Cadmium Accumulation Research Articles

Exploring Transcriptional Regulation of Hyperaccumulation in Sedum plumbizincicola through Integrated Transcriptome Analysis and CRISPR/Cas9 Technology.

The cadmium hyperaccumulator Sedum plumbizincicola has remarkable abilities for cadmium (Cd) transport, accumulation and detoxification, but the transcriptional regulation mechanisms responsible for its Cd hyperaccumulation remain unknown. To address this knowledge gap, we conducted a comparative transcriptome study between S. plumbizincicola and the non-hyperaccumulating ecotype (NHE) of Sedum alfredii with or without Cd treatment. Our results revealed many differentially expressed genes involved in heavy metal transport and detoxification that were abundantly expressed in S. plumbizincicola. Additionally, we identified a large number of differentially expressed transcription factor genes, highlighting the complexity of transcriptional regulatory networks. We further screened four transcription factor genes that were highly expressed in the roots of S. plumbizincicola as candidate genes for creating CRISPR/Cas9 knockout mutations. Among these, the SpARR11 and SpMYB84 mutant lines exhibited decreased Cd accumulation in their aboveground parts, suggesting that these two transcription factors may play a role in the regulation of the Cd hyperaccumulation in S. plumbizincicola. Although further research will be required to determine the precise targeted genes of these transcription factors, combined transcriptome analysis and CRISPR/Cas9 technology provides unprecedented opportunities for identifying transcription factors related to Cd hyperaccumulation and contributes to the understanding of the transcriptional regulation mechanism of hyperaccumulation in S. plumbizincicola.

Feasibility of feeding cadmium accumulator maize (Zea mays L.) to beef cattle: Discovering a strategy for eliminating phytoremediation residues

Eco-friendly and efficient strategies for eliminating cadmium (Cd) phytoremediation plant residues are needed. The present study investigated the feasibility of feeding Cd accumulator maize to beef cattle. In total, 20 cattle at 6 months of age were selected and randomly allocated into two groups fed with 85.82% (fresh basis) Cd accumulator maize (CAM) or normal maize (control [Con]) silage diets for 107 d. Feeding CAM did not affect the body weight (P = 0.24), while it decreased feed intake and increased feed efficiency of beef cattle (P < 0.01). Feeding CAM increased serum concentrations of immunoglobulin A and G, complement 3 and 4, blood urea nitrogen, and low-density lipoprotein cholesterol, decreased serum concentrations of interleukin-6 and lipopolysaccharide (P < 0.05), and caused wider lumens in the renal tubules. The Cd residue in meat was 7 μg/kg beyond the restriction for human food. In the muscle, the unsaturated fatty acids (t11C18:1 and C20:4), Lys, Arg, Pro, and Cys were decreased, while the saturated fatty acids (C10:0, C12:0, and C17:0) and Leu were increased (P < 0.05). Therefore, at the current feeding level, phytoremediation maize increased the feed efficiency of beef cattle, but did present risks to cattle health and production safety, and decreased the meat nutrition and flavor. Further research must be performed to determine whether a lower proper dose of phytoremediation maize and an appropriate feeding period may be possible to ensure no risk to cattle health and the supply of safe meat for humans.

Effects of Waste Cement on the Extractability of Cd, Soil Enzyme Activities, Cadmium Accumulation, Activities of Antioxidant Enzymes, and Malondialdehyde (MDA) Content in Lettuce

Waste cement, a common by-product of urban construction, is often wasted in huge quantities and is worthless. However, some studies have confirmed that waste cement can be used as an alternative heavy metal immobilizing agent. Waste cements, derived from hydrated cement mortar products, were evaluated for soil Cd bioavailability by DTPA extraction and for their efficacy in ameliorating the toxicity of cadmium to soil enzymes and plant antioxidant enzymes. Soil incubation and pot experiments were conducted on three types of waste cement (OPC (ordinary Portland cement), FAC (fly ash cement) and ZEC (zeolite cement)) with an application rate of 1%, 2%, and 3%. The addition of OPC, FAC, and ZEC significantly increased the pH and cation exchange capacity of the soil (p &lt; 0.05). The concentration of DTPA-extractable Cd significantly reduced with a consequential decrease in Cd uptake and transport in lettuce. OPC, FAC, and ZEC application significantly (p &lt; 0.05) enhanced FDA hydrolysis and soil urease activity, except for catalase activity. OPC, FAC, and ZEC, when applied to soil, enhanced the total dry biomass (shoots and roots). Furthermore, the activities of guaiacol peroxidase (POD), catalase (CAT) and superoxide dismutase (SOD) declined in lettuce treated with OPC, FAC, and ZEC. With the addition OPC, FAC, and ZEC, the content of MDA in lettuce leaves displayed a remarkable decrease. In conclusion, the waste cements effectively reduced Cd bioavailability and enhanced the antioxidant system of lettuce.

Root cell-type specific expressions of bacterial mercury transporter MerC and plant SNARE SYP121 fusion protein differentially affect cadmium accumulation patterns of Arabidopsis

ABSTRACT There is increasing demand for solutions against cadmium pollution to secure food safety, and phytoremediation is one of the potential tools. We previously found that a bacterial mercury transporter MerC possesses cadmium uptake activity and its overexpression as a fusion protein with a plasma-membrane resident SNARE protein, SYP121 enhances the cadmium uptake ability of Arabidopsis plants. In this study, we examined whether two different root cell-type specific expression systems of MerC-SYP121 fusion protein could efficiently enhance cadmium accumulation of Arabidopsis plants, compared to the p35S-driven ubiquitous expression system. Representative transgenic lines expressing MerC-SYP121 in root surface cells (pEpi lines) or root endodermal cells (pSCR lines), established in our previous studies, were subjected to different cadmium treatments along with the p35S line. A vertical agar plate assay showed that root surface-specific line pEpi, as well as the p35S line, showed about 15% higher cadmium accumulation in shoots after one-day 10 µM cadmium treatment, compared to the wild-type Col-0. On the other hand, the endodermis-specific line pSCR accumulated 30% less cadmium in its shoots. A similar cadmium accumulation pattern in shoots was observed under the environmentally relevant much lower cadmium treatment of 0.1 µM for 4 d, using the hydroponic culture system. To further examine the potential of the MerC-SYP121 expression system for cadmium phytoremediation, the transgenic plants were hydroponically exposed to 0.1 µM for 4 weeks. The cadmium accumulation after the 4 weeks of treatment was again 16% higher in the pEpi shoots compared to that of Col-0, whereas the p35S line only showed 6% higher Cd concentration. Shoots of the pSCR line accumulated slightly less cadmium compared to Col-0. Ionomic profiles in these plants were analyzed, however, pSCR-specific patterns were not evident. Nevertheless, in our previous studies, pEpi and pSCR lines both efficiently accumulated more mercury in shoots than in the wild-type. The presented results suggest that the effects of cell-type-specific MerC-SYP121 expression differ by the target metals and its expression in root surface cells rather than that in endodermis is suitable for enhancing root cadmium uptake and subsequent shoot accumulation.

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

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

Prediction of the cadmium content in grains of low-accumulating wheat cultivars and soil cadmium threshold for safe production

Wheat cultivars with low cadmium (Cd) accumulation (WCCA-Cd) are widely used on Cd-contaminated farmland and can effectively reduce the grains Cd content to achieve the clean production in agriculture. However, there is a lack of soil Cd content thresholds specifically for the WCCA-Cd. To achieve safer production of wheat grains, a prediction model for WCCA-Cd was developed based on total Cd content in wheat grains (Grain-Cd) and soil factors using 379 soil‒wheat datasets from 10 field experiments in this research. The adaptability of the prediction model was tested using 312 pairs of data. Descriptive statistics (N = 379) showed that soil pH ranged from 4.28 to 8.76, the total Cd content in soil (Soil-Cd) ranged from 0.09 to 10.25 mg kg−1, and Grain-Cd ranged from 0.002 to 1.35 mg kg−1. Correlation analysis showed that Grain-Cd had a highly significant negative correlation with soil organic matter (SOM), soil pH, and soil conductivity (EC) and a highly significant positive correlation with Soil-Cd and Cd content in the diethylenetriaminepentaacetic acid extraction state (DTPA-Cd) (P < 0.001). The bioconcentration factor (BCF) decreased with increaseing soil pH. Both random forest and stepwise regression equations indicated that the most important factors affecting Cd bioeffectiveness were Soil-Cd and soil pH, explaining 80% of the variation in Grain-Cd. The prediction model indicated a soil Cd threshold (0.23–1.25 mg kg−1) for the safe production of WCCA-Cd at soil pH (4–9), which has a wider range of applicability compared with the Chinese Soil Safety Standards. Therefore, these results can quantify the grain Cd content of WCCA-Cd and guide the safe and clean production of WCCA-Cd on different Cd contaminated farmlands.

Fertilizer-induced manganese oxide formation enhances cadmium removal by paddy crusts from irrigation water

Fertilization is a crucial agrological measure for agricultural production that can significantly impact the removal of Cd from irrigation water by paddy crusts (PC). In this study, laboratory and field experiments were conducted to investigate the impact of fertilization at low, medium, and high concentrations on the accumulation of Cadmium (Cd) in PC and the underlying mechanisms involved. The results showed that only low fertilizer concentration could promote the removal of Cd by PC, which reduced the Cd concentration in irrigation water from 19.52 μg/L to 5.35 μg/L. Conversely, medium and high fertilizer concentrations reduced the accumulation of Cd by PC. After fertilizer addition, the proportion of Fe-Mn oxidizable-Cd in PC reached 55 % (with low concentration of fertilizer treatment). The application of low concentration of fertilizer was found to stimulate the growth of filamentous green algae, leading to a significant increase in the relative abundance of sphingomonadaceae (by 1.39 %) and comamonadaceae (by 1.29 %). The XRD, SEM and correlation analysis show that a large amount of manganese oxide is formed on the surface of PC, which increases the fixation of Cd. These findings provide a new perspective for the remediation of heavy metal contamination in paddy fields.

Transcriptome Analysis Reveals Differentially Expressed Genes Involved in Aluminum, Copper and Cadmium Accumulation in Tea 'Qianmei 419' and 'Qianfu 4'.

Tea, as a global nonalcoholic beverage, is widely consumed due to its economic, health and cultural importance. Polyploids have the ability to solve the problems of low yield, cold resistance and insect resistance in tea tree varieties. However, the response mechanism to aluminum and heavy metal remains unclear. In this study, the content of Al, Cu and Cd were measured in the leaves and roots of 'Qianmei 419' and 'Qianfu 4', respectively. The content of Al, Cd and Cu in the roots of the 'Qianmei 419' tea variety were significantly higher than in 'Qianfu 4' roots. Only the content of Cu in the leaves of the 'Qianmei 419' tea variety was significantly higher than that in the roots of the 'Qianfu 4' tea variety. Moreover, we found that the content of Al, Cu and Cd in the soil around the root of 'Qianfu 4' were higher than in the soil around the root of 'Qianmei 419'. RNA-seq was performed to identify the DEGs involved in the accumulation of Al, Cu and Cd between 'Qianmei 419' and 'Qianfu 4'. A total of 23,813 DEGs were identified in the triploid tea variety, including 16,459 upregulated DEGs and 7354 downregulated DEGs. Among them, by analyzing the expression levels of some metal transporter genes, it was found that most of the metal transporter genes were downregulated in the triploid tea plants. In short, through the analysis of transcriptome data and metal content, it was found that changes in metal transporter gene expression affect the accumulation of metals in tea plants. These results provide candidate genes to enhance multi-metal tolerance through genetic engineering technology.

Biochar performance for preventing cadmium and arsenic accumulation, and the health risks associated with mustard (Brassica juncea) grown in co-contaminated soils

Cadmium (Cd) and arsenic (As) in co-contaminated soil can enter the human body harming health via the food chain, such as vegetables. Biochar derived from waste has been used to reduce heavy metal uptake by plant, but long-term effects of biochar under Cd and As co-contaminated soil needs to be investigated. A following mustard (Brassica juncea) was grown on co-contaminated soil amended with different raw materials of biochar including biochars pyrolyzed by lignite coal (LCB), rice straw (RSB), silkworm excrement (SEB), and sugar refinery sludge (SSB). The results showed that compared to the control, Cd and As contents of mustard shoot in SSB treatment decreased by 45–49% and 19–37% in two growing seasons, respectively, which was the most effective among 4 biochars. This probably due to SSB owns more abundant Fe-O functional groups. Biochar also altered the microbial community composition, specifically SSB increased proteobacteria abundance by 50% and 80% in the first and second growing seasons, thereby promoted the simultaneous immobilization of Cd and As in soils which may reduce the potential risks to humans. In summary, considering the long-term effects and security of SSB application on mustard, not only is it an effective waste recycle option, but it should also be promoted as a promising approach for safe vegetable production in Cd and As co-contaminated soils.

Cadmium accumulation in duckweed relates to pH and oxalate synthesis in Cd shock

Cadmium accumulation in duckweed relates to pH and oxalate synthesis in Cd shock

Analysis of Cadmium Accumulation in Linseed (Linum Usitatissimum L.) Depending on Soil pH and Fertilizer Level

ABSTRACT Flax (Linum usitatissimum L.) has great potential for the production of oil with functional properties. There are several factors drastically reducing the quality of linseeds. One of them is the cadmium uptake and accumulation in seeds. The aim of this study was to assess the control capability of Cd uptake level by fertilization and soil pH. The experiment was carried with four Polish varieties of linseed: Bukoz, Szafir, Olivin, and Jantarol. The soil with two different pH was used in the experiment: acidic (pH 4.5) and alkaline (pH 7.5). Two concentrations of aqueous solution of cadmium nitrate (Cd(NO3)2) were added to the soil to obtain the final concentration of Cd: 2 mg/kg and 4 mg/kg of soil, respectively. The phosphorous fertilizer was supplied in the amounts of: 50 kg/ha, 100 kg/ha, 150 kg/ha. The results revealed that the pH level is important factors in the cultivation of linseed. The cadmium uptake by linseed can be significantly weakened by increasing the soil pH. Among the four flax varieties examined, the highest seed yield with the lowest Cd content at the same time was obtained for “Bukoz” during cultivation with 100 kg/ha phosphorous fertilization and pH 7.5.

A combined strategy to mitigate the accumulation of arsenic and cadmium in rice (Oryza sativa L.)

Arsenic and cadmium in rice grain are of growing concern in the global food supply chain. Paradoxically, the two elements have contrasting behaviors in soils, making it difficult to develop a strategy that can concurrently reduce their uptake and accumulation by rice plant. This study examined the combined impacts of watering (irrigation) schemes, different fertilizers and microbial populations on the bioaccumulation of arsenic and cadmium by rice as well as on rice grain yield. Compared to drain-flood and flood-drain treatments, continuously flooded condition significantly reduced the accumulation of cadmium in rice plant but the level of arsenic in rice grain remained above 0.2 mg/kg, which exceeded the China national food safety standard. Application of different fertilizers under continuously flooded condition showed that compared to inorganic fertilizer and biochar, manure addition effectively reduced the accumulation of arsenic over three to four times in rice grain and both elements were below the food safety standard (0.2 mg/kg) while significantly increasing the rice yield. Soil Eh was the critical factor in the bioavailability of cadmium, while the behavior of arsenic in rhizosphere was associated with the iron cycle. The results of the multi-parametric experiments can be used as a roadmap for low-cost and in-situ approach for producing safe rice without compromising the yield.

A vacuolar transporter plays important roles in zinc and cadmium accumulation in rice grain.

Rice grain is a poor dietary source of zinc (Zn) but the primary source of cadmium (Cd) for humans; however, the molecular mechanisms for their accumulation in rice grain remain incompletely understood. This study functionally characterized a tonoplast-localized transporter, OsMTP1. OsMTP1 was preferentially expressed in the roots, aleurone layer, and embryo of seeds. OsMTP1 knockout decreased Zn concentration in the root cell sap, roots, aleurone layer and embryo, and subsequently increased Zn concentration in shoots and polished rice (endosperm) without yield penalty. OsMTP1 haplotype analysis revealed elite alleles associated with increased Zn level in polished rice, mostly because of the decreased OsMTP1 transcripts. OsMTP1 expression in yeast enhanced Zn tolerance but did not affect that of Cd. While OsMTP1 knockout resulted in decreased uptake, translocation and accumulation of Cd in plant and rice grain, which could be attributed to the indirect effects of altered Zn accumulation. Our results suggest that rice OsMTP1 primarily functions as a tonoplast-localized transporter for sequestrating Zn into vacuole. OsMTP1 knockout elevated Zn concentration but prevented Cd deposition in polished rice without yield penalty. Thus, OsMTP1 is a candidate gene for enhancing Zn level and reducing Cd level in rice grains.

Foliar application with salicylic acid alleviates cadmium toxicity in chia (Salvia hispanica L.)

Cadmium (Cd) accumulation is one of the serious global issues among the multitude of food security challenges. Their toxic effects are evident in different physiological and metabolic behaviors of plants. In this context, a potted study was conducted to investigate the effectiveness of salicylic acid (SA) spraying in alleviating Cd toxicity in chia (Salvia hispanica) seedlings. This pseudocereal as a superfood is characterized by high nutritional value and high therapeutic potential. We examined some growth traits, photosynthetic pigments, anthocyanin, antioxidant defense system, malondialdehyde (MDA), and certain osmoregulatory molecules. The results showed that the chia seedlings exposed to Cd showed a substantial decline in growth, especially in shoot and root length and number of leaves (25.5, 21.5, and 22.6%, respectively), whereas the aforesaid biochemical parameters were not significantly affected. However, SA treatment alleviated the Cd stress applied and markedly enhanced the stem and root growth, especially shoot length of about 32.3% compared to Cd treatment. Under combined treatment Cd+SA, we also recorded a significant increase in the accumulation of proline (85.3%) and anthocyanin (83.1%), and a significant enhancement in peroxidase activity (34.9%), compared to control. These responses exhibit the involvement of SA in mitigating Cd-induced oxidative damage and improving Cd tolerance in Chia. Principal component analysis and cluster analysis showed differences between individual and combined treatment. Based on these results, exogenous SA used in the right amounts could alleviate Cd-induced stress and boost chia seedlings’ growth.

Straw removal or non-removal affects cadmium (Cd) accumulation in soil–rice (Oryza sativa L.) system at different ambient air Cd levels

Despite the potential importance of the removal of contaminated straw for heavy metal output from agricultural soils, previous studies have primarily focused on the variation in the metal concentration without considering the impact input of heavy metals from atmospheric deposition. Here, rice was grown under field conditions, and, as a reference, in a deposition-free environment, and exposed to different ambient air Cd levels. Two consecutive years of pot experiments were conducted in two study areas (ZZ and LY) to examine the changes in soil physicochemical properties as well as Cd accumulation in the soil–rice (Oryza sativa L.) system in response to straw return or removal. The results showed that rice straw return enhanced the soil pH and organic matter (OM) content, but reduced the soil redox potential (Eh); and the variation in amplitude increased with number of cultivation years. After two years of cultivation, the concentrations of soil total Cd and extractable Cd in the straw-removal treatments reduced by 9.89–29.49% and 4.88–37.74%, respectively, whereas those in the straw-return treatments exhibited a slight decrease, or even an increase. This indicated that straw removal could effectively reduce the concentration and bioavailability of Cd in contaminated farmland, which was further confirmed by the results for accumulation of Cd in rice tissues. In addition, the contribution from atmospheric deposition was confirmed by the greater variation in Cd concentration in soils and rice tissues under deposition-free conditions. A major implication of our findings is that the adoption of reasonable straw-treatment measures and proper control over ambient air heavy metals can promote the remediation efficiency of Cd-contaminated fields.

Bioaccumulation of heavy metals in gills and muscles of selected fish species from Owerrinta section of Imo River

Bioaccumulation of heavy metals in aquatic organisms had been known to occur naturally. Over the years the levels of these accumulations keep increasing due to various human activities which make it detrimental to the life of aquatic organism and humans. The study assessed bioaccumulation of some heavy metals in the gills and muscles of some fish species. Fish samples were collected for a period of 4 months, identified and stored for further analysis. The following heavy metals: Zinc (Zn), Copper (Cu), Iron (Fe), Lead (Pb) and Cadnium (Cd) were assessed on the fish gills and muscles using standard procedure. Results showed that the fish species sampled (Clarias gariepinus, Tilapia zilli, Oreochromis niloticus, Alestes baremose and Pareutropius buffei) showed some levels of metal accumulation both in the gills and muscles. Levels of Zn in muscles of A. baremose, P. buffei, C. gariepinus, T. zilli and O. niloticus were 3.63±0.12, 1.45±0.26, 4.27±0.15, 4.03±1.42 and 2.00±0.15mg/kg respectively. The highest level of Zn (3.44±0.15mg/kg) in the gills was observed in T. zilli. Other results showed that P. buffei had the highest Pb concentrations (0.48±0.22mg/kg in muscle) and (0.17±2mg/kg in gills) while T. zilli had 2.24±0.54mg/kg and 1.46±0.65mg/l as the highest concentration of Fe in muscles and gills respectively. The levels of Zn, Cu, Fe and Pb recorded in the fish muscles where below the World Health Organization (WHO) and Food and Agricultural Organization (FAO) standards while Cadmium levels in all the fish sampled were above the recommended standard of 0.5mg/kg. This high cadmium accumulation in fish samples calls for concern considering the adverse effect it may cause if transferred to humans through fish consumption. There is therefore need to intensify efforts in mitigating some of the activities that amplify the levels of bioaccumulation of these metals in the aquatic environment towards a healthier environment.

Phytoremediation method and Brassica family: Removal of chromium, cadmium and lead accumulation with broccoli (Brassica oleracea var. italica)

Phytoremediation is the most cost effective and applicable technique to clean contaminated soils. The study was carried out in controlled conditions. Cadmium was applied as only cadmium (30 mgkg−1), and together with a chelator as Cd (30 mgkg−1) + EDTA, in triplicates. Chromium was applied as only chromium (10 mg/kg−1), and together with a chelator as Cr (10 mgkg−1) + EDTA. Similarly, lead was applied as only lead (100 mgkg−1), and together with a chelator as Pb (100 mgkg−1) + EDTA. The highest root and shoot dry weights were detected in lead and chromium applied pots. The highest lead, cadmium and chromium concentrations in the shoot of broccoli (Brassica oleracea var.italica) were found to be 14.0 mgkg−1, 6.67 mg kg-1and, 5.17 mg kg−1, respectively, in the chelated applications. The order of accumulation in the root was Cr > Pb > Cd. Broccoli was shown to be effective in phytoextraction of Pb Chromium was especially accumulated in the roots of broccoli which indicated that this plant was successful for phytostabilization of Cr. Broccoli can be employed for both phytostabilization and phytoextraction of cadmium. The results revealed that broccoli played a role in the remediation of lead, chromium and cadmium heavy metals as a hyper accumulator plant.

Inoculation of Escherichia coli enriched the key functional bacteria that intensified cadmium accumulation by halophyte Suaeda salsa in saline soils

The enhancement of cadmium (Cd) extraction by plants from contaminated soils associated with phosphate-solubilizing bacteria (PSB) has been widely reported, but the underlying mechanism remains scarcely, especially in Cd-contaminated saline soils. In this study, a green fluorescent protein-labeled PSB, the strain E. coli-10527, was observed to be abundantly colonized in the rhizosphere soils and roots of halophyte Suaeda salsa after inoculation in saline soil pot tests. Cd extraction by plants was significantly promoted. The enhanced Cd phytoextraction by E. coli-10527 was not solely dependent on bacterial efficient colonization, but more significantly, relied on the remodeling of rhizosphere microbiota, as confirmed by soil sterilization test. Taxonomic distribution and co-occurrence network analyses suggested that E. coli-10527 strengthened the interactive effects of keystone taxa in the rhizosphere soils, and enriched the key functional bacteria that involved in plant growth promotion and soil Cd mobilization. Seven enriched rhizospheric taxa (Phyllobacterium, Bacillus, Streptomyces mirabilis, Pseudomonas mirabilis, Rhodospirillale, Clostridium, and Agrobacterium) were obtained from 213 isolated strains, and were verified to produce phytohormone and promote soil Cd mobilization. E. coli-10527 and those enriched taxa could assemble as a simplified synthetic community to strengthen Cd phytoextraction through their synergistic interactions. Therefore, the specific microbiota in rhizosphere soils enriched by the inoculated PSB were also the key to intensifying Cd phytoextraction.

Nitrogen Addition Alleviates Cadmium Toxicity in Eleocarpus glabripetalus Seedlings

Cadmium (Cd) accumulation in soil is a serious form of heavy metal pollution affecting environmental safety and human health. In order to clarify the tolerance mechanisms to Cd-contaminated soils under N deposition, changes in plant growth, root architecture and physiological characteristics of Eleocarpus glabripetalus seedlings under combined nitrogen (N) and cadmium (Cd) treatments were determined in this study. The results indicated that Cd-induced negative effects inhibited the growth of E. glabripetalus seedlings through increased underground biomass allocation, and affected transpiration and respiratory processes, resulting in a decreased soluble sugars concentration in leaves and non-structural carbohydrates (NSC) in the roots. Root systems might play a major role in Cd absorption. Cd stress restricted the growth of fine roots (&lt;0.5 mm), and affected the uptake of N and P. N addition alleviated the Cd-induced negative effect on plant growth through improving the root system, increasing starch and NSC contents in the roots and increasing total biomass. These findings have important implications for understanding the underlying tolerance mechanisms of Cd pollution under N deposition in arbor species.

Effect of gluconic acid rinsing on cadmium decontamination from rice protein.

Cadmium (Cd) accumulation in rice protein has long been considered a significant threat to human health. In the present study, a costless and effective method based on gluconic acid (GA) rinsing of rice protein was developed to reduce Cd contamination in rice protein. Moreover, the effect of GA on the structural and functional properties of rice protein was evaluated. With liquid-solid ratio of 30mL/g and oscillation time of 120min, 96.0% and 93.6% of Cd were eliminated from rice protein-H and rice protein-L, respectively. In addition, the results of scanning electron microscopy, Fourier transform infrared, and sodium dodecyl sulfate polyacrylamide gel electrophoresis analyses showed that GA treatment did not significantly change the structural properties of rice protein. However, GA treatment increased foaming properties, water holding capacity, and oil holding capacity of the rice protein, without affecting its further applicability. Thus, the proposed GA rinsing method can be considered a green and efficient strategy to solve the issue brought by Cd residual contamination in rice protein. PRACTICAL APPLICATION: Given the advantages of green and efficient agriculture, gluconic acid (GA) has emerged as a powerful strategy for removing the Cd from rice protein. The method developed herein showed great potentials for applications in the manufacture of rice-based products.