopy and transcriptome sequencing, etc. The results of biochemical test kits and FTIR revealed that MYQZ enhanced pectin methylesterase (PME) activity, and lignin and pectin content in the root cell wall, which was associated with the upregulation of PME, cinnamyl-alcohol dehydrogenase and peroxidase (PODs). Higher levels of cysteine and glutathione (GSH) contents and upregulation of genes associated with sulfur metabolism, as well as higher expression of ATP-binding cassette transporters (ABCs), cation exchangers (CAX) and metal tolerance proteins (MTPs) were observed in MYQZ. In BXGZ, the higher stomatal density and stomatal aperture as well as higher levels of Ca2+ binding protein-1 (PCaP1) and aquaporins and lower levels of A2-type cyclins (CYCA2-1) are consistent with an enhanced transpiration rate in BXGZ. Furthermore, a more developed root system was shown to be associated with higher levels of auxin response factor (ARF19), GATA transcription factors (GATA4, 5 and 11) and auxin efflux carrier component (PIN5) in BXGZ. In conclusion, highly active PME, and higher levels of lignin and pectin in MYQZ are expected to reduce Cd toxicity, while Cd translocation can be inhibited with the help of ABC and other Cd transporters. As for BXGZ, the uptake and translocation of Cd were enhanced by the developed root system and stronger transpiration.

The Validity of Benchmark Dose Limit Analysis for Estimating Permissible Accumulation of Cadmium.

Cadmium (Cd) is a toxic metal pollutant that accumulates, especially in the proximal tubular epithelial cells of kidneys, where it causes tubular cell injury, cell death and a reduction in glomerular filtration rate (GFR). Diet is the main Cd exposure source in non-occupationally exposed and non-smoking populations. The present study aimed to evaluate the reliability of a tolerable Cd intake of 0.83 μg/kg body weight/day, and its corresponding toxicity threshold level of 5.24 μg/g creatinine. The PROAST software was used to calculate the lower 95% confidence bound of the benchmark dose (BMDL) values of Cd excretion (ECd) associated with injury to kidney tubular cells, a defective tubular reabsorption of filtered proteins, and a reduction in the estimated GFR (eGFR). Data were from 289 males and 445 females, mean age of 48.1 years of which 42.8% were smokers, while 31.7% had hypertension, and 9% had chronic kidney disease (CKD). The BMDL value of ECd associated with kidney tubular cell injury was 0.67 ng/L of filtrate in both men and women. Therefore, an environmental Cd exposure producing ECd of 0.67 ng/L filtrate could be considered as Cd accumulation levels below which renal effects are likely to be negligible. A reduction in eGFR and CKD may follow when ECd rises from 0.67 to 1 ng/L of filtrate. These adverse health effects occur at the body burdens lower than those associated with ECd of 5.24 µg/g creatinine, thereby arguing that current health-guiding values do not provide a sufficient health protection.

OsPDR20 is an ABCG metal transporter regulating cadmium accumulation in rice

Cadmium (Cd) is a non-essential toxic heavy metal, seriously posing high environmental risks to human health. Digging genetic resources relevant to functional genes is important for understanding the metal absorption and accumulation in crops and bioremediation of Cd-polluted environments. This study investigated a functionally uncharacterized ATP binding cassette transporter G family (ABCG) gene encoding a Pleiotropic Drug Resistance 20 (PDR20) type metal transporter which is localized to the plasma membrane of rice. OsPDR20 was transcriptionally expressed in almost all tissues and organs in lifespan and was strongly induced in roots and shoots of young rice under Cd stress. Ectopic expression of OsPDR20 in a yeast mutant ycf1 sensitive to Cd conferred cellular tolerance with less Cd accumulation. Knockdown of OsPDR20 by RNA interference (RNAi) moderately attenuated root/shoot elongation and biomass, with reduced chlorophylls in rice grown under hydroponic medium with 2 and 10 µmol/L Cd, but led to more Cd accumulation. A field trial of rice grown in a realistic Cd-contaminated soil (0.40 mg/kg) showed that RNAi plants growth and development were also compromised compared to wild-type (WT), with smaller panicles and lower spikelet fertility but little effect on yield of grains. However, OsPDR20 suppression resulted in unexpectedly higher levels of Cd accumulation in rice straw including lower leaves and culm and grain. These results suggest that OsPDR20 is actively involved in Cd accumulation and homeostasis in rice crops. The increased Cd accumulation in the RNAi plants has the potential application in phytoremediation of Cd-polluted wetland soils.

Accumulation and Elimination of Cadmium by the Nile Tilapia (Oreochromis niloticus) in differing Temperatures and Responses of Oxidative Stress Biomarkers.

The aims of this study were to investigate the accumulation (15 days) and elimination (15 and 30 days) of cadmium (Cd) in the liver, gill, kidney and muscle of Oreochromis niloticus following exposures to different concentrations (1 and 2mg/L) of Cd at different water temperatures (20, 25, 30 oC). Additionally, responses of oxidative stress biomarkers (superoxide dismutase, SOD; catalase CAT; glutathione peroxidase, GPx and malondialdehyde, MDA) of the liver were determined following Cd exposures. In accumulation period, Cd levels increased significantly in all the tissues at all temperatures and tissue accumulation order was kidney > liver > gill. All tissues, except the muscle, accumulated Cd in relation to exposure concentrations and water temperatures. There was no measurable level of Cd accumulation in the muscle, except in fish exposed to 2mg Cd/L at 30 oC. Likewise, elimination of Cd from the tissues also increased in depends on periods and water temperatures. The order of Cd elimination from the tissues was gill > liver > kidney. The oxidative stress biomarkers also responded to both Cd exposure and temperature increases. The activities of antioxidant enzymes such as SOD, CAT, GPx and MDA levels in the liver increased in relation to increases in Cd concentrations and water temperatures.

The Potential of Nitrogen Applied Rapeseed (Brassica napus L) in Remediation of Cadmium Polluted Soil

This study aims to determine the Cd accumulation levels of rapeseed (Brassica napus L.) based on nitrogen (N) (0, 100, 200 and 400 mg kg-1) and Cd (0, 1.5, 3 and 6 mg kg-1) applications to the soil on pot trials conducted under controlled environmental conditions. The highest chlorophyll content was obtained at 400 mg N kg-1 without Cd. The highest dry weight amount in rapeseed was obtained with the application of 100 mg N kg-1 × 1.5 mg Cd kg-1, however, the highest rates of both N and Cd resulted in the lowest dry weight. In 400 mg N kg-1 × 6 mg Cd kg-1 (131 mg Cd kg-1) and 200 mg N kg-1 × 6 mg Cd kg-1 (113.80 mg Cd kg-1) applications, Cd concentration of the rapeseed was determined to be higher than critical Cd hyperaccumulation level. The capacity of Cd uptake and accumulation in rapeseed shoots were enhanced with N applications, thus promoting the phytoextraction of Cd from Cd-contaminated soils. Cadmium rates did not affect Fe, Cu, Mn and Zn uptake levels when N was not applied. However, Cd ratios increased the microelement uptake levels, except Zn, when applied to 100 and 200 N kg-1 ratios as compared to control plants. Eventually, increase in Cd uptake of plants with N fertilization is possible; however, excessive N rates may not result in an increase in rapeseed biomass.

Physiological and Transcriptomic Comparison of Two Sunflower (Helianthus annuus L.) Cultivars With High/Low Cadmium Accumulation

The toxic heavy metal cadmium (Cd) is easily absorbed and accumulated in crops and affects human health through the food chains. Sunflower (Helianthus annuus L.) is a globally important oil crop. In this study, two sunflower cultivars 62\\3 (high Cd) and JB231AC (low Cd), were chosen to compare physiological and transcriptomic responses at different Cd concentrations (0, 25, 50, and 100 μM). The results showed that JB231AC had better Cd tolerance than 62\\3. The contents of H2O2 and MDA (malondialdehyde) in 62\\3 were lower than that in JB231AC under Cd stress, but the activities of SOD (superoxide dismutase) and POD (peroxidase) in JB231AC were higher than in 62\\3, which indicated that JB231AC had a strong ability to remove reactive oxygen species (ROS)-induced toxic substances. Many deferentially expressed ABC (ATP-binding cassette) and ZIP (Zn-regulated transporter, Iron-regulated transporter-like protein) genes indicated that the two gene families might play important roles in different levels of Cd accumulation in the two cultivars. One up-regulated NRAMP (Natural resistance-associated macrophage protein) gene was identified and had a higher expression level in 62\\3. These results provide valuable information to further understand the mechanism of Cd accumulation and provide insights into breeding new low Cd sunflower cultivars.

SELECTION OF CADMIUM NON-ACCUMULATING RICE GENOTYPES TO REDUCE HEALTH RISK

Cadmium (Cd) is regarded as one the most toxic heavy metals. Long term exposure to Cd via air, water, soil or food can be carcinogenic and can also lead to other bone, urinary, reproductive, cardiovascular and nervous disorders. Farmers in order to achieve high quality crops often use excess phosphorus fertilizers and in addition to this leakage of sewage sludge in the agricultural farmlands often leads to Cd contamination in agricultural fields. This holds a long term consequence because the Cd can be easily absorbed by the plants and thus Cd enters the food chain and can get accumulated in human organs. Rice is a major staple crop across the world which holds a vast genotypic variation. Different rice cultivars tends to accumulate different levels of Cd in the rice grains and hence detailed study is required to identify the rice genotypes which do not accumulate Cd in the grains so that they can be regarded as “Cdsafe” cultivars. In the present study, 58 different indica rice cultivars which are popularly grown all over India, have been grown in moderately Cd contaminated soil and results showed differential levels of Cd in the rice grains. Among 58 rice cultivars, 32 cultivars accumulated Cd in the rice grains and rest did not. The rice cultivars namely, Suma, Ranjit, Pratiksha, Kausallya, Ratna, Khitish, Mali-4, Barsha and Annada can be considered to be Cd hyperaccumulators based on the level of Cd accumulation in the rice grains.

Salicylate and glutamate mediate different Cd accumulation and tolerance between Brassica napus and B. juncea

Most hyperaccumulator plants have little economic values, and therefore have not been widely used in Cd-contaminated soils. Rape species are Cd hyperaccumulators with high economic values. Black mustard seed (Brassica juncea) has a higher accumulation ability and a higher tolerance for Cd than oilseed rape (Brassica napus), but its biomass is relatively low and its geographical distribution is limited. However, it is unknown why B. juncea (Bj) is more tolerant to and accumulates more Cd than B. napus (Bn). Here, we found that the differences in Cd accumulation and tolerance between the two species is mainly because Bj plants have higher levels of salicylic acid and glutamic acid than Bn plants. Exogenous salicylate and glutamate treatments enhanced Cd accumulation (salicylate + glutamate co-treatment doubled Cd accumulation level in Bn seedlings) but reduced oxidative stresses by increasing glutathione biosynthesis and activating phytochelatin-based sequestration of Cd into vacuoles. Our results provide a new idea to simultaneously improve Cd accumulation and Cd tolerance in B. napus.

The Road to Practical Application of Cadmium Phytoremediation Using Rice

Cadmium (Cd) is a toxic heavy metal that causes severe health issues in humans. Cd accumulates in the human body when foods produced in Cd-contaminated fields are eaten. Therefore, soil remediation of contaminated fields is necessary to provide safe foods. Rice is one of the primary candidates for phytoremediation. There is a genotypic variation of Cd concentration in the shoots and grains of rice. Using the world rice core collection, ‘Jarjan’, ‘Anjana Dhan’, and ‘Cho-ko-koku’ were observed with a significantly higher level of Cd accumulation in the shoots and grains. Moreover, OsHMA3, a heavy metal transporter, was identified as a responsive gene of quantitative trait locus (QTL) for high Cd concentration in the shoots of these three varieties likewise. However, it is difficult to apply practical phytoremediation to these varieties because of their unfavorable agricultural traits, such as shatter and easily lodged. New rice varieties and lines were bred for Cd phytoremediation using OsHMA3 as a DNA marker selection. All of them accumulated Cd in the shoots equal to or higher than ‘Cho-ko-koku’ with improved cultivation traits. Therefore, they can be used for practical Cd phytoremediation.