High Accumulation Of Cadmium Research Articles

Genetic properties of cadmium translocation from straw to brown rice in low-grain cadmium rice (Oryza sativa L.) line

Breeding the rice cultivar with high cadmium (Cd) accumulation in straw but with low Cd in brown rice using marker-assisted selection (MAS) based on quantitative trait loci (QTL) is meaningful for phytoremediation as well as safety in production. A restorer rice line, YaHui2816, steadily showed low Cd translocation from straw to brown rice and carried alleles for reducing Cd concentration in brown rice (BRCdC). In this study, one F2 population (C268A/YaHui2816) was used to identify the QTLs for BRCdC in 2016, and other two different F2 populations (Lu98A/YaHui2816 and 5406A/YaHui2816) were used to furtherly validate the QTLs in 2017. Furthermore, a pot experiment was conducted to investigate the relative expression of predicted genes in the regions of these QTLs for BRCdC. Here 4 QTLs for BRCdC were identified, among which, 2 novel QTLs (qBRCdC-9 and qBRCdC-12) were identified on chromosomes 9 and 12 in rice. The YaHui2816 alleles in the QTLs qBRCdC-9 and qBRCdC-12 could effectively reduce BRCdC under different genetic backgrounds. Importantly, the QTL qBRCdC-12 was simultaneously associated with the Cd translocation from shoot to brown rice (T-s-b), genetically explaining that the low T-s-b of the YaHui2816 resulted in its low BRCdC. The interval length of the QTL qBRCdC-12 was only narrowed to 0.28 cM, making it possible to develop molecular markers and excavate genes for reducing BRCdC. It is worth noting that genes existed in these QTL regions have not been reported for regulating the Cd translocation in rice. 6 candidate genes (OS05G0198400, OS05G0178300, OS09G0544400, OS12G0161100, OS12G0162100 and OS12G0165200) up-regulated expressed in nodeⅡof the YaHui2816 in response to Cd treatment, and encoded ZRT/IRT-like protein (ZIP) 4, the protein similar to glutathione transferase (GSTs) 16, heat shock protein Hsp20 domain containing protein, MAP kinase-like protein and Cd tolerant protein 5, respectively.

Study of the contamination rate and change in growth features of lettuce (Lactuca sativa Linn.) in response to cadmium and a survey of its phytochelatin synthase gene

Crops can become contaminated when grown in soils containing heavy metals. Cadmium is a heavy metal that poses a significant health risk to humans. The purpose of this study was to evaluate the effect of cadmium on lettuce (Lactuca sativa Linn) and the contamination risk of lettuce grown in cadmium environments. The results showed that photosynthesis and growth parameters were significantly affected by cadmium. Lettuce has the ability to absorb large amounts of cadmium from the contaminated environment and so is a cadmium hyperaccumulator plant. The study showed that approximately 35% of the total absorbed cadmium is transmitted to aerial and edible parts of lettuce. This study was undertaken as lettuce has the ability to absorb and accumulate high levels of cadmium. There are however are no reports on the PCS gene and the potential for high cadmium accumulation in lettuce. The bioinformatics study revealed that lettuce has two phytochelatin synthase genes that produce 6 PCSs through splicing leading to the ability of lettuce to store high levels of cadmium. These six sequences although different in length have high similarity. Sequence structure, cellular location, three-dimensional structure, phylogeny and a comparison of their catalytic power were evaluated. The high accumulation of cadmium in lettuce and the presence of several PCSs contribute to the accumulation of cadmium in aerial tissues. The cultivation of lettuce in contaminated environments led us to evaluate suspected farms for the presence of cadmium in produce. Lettuce grown in industrial environments contaminated with cadmium can pose a serious threat to human health.

Durum wheat genome highlights past domestication signatures and future improvement targets

The domestication of wild emmer wheat led to the selection of modern durum wheat, grown mainly for pasta production. We describe the 10.45 gigabase (Gb) assembly of the genome of durum wheat cultivar Svevo. The assembly enabled genome-wide genetic diversity analyses revealing the changes imposed by thousands of years of empirical selection and breeding. Regions exhibiting strong signatures of genetic divergence associated with domestication and breeding were widespread in the genome with several major diversity losses in the pericentromeric regions. A locus on chromosome 5B carries a gene encoding a metal transporter (TdHMA3-B1) with a non-functional variant causing high accumulation of cadmium in grain. The high-cadmium allele, widespread among durum cultivars but undetected in wild emmer accessions, increased in frequency from domesticated emmer to modern durum wheat. The rapid cloning of TdHMA3-B1 rescues a wild beneficial allele and demonstrates the practical use of the Svevo genome for wheat improvement.

Map-based cloning of a new total loss-of-function allele of OsHMA3 causes high cadmium accumulation in rice grain.

Rice (Oryza sativa) is a major dietary source of the toxic metal cadmium (Cd). Reducing Cd transfer from soil to the rice grain is important for food safety. Rice cultivars vary widely in their Cd accumulation, but the genetic basis for this variation is not fully understood. Based on field and pot experiments comparing 26 rice cultivars, we identified a cultivar with high Cd accumulation in grain (BG367, coded as W4) and a cultivar with low grain Cd accumulation (Huajingxian 74, coded as W0). W4 showed a higher Cd translocation from roots to shoots than W0. Using chromosome single segment substitution lines derived from the two cultivars, we mapped a quantitative trait locus for Cd accumulation in grain to a 400 kb region in chromosome 7. Using yeast expression assays and transgenic complementation, we identified OsHMA3 as the causal gene at this locus. Compared with OsHMA3W0, OsHMA3W4 has a deletion of 14 amino acids predicted to be in the ATP binding domain. OsHMA3W4 showed a complete loss of transport activity for Cd in yeast assays. Taking our findings together, we have identified a new allele of OsHMA3 with a total loss-of-function, resulting in greatly elevated Cd translocation to rice shoots and grain.

Evaluation of Cadmium Concentration in Wheat Crop Affected by Cropping System

Background: Cadmium accumulation is a growing problem for foodstuff and the environment; it has negative impacts on humans including the damage to kidneys and liver tissue, as well as carcinogenesis, and emphysema. Objectives: The current research aimed at evaluating the effect of planting systems of agricultural products and different growth stages on cadmium concentration in wheat seed. Methods: The study was carried out as a split plot experiment based a randomized complete-block design with 3 replications in the seasonal year of 2014 - 2015. The main factor included 2 cropping systems (wheat-rice, fallow-wheat) and the subfactor were the growth stages (tillering, flowering, and maturity). Comparison of the amount of wheat seed cadmium concentrations between the 2 cropping systems was performed by t test. Results: The difference in seed cadmium concentration between the 2 cropping systems was significant (P < 0.01), and seed cadmium concentration in rice-wheat cropping system with an average of 0.31 mg/kg was higher than that of the fallow-wheat planting system (0.27 mg/kg) as well as the world health organization (WHO) standard (0.20 mg/kg). The ANOVA results showed the significant effect of cropping systems and different growth stages on the cadmium concentration of plant, root, stem, and soil phosphorus content (P < 0.01). Rice-wheat cropping system, due to high consumption of non-standard phosphate fertilizers (such as cadmium), higher soil phosphorus concentrations (9.03 mg/kg), and residues of the previous products had high cadmium concentration in plant (1.83 mg/kg), root (1.09 mg/kg) and stem (0.73 mg/kg) than those of the fallow-wheat cropping system. Conclusions: Due to high accumulation of cadmium in wheat yield, management of phosphate consumption based the standards of Soil and Water Research Institute is recommended.

Nutritional Composition, Physical Characteristics and Sanitary Quality of the Tomato Variety Mongol F1 from Burkina Faso

Tomato (Lycopersicon esculentum Mill) is quantitatively the highest vegetable consumed in Burkina Faso. The objective of this study was to evaluate the physico-chemical, nutritional characteristics, and sanitary quality of the tomato variety Mongal F1 from different production sites. Twenty-eight (28) samples of Mongal F1 fresh tomatoes were collected from 28 producers at three different localities of Ouahigouya, Loumbila and Ouagadougou. The physico-chemical and nutritional characteristics were determined by standardized methods and the traces metallic elements by atomic absorption spectrophotometry. The results revealed a degree brix varying from 4.07° to 5.50° and a pH ranging from 3.71 to 4.08 corresponding to a total acidity of 0.39% to 0.55% citric acid equivalents. The moisture content, the ash content, the total carbohydrates content, the reducing carbohydrates content, the lipids content and the protein content were ranged from 95.09% to 96.17%, 9.25% to 10.60%, 47.00% to 53.43%, 30.03% to 41.21%, 3.04% to 7.71% and 17.09% to 25.03% respectively. The results of the trace metals showed a high accumulation of total cadmium from 0.11 to 0.22 ppm, of total lead of 1.15 to 1.27 ppm and arsenic total of 0.19 to 0.20 ppm. The results proved that environmental conditions influence the quality of the tomato Mongal F1. Detection of trace elements in the tomato fruits suggests that a better production practices are needed.

ЦИНК И КАДМИЙ В ФИТОМАССЕ ДРЕВЕСНЫХ РАСТЕНИЙ ЛЕСНЫХ ЭКОСИСТЕМ: ЗАКОНОМЕРНОСТИ ТРАНСЛОКАЦИИ, АККУМУЛЯЦИИ И БАРЬЕРНЫХ МЕХАНИЗМОВ

This paper has been devoted to the problem of zinc and cadmium accumulation and distribution in the tree organs (on the example of forest ecosystems in the center of the East European plain). Using the translocation and discrimination factors it has been found that zinc as a rule translocated to the aboveground tree phytomass while cadmium was located to a greater extent within the roots. It has been found that the selectivity of the membrane transport systems of plantsincreased toward photosynthetic organs. It has been shown that the main reason of high cadmium accumulation in the stem wood is predominant cadmium xylem transport in the form of free ion Cd2+. In addition it has been foundsome aspects of species-specific accumulation of zinc and cadmium in tree species, associated with their geochemical specialization and peculiarities of the thiol compounds metabolism

Photosynthetic and antioxidant variability in soybean genotypes under Cadmium stress

Soybean, the worldwide main source of oil and high protein feeds for the livestock sector has a high cadmium (Cd) accumulation capacity. With this background, the hydroponic culture experiments were conducted to investigate the effects of different concentrations of Cd (0-100 µM) on growth, water relations, photosynthetic variables, oxidative stress, and antioxidant response in two soybean genotypes P-218 and P-898. Ten days old seedlings were subjected to (0-100 µM CdCl2) for 15 days. The results indicated that the growth of genotype P-218 was not affected significantly upto 75 µM CdCl2 treatment growth of P-828 was reduced significantly beyond 25 µM CdCl2 treatments. Cd toxicity caused severe impairments in photosynthetic variables like photosynthetic rate, chlorophyll fluorescence and chlorophyll content, in P-898 than in P-218. The activities of antioxidant enzymes (superoxide dismutase, catalase, ascorbate peroxidase and glutathione reductase) were higher in P-218 than in P-828 at various levels of Cd treatments. Chlorophyll fluorescence measurements revealed that non-photochemical quenching increased in P-218 and decreased in P-828 whereas the electron transport rate increased under Cd stress in P-828 and decreased in P-218. It is concluded that tolerance capacity of P-218 against Cd can be associated with the capability of this genotype in keeping an active photosynthetic system and strong antioxidant defense system.

A loss-of-function allele of OsHMA3 associated with high cadmium accumulation in shoots and grain of Japonica rice cultivars.

Excessive cadmium (Cd) accumulation in rice poses a risk to food safety. OsHMA3 plays an important role in restricting Cd translocation from roots to shoots. A non-functional allele of OsHMA3 has been reported in some Indica rice cultivars with high Cd accumulation, but it is not known if OsHMA3 allelic variation is associated with Cd accumulation in Japonica cultivars. In this study, we identified a Japonica cultivar with consistently high Cd accumulation in shoots and grain in both field and greenhouse experiments. The cultivar possesses an OsHMA3 allele with a predicted amino acid mutation at the 380(th) position from Ser to Arg. The haplotype had no Cd transport activity when the gene was expressed in yeast, and the allele did not complement a known nonfunctional allele of OsHMA3 in F1 test. The allele is present only in temperate Japonica cultivars among diversity panels of 1483 rice cultivars. Different cultivars possessing this allele showed greatly increased root-to-shoot Cd translocation and a shift in root Cd speciation from Cd-S to Cd-O bonding determined by synchrotron X-ray absorption spectroscopy. Our study has identified a new loss-of-function allele of OsHMA3 in Japonica rice cultivars leading to high Cd accumulation in shoots and grain.

Effect of Low Level Cadmium Exposure on Superoxide Dismutase Activity in Rat

Purpose: To investigate the effect of low level cadmium (Cd) exposure on the activity of superoxide dismutase (SOD) in rat.Methods: Thirty-two male albino rats were divided into four groups of eight animals each. Group one received distilled water and served as control. The other three groups were exposed to 100, 200 and 300 ppm cadmium doses, respectively, in their drinking water for 6 weeks. At the end of 6 weeks, blood, brain and liver were removed from the animals and SOD activities were investigated spectrophotometrically at 480 nm.Results: The data revealed a significant (p &lt; 0.05) decrease in organ weight of the exposed rats, and with the highest cadmium accumulation in liver ranging from 2.99 ± 0.20 μg Cd/g tissue in control to 34.57 ± 2.06 μg Cd/g tissue for the 300 ppm dose group. Exposure to cadmium resulted in significant (p &lt; 0.05) decrease in SOD activity in plasma, erythrocytes, brain and liver in a dose-dependent manner compared to control. The data showed a negative correlation between tissue cadmium and SOD in plasma, erythrocyte and brain. While positive associations were observed between blood and tissue (brain and liver) cadmium and SOD, a significant (p &lt; 0.01), negative correlation was found between tissue cadmium and SOD.Conclusion: As Cd dose increase, plasma, erythrocyte, brain and liver SOD activities decrease. This might affect the maintenance of the normal body physiological conditions.Keywords: Cadmium, Superoxide dismutase, Liver, Brain, Toxicity, Environmental contaminant

Phytoremediation of cadmium by the facultative halophyte plant Bolboschoenus maritimus (L.) Palla, at different salinities.

The cadmium phytoremediation capacity of the halophyte plant Bolboschoenus maritimus (L.) Palla and the influence of water salinity were assessed in a greenhouse experiment, in order to better understand the bioremediation capacity of this plant. Three concentrations of cadmium (0, 50 and 100 μg l(-1)) and four salinity conditions (0, 5, 10 and 20) were chosen to evaluate the cadmium accumulation, in order to test these plants as a potential phytoremediation tool in brackish environments. The cadmium content in water and plants (underground organs, stems and leaves) was analysed with graphite furnace atomic absorption spectrometry. All the plants submitted to salinity 20 and in the three cadmium treatments died. The plants' survival was highest in the lowest salinities, where highest growth and biomasses were also obtained. The plants presented more cadmium content in the rhizomes, followed by stems and even less in leaves. The salt stress of the plants interfered with their cadmium accumulation capacity. The highest cadmium accumulation in the rhizomes occurred at salinity 0, while the salinities 0 and 5 were the most adequate for stems and leaves. The experiment pointed out that B. maritimus represents a good possible intervenient for cadmium bioremediation in freshwater and low salinity brackish water environments, but its use is limited in the habitats of higher salinity.

Effect of EDTA on Cadmium and Zinc Uptake by Sugarcane Grown in Contaminated Soil

The effect of EDTA on cadmium and zinc uptake by sugarcane (Saccarumofficinarum L.) grown in contaminated soil was investigated. Sugarcane was grown in pots for 1 month and EDTA was added at concentration levels of 0(control), 0.5, 1 and 2 millimole per 1 kilogram of soil. Plants were harvested at 2, 4, 6 and 8 months. Soil samples were analyzed to determined levels of cadmium and zinc. Plants were separated into 5 parts: Leaves, bagasses, underground stem, root and juice, including the phytotoxicity. Moreover, the plants were also analyzed for cadmium and zinc accumulation. This result shows that the concentration of EDTA at 1 millimole per 1 kilogram of soil had the highest cadmium accumulation in the root of sugarcane at 21.87, 44.68, 57.52 and 41.97 mg kg-1, at the contact time, respectively. Furthermore, the root showed the most efficient sugarcane uptake compared to the underground stem, bagasses, leaves and juice (root > undergroundstem > bagasses > leaves > juice). The EDTA concentration at 2 millimoles per 1 kilogram of soil has maximum zinc accumulation in various parts of sugarcane. The harvested time at 2 months showed zinc uptake much higher than for leaves and bagasses, while the maximum accumulation of zinc was found in roots and the underground stem at 4 months.

Engineering chlorpyrifos-degrading Stenotrophomonas sp. YC-1 for heavy metal accumulation and enhanced chlorpyrifos degradation.

Many ecosystems are currently co-contaminated with pesticides and heavy metals, such as chlorpyrifos and cadmium. A promising strategy to remediate mixed chlorpyrifos-cadmium-contaminated sites is the use of chlorpyrifos-degrading bacteria endowed with cadmium removal capabilities. In this work, a gene coding for synthetic phytochelatins (EC20) with high cadmium-binding capacity was introduced into a chlorpyrifos-degrading bacterium, Stenotrophomonas sp. YC-1, resulting in an engineered strain with both cadmium accumulation and chlorpyrifos degradation capabilities. To improve the cadmium-binding efficiency of whole cells, EC20 was displayed on the cell surface of Stenotrophomonas sp. YC-1 using the truncated ice nucleation protein (INPNC) anchor. The surface localization of the INPNC-EC20 fusion protein was demonstrated by cell fractionation, Western blot analysis, and immunofluorescence microscopy. Expression of EC20 on the cell surface not only improved cadmium binding, but also alleviated the cellular toxicity of cadmium. As expected, the chlorpyrifos degradation rate was reduced in the presence of cadmium for cells without EC20 expression. However, expression of EC20 (higher cadmium accumulation) completely restored the level of chlorpyrifos degradation. These results demonstrated that EC20 expression not only enhanced cadmium accumulation, but also reduced the toxic effect of cadmium on chlorpyrifos degradation.

Amino Acid, Fatty Acid, and Metal Compositions in Edible Parts of Three Cultured Economic Crabs: Scylla paramamosain, Portunus trituberculatus, and Eriocheir sinensis

Mud crab, swimming crab, and Chinese mitten crab are the most popular economic crabs cultured in China. However, little knowledge is available about the composition of amino acids, fatty acids, and heavy metals in those cultured crabs, despite the large amounts consumed. Scylla paramamosain, Portunus trituberculatus, and Eriocheir sinensis were, respectively, employed for an investigation of these three crabs. The results on the three representative species revealed that muscle, hepatopancreas, and ovary each had its own compositional pattern. The composition of total amino acids in all the crabs was well balanced. The proportion of flavor amino acid in muscles was higher than that in hepatopancreas and ovary. The composition of total fatty acids showed that two functional unsaturated fatty acids, docosahexaenoic acid (DHA, C22:6n-3) and eicosapentaenoic acid (EPA, C20:5n-3), were both abundant in the three crabs. The ratios of n-3/n-6 polyunsaturated fatty acids (PUFAs) in these crabs also showed that they were rich in n-3 PUFA. Among the seven metals explored, zinc, copper, and chromium were the most abundant. It also deserved attention that these crabs were threatened by high accumulation of cadmium in the edible hepatopancreas, which might arise from the pollution of water used for aquaculture. This data could be used as a reference baseline for monitoring the food properties of the three crabs in levels of amino acids, fatty acids, and metals.

Bioaccumulation, Elimination, and Toxic Effect of Cadmium on Structure of Gills and Hepatopancreas of Freshwater Prawn Macrobrachium sintangese (De Man, 1898)

The objectives of this study were to determine the acute toxicity of cadmium and to examine the bioaccumulation and elimination of cadmium in different tissues of the freshwater prawn Macrobrachium sintangese. It also evaluated the structural damage of gills and hepatopancreas of M. sintangese when administered to sublethal cadmium concentration and when exposed prawns were transferred to cadmium-free media. According to the mortality data, the 96 h LC50 value of Cd to M. sintangese was 86 μg/L. The highest cadmium accumulation was observed in gills, followed by the hepatopancreas, and the abdominal muscle. After being transferred to cadmium-free media, the highest cadmium elimination was observed in abdominal muscle, followed by the gills and hepatopancreas. The gills of prawns exposed to cadmium exhibited a severe hyperplasia, vacuolization, and multiple necroses which resulted to the swelling of lamellae. After transferring the cadmium-exposed prawns into the control media, the histopathological effects decreased. Severe alterations to the hepatopancreatic tissue were observed in prawns exposed to cadmium. The tubular epithelial cells were heavily vacuolated and even ruptured. The number of large vacuoles and R cells appeared in the tubular epithelial cells of the hepatopancreas. After transferring to the control media, the histological alterations of the hepatopancreas decreased. The tubular epithelial cells began to rearrange to the normal structure. The number of R cells and B cells were noted in the epithelial cells. The thickness of tubular epithelial cells was comparable to the controls. Due to the sensitivity of M. sintangese to cadmium, therefore this species potentially can be used as a test organism in toxicity assays.

Age-relevant renal effects of cadmium exposure through consumption of home-harvested rice in female Japanese farmers

There are cadmium-polluted areas in Japan, where farmers may be at risk of renal dysfunction due to cadmium exposure through consumption of home-harvested rice. The aims of this study were to investigate levels of cadmium exposure and accumulation and their renal effects in female farmers residing in cadmium-polluted areas, and to consider the relevance of age to the effects of cadmium. We conducted a cross-sectional study of 1200 women (40–79years old) without symptomatic disorders in two cadmium-polluted areas and one unpolluted area as a control. Rice, blood, and urine samples were collected to measure the cadmium levels, together with urinary levels of α1-microglobulin and β2-microglobulin for renal tubular function. Cadmium levels in rice were significantly higher in the polluted areas than control area. Blood and urinary cadmium levels, along with urinary protein levels, were also significantly higher in the polluted areas, especially among the elder subjects. There was one case of cadmium nephropathy in the polluted areas. Age- and urinary cadmium-specific analysis for all the subjects showed a mild linear dose–response relationship between urinary cadmium and proteins in the younger women, and a steep progress of renal dysfunction over the threshold of urinary cadmium (10μg/g creatinine) in the older women. In conclusion, the aged women in the polluted areas showed high accumulation of cadmium and deterioration of renal function through consumption of rice. Also, the aging process itself appeared to contribute to the different renal effects of cadmium observed in the elderly population.

Bioaugmentation with cadmium-resistant plant growth-promoting rhizobacteria to assist cadmium phytoextraction by Helianthus annuus

Micrococcus sp. MU1 and Klebsiella sp. BAM1, the cadmium-resistant plant growth-promoting rhizobacteria (PGPR), produce high levels of indole-3-acetic acid (IAA) during the late stationary phase of their growth. The ability of PGPR to promote root elongation, plant growth and cadmium uptake in sunflowers (Helianthus annuus) was evaluated. Both species of bacteria were able to remove cadmium ions from an aqueous solution and enhanced cadmium mobilization in contaminated soil. Micrococcus sp. and Klebsiella sp. use aminocyclopropane carboxylic acid as a nitrogen source to support their growth, and the minimum inhibitory concentrations of cadmium for Micrococcus sp. and Klebsiella sp. were 1000 and 800mM, respectively. These bacteria promoted root elongation in H. annuus seedlings in both the absence and presence of cadmium compared to uninoculated seedlings. Inoculation with these bacteria was found to increase the root lengths of H. annuus that had been planted in cadmium-contaminated soil. An increase in dry weight was observed for H. annuus inoculated with Micrococcus sp. Moreover, Micrococcus sp. enhanced the accumulation of cadmium in the root and leaf of H. annuus compared to untreated plants. The highest cadmium accumulation in the whole plant was observed when the plants were treated with EDTA following the treatment with Micrococcus sp. In addition, the highest translocation of cadmium from root to the above-ground tissues of H. annuus was found after treatment with Klebsiella sp. in the fourth week after planting. Our results show that plant growth and cadmium accumulation in H. annuus was significantly enhanced by cadmium-resistant PGPRs, and these bacterial inoculants are excellent promoters of phytoextraction for the rehabilitation of heavy metal-polluted environments.

Concentrations of Zn, Mn, Cu and Cd in different tissues of perch (Perca fluviatilis) and in perch intestinal parasite (Acanthocephalus lucii) from the stream near Prague (Czech Republic)

We monitored concentrations of Cd, Cu, Mn and Zn in acantocephalan parasites (Acanthocephalus lucii) and its final host (Perca fluviatilis). The concentrations in parasites were found to be significantly higher than those found in the muscle, gonads and liver of fish host. The bioaccumulation factor values (BF=Cparasite/Chost muscle) were 194, 24.4, 2.2 and 4.7 for Cd, Cu, Mn and Zn, respectively. This suggests a benefit for the host due to the high accumulation of toxic cadmium.

Accumulation of dietary and aqueous cadmium into the epidermal mucus of the discus fish Symphysodon sp.

The discus fish Symphysodon sp. is an Amazonian cichlid with a unusual form of parental care where fry obligately feed from parental mucus for the first few weeks of life. Here, we investigated the possible impact of environmental cadmium on this species, particularly with respect to mucus contamination. We exposed groups of fish to cadmium either through their food (400 mg kg −1) or through the water (3 μg l −1) for 4 weeks, and measured tissue concentrations and ATPase activities at weekly intervals. Cadmium significantly accumulated in all tissues (except for muscle) after 7 days, and tissue concentrations increased until the end of the experiment. Significant alterations in ATPase activities of intestine and kidney were observed at day 7 and 14, but no alterations in gill ATPase activities occurred. The epidermal mucus showed a high accumulation of cadmium from both exposures, but particularly from the diet, indicating that dietary cadmium can be transferred from gut to mucus. Combining this data with approximations of fry bite volumes and bite frequencies, we constructed daily estimates of the cadmium that could potentially be consumed by newly hatched fry feeding on this mucus. These calculations suggest that feeding fry might consume up to 11 μg g −1 day −1, and hence indicate that this species’ dependency on parental mucus feeding of fry could make them particularly susceptible to cadmium contamination of their native habitat.

Identification of three relationships linking cadmium accumulation to cadmium tolerance and zinc and citrate accumulation in lettuce

Lettuce ( Lactuca sativa) is a plant species that shows high accumulation of cadmium, a toxic heavy metal. Lettuce is therefore a good model both for identifying determinants controlling cadmium accumulation in plant tissues and for developing breeding strategies aimed at limiting cadmium accumulation in edible tissues. In this work, 14-day-old plants from three lettuce varieties were grown for 8 days on media supplemented with cadmium concentrations ranging from 0 to 50 μM. Growth, as well as Cd 2+, Zn 2+, K +, Ca 2+, NO 3 −, SO 4 2−, Cl −, phosphate, malate and citrate root an shoot contents were analyzed. The three lettuce varieties Paris Island Cos, Red Salad Bowl and Kordaat displayed differential abilities to accumulate cadmium in roots and shoots, Paris Island Cos displaying the lowest cadmium content and Kordaat the highest. From the global analysis of the three varieties, three main trends were identified. First, a common negative correlation linked cadmium tissue content and relative dry weight reduction in response to cadmium treatments in the three varieties. Second, increasing cadmium concentration in the culture medium resulted in a parallel increase in zinc tissue content in all lettuce varieties. A common strong positive correlation between cadmium and zinc contents was observed for all varieties. This suggested that systems enabling zinc and cadmium transport were induced by cadmium. Finally, the cadmium treatments had a contrasting effect on anion contents in tissues. Interestingly, citrate content in shoots was correlated with cadmium translocation from roots to shoots, suggesting that citrate might play a role in cadmium transport in the xylem vessels. Altogether, these results shed light on three main strategies developed by lettuce to cope with cadmium, which could help to develop breeding strategies aimed at limiting cadmium accumulation in lettuce.