Reducing Cadmium Accumulation Research Articles

Application of Lanthanum at the Heading Stage Effectively Suppresses Cadmium Accumulation in Wheat Grains by Downregulating the Expression of TaZIP7 to Increase Cadmium Retention in Nodes.

Reducing cadmium (Cd) accumulation in wheat is an effective way to decrease the potential threats of Cd to human health. The application of lanthanum (La) in agricultural fields is eliciting extensive attention due to its beneficial effects on improving yields and inhibiting Cd accumulation in edible parts of crops. However, the potential mechanism of La-restricted Cd accumulation in crop grains is not entirely understood. Here, we investigated the effects of La and Cd accumulation in wheat grains by implementing application at the shooting and heading stages. Some associated mechanisms were explored. Results showed that La application at the shooting and heading stages considerably promoted the thousand-grain weight. La application at the shooting and heading stages increased Cd accumulation in the first node beneath the panicle (N1) but reduced Cd levels in the other tissues. La application at the heading stage exerted greater effects on Cd storage in N1 while reducing Cd concentrations in the other tissues compared with La application at the shooting stage. La addition substantially decreased the translocation of Cd from the lower nodes to the upper internodes, but increased Cd translocation from the lower internodes to the upper nodes. The expression of TaZIP7 in N1 was downregulated by La treatment. These results suggest that the effective reduction in Cd in wheat grains by La application at the heading stage is probably a consequence of the successful promotion of Cd storage in nodes by downregulating the expression of TaZIP7 during the grain-filling stage, thereby hindering the redirection Cd from nodes to grains.

Zinc oxide nanoparticles reduce cadmium accumulation in hydroponic lettuce (Lactuca sativa L.) by increasing photosynthetic capacity and regulating phenylpropane metabolism

Due to the continuous production of industrial wastes and the excessive use of chemical fertilizers and pesticides, severe cadmium (Cd) pollution in soil has occurred globally. This study investigated the impacts of incorporating zinc oxide nanoparticles (ZnONPs) into hydroponically grown lettuce (Lactuca sativa) under cadmium stress conditions, to seek effective methods to minimize Cd buildup in green leafy vegetables. The results showed that 1 mg/L of Cd significantly inhibited lettuce growth, decreasing in leaves (29 %) and roots (33 %) biomass. However, when lettuce was exposed to 2.5 mg/L ZnONPs under cadmium stress, the growth, chlorophyll content, net photosynthetic rate (Pn), stomatal conductance (Gs), actual photochemical efficiency of PSII (φPSII), and activity of key enzymes in photosynthesis were all significantly enhanced. Furthermore, ZnONPs significantly decreased the accumulation of Cd in lettuce leaves (36 %) and roots (13 %). They altered the subcellular distribution and chemical morphology of Cd in lettuce by modifying the composition of cell walls (such as pectin content) and the levels of phenolic compounds, resulting in a reduction of 27 % in Cd translocation from roots to leaves. RNA sequencing yielded 45.9 × 107 and 53.4 × 107 clean reads from plant leaves and roots in control (T0), Cd (T1), Cd+ZnONPs (T2), and ZnONPs (T3) treatment groups respectively, and 3614 and 1873 differentially expressed genes (DEGs) were identified. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis identified photosynthesis, carbon fixation, and phenylpropanoid metabolism as the main causes of ZnONPs-mediated alleviation of Cd stress in lettuce. Specifically, the DEGs identified included 12 associated with photosystem I, 13 with photosystem II and 23 DEGs with the carbon fixation pathway of photosynthesis. Additionally, DEGs related to phenylalanine ammonia-lyase, caffeoyl CoA 3-O-methyltransferase, peroxidase, 4-coumarate-CoA ligase, hydroxycinnamoyl transferase, and cytochrome P450 proteins were also identified. Therefore, further research is recommended to elucidate the molecular mechanisms by which ZnONPs reduce Cd absorption in lettuce through phenolic acid components in the phenylpropanoid metabolism pathway. Overall, treatments with ZnONPs are recommended to effectively reduce Cd accumulation in the edible portion of lettuce.

Screening nitrogen-fixing cyanobacteria that can alleviate cadmium toxicity to rice and reduce cadmium accumulation in brown rice

Among food crops, rice is the most serious food crop contaminated with cadmium (Cd). It is critical to reduce Cd bioavailability in the soil and prevent its accumulation in brown rice. The use of microorganisms to lessen Cd toxicity in rice has been the subject of numerous studies carried out in recent years. The nitrogen-fixing cyanobacterium (NFC) is a potent biofertilizer and heavy metal biosorbent. However, there is a dearth of research on the impact of NFC supplementation on rice's susceptibility to Cd poisoning. This study screened for Cd-tolerant NFCs and assessed how well they might promote growth and lower the amount of Cd in rice. Four NFCs with tolerance to 1 mg L−1 Cd were selected from ten NFCs. The results of seedling experiment showed that SCAU-10 treatment increased plant height and biomass while reducing Cd levels in seedlings by 62.0 %. The pot experiment also demonstrated that SCAU-10 was effective in lowering Cd content in brown rice by 85.3 %. Reducing the bioavailability of soil Cd, shielding rice roots, preventing Cd transfer from below to above ground, generating phytohormones, and enhancing the photochemical electron quantum yield of rice leaves are a few possible action mechanisms of the NFC. It indicates that Trichormus sp. SCAU-10 has a great deal of promise for use as a biofertilizer in the safe management of Cd-contaminated rice fields. This is the first report on using Trichormus sp. biofertilizer for relieving the toxicity of Cd to rice and reducing Cd accumulation in brown rice.

Over-expression of LsEXPA6, a lettuce expansin gene, improves cadmium stress tolerance in transgenic Arabidopsis

Cadmium (Cd) is a harmful heavy metal that is highly toxic to plants and animals. Expansins are cell wall proteins inducing cell wall loosening and participate in all plant growth and development processes which are associated with cell wall modifications. We investigated lettuce’s expansin gene LsEXPA6 and found that LsEXPA6 overexpression Arabidopsis lines were much more resistant to cadmium stress. Our results revealed that the root system of the expa6 mutant was suppressed under cadmium stress, resulting in shorter plant height, reduced biomass, and a significant increase in cadmium content in the plants compared with wild-type plants, whereas LsEXPA6 overexpression lines had a well-developed root system and reduced cadmium accumulation in the roots and shoots of the plants. The above results indicated that overexpression of LsEXPA6 affected root development and reduced Cd absorption in Arabidopsis. In addition, the higher absorption capacity of nutrients, increased antioxidant enzymes activities, improved chlorophyll and photosynthetic function in the overexpression Arabidopsis plants, supported the Cd stress tolerance mechanism. Taken together, these results provided a new insight on the role of expansin proteins in the tolerance of plants to Cd stress by root cell elongation.

Pretreatment with aqueous Moringa oleifera Lam. leaf extract prevents cadmium-induced hepatotoxicity by improving cellular antioxidant machinery and reducing cadmium accumulation

Cadmium (Cd) is a highly harmful pollutant that poses a serious threat to human health. The liver is the primary organ for Cd accumulation, and Cd-induced hepatotoxicity has been shown to be strongly correlated with an oxidative imbalance in hepatocytes. Our previous studies in the eukaryotic model organism Saccharomyces cerevisiae revealed that not only co-treatment but also pretreatment with aqueous Moringa oleifera Lam. leaf extract (AMOLE) effectively mitigated Cd toxicity by reducing intracellular Cd accumulation and Cd-mediated oxidative stress. In this study, we therefore investigated the preventive effect of AMOLE against Cd toxicity in human HepG2 hepatocytes. The results showed that, similar to the case of the yeast model, pretreatment with AMOLE prior to Cd exposure also significantly inhibited Cd-induced oxidative stress in HepG2 cells. Untargeted LC-MS/MS-based metabolomic analysis of AMOLE revealed that its major phytochemical constituents were organic acids, particularly phenolic acids and carboxylic acids. Additionally, DPPH-HPTLC fingerprints suggested that quercetin and other flavonoids possibly contribute to the antioxidant activities of AMOLE. Based on our findings, it appears that pretreatment with AMOLE prevented Cd-induced hepatotoxicity via three possible mechanisms: i) direct elimination of free radicals by AMOLE antioxidant compounds; ii) upregulation of antioxidant defensive machinery (GPx1, and HO-1) via Nrf2 signaling cascade to improve cellular antioxidant capacity; and iii) reduction of intracellular Cd accumulation, probably by suppressing Cd uptake. These data strongly suggest the high potential of AMOLE for clinical utility in the prevention of Cd toxicity.

Metabolic regulation mechanism of melatonin for reducing cadmium accumulation and improving quality in rice

Melatonin acts as a potential regulator of cadmium (Cd) tolerance in rice. However, its practical value in rice production remains unclear. To validate the hypothesis that melatonin affects Cd accumulation and rice quality, a series of experiments were conducted. The results showed that exogenous melatonin application was associated with reduced Cd accumulation (23–43%) in brown rice. Fourier transform infrared spectroscopy (FTIR) analysis showed that exogenous melatonin affected the rice protein secondary structure and starch short-range structure. Metabolomics based on LC–MS/MS revealed that exogenous melatonin altered the brown rice metabolic profile, decreased fatty acid metabolite content, but increased amino acid metabolite, citric acid, melatonin biosynthetic metabolite, and plant hormone contents. These findings indicate that exogenous melatonin can effectively reduced Cd accumulation and improve rice quality through metabolic network regulation, serving as an effective treatment for rice cultivated in Cd-contaminated soil.

Potential Protective Effect of Selenium-Enriched Lactobacillus plantarum on Cadmium-Induced Liver Injury in Mice.

Cadmium (Cd) is a prevalent environmental contaminant that poses a potential hazard to the health of both humans and animals. In this study, biosynthesized selenium-enriched Lactobacillus plantarum and selenium nanoparticles (SeNPs) were developed and evaluated for their protective effects against Cd-induced hepatic injury in mice through oral administration for 4 weeks. Cadmium exposure resulted in severe impairment of liver function, as evidenced by increased levels of serum markers of liver injury and, oxidative stress and significant damage to liver tissue, and a notable decrease in the diversity of the intestinal microbiota. Oral administration of Se-enriched L. plantarum (LS) reduced cadmium accumulation in the liver by 49.5% and, restored other cadmium-induced damage markers to normal levels. A comparison of the effects with those of L. plantarum (L) and SeNPs isolated from LS revealed that LS could more effectively alleviate hepatic oxidative stress and reduce the intrahepatic inflammatory responses of the liver, further protecting against cadmium-induced liver injury. These findings suggest that the development of LS may be effective at protecting the liver and intestinal tract from cadmium-induced damage.

Melatonin reduces cadmium accumulation through cell wall fraction fixation capacity in cotton seedlings

Melatonin (MT) participates in plants' responses in plants’ response to cadmium (Cd) tolerance, although its work model remains elusive. Here, the function of MT in adjusting Cd accumulation in Gossypium hirsutum (CCRI12) was investigated. In this research we observed that exogenous 50 μM MT significantly reduced the Cd accumulation under 100 μМ Cd stress for 7 days of treatment in cotton seedlings. Cd markedly induced the ROS (H2O2, O2-) accumulation and elevated the expression of transporters for Cd uptake and translocation. After application of MT reduced ROS and MDA accumulation in response to high induction of antioxidant defense system; the genes encoding superoxide dismutase (GhSOD), catalase (GhCAT), and peroxidase (GhPOD), ascorbate peroxidase (GhAPX), and glutathione S-transferase (GhGST) were significantly upregulated accompanied by their level of content. Furthermore, MT down-regulated transporters for Cd uptake include Natural Resistance-Associated Macrophage Protein 1 (GhNRAMP3), Zinc/Iron-regulated transporter-like protein (GhZIP1/4/6), Heavy Metal ATPase gene (GhHMA2), and ATP-binding Cassette sub family C (GhABCC3/2). Exogenous application of MT raised the hemicelluloses, cellulose and pectin content accompanied by their expression levels, xyloglucan endotransglucosylase/hydrolase (GhXTH28/6/9/B), cellulose synthase like (GhCSLG1/2) and COBRA-like (GhCOBL4), pectin acetylesterases (GhPAE8/7), pectin methylesterases (GhPME31) which in turn increased the cell wall's binding capacity to Cd.

Green manuring reduces cadmium accumulation in rice: Roles of iron plaque and dissolved organic matter

In southern China, winter green manure is widely used in rice cropping systems for improving grain yields and soil fertility. Cd pollution has recently been reported in some of these paddy fields. Research on the in-depth understanding of how green manuring affects Cd absorption in rice is limited. This study aimed to investigate the impacts of different green manures, including single plantation and mixed plantation on the absorption of Cd by rice and explore the underlying mechanisms. Pot experiments demonstrated that compared with winter fallow–rice, green manuring treatments considerably decreased rice Cd content, promoted the conversion of bioavailable Cd fraction into a more stable form, induced the formation of iron plaque, and increased the content of humic-like fraction (HF) in soil dissolved organic matter (DOM). Treatment with mixed plantation resulted in a greater decrease in rice Cd content and an increase in HF and iron plaque contents than single plantation. Hydroponic experiments confirmed that both iron plaque and green manure-derived DOM significantly reduced the Cd content in rice seedlings. In conclusion, green manure incorporation is an efficient measure for the safe utilization of Cd-contaminated soil, and mixed plantation of different green manures exerts stronger effects.

Limestone and yellow gypsum can reduce cadmium accumulation in groundnut (Arachis hypogaea): A study from a three-decade old landfill site

Cadmium (Cd) toxicity has cropped up as an important menace in the soil-plant system. The use of industrial by-products to immobilise Cd in situ in polluted soils is an interesting remediation strategy. In the current investigation, two immobilizing amendments of Cd viz., Limestone (traditionally used) and Yellow gypsum (industrial by-product) have been used through a green-house pot culture experiment. Soil samples were collected from four locations based on four graded levels of DTPA extractable Cd as Site 1 (0.43 mg kg−1), Site 2 (0.92 mg kg−1), Site 3 (1.77 mg kg−1) and Site 4 (4.48 mg kg−1). The experiment was laid out in a thrice replicated Factorial Complete Randomized Design, with one factor as limestone (0, 250, 500 mg kg−1) and the other being yellow gypsum (0, 250, 500 mg kg−1) on the collected soils and groundnut was grown as a test crop. Results revealed that the DTPA-extractable Cd content in soil and Cd concentration in plants decreased significantly with the increasing doses of amendments irrespective of initial soil available Cd and types of amendment used. The effect of amendment was soil specific and in case of Site 1 (low initial Cd) the effect was more prominent. The reduction in DTPA-extractable Cd in combined application of limestone and yellow gypsum @500 mg kg−1 over the absolute control in soil under groundnut for the sites was by far the highest with the values of 83.72%, 77.17%, 48.59% and 40.63% respectively. With the combined application, Target Cancer Risk (TCR) of Cd was also reduced. Hence, combined application of limestone and yellow gypsum can be beneficial in the long run for mitigating Cd pollution.

Vitamin E: An assistant for black soldier fly to reduce cadmium accumulation and toxicity

Cadmium (Cd) is a toxic heavy metal associated with osteoporosis, liver, and kidney disease. The black soldier fly (BSF) Hermetia illucens may be exposed to Cd during the transformation of livestock manure. The BSF has a high tolerance to Cd. In the previous work of the laboratory, we found that vitamin E (VE) may play a role in the tolerance of BSF to Cd exposure. The main findings are as follows: The BSF larvae pretreated with exogenous VE had heavier body weight, lower content and toxicity of Cd under similar Cd exposure. Even in high Cd exposure at the concentrations of 300 and 700 mg/kg, the BSF larvae pretreated with exogenous VE at a concentration of 100 mg/kg still reduced the Cd toxicity to 85.33 % and 84.43 %, respectively. The best-fitting models showed that metallothionein (MT) content, oxidative damage (8-hydroxydeoxyguanosine content, malondialdehyde content), antioxidant power (total antioxidant power, peroxidase activity) had a great influence on content and toxicity of Cd bioaccumulated in the larvae. The degree of oxidative damage was reduced in the larvae with exogenous VE pretreatments. This variation can be explained by their changed MT content and increased antioxidant power because of exogenous VE. These results reveal the roles of VE in insects defense against Cd exposure and provide a new option for the prevention and therapy of damage caused by Cd exposure.

Encapsulated lignin-based slow-release manganese fertilizer with reduced cadmium accumulation in rice (Oryza sativa L.)

As an essential trace element for plant growth and development, manganese plays a crucial role in the uptake of the heavy metal cadmium by rice (Oryza sativa L.). In this study, we developed a novel slow-release manganese fertilizer named Mn@LNS-EL. Initially, lignin nanoparticles were derived from sodium lignosulfonate, and a one-step emulsification strategy was employed to prepare a water-in-oil-in-water (W/O/W) Pickering double emulsions. These double emulsions served as the template for interfacial polymerization of lignin nanoparticles and epichlorohydrin, resulting in the formation of microcapsule wall materials. Subsequently, manganese fertilizer (MnSO4) was successfully encapsulated within the microcapsules. Hydroponic experiments were conducted to investigate the effects of Mn@LNS-EL on rice growth and the cadmium and manganese contents in the roots and shoots of rice under cadmium stress conditions. The results revealed that the treatment with Mn@LNS-EL markedly alleviated the inhibitory effects of cadmium on rice growth, leading to notably lower cadmium levels in the rice roots and shoots compared to the specimens treated without manganese fertilizer. Specifically, there was a reduction of 37.9 % in the root cadmium content and a 17.1 % decrease in the shoot cadmium content. In conclusion, this study presents an innovative approach for the high-value utilization of lignin through effective encapsulation and slow-release mechanisms of trace-element fertilizers while offering a promising strategy for efficiently remediating cadmium pollution in rice.

Overexpression of vacuolar transporters OsVIT1 and OsVIT2 reduces cadmium accumulation in rice.

Excessive cadmium in rice grain in agricultural production is an important issue to be addressed in some southern regions of China. In this study, we constructed transgenic rice overexpressing OsVIT1 and OsVIT2 driven by 35S promoter in the cultivar ZH11. Compared with ZH11, OsVIT1 expression in leaves was significantly increased by 3-6.6 times and OsVIT2 expression in leaves was significantly increased by 2-2.5 times. Hydroponic experiments showed that overexpression of OsVIT1 and OsVIT2 increased the tolerance to Fe deficiency, significantly reduced Cd content in shoot and xylem sap, and had no effect on Cd tolerance in rice. Two years of field trials showed that the Fe content in the grain of OsVIT1 and OsVIT2 overexpressed materials was significantly reduced by 20-40% and the straw Fe content was significantly increased by 10-45%, and the grain Fe content distribution ratio was significantly decreased and the straw Fe distribution ratio was significantly increased compared with the wild type. The OsVIT1 and OsVIT2 overexpressed materials significantly reduced the Cd content of grain by 40-80% and the Cd content of straws by 37-77%, and the bioconcentration factor of Cd was significantly reduced in both grains and straw of OsVIT1 and OsVIT2 overexpressed materials. Overexpression of OsVIT1 and OsVIT2 did not affect the concentration of other metal ions in rice straw and grain. qRT-PCR analysis showed that the expression of the low affinity cation transporter OsLCT1 was significantly downregulated in the OsVIT1 and OsVIT2 overexpressed materials. In conclusion, overexpression of OsVIT1 and OsVIT2 reduced Cd accumulation in straw and grains, providing a strategy for Cd reduction in rice.

Reducing cadmium accumulation and increasing grain yield with proper timing of flood irrigation in the second season of ratoon rice

Context or problemThe second season of ratoon rice (ratoon crop, RC) exhibits a high risk of cadmium (Cd) contamination in grains, requiring effective irrigation management strategies to reduce its grain Cd concentration. Objective or research questionThis study aimed to determine the crucial growing period for Cd accumulation and provide irrigation recommendations for reducing grain Cd concentrations with limited water input in the ratoon season. MethodsA two-year field experiment was conducted in Hubei province, central China. The entire growth duration of RC was divided into three short periods: from harvest of the main crop (HM) to initial heading of RC (IH), from IH to full heading of RC (FH), and from FH to maturity of RC (MR). During each growth period of RC, two water regimes (flooded and rainfed) were established. Therefore, there were a total of eight water treatment combinations in this experiment, using a randomized complete block design. Two hybrid varieties were planted in this study. ResultsAcross years, varieties and treatments, the grain Cd concentration of RC ranged from 27.8 to 314.1 µg kg−1, with 37.5% of rice samples exceeding the national food safety standard for Cd (200 µg kg−1). RC grown under continuous flooding conditions produced the lowest grain Cd concentration and highest grain yield. Compared with rainfed conditions, maintaining flooded conditions from HM to IH, from IH to FH, and from FH to MR resulted in decreases of 28.4%, 62.7%, and 12.0% in grain Cd concentration and decreases of 25.5%, 49.9%, and 16.3% in total Cd accumulation at maturity, respectively. RC took up the most Cd during the period from IH to FH under rainfed conditions; however, maintaining flooded conditions reduced Cd uptake by 95.4% during this period. Moreover, flooding from IH to FH had the most positive impact on the grain yield of RC, with an increase of 8.1% compared with rainfed conditions. ConclusionsMaintaining flooded conditions from initial to full heading for 15–18 days was not only effective in reducing grain Cd concentration but also beneficial for improving grain yield in the ratoon season. Implications and significanceThis study clarified the effects of water management during different growing periods on Cd accumulation and grain yield in the ratoon season. We emphasized the necessity of flooding during heading period to control Cd accumulation in RC grains, especially in areas with limited water resources and high soil Cd concentration.

Role of green synthesized nano iron oxide in alleviating the cadmium toxicity in Brassica oleracea var. italica seedlings

This work accounts for the green synthesis of iron oxide nanoparticles using Moringa oleifera leaf extract as a stabilizing and reducing agent. The preliminary confirmation of synthesized Fe3O4NPs was done by UV–visible spectroscopy in the wavelength range of 190–900 nm. The crystalline nature of Fe3O4 NPs was established via X-ray diffraction analysis. FT-IR studies reveal the bioactive phytochemicals present in the Moringa leaf extract based Fe3O4 NPs. A DLS particle size analyser was used to determine the size of green synthesized Fe3O4 NPs and its spherical morphology was determined by using SEM and TEM techniques. The growth of Brassica oleracea var. italica seedlings was measured by analysing biophysical and biochemical parameters in two concentrations of Fe3O4 NPs i.e. 15 mg/L and 30 mg/L alone and in combination with cadmium. Treatments were designated as control C, NP1, NP2, Cd+NP1, Cd+NP2, and Cd. Fe3O4 NPs treated broccoli seedlings showed noteworthy improvement in shoot length, root length, plant biomass, total chlorophyll content, carotenoid content, total soluble sugars, protein content, and nitrate reductase activity, while decline in electrolyte leakage, lipid peroxidation, proline content, superoxide dismutase activity and catalase activity was reported as compared to control. Exposure of iron oxide nano-treatments was found efficacious in reducing cadmium accumulation at a concentration of 30 mg/L. The seedlings exposed to NP2 (30 mg/L) concentration of green synthesized nano iron oxide increased nutrient uptake and thus stimulating plant growth, and also improved morphological and physiological characteristics of Brassica oleracea seedlings. Therefore, the present study reported that bio-based iron oxide nanoparticles were significantly useful for plant growth, by enhancing the plant defense mechanism in response to cadmium induced toxicity.

Silicon reduces cadmium accumulation and toxicity by regulating transcriptional and physiological pathways, and promotes the early growth of tomato seedlings

Cadmium (Cd) pollution is a serious threat to plant growth and human health. Ample evidence suggests that silicon (Si) enhances plant Cd resistance; however, the precise underlying mechanism remains unclear. In this study, tomato (Solanum lycopersicum) was used as the test material for exploring the alleviating effect of 1 mM Na2SiO3 on Cd stress induced by 10 µM CdCl2. The transcriptional and physiological experiments revealed that (Ⅰ) Si downregulated the iron-regulated transporter (SlIRT1), zinc and iron regulated transporter-like proteins (SlZIP4), and reduced Cd absorption by tomato seedlings. (Ⅱ) Si upregulated the genes related to plant Cd resistance (SlPCR), pleiotropic drug resistance (SlPDR), and ATP-binding cassette G transporters (SlABCG), which promoted Cd efflux and suppressed Cd accumulation in tomato seedlings. (Ⅲ) Si increased the activities of antioxidant enzymes and contents of non-enzymatic antioxidants, reduced the contents of reactive oxygen species and malondialdehyde, and suppressed Cd-induced oxidative damages. (Ⅳ) Si inhibited Cd-induced chlorophyll degradation, alleviated damages to chloroplast ultrastructure. (Ⅴ) Si enhanced the activity of enzymes related to carbon-nitrogen metabolism, and promoted the growth of tomato seedlings. (Ⅵ) Si increased the contents of auxin and gibberellin, reduced the salicylic acid content, and maintained growth and resistance. (Ⅶ) Si regulated the expression of WRKY, NAC, ERF, MYB, HSF, and bHLH transcription factors, reduced Cd accumulation and improved Cd tolerance in tomato seedlings. These results indicated that Si effectively reduced Cd accumulation in tomato seedlings and improved Cd tolerance, and may therefore be applied for alleviating the inhibitory effect of Cd on crop growth and ensuring food security.

Synergistic effect of silicon and arbuscular mycorrhizal fungi reduces cadmium accumulation by regulating hormonal transduction and lignin accumulation in maize

Cadmium (Cd) stress causes serious damage to plants, inducing various physiological and biochemical disruptions that lead to reduced plant biomass and compromised growth. The study investigated the combined effects of silicon (Si) and arbuscular mycorrhizal fungi (AMF) on mitigating Cd stress in plants, revealing promising results in enhancing plant tolerance to Cd toxicity. Under Cd stress, plant biomass was significantly reduced (−33% and −30% shoot and root dry weights) as compared to control. However, Si and AMF application ameliorated this effect, leading to increased shoot and root dry weights (+47% and +39%). Furthermore, Si and AMF demonstrated their potential in reducing the relative Cd content (−43% and −36% in shoot and root) in plants and positively influencing plant colonization (+648%), providing eco-friendly and sustainable strategies to combat Cd toxicity in contaminated soils. Additionally, the combined treatment in the Cd-stressed conditions resulted in notable increases in saccharide compounds and hormone levels in both leaf and root tissues, further enhancing the plant's resilience to Cd-induced stress. Si and AMF also played a vital role in positively regulating key lignin biosynthesis genes and altering lignin-related metabolites, shedding light on their potential to fortify plants against Cd stress. These findings underscore the significance of Si and AMF as promising tools in addressing Cd toxicity and enhancing plant performance in Cd-contaminated environments.

The effects of earthworm inoculation on cadmium-contaminated rice field in Southern China: a pot experiment and a field test.

Currently, the effects of earthworm inoculation on cadmium-contaminated rice field remain unclear. In this study, four treatments were tested, including rice monoculture (CK), earthworm inoculation with low density (L, 30 g/m2), middle density (M, 60 g/m2), and high density (H, 90 g/m2). The pot and field experiment were conducted in Hunan Province, China. In the pot experiment, the H treatment significantly decreased the available cadmium concentration in 0 ~ 20 cm soil by 5.21% ~ 16.51%, and the M treatment significantly decreased in 0 ~ 10 cm soil by 7.29% ~ 8.96%. The H treatment significantly decreased the total cadmium concentration in 0 ~ 5 cm soil by 10.36%. Moreover, the earthworm inoculation treatments significantly reduced cadmium accumulation in rice organs. In the field experiment, the M and H treatment decreased the available cadmium concentration in 0 ~ 20 cm soil by 14.05% ~ 47.52% and the H treatment decreased the total cadmium concentration in 0 ~ 20 cm soil by 0.78% ~ 5.75% although there was no significant difference. Furthermore, the earthworm inoculation treatments significantly decreased cadmium accumulation in part of rice organs. In conclusion, this study recommends that earthworm inoculation is an effective method of controlling cadmium contamination for rice production.

Silicon Combined with Melatonin Reduces Cd Absorption and Translocation in Maize.

Cadmium (Cd) is one of the most toxic and widely distributed heavy metal pollutants, posing a huge threat to crop production, food security, and human health. Corn is an important food source and feed crop. Corn growth is subject to Cd stress; thus, reducing cadmium stress, absorption, and transportation is of great significance for achieving high yields, a high efficiency, and sustainable and safe corn production. The use of silicon or melatonin alone can reduce cadmium accumulation and toxicity in plants, but it is unclear whether the combination of silicon and melatonin can further reduce the damage caused by cadmium. Therefore, pot experiments were conducted to study the effects of melatonin and silicon on maize growth and cadmium accumulation. The results showed that cadmium stress significantly inhibited the growth of maize, disrupted its physiological processes, and led to cadmium accumulation in plants. Compared to the single treatment of silicon or melatonin, the combined application of melatonin and silicon significantly alleviated the inhibition of the growth of maize seedlings caused by cadmium stress. This was demonstrated by the increased plant heights, stem diameters, and characteristic root parameters and the bioaccumulation in maize seedlings. Under cadmium stress, the combined application of silicon and melatonin increased the plant height and stem diameter by 17.03% and 59.33%, respectively, and increased the total leaf area by 43.98%. The promotion of corn growth is related to the reduced oxidative damage under cadmium stress, manifested in decreases in the malondialdehyde content and relative conductivity and increases in antioxidant enzyme superoxide dismutase and guaiacol peroxidase activities, as well as in soluble protein and chlorophyll contents. In addition, cadmium accumulation in different parts of maize seedlings and the health risk index of cadmium were significantly reduced, reaching 48.44% (leaves), 19.15% (roots), and 20.86% (health risk index), respectively. Therefore, melatonin and silicon have a significant synergistic effect in inhibiting cadmium absorption and reducing the adverse effects of cadmium toxicity.

Placental BCRP transporter reduces cadmium accumulation and toxicity in immortalized human trophoblasts

Cadmium (Cd) is a ubiquitous environmental metal detectable in most pregnant women. Animal and human studies demonstrate that in utero exposure to Cd reduces birth weight and impairs perinatal growth due to placental toxicity. BCRP is a prominent transporter that can efflux xenobiotics from the placenta. This study sought to investigate Cd transport and toxicity in cultured human BeWo trophoblasts with reduced expression and function of the placental barrier transporter BCRP. Knockdown (KD) of BCRP protein expression and function in BeWo trophoblasts increased the intracellular accumulation of Cd by 100% following treatment with 1 μM CdCl2. No change in the expression of Cd uptake transporters was observed between control and BCRP-KD cells. Reduced BCRP expression impaired viability of BeWo cells exposed to CdCl2 for 48 hr (BCRP-KD IC50: 11 μM, control cells IC50: 18 μM). Moreover, BCRP-KD cells were more sensitive to CdCl2-induced cytotoxicity compared to control BeWo cells. CdCl2 treatment strongly induced the expression of the metal-binding protein metallothionein (MT) in both control and BCRP-KD cells, with significantly greater MT upregulation in Cd-treated BCRP-KD cells. These data suggest that the BCRP transporter reduces Cd accumulation in syncytiotrophoblasts, which may be one mechanism to reduce subsequent toxicity to the placenta and developing fetus.