Cadmium toxicity in plants: Impacts and remediation strategies

The protective roles of Oryza glumaepatula and phytohormone in enhancing rice tolerance to cadmium stress by regulating gene expression, morphological, physiological, and antioxidant defense system

The heavy metal cadmium (Cd) is highly poisonous and has received significant attention from environmental scientists due to its harmful impacts on plants. Oryza glumaepatula is a wild rice that contains useful genes against biotic and abiotic stresses. Therefore, the current study used SG007, a single-segment substitution line (SSSL), generated by crossing O. glumaepatula with an elite rice cultivar (HJX74), to evaluate the resistance potential against Cd. Moreover, we assessed the efficacy of strigolactone GR24 (1 μM) against Cd toxicity (100 μM) by investigating physiological, biochemical, and molecular mechanisms in both cultivars (i.e., SG007 and HJX74). The findings of this study revealed that Cd toxicity declined the chlorophyll a, chlorophyll b, and carotenoids by 50%, 20%, and 44% in SG007, and 58%, 39%, and 59% in HJX74 by enhancing electrolyte leakage (EL), malondialdehyde (MDA), and hydrogen peroxide (H2O2) by 113%, 184%, and 119% in SG007 and 248%, 273% and 195% in HJX74, respectively. GR24 improved growth under Cd stress in both cultivars, and SG007 exhibited better plant growth parameters, antioxidant enzymatic activities, nitric oxide synthase (NOS), and nitric oxide (NO) levels than HJX74 under Cd toxicity. GR24 with SG007 regulated expressions of Cd transporters and reduced the cytological disruptions in cell organelles. The combined utilization of SG007 and GR24 reduced Cd accumulation and oxidative stress and improved plant growth parameters and enzymatic activities. In conclusion, our study highlights the potential of utilizing SG007 in conjunction with GR24 as a practical strategy to mitigate Cd pollution in rice. The results not only underscore the beneficial effects of strigolactone GR24 in alleviating Cd-induced stress but also emphasize the valuable genetic traits of O. glumaepatula in developing rice lines with enhanced tolerance to heavy metals, offering broader implications for sustainable agriculture and crop improvement in contaminated environments.

Nanosilica and salicylic acid synergistically regulate cadmium toxicity in rice

Cadmium (Cd) toxicity negatively impacts plant health and productivity. Nanosilica (SiO2NPs) and salicylic acid (SA) enhance plant performance and alleviate heavy metals stress. Yet, their combined effects against Cd-toxicity in rice remained less-explored. Thus, a hydroponic study investigated the individual and combined effects of SiO2NPs and SA on Cd-stress mitigation in rice at physio-biochemical, cellular, and molecular levels. Results indicated that Cd-alone treatment caused a significant reduction in rice growth and biomass and photosynthetic efficiency, which was associated with oxidative damage caused by enhanced Cd-accumulation in plant tissues. Cd-induction also potentiated its phytotoxicity by triggering enzymatic antioxidants against the extra production of reactive oxygen species (ROS). The addition of SiO2NPs and/or SA markedly minimized the Cd-induced toxicity by reducing Cd-bioaccumulation (42-56%), protecting photosynthetic efficiency, which were directly correlated with seedling biomass and restored cellular structures (leaf ultrastructure and surface morphology). The combined application of SiO2NPs and SA was more effective in activating antioxidant enzymes, phytohormones biosynthesis, and reducing oxidative damages caused by Cd than sole application. This was evident in the decreased production of ROS, malondialdehyde contents (29-37%), and recovered membrane stability. Moreover, SiO2NPs and/or SA relieved Cd-bioaccumulation (41-56%) by downregulating the Cd-related transporter genes (OsNramp1, OsNramp5, OsHMA2, and OsHMA3). Altogether, the cellular Cd-accumulation, photosynthesis, antioxidant defense, and phytohormones against oxidative stress can be ideal markers for cultivating rice in Cd-contaminated soils.

Rice and heavy metals: A review of cadmium impact and potential remediation techniques

In recent decades, the menace of heavy metals to food security and human health has become a serious concern. Given its status as the primary provider of food globally, significant research has been done to ensure the safe cultivation of rice, particularly concerning the mitigation of heavy metal contamination. Therefore, this article focuses on the effects and poisoning mechanism of heavy metals, primarily cadmium, on rice. Here, we have discussed the absorption, translocation, and toxicity mechanism of cadmium in rice and the external factors, such as soil pH, organic matter, microorganisms, and climate change, associated with this pollution. It also discusses in detail the sources of heavy metal pollution and the countermeasures against their effects on rice, such as the use of nanoparticles, biochar, plant growth regulators, nutrient management, molecular approaches, tolerant genotypes, and associated genes/proteins. Lastly, a number of significant research prospects concerning heavy metals in rice fields were suggested for future investigation. This review serves as a crucial reference for addressing the issue of heavy metal contamination in paddy fields, ensuring the safe cultivation of rice, promoting environmentally friendly fish farming practices, and safeguarding future food security and human health.

Exogenous organic acids promoted phytoremediation by Hydrangea macrophylla in cadmium‑contaminated soil

Cadmium (Cd) contaminants with high toxicity and mobility seriously threatens the ecological environment and human safety. Hydrangea macrophylla is a potential plant for Cd-contaminated soil remediation. Exogenous organic acids have been proven to effectively enhance the phytoremediation of soil contaminated with Cd. However, research on the effects of organic acids on Cd tolerance and accumulation of H. macrophylla remains scarce. In this study, a potted experiment was performed with H. macrophylla as the research object. The effects of acetic acid (AA), citric acid (CA), and malic acid (MA) with different concentrations (2.5, 5, and 10 mmol·kg-1) on the growth physiology, Cd absorption and accumulation of H. macrophylla and soil microecological environment under Cd stress were systematically studied. Results indicated that organic acids increased chlorophyll content and promoted the growth of H. macrophylla, the biomass of shoots and roots increased by 165.44 % , 161.50 % under 5 mmol·kg-1 citric acid treatment. Furthermore, organic acids reduced the level of membrane lipid peroxidation in leaves, increased plant biomass and promoted root growth of H. macrophylla. By boosting superoxide dismutase (SOD), peroxidase (POD), and catalase activities (CAT), elevating levels of proline (Pro), non-protein thiol (NPT), glutathione (GSH) and phytochelatins (PCs), exogenous organic acids promoted the Cd tolerance of H. macrophylla. In particular, 5 mmol·kg-1 CA had the best effect on improving the Cd tolerance of H. macrophylla. The roots of H. macrophylla accumulated a large amount of Cd, ranging from 365.04 to1111.67 μg·plant-1. Appropriate concentration of organic acids increased the total Cd accumulation by 1.12-2.07 times of H. macrophylla. The translocation factor (TF) increased by 97.91 %, 107.95 % under 5 mmol·kg-1 CA and 10 mmol·kg-1 MA treatments. Nevertheless, TF values were all less than 1. We posit that using H. macrophylla and organic acids could reduce the Cd bioavailability in the soil mainly through rhizosphere immobilization and plant absorption. Additionally, organic acids increased the soil pH, accompanied by changes in soil enzyme activities. 10 mmol·kg-1AA and MA reduced the available Cd concentration by 20.42 % and 31.65 %, respectively. Overall, exogenous organic acids can assist H. macrophylla in phytoremediation. 5 mmol·kg-1 CA treatment was considered the best choice for the remediation of heavy Cd-contaminated soil by H. macrophylla.

Mycorrhizal extraradical mycelium can reduce cadmium uptake by maize and cadmium leaching from contaminated soil: based on an in-growth core experiment

Arbuscular mycorrhizal fungi (AMF) are commonly found in heavy metal-contaminated environments and form extraradical mycelium (ERM), but knowledge of their ecological functions is limited. In the present study, a soil column was filled with sterilized cadmium (Cd)-contaminated soil and contained an in-growth core for AMF-inoculated maize seedling growth. The in-growth core was static to maintain or rotated to disrupt ERM growth. Compared with the static treatment, the rotation treatment caused significant decreases in the content of glomalin-related soil protein (GRSP), the photosynthetic physiology of leaves, and maize growth, while increasing the Cd content in shoots and roots by 64 and 82%, respectively; additionally, the rotation treatment resulted in increases in the Cd concentration of the soil solution inside and outside the growth core by 30-38 and 17-52%, respectively, and Cd leaching loss by 29-39%. Moreover, the rotation treatment significantly altered the Cd forms in the soil solution and leachate, increasing the proportion of free Cd2+ by 0.8-2.1% and decreasing the proportions of CdSO4(aq) and CdOH+ by 6.1-56.1% and 26.1-48.7%, respectively. The structural equation model indicated that AMF directly and indirectly reduced maize Cd uptake and Cd leaching loss by decreasing Cd availability in the soil and soil solution through the GRSP secreted by ERM. Thus, AMF plays a crucial role in inhibiting Cd migration in soil through mycelial exudates.

Two strains of cadmium (Cd)-resistant bacteria isolated from soils and their ability to promote oilseed rape (Brassica juncea L.) to grow and absorb Cd in soils

As a highly toxic, mobile, and persistent heavy metal, cadmium (Cd) in soils is becoming a crucial environmental problem. Most of classical physical and chemical remediation measures for Cd-contaminated soils possibly cause some dangers to soil structure and characteristics and potential secondary pollution, however, Cd-resistant microbial which can sequestrate Cd by releasing extracellular polymeric substances (EPS) capable of ion exchange, coordination, and adsorption and improve plant growth should be favorable for remediation of Cd-contaminated soils due to being environmentally friendly and cost-effective. Therefore, the plant-microbe combination is becoming a priority option in the remediation of Cd-contaminated soils. Here, we isolated two strains of Cd-resistant bacteria from soils and investigated the ability of the two strains to promote growth of oilseed rape (Brassica juncea L.) and Cd uptake by the plants. Citrobacter farmeri and Cupriavidus gilardii were isolated from soils via culture media containing 30 and 50 mg/L Cd, respectively, which could release EPS including proteins, polysaccharide, and DNA. The EPS from C. gilardii was significantly higher than that from C. farmeri, and the proportion of protein in EPS was the highest for two strains. Additionally, two strains secreted indole-3-acetic acid (IAA) and could solubilize phosphorus, and the ability of C. gilardii to secret IAA was significantly higher than that of C. farmeri. The pot experiment indicated that C. farmeri and C. gilardii significantly enhanced oilseed rape biomass (by 81.99% and 76.57%, respectively), C and N contents, Cd accumulation in plants by 229.03% and 264.63%, respectively, and remediation efficiency at 40 days after emergence (flowering stage). However, the difference in promoting plant growth and Cd uptake and phytoremediation efficiency of Cd-contaminated soils between the two strains was not significant. Overall, C. farmeri and C. gilardii isolated from soils might be promising strains in enhancing phytoremediation of Cd-contaminated soils.

Analysis of the phytoremediation potential, rice safety, and economic benefits of light to moderate Cd-contaminated farmland in oilseed rape-rice rotation with straw removal: A three-year field trial

Under the dual pressures of food security and soil cadmium (Cd) pollution in China, the use of an oilseed rape-rice rotation system and phytoremediation has been proposed as an effective measure to extract heavy metals from soil, achieve safe rice production, and alleviate soil heavy metal stress. A three-year field rotation experiment by straw removal was conducted in light to moderate Cd-contaminated soil in Hunan, China. The experiment involved rotating two oilseed rape varieties, LSYH and ZYZ, with two rice varieties, the low-accumulation variety XWX and the high-accumulation variety TYHZ. The structural equation model (SEM) indicated that the correlation coefficients of total nitrogen (N) and available phosphorus (P) with CaCl2-Cd in the soil under oilseed rape-rice rotation were higher than those in rice monoculture, indicating that changes in soil nutrients have a significant impact on CaCl2-Cd during rotation. During continuous rice monoculture, the Cd content in brown rice exceeded safety standards in all three years. Crop rotation effectively reduced the Cd content in the aboveground parts of rice, particularly inhibiting its transfer to brown rice. By the second year of rotation, the minimum Cd content in brown rice from XWX and TYHZ was only 0.10 and 0.11 mg kg⁻1, respectively. Cd levels in rice met the safety standard (<0.2 mg kg⁻1). Although the Cd content in the third-year rice was higher than in the second year, it remained significantly lower than in the first year. The TPE in the aerial portion for the ZYZ-XWX rotation was 4.88%, while for the rotation of ZYZ-TYHZ rotation, it was 6.37%. Economic benefits were enhanced by this rotation mode, with profit-to-cost ratios exceeded 1. Overall, oilseed rape-rice rotation is an economical and environmentally friendly method for remediating soil Cd contamination, but it requires selecting the appropriate varieties.

Overexpression of ZmSKD1 improves cadmium tolerance through the vesicle trafficking pathway in tobacco

Cadmium (Cd) is a major soil pollutant that threatens plant growth and human health. The plant ATPase associated with various cellular activities (AAA) SKD1 utilizes ATP hydrolysis energy to mediate cellular responses to environmental stress. However, the role and regulatory mechanisms of SKD1 in plant responses to Cd stress are not well understood. This study has demonstrated that the maize SKD1 gene (ZmSKD1) enhanced tobacco's tolerance to Cd stress. Overexpression of ZmSKD1 in tobacco reduced Cd accumulation and improved Cd tolerance. Moreover, ZmSKD1 overexpression enhanced the antioxidant capacity of tobacco, maintaining reactive oxygen species homeostasis and mitigating oxidative damage under Cd stress. The transcription factor AGL8 directly activated ZmSKD1 transcription, which in turn boosted ATPase activity in tobacco. This activation enhanced vesicle trafficking in root cells and accelerated Cd excretion in transgenic tobacco plants. Concurrently, the AGL8-ZmSKD1 module inhibited the expression of several Cd transport-related genes, thereby reducing Cd uptake by tobacco roots. These findings identified the AGL8-ZmSKD1 module as a crucial player in managing Cd stress through the vesicle trafficking pathway, offering valuable insights into strategies for developing crops with reduced Cd accumulation to ensure global food security and human health.

Interactive effects of rhizospheric soil microbes and litter on the growth of the invasive hyperaccumulator Bidens pilosa in cadmium-contaminated soil

Both rhizospheric soil microbes and shoot litter input can have profound effects on plant performance; however, their interactive effects on plants in Cd-contaminated soils remain poorly understood. We grew an invasive hyperaccumulator, Bidens pilosa, in sterilized and unsterilized rhizosphere soil without litter or with a low (0.2%, dry weight ratio) or a high amount (1%) of litter from B. pilosa in soil with low (5 mg kg-1) or high (10 mg kg-1) concentrations of Cd. The total, shoot, and root biomass of B. pilosa increased significantly with litter addition, by an average of 27%, 28%, and 20%, respectively. The biomass of B. pilosa was significantly lower in unsterilized rhizosphere soil than in sterilized rhizosphere soil, decreasing by 19% for total, 18% for shoot, and 24% for root, respectively. Furthermore, the effects of different litter amounts (0.2% vs. 1%) on biomass did not vary in sterilized rhizosphere soils but significantly varied in unsterilized rhizosphere soils, showing that the biomass was significantly lower with 1% litter addition than with 0.2% litter addition in unsterilized rhizosphere soils, decreasing by 28% for total, 29% for shoot, and 21% for root, respectively. Tissue Cd concentrations were significantly higher in highly Cd-contaminated soils (+75% for shoot and +51% for root) than in low Cd-contaminated soils; however, higher tissue Cd concentrations did not cause a significant decrease in the biomass of B. pilosa. Soil fungal communities, particularly the dominant phyla, Ascomycota and Basidiomycota, play crucial roles in modulating the effects of rhizosphere soil microbes and litter on the growth of B. pilosa. Our results suggest that rhizosphere soil microbes and litter interact and affect the growth of B. pilosa: litter addition promoted growth by increasing the abundance of saprotrophs (especially Basidiomycota) and decreasing Cd accumulation in plant tissues, and rhizosphere soil inhibition was associated with a decreased abundance of Basidiomycota. Our findings highlight the importance of the interactive effects of rhizospheric soil microbes and litter on plant growth in Cd-contaminated soils.

Removal of Lead, Cadmium, and Mercury in Monometallic and Trimetallic Aqueous Systems Using Chenopodium album L

The presence of heavy metals in water represents a risk to the life of all species on the planet. Phytoremediation is an effective alternative to remove heavy metals from contaminated aqueous environments. In the present research, Chenopodium album L. was examined for the remediation of waters contaminated with Cd, Pb, and Hg. Studies were carried out in waters containing each metal separately (monometallic aqueous systems) and in mixtures (trimetallic aqueous systems). First, the adaptation of Chenopodium album to different concentrations of Hoagland's nutrient solution (HNS) was evaluated, then, a phytotoxicity study was carried out to determine the appropriate concentrations of each metal to test the tolerance of the plant during the accumulation study, and finally, the bioaccumulation capacity of Chenopodium album for Cd, Pb, and Hg was evaluated. Chenopodium album showed tolerance to levels of 5 mg/L Hg and 10 mg/L Cd and Pb in 25% HNS. The bioaccumulation tests showed that Chenopodium album can remediate Cd, Pb, and Hg contaminated waters in both monometallic and trimetallic aqueous systems. These findings suggest important future applications in the food industry for the production of Chenopodium album as we demonstrate that this species adapts and grows in hydroponic media. In particular, the ability of Chenopodium album to adapt to extreme conditions could be exploited for further studies on phytoremediation of heavy metals in river water, irrigation water, wastewater, effluents, and mine tailings.

Ammonium mitigates cadmium toxicity by activating the bZIP20-APX2/CATA transcriptional module in rice seedlings in an ABA-dependent manner

The amelioration of cadmium (Cd2+) toxicity in plants by ammonium (NH4+) has been widely investigated. However, the molecular mechanisms underpinning this amelioration have remained ambiguous. Here, we found that NH4+ significantly reduces Cd2+ accumulation and enhances antioxidant capacity by increasing ABA accumulation, which, in turn, improves Cd2+ tolerance in rice seedlings. A combination of qPCR, yeast-one-hybrid and dual-luciferase assays, and CUT&RUN-qPCR methods demonstrates that OsbZIP20 directly binds to the promoters of OsAPX2 and OsCATA, activating their transcription, and we show that the process requires phosphorylation modification of OsbZIP20 by OsSAPK9. Under Cd2+ stress, Osbzip20 and Ossapk9 mutants show reduced peroxidase and catalase activities, higher H2O2 accumulation, and reduced Cd2+ tolerance. In sum, our results elucidate a novel mechanism by which NH4+ enhances Cd2+ resistance, through ABA-SAPK9-bZIP20-APX2/CATA, offering a new strategy for improving Cd2+ resistance in rice.

Green synthesized silicon dioxide nanoparticles (SiO2NPs) ameliorated the cadmium toxicity in melon by regulating antioxidant enzymes activity and stress-related genes expression

Green synthesized nanoparticles (NPs) are an eco-friendly and cost-effective approach to reduce heavy metal stress in plants. Among heavy metals, cadmium (Cd) possesses higher toxicity to the crops and ultimately reduces their growth and yield. The current study aims to evaluate the effectiveness of green synthesized SiO2NPs to reduce toxic effects of Cd in melon (Cucumis melo) by regulating physiological parameters, enhancing antioxidant enzyme activity, and modulating stress-related gene expression. The SiO2NPs were synthesized using Artemisia annua plant extract having spherical shape and size within the range of 40-70 nm and characterized using advanced spectroscopic and analytical techniques. The application of SiO2NPs (75 mg/L) significantly improved physiological parameters such as shoot length (SL), root length (RL), leaf fresh weight (LFW), root fresh weight (RFW), leaf dry weight (LDW) and root dry weight (RDW) by 14%, 20%, 15%, 16%, 14%, and 28%, respectively, compared to Cd-stressed plants. Photosynthetic pigments (chlorophyll and carotenoids) showed a notable increase of 15% and 40%, respectively. Furthermore, the activities of antioxidant enzymes such as SOD, POD, CAT, and APX were enhanced by 28.67%, 35.45%, 32.07%, and 42.75%, respectively. In addition, applying SiO2NPs increased the concentration of macronutrients N, P, and K by 33%, 40%, and 37%, respectively, compared to Cd-stressed plants. Moreover, SiO2NPs upregulated the expression of several stress-related genes and reduced Cd accumulation in shoots and roots. This study reveals that green synthesized SiO2NPs effectively reduced the Cd toxicity in melon by improving morphological and physiological parameters, enhancing antioxidant enzyme activity, and regulating the expression of stress-related genes. These findings suggest that green synthesized SiO2NPs could play a crucial role in sustainable agriculture by protecting crops from heavy metal stress.

Manganese enhances cadmium tolerance in barley through mediating chloroplast integrity, antioxidant system, and HvNRAMP expression

Cadmium (Cd) is a toxic heavy metal that poses risks to crop production and food safety worldwide. This study evaluated whether manganese (Mn) addition could mitigate Cd toxicity and reduce Cd accumulation in barley seedlings. Hydroponically grown seedlings of Cd-tolerant (WSBZ) and Cd-sensitive (Dong17) barley cultivars were treated with 0.1 μM and 1 μM Cd as well as 0.2 mM Mn alone and in a combination with 0.1 or 1.0 μM Cd for 21 days. Cd exposure caused the dramatic alteration of growth and physiological parameters by disrupting chloroplast, and increased Cd accumulation in both genotypes. However, Mn addition markedly alleviated the negative impacts of all examined parameters caused by Cd stress. Cd addition enhanced expression of anti-oxidative enzyme related genes, including HvSOD, HvCAT, HvAPX, HvPOD in the two barley genotypes exposed to Cd stress. The expression analysis showed nearly all HvNRAMPs genes are dramatically up regulated by both Mn and Cd, with WSBZ having higher expression than Dong 17. Notably, HvNRAMP1 showed the highest expression due to Mn addition, highlighting its crucial role in Mn uptake and transportation in barley. Moreover, Cd stress and Mn addition increased and suppressed the expression of HvYSL5, HvHMA2 and HvHMA3, respectively. Conversely, the expression of HvYSL2, HvIRT1 and HvMTP8 was upregulated by both Mn and Cd treatments, with a further increase observed in the combined Cd and Mn treatments. It may be concluded that sufficient Mn supply is quite important for reducing Cd uptake and accumulation in plants.

SpbZIP60 confers cadmium tolerance by strengthening the root cell wall compartmentalization in Sedum plumbizincicola

Cadmium (Cd) is a prominent heavy metal pollutant that inhibits plant growth and poses risks to human health. Sedum plumbizincicola, as a Cd/Zn/Pb hyperaccumulator species, exhibits robust resistance to heavy metals and effective enrichment capacities. In our previous study, overexpressing SpbZIP60 in Arabidopsis enhanced Cd tolerance; however, the underlying the molecular mechanism remains to be elucidated. Here, we identified SpbZIP60 as a representative Cd stress response factor with nuclear localization and transcriptional activation activity. SpbZIP60 underwent conservative splicing in response to endoplasmic reticulum (ER) stress, while its response to Cd stress is independent of the ER stress-mediated unfolded protein response pathway. Overexpression of SpbZIP60 in S. alfredii increased the Cd tolerance and antioxidant activity. Furthermore, SpbZIP60 increased the content of cell wall components and thickened cell wall under Cd stress. Transcriptome analysis indicated a significant enrichment of differentially expressed genes within the phenylpropanoid metabolism pathway. Besides, the binding of SpbZIP60 to the promoter region of SpBglu resulted in the activation of gene expression, thereby enhancing the process of lignin deposition. Collectively, our results elucidated a molecular regulatory model in which SpbZIP60 increased the thickness of the root cell wall to impede Cd entry into the cell, consequently improving Cd tolerance.

Synergistic promotion mechanism and structure-function relationship of nonmetallic atoms doped carbon nanodots driving Tagetes patula L. to remediate cadmium-contaminated soils

Phytoremediation is an economical and effective strategy to remove cadmium (Cd) from polluted environments. To improve its efficiency, nanotechnology has been proposed to collaborate with hyperaccumulators in the remediation of Cd-polluted soils. However, the intricate structure-function relationship and the underlying regulatory mechanisms by which nanomaterials regulate Cd migration and conversion within the soil-plant system remained unrevealed. In this study, functional carbon nanodots (FCNs) were modified by doping with nitrogen and (or) sulfur elements. The synthesized nonmetallic atoms-doped FCNs were utilized to investigate their structure-function relationship and the regulatory mechanisms underlying their role in the phytoremediation of Cd-polluted soils by Tagetes patula L. FCNs-based nanomaterials can regulate the migration and bioaccumulation of Cd in the soil-plant system, which exhibits an obvious structural dependency. Specifically, the synergistic application of sulfur doped FCNs and Tagetes patula L. had the highest Cd removal efficiency of 53.2 %, which was 20.1 % higher than Tagetes patula L. alone. The uptake and migration of Cd in the soil-plant system are regulated by FCNs-based nanomaterials through both direct and indirect mechanisms, involving interfacial reactions, plant physiology regulation and environmental influence. This study not only sheds light on the fate of FCNs-based nanomaterials and Cd in the soil-plant system, but also provides innovative nanotools for reinforcing phytoremediation efficiency in contaminated soils.

Mapping soil cadmium content using multi-spectral satellite images and multiple-residual-stacking model: Incorporating information from homologous pollution and spectrally active materials

Soil cadmium (Cd) contamination significantly threatens ecosystems and human health. Traditional geochemical investigation, although accurate, is impractical for wide-area and frequent monitoring applications. Multi-spectral satellite images combined with the homologous pollution information (HPI) and the spectral and content information of soil organic matter (SOMSCI) is an unconventional and promising approach for large-scale, dynamic soil heavy metal (SHM) monitoring. Based on a novel Multiple-Residual-Stacked (MRS) machine-learning framework, the study estimated the soil Cd content in Yueyang City, China, during the past decade (2014-2023) using Landsat 8 images. Within it, three feature construction methods and four models were employed. The experimental results indicate that the XGB-MRS model incorporating HPI and SOMSCI significantly improved the estimation performance (RPD exceeded 90 %, R2, RMSE, and MAE exceeded 40 %). Moreover, against 243 ground samples during 2016-2022, the average overall estimation accuracy exceeded 80 %, validating the model's robustness and practicality. Furthermore, the descending order of contribution in the modelling is environmental auxiliary variables (55 %), HPI and SOMSCI (26 %), and spectral information (19 %). The fertilizer usage has direct (up to 2 years) and delayed (3-5 years) effects on soil Cd accumulation. Overall, our study provides a scalable framework for monitoring global SHM pollution using open-source multi-spectral satellite data.

Vermicompost application improves leaf physiological activity, 2-acetyl-1-pyrroline, and grain yield of fragrant rice through efficient nitrogen assimilation under Cd stress

Cadmium (Cd) pollution in arable soils and its accumulation in rice plants have become a global concern because of their harmful effects on crop yield and human health. The in-situ stabilization method which involves the application of organic amendments such as vermicompost (VC), is frequently utilized for the remediation of Cd-contaminated soils. This study investigated the effects of VC on the soil chemical properties and the physio-biochemical functions of fragrant rice, as well as nitrogen (N) metabolism and assimilatory enzyme activities, 2-acetyl-1-pyrroline (2AP) content in rice grains, and the grain yields of fragrant rice cultivars, i.e., Xiangyaxiangzhan (XGZ) and.Meixiangzhan-2 (MXZ-2) under Cd stress condition. Four doses of VC (.VC1 = 0, VC2 = 3 t. ha-1, VC3 = 4 t ha-1, and VC4 = 6 t ha-1) and two levels of Cd (0 and 25 mg Cd kg-1) were used in this study. Our results showed that VC supplementation significantly (p < 0.05) improved soil characteristics, including soil organic carbon, available N, total N, phosphorus (P), and potassium (K). Furthermore, VC enhanced plant physiological and biochemical attributes in fragrant rice, such as net photosynthetic rate (Pn), nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS), glutamate oxoglutarate aminotransferase (GOGAT) enzyme activities, protein contents, amino acid, and 2-acetyl-1-pyrroline (2AP) contents under Cd stress condition. Specifically, the VC-amended treatment, Cd2 + VC3, led to an 86.75% increase in Pn and 2AP, and a 60.05% and 77.55% increase in grain yield for MXZ-2 and XGZ cultivars, respectively, compared to Cd-only treated plants (Cd2 + VC1). In addition, VC application significantly (p < 0.05) decreased the Cd uptake and accumulation in rice plants. The correlation analysis indicated that leaf physiological activity and biochemical traits are strongly correlated with soil qualitative traits, suggesting that improved soil health leads to enhanced leaf physiological activity, N metabolism, grain 2AP content, and grain yields. Among the treatments, Cd2 + VC3 showed the best performance in terms of soil fertility and rice quality and production. Consequently, our study indicates that using VC in soils may benefit rice growers by improving soil fertility and supporting sustainable rice productivity and quality in soils contaminated with Cd.

Root acid phosphatases and microbial biomass phosphorus induced Cd tolerance and P acquisition in wheat inoculated with P solubilizing bacteria

Microbial bioremediation has emerged promisingly to improve crop tolerance to cadmium (Cd). Moreover, Cd tolerance and phosphate acquisition in plants positively correlated under P solubilizing bacteria inoculation, yet there is no evidence on specific mechanisms influencing Cd tolerance and plant P acquisition. The present study evaluates Cd tolerance in rock P-amended durum wheat in response to inoculation with P solubilizing bacteria (PSB) [three individual isolates Bacillus siamensis, Rahnella aceris, Bacillus cereus and their consortium (PSBCs)] and consequently reveals key rhizosphere mechanisms involved in both Cd tolerance and P use efficiency. Results show that inoculation overall improved plant growth, rhizosphere parameters and nutrient uptake (P, N, K) under increasing Cd concentrations [8 (Cd8) and 16 (Cd16) ppm Cd2+]. Under Cd16, Rahnella aceris induced the most significant plant responses in terms of biomass [shoots (31 %), roots (40 %), and spikes (92 %)], rhizosphere available P (234 %) and root inorganic P (109 %) compared to uninoculated plant. Microbial biomass P (MBP) and root acid phosphatases (APase) were 33-and 13-times higher, respectively, than in uninoculated plants. In addition, inoculation (particularly using PSBCs) significantly decreased Cd translocation factor (TF) (Cd8: -17 % and Cd16: -22 %) and Cd bioaccumulation factor (BAF) (Cd8: -6 % and Cd16: -40 %) concomitantly to enhanced root morphological traits and P contents in shoots and spikes. Furthermore, PSB inoculation under Cd constraint increased (rhizosphere available P / MBP) and (Root APase / Rhizosphere Apase) ratios that significantly (p < 0.05) correlate with plant P uptake in shoots and spikes. Increase in both ratios was concomitant to a significant decrease in TF and BAF of Cd exemplified by negatively significant correlations (r2=0.70 and r2=0.57, p < 0.05). This finding elucidates the key role of bacterial inoculation that presumably triggered Cd tolerance and aboveground P owing to increased (rhizosphere available P / MBP) and (Root / Rhizosphere APase) ratios in PSB-inoculated wheat.

Quantitative assessment of Cd sources in rice grains through Cd isotopes and MixSIAR model in a typical e-waste dismantling area of Southeast China

Identification of Cd sources and quantification of their contribution to rice grain Cd is crucial for controlling accumulation of this toxic metal in rice grains. However, accurate assessment of the contribution of different Cd sources to grain Cd concentration in rice under actual field conditions is a challenge. In this study, we determined Cd concentration and their isotopic compositions in rice grains with respect to three potential Cd sources around an e-waste dismantling area in Taizhou City, Zhejiang Province, China. Results demonstrated that average Cd concentrations in grains, surface soils, atmospheric deposition and surface water were 0.32, 0.91, 1.99 mg kg-1 and 2.02 μg L-1, respectively. The δ114/110Cd values of grains, surface soils, surface water and atmospheric deposition ranged from 0.00 ‰ to 0.31 ‰, -0.21 ‰ to 0.14 ‰, -0.04 ‰ to 0.47 ‰, and - 0.25 ‰ to -0.18 ‰, respectively. The MixSIAR model indicated that contribution of soils, irrigation water and atmospheric deposition to grain Cd was 56.8 %, 24.8 % and 18.4 %, respectively, demonstrating soils as the major source of grain Cd in the study area. This study also highlighted significant contribution of irrigation water and atmospheric deposition to Cd concentration in rice grains. The Cd isotopic analysis provides a practical approach for source apportionment of grain Cd and data support for controlling Cd accumulation in rice around the e-waste dismantling area.

Cadmium absorption and translocation in rice plants are influenced by lower air temperatures during grain filling stage

The increasing frequency and severity of low temperatures, and soil cadmium (Cd) pollution threaten food security. However, the interactive effects of Cd exposure and low temperatures on rice yield and quality, as well as the mechanisms of Cd absorption and translocation, remain unclear. In this study, two rice varieties were cultivated in soils with two Cd contamination levels (Cdhigh and Cdlow) and exposed to control (CT25) or lower temperatures of 20 °C (LT20) and 17 °C (LT17) during grain-filling stage. Results showed significant decreases in seed setting rate and grain weight, reduced head rice yield, and increased chalkiness due to low temperatures, particularly in Cdhigh soils. Compared to CT25, LT17 and LT20 increased Cd concentration by 37.6 % and accumulation by 14.8 % in grains grown in Cdhigh soils. Enhanced root activity and upregulation of OsNramp1 and OsNramp5 under both low-temperatures increased Cd levels in roots. Lower temperatures also decreased phytochelatins (PCs) and increased expression of OsHMA2 and OsCAL1, facilitating Cd transport and raising Cd levels in stems. Furthermore, upregulated OsHMA2, OsLCT1, and OsZIP7 in stems under low-temperatures promoted Cd transport to panicles. Overall, low temperatures during grain filling increased Cd uptake and translocation into rice grains, especially in high Cd contaminated soils, raising health risks. The study highlights the need to address climate change's impact on cadmium hazards in rice.

Nitric oxide and ascorbic acid confer cadmium (Cd) tolerance by improving plant terpenoid metabolism and epigenetically modifying DNA methylation

This study investigated the efficacy of incorporating nitric oxide (NO; 10 μM) and ascorbic acid (Asc; 10 μM) into the culture medium to confer cadmium (Cd; 5 μM) tolerance in thyme (Zataria multiflora). The phytotoxicity of Cd resulted in a decrease in shoot biomass, which NO or Asc mitigated. Adding Asc and NO to the culture medium was associated with substantial DNA hypomethylation. The NO + Cd and Asc + Cd treatments were accompanied by an increase in the unmethylation percentages, about 3-fold higher than the control. The hemi-methylation percentages in the Asc-supplemented seedlings also displayed an upward trend. The transcriptional upregulation in the γ-terpinene synthase (TPS) gene resulted from the applied elicitors, especially NO. In response to the NO and Asc treatments, the transcription of two cytochrome P450 monooxygenase genes (CYP71D178 and CYP71D180) went up. Incorporating Asc or NO into the culture medium enhanced the concentrations of proline, carvacrol, and thymol metabolites. Employing NO or Asc mitigated the 43% decrease in protein content due to the Cd cytotoxicity. The NO and Asc applications improved the activity of the phenylalanine ammonia-lyase (PAL) enzyme. NO and Asc utilization increased the accumulation of flavonoids. NO and Asc also up-regulated the activities of two enzymatic antioxidants (catalase and peroxidase). Collectively, this study provided novel insight into how Asc or NO confers Cd tolerance by epigenetically remodeling DNA methylation, transcriptionally up-regulating terpenoid and phenylpropanoid metabolism, increasing proline concentration, and improving antioxidants.

From stress to resilience: Unraveling the molecular mechanisms of cadmium toxicity, detoxification and tolerance in plants

Soil contamination with cadmium (Cd) has become a global issue due to increasing human activities. Cd contamination poses threats to plant growth as well as jeopardizing food safety and human health through the accumulation of Cd in edible parts of plants. Unraveling the Cd toxicity mechanisms and responses of plants to Cd stress is critical for promoting plant growth and ensuring food safety in Cd-contaminated soils. Toxicological research on plant responses to heavy metal stress has extensively studied Cd, as it can disrupt multiple physiological processes. In addition to morpho-anatomical, hormonal, and biochemical responses, plants rapidly initiate transcriptional modifications to combat Cd stress-induced oxidative and genotoxic damage. Various families of transcription factors play crucial roles in triggering such responses. Moreover, epigenetic modifications have been identified as essential players in maintaining plant genome stability under genotoxic stress. Plants have developed several detoxification strategies to mitigate Cd-induced toxicity, such as cell-wall binding, complexation, vacuolar sequestration, efflux, and translocation. This review provides a comprehensive update on understanding of molecular mechanisms involved in Cd uptake, transportation, and detoxification, with a particular emphasis on the signaling pathways that involve transcriptional and epigenetic responses in plants. This review highlights the innovative strategies for enhancing Cd tolerance and explores their potential application in various crops. Furthermore, this review offers strategies for increasing Cd tolerance and limiting Cd bioavailability in edible parts of plants, thereby improving the safety of food crops.

Arbuscular Mycorrhizal Fungi-Assisted Phytoremediation: A Promising Strategy for Cadmium-Contaminated Soils

Arbuscular mycorrhizal fungi (AMF) have been shown to play a major role in regulating the accumulation, transport, and toxicity of cadmium (Cd) in plant tissues. This review aims to highlight the current understanding of the mechanisms by which AMF alleviate Cd toxicity in plants. Cd accumulation in agricultural soils has become an increasing global concern due to industrial activities and the use of phosphatic fertilizers. Cd toxicity disrupts various physiological processes in plants, adversely affecting growth, photosynthesis, oxidative stress responses, and secondary metabolism. AMF alleviate Cd stress in plants through multiple mechanisms, including reduced Cd transport into plant roots, improved plant nutritional status, modulation of organic acid and protein exudation, enhanced antioxidant capacity, and maintenance of ion homeostasis. AMF colonization also influences Cd speciation, bioavailability, and compartmentalization within plant tissues. The expression of metal transporter genes, as well as the synthesis of phytochelatins and metallothioneins, are modulated by AMF during Cd stress. However, the efficacy of AMF in mitigating Cd toxicity depends on several factors, such as soil properties, plant species, AMF taxa, and experimental duration. Further knowledge of the intricate plant-AMF-Cd interactions is crucial for optimizing AMF-assisted phytoremediation strategies and developing Cd-tolerant and high-yielding crop varieties for cultivation in contaminated soils.

Landfill leachate: An invisible threat to soil quality of temperate Himalayas

Landfills are the most affordable and popular method for managing waste in many parts of the world, However, in most developing nations, including India, the infiltration of hazardous materials from improperly managed dumping site continues to be a significant environmental problem. Around the world, leachate is a significant point source of contamination in numerous environmental media, including soil, groundwater, and surface water. Soil is an important asset as it is the key factor for food production and has tremendous significance in achieving sustainable development goals (SDGs). The contaminants from soil enter into food chain and ultimately reach humans. So in order to prevent the adverse effects of toxic elements on humans, there is need to maintain the soil quality and to prevent deterioration. Keeping in view the consequences of unscientific management of waste, the goal of the experiment was to determine how landfill leachate from Achan landfill affected the soil quality in the temperate Himalayas. All four seasons of the year, viz Spring, Summer, Autumn, and Winter, at four sites viz, Center of dumping site, inside, Outside and Control were monitored. Among sites center was found to have maximum value of EC (3.04 dS/m), Moisture content (42.51%), N (285.43 mg/kg), P (70.07 mg/kg), K (265.71 mg/kg), Ca (957.67 mg/kg), Mg(402.42 mg/kg), Zn (2.02 mg/kg), Fe (10.56 mg/kg), Cu (2.07 mg/kg), Mn (10.73 mg/kg), Pb (85.02 mg/kg), Cd (4.50 mg/kg), Ni (29.04 mg/kg), Cr (23.37 mg/kg), As (14.10 mg/kg). While as the lowest value of all parameters was reported at control site. From the study it is recommended that the waste generated is mostly organic (65-75%), thus can be segregated and treated at source. The waste can be treated at source using microbial consortium technology in order to transform the waste in to wealth in a sustainable way and to prevent the deterioration of soil quality.

Addressing cadmium stress in rice with potassium-enriched biochar and Bacillus altitudinis rhizobacteria

Cadmium (Cd) is a potentially harmful metal with significant biological toxicity that adversely affects plant growth and physiological metabolism. Excessive Cd exposure in plants leads to stunted plant growth owing to its negative impact on physiological functions such as photosynthesis, nutrient uptake, and water balance. Potassium-enriched biochar (KBC) and Bacillus altitudinis rhizobacteria (RB) can effectively overcome this problem. Potassium-enriched biochar (KBC) significantly enhances plant growth by improving the soil structure, encouraging water retention, and enhancing microbial activity as a slow-release nutrient. Rhizobacteria promote plant growth by improving root ion transport and nutrient availability while promoting soil health and water conservation through RB production. This study examined the effects of combining RB + KBC as an amendment to rice, both with and without Cd stress. Four treatments (control, KBC, RB, and RB + KBC) were applied using a completely randomized design (CRD) in four replications. The results showed that the combination of RB + KBC increased rice plant height (38.40%), shoot length (53.90%), and root length (12.49%) above the control under Cd stress. Additionally, there were notable improvements in chlorophyll a (15.31%), chlorophyll b (25.01%), and total chlorophyll (19.37%) compared to the control under Cd stress, which also showed the potential of RB + KBC treatment. Moreover, increased N, P, and K concentrations in the roots and shoots confirmed that RB + KBC could improve rice plant growth under Cd stress. Consequently, these findings suggest that RB + KBC is an effective amendment to alleviate Cd stress in rice. Farmers should use RB + KBC to achieve better rice growth under cadmium stress.

Co-application of cadmium-immobilizing bacteria and organic fertilizers alter the wheat root soil chemistry and microbial communities

Cadmium contamination poses a significant risk to soil ecosystems in certain parts of the world. Using eco-friendly fertilizers alongside beneficial microorganisms offers a viable solution to mitigate Cd pollution in agricultural soil. This study used an outdoor experiment to evaluate the impact of administering a Cd-immobilizing bacterial (Bacillus) inoculant with two biologically-enriched organic fertilizers (either fermentative edible fungi residue or fermented cow dung) on wheat plants and associated microbial populations in a field contaminated with Cd. The mixed application of fermentative cow dung with the Cd-immobilizing bacterium reduced the effective Cd content of wheat root-soil by 13,0 %. Application of Cd-immobilizing Bacillus inoculant reduced the Cd enrichment of wheat roots by 0.07 mg/kg. Co-application of fermentative cow dung with the bacterial inoculant reduced the Cd enrichment of wheat seeds by 20,0 %. Co-application of the two organic fertilizers could improve some of the nutrients related to wheat and soil fertility; however, the diversity of the soil microbial community changed less and its species richness decreased. Applying the Bacillus inoculant inhibited the growth of native pathogenic bacteria, such as Proteobacteria. Whether administering it with either fermented cow manure or fermented edible fungus residue, the relative abundance of nitrate-reducing bacteria such as Rhodobacter increased, which should promote the soil nitrogen cycle. The main factors influencing soil microbial community structure of wheat plants were pH, available potassium, and available Cd content. Symbiotic network analysis revealed bacterial inoculant and organic fertilizer inoculum further altering the ecological relationships of microbial communities. According to the FAPROTAX functional prediction, Rhodanobacter may play a key role in nitrate respiration in the soil nitrogen cycle. In conclusion, this study provides a comprehensive, timely reference for understanding microbial changes caused by the combined application of this type of bacterial inoculant and organic soil amendments in Cd-contaminated fields.

Determination of Elemental Content in Vineyard Soil, Leaves, and Grapes of Sangiovese Grapes from the Chianti Region Using ICP-MS for Geographical Identification

To fight counterfeits and to protect the consumer, the interest in certifying the origin of agricultural goods has been steadily growing in the last years. While numerous works focus on the finished product, an aspect often overlooked is the origin of the raw materials and the direct correlation between chemicals in the soil and the plants. With inductively coupled plasma mass spectrometry (ICP-MS) analysis, trace and ultratrace elements in Sangiovese grapes (the main component of Chianti wine) were measured and their levels were used to investigate the geographical origin of the samples. This was achieved despite the extreme closeness of some of the vineyard partners of this study (10-20 km range) by computing a multivariate model using selected elements as levels. The model was then validated on samples coming from different zones of the Chianti area, with good results for discriminating even extremely close regions.

Efficacy of soil drench and foliar application of iron nanoparticles on the growth and physiology of Solanum lycopersicum L. exposed to cadmium stress

Cadmium (Cd) can harm the yield and quality of vegetables, threatening food safety. Essential microelements such as iron are crucial for plant growth and can help alleviate heavy metal stress. Recently, nanoparticles have been studied as eco-friendly solutions for mitigating heavy metal stress in plants. In the present study, iron nanoparticles (FeNPs) at 0, 100, and 300 mg/L were applied as soil drenches and foliar sprays to tomato plants under cadmium stress. A comparison was made between the application methods of FeNPs by evaluating the growth parameters of tomato plants, including shoot length (SL), root length (RL), number of branches (NB), number of leaves per plant (NL), and leaf area (LA), as well as by assessing biochemical and antioxidant enzyme parameters. In the Cd stress treatment, the protein content decreased by 24.71%, and the phenolic and flavonoid content of the tomato plants also decreased due to cadmium stress, with levels decreasing from 16.07 to 6.9 µg and from 0.36 to 0.16 µg, respectively. Compared with the soil drench, 100 mg/L FeNPs significantly improved the parameters of Cd-stressed plants when used as a foliar spray, leading to increases in shoot length, root length, fruit weight, number of fruits, number of leaves, and number of branches by 42%, 66%, 24%, 66%, 173%, and 45%, respectively. Tomato plants treated with this spray presented increased carotenoid and lycopene contents. FeNP foliar spray also reduced Cd accumulation in plant tissues. This technique shows promise in alleviating Cd stress in vulnerable vegetable plants such as tomatoes.

Investigating the synergistic effects of nano-zinc and biochar in mitigating aluminum toxicity in soybeans

Aluminum (Al) toxicity limited root growth by reducing nutrient translocation and promoting reactive oxygen species (ROS) accumulation, particularly in soybean. The endophyte of root could be modified by plant metabolites, which could potentially alter the tolerance to environmental toxicity of plants in acidic-Al soils. To explore how they help soybean mitigate Al toxicity by altering root endophytes, zinc oxide nanoparticles (ZnO NPs) at doses of 0, 30, 60, 90 mg/kg and 2% biochar (BC) were selected as bio modifiers, and Al2(SO4)3 at 19 mg/kg was used to simulate Al toxicity. We analyzed root endophytes and metabolites by high-throughput sequencing and gas chromatography-mass spectrometry (GC-MS). We found that ZnO NPs with BC could bolster soybean resilience against Al toxicity by enriching soil nutrients, activating enzymes, and bolstering antioxidant mechanisms. We also observed that it enriched root endophytic microbial diversity, notably increasing populations of Nakamurella, Aureimonas, Luteimonas, and Sphingomonas. These changes in the endophytes contributed to the improved adaptability of plants to adversity under Al toxicity. This study highlighted the potential of using ZnO NPs and BC as a sustainable approach to combat Al toxicity, emphasizing the intricate interplay between plant physiology and rhizosphere microbial dynamics in mitigating the effects of environmental toxicity.

The MYC2 and MYB43 transcription factors cooperate to repress HMA2 and HMA4 expression, altering cadmium tolerance in Arabidopsis thaliana

Cadmium (Cd) represents a hazardous heavy metal, prevalent in agricultural soil due to industrial and agricultural expansion. Its propensity for being absorbed by edible plants, even at minimal concentrations, and subsequently transferred along the food chain poses significant risks to human health. Accordingly, it is imperative to investigate novel genes and mechanisms that govern Cd tolerance and detoxification in plants. Here, we discovered that the transcription factor MYC2 directly binds to the promoters of HMA2 and HMA4 to repress their expression, thereby altering the distribution of Cd in plant tissues and negatively regulating Cd stress tolerance. Additionally, molecular, biochemical, and genetic analyses revealed that MYC2 interacts and cooperates with MYB43 to negatively regulate the expression of HMA2 and HMA4 and Cd stress tolerance. Notably, under Cd stress conditions, MYC2 undergoes degradation, thereby alleviating its inhibitory effect on HMA2 and HMA4 expression and plant tolerance to Cd stress. Thus, our study highlights the dynamic regulatory role of MYC2, in concert with MYB43, in regulating the expression of HMA2 and HMA4 under both normal and Cd stress conditions. These findings present MYC2 as a promising target for directed breeding efforts aimed at mitigating Cd accumulation in edible plant roots.

S-nitrosoglutathione reductase disfavors cadmium tolerance in shoots of Arabidopsis

S-nitrosoglutathione reductase (GSNOR) is involved in the response to cadmium (Cd) exposure. In this study, the plants of mutant (gsnor1-3) with lossing-function of- and over-expression (GSNOROE5) of GSNOR were used to clear the role of GSNOR in Cd tolerance. GSNOR activity increased through upregulating the expression of the AtGSNOR gene and protein in Arabidopsis thaliana under Cd stress, which attenuated Cd tolerance. Oxidative damage was more serious in GSNOROE5 and was alleviated in gsnor1-3 under Cd stress, compared with Col-0. Induction of GSNOR facilitated H2O2 accumulation but inhibited catalase (CAT) activity in shoots under Cd stress. This phenotype was eliminated by 3-amino-1,2,4-triazole (3-AT), a CAT inhibitor. In addition, the expressions of AtCAT1 and AtCAT2 were down-regulated with increasing GSNOR activity under Cd stress. This suggested that GSNOR was involved in the accumulation of hydrogen peroxide (H2O2) through regulating CAT expression and activity under Cd exposure. Furthermore, Cd tolerance and CAT activity were improved by spraying S-nitrosoglutathione (GSNO) onto the surface of the leaves. The in vitro activity of CAT increased with GSNO concentration until a GSNO/CAT ratio of 2 was reached. Thus, CAT activity was relative to GSNOR through regulating the expression and S-nitrosylation level of proteins. In summary, the Cd-induced promotion of GSNOR activity aggravated Cd toxicity in plants by mediating H2O2 accumulation controlled by CAT.

Synthesis and Characterization of Mesoporous Materials Functionalized with Phosphinic Acid Ligand and Their Capability to Remove Cd(II)

This article presents a study of cadmium removal from nitrate medium using adsorption in calcined mesoporous silica (MCM-C), mesoporous silica doped (MCM_DIOPA), and calcined and impregnated mesoporous silica (MCM@DIOPA), with diisooctylphosphinic acid (DIOPA). The sorbents were synthesized via a sol-gel method. Several characterization techniques, such as XRD, FTIR spectroscopy, N2 sorption and elemental analysis, have been used to determine the main structural, textural, and chemical properties of prepared sorbents. Batch adsorption and kinetics tests were carried out, where the influence of pH and contact time of the sorbents and their role in cation removal were studied. Experimental results show poor sorption efficiencies with MCM-C and MCM_DIOPA at pH 5.85. At the same pH, better cadmium extraction was attained by MCM@DIOPA and was achieved within 30 min. The pseudo-second-order model is the most appropriate model to describe the elimination mechanism of Cd(II) ions. The Langmuir equation was used to model the sorption isotherm and the maximum sorption capacity of Cd(II) is 22.16 mg/g (200 mmol/kg). The complex type of the probable extracted species isCdL2-HL.

Mechanism of foliar application of boron to alleviate cadmium toxicity in winter wheat (Triticum aestivum L.)

Our previous work shown that boron (B) can inhibit cadmium (Cd) absorption in winter wheat, while the mechanism is not well understood. In this study, the mechanism of foliage spray B on Cd uptake in Cd-contaminated farmland was characterized with three treatments: spraying distilled water (CK), spraying 0.3% B fertilizer (F0.3%), and spraying 0.6% B fertilizer (F0.6%). The spraying treatment was conducted during the jointing stage and booting stage, respectively. The objective was to investigate the impact of different concentrations of B fertilizer application on Cd content, yield, physiological biochemical response, Cd transporter in wheat. Results showed that the yield increased with increasing B spray concentration compared with CK treatment. The wheat yield increased by 1.29%∼12.50% under foliar B application. The Cd concentration in both shoot and root of wheat seedlings were significantly decreased with foliar application of B at jointing stage and booting stage. The Cd concentrations in root and seed were also decreased with B treatment at maturity stage, especially after treatment with F0.6%, the Cd absorption in wheat grains exhibited a significant reduction of 31.20%. In addition, foliar application of B significantly increased antioxidant enzyme activities, include APX, SOD, CAT, and POD. Compared with CK, the MDA content in leaves showed a significant decrease with 30.48%-50.14%, while the GSH content showed an increase with 76.32%-1.05%. The down-regulation of the uptake and transport genes (TaNramp5, TaLCT1 and TaHMA2) and the up-regulation of compartmentalization transport genes (TaTM20 and TaHMA3) may contribute to the reduction of Cd accumulation in shoot. Overall, our results suggest that foliar spraying of B could increase B accumulation and yield, and alleviate Cd toxicity by reducing Cd uptake, enhancing the antioxidant capacity, regulating the expression of Cd genes in wheat.

Spontaneous growth of plants enhances phytoextraction on abandoned coal mine wastes in Central Alborz coalfield, Iran

Coal mining disperses heavy metals into the environment, necessitating the identification of metal-tolerant plants for ecosystem restoration. This study evaluated the phytoremediation potential of plant species in abandoned coal wastes in northern Iran. Pollution indices indicated moderate contamination of Cu, Ni, V, Zn, Pb, Cr, and As in coal wastes. The plants varied in their ability to accumulate and translocate these metals, with most showing efficient root-to-shoot translocation. Artemisia scoparia (41.06 mg.kg-1) and Capparis spinosa (42.48 mg.kg-1) were effective for Cu phytoextraction. Most species, notably Cynodon dactylon (3.4 mg.kg-1), showed promise for phytoextraction of Cr. Capparis spinosa (7.67 mg.kg-1) exhibited potential for Pb phytoextraction. Most plants, particularly Hordeum vulgare and Melica persica, were effective phytoextractors of Ni. Sylibum marianum accumulated V beyond phytotoxic levels. Chenopodium album and Glaucium fimbriligerum were identified as phytoextractors of Zn while Cynodon dactylon and Hordeum vulgare, accumulating >100 mg.kg-1 Zn in roots, showed potential for phytostabilization. Sylibum marianum and Glaucium fimbriligerum, acted as excluders for As. Kochia prostrata and Artemisia aucheri were excluders for Cu, Cr, Ni, and Pb. This study provided the role of multiple indigenous plants, including perennials and annuals with diverse life forms, in metal extraction and stabilization for sustainable coal waste management.

Cadmium-induced protein AS8: A protein to improve Cd accumulation and transport via Cd uptake in poplar

The pollution of soil with heavy metals (HMs) has become an environmental problem of global concern. Phytoremediation, whereby plants extract HMs from soil, can efficiently and substantially reduce HM pollution in soil in an environmentally friendly manner. Cadmium-induced protein AS8 (CIPAS8) is present in many plants and its expression is induced by HMs. In this study, PeCIPAS8 and SlCIPAS8 were transformed into 84K poplar to study their effects on tolerance to, and translocation of, cadmium (Cd) in woody plants. Localization analyses showed that two CIPAS8 proteins were localized at the plasma membrane when transiently expressed in tobacco leaf epidermal cells. Compared with wild-type 84K poplar seedlings, transgenic poplar lines overexpressing PeCIPAS8 or SlCIPAS8 showed increased Cd contents and decreased Cd tolerance. Transgenic poplar lines overexpressing PeCIPAS8 or SlCIPAS8 accumulated more Cd in the roots, stems, and leaves, but the plant height did not differ significantly, compared with wild-type 84K poplar under Cd stress during the vegetative stage. CIPAS8 increased the Cd influx rate of transgenic poplar roots compared with that of the wild type, and affected the transcription levels of other metal transporters. These findings show that CIPAS8 increases Cd flux into plant tissues and demonstrate moderate Cd sensitivity of the plant. Therefore, CIPAS8 is an influx transporter with the potential to increase the uptake of toxic HMs by woody plants growing in HM-contaminated soils.

Posphoproteomics profiling reveals the regulatory role of a phosphorylated protein PvFBA1 in cadmium tolerance in seashore paspalum

Seashore paspalum (Paspalum vaginatum) is a warm-season and perennial turfgrass and is known for its cadmium (Cd)-stress tolerance. Here, a Phosphoproteomics analysis was performed to examine the key proteins relating to Cd tolerance in seashore paspalum. Fructose 1,6-biphosphate aldolase, PvFBA1, was identified for its phosphorylated state after exposure to Cd stress. Specifically, the phosphorylation of PvFBA1 was enhanced in several metabolic pathways, including pentose phosphate pathway (PPP), carbon fixation and biosynthesis of amino acids under Cd stress. By transforming PvFBA1 into Arabidopsis, the PvFBA1-OE plants exhibited longer roots, greater FBA activity and higher soluble sugar content than WT under 100 µM CdCl2 treatment. By expressing the PvFBA1 in yeast, a serine 50 phosphorylation site was identified as functional site. By microscale thermophoresis experiment, we indicted that PvFBA1can bind Cd directly enhancing its phosphorylation level to alleviate the damage of Cd. This finding may provide new insights into the molecular mechanisms of plants Cd tolerance.

Transfer and biological effects of cadmium along a tomato - thrip - predatory bug food chain

The heavy metal, cadmium (Cd) is an increasingly serious issue in agricultural ecosystems, mediating bottom-up effects on plants, herbivores and natural enemies. We measured how Cd modifies interactions between tomato Solanum lycopersicum, western flower thrips Frankliniella occidentalis, and the predatory bug Orius sauteri by examining Cd effects on the growth of tomato, the fitness of western flower thrips, and the survival and behavior of predators. The photosynthetic parameters of Pn (net photosynthetic rate), Gs (stomatal conductance), Ci (intercellular CO2 concentration), and Tr (transpiration rate) of tomato plants significantly decreased with the increase of Cd concentration. The total survival number of western flower thrips fed on tomato plants treated with different concentrations of Cd was significantly lower than that of the control, and sex ratios (female/male) gradually increased with the increase of Cd concentration. The numbers of thrips predated by O. sauteri on tomato plants treated with high concentrations of Cd (2.0 or 4.0 mg/L) were significantly reduced by the second day. Cadmium was accumulated and bioconcentrated in the roots, stems, leaves of tomato plants, and transferred to F. occidentalis, and O. sauteri. Cadmium translocated in significant quantities from roots to the stems and leaves of tomato plants, and from the tomato leaf to F. occidentalis. However, there was minimal (non-significant) transfer of Cd from F. occidentalis to O. sauteri. The presence of Cd significantly reduced the growth of tomato plants, the fitness of F. occidentalis, and the predation efficiency of O. sauteri. Collectively, Cd can mediate bottom-up effects on tomato, thrip, and predatory bug along food chain, potentially interrupting pest biological control in tomato in heavy metal-contaminated ecosystems.

Carbon-mediated modulation pathways of phytotoxicity in chicken manure composting

Compost phytotoxicity affects the safety of organic fertilizers returned to the field, thus hindering the breeding cycle, so it is essential to reduce the compost phytotoxicity. The phytotoxicity of compost was estimated utilizing the germination index (GI) and the aqueous substances (organics and ions) present in compost correlated closely with GI. This study assessed the effect of carbon additives from different plant sources (mushroom substrates (MS), cornstalks (CS) and garden substrates (GS)) on maturity parameters (temperature, pH, EC, C/N), content of aqueous carbon and nitrogen matters, salt ions, heavy metal ions, and microbiome of piles when composting with chicken manure and especially focused on their effect on GI. Results showed that all additives significantly improved GI (85.25%-106.28%). The primary factors influencing seed germination were Mg2+ and SO42- in CM compost, acetic acid and NH4+ in CM + MS compost, humic acid in CM + CS compost, and dissolved total nitrogen in CM + GS compost. During composting, the growth of heavy metal passivating bacteria (Bacillus) and organic matter degrading bacteria (Desemzia and Turicibacter) can be promoted by decreasing aqueous carbon and nitrogen substances (volatile fatty acids, NH4+, dissolved total nitrogen, amino acids) and increasing the content of humic acid, which improved the composting environment and provided favorable conditions for the germination of seeds, thereby increasing GI. Therefore, GS showed the best potential for accelerating degradation of organic matter and improving GI during composting with chicken manure.

Co-application of Parthenium biochar and urea effectively mitigate cadmium toxicity during wheat growth

Environmental contamination by cadmium (Cd), a highly toxic heavy metal, poses significant health risks to plants and humans. Biochar has been effectively used to promote plant growth and productivity under Cd stress. This study presents an innovative application of biochar derived from the invasive weed Parthenium hysterophorus to promote plant growth and productivity under Cd stress. Our study includes detailed soil and plant analyses, providing a holistic perspective on how biochar and urea amendments influence soil properties, nutrient availability, and plant physiological responses. To address these, we established seven treatments: the control, Cd alone (5 mg kg-1), biochar alone (5 %), urea alone (3 g kg-1), biochar with Cd, urea with Cd, and a combination of biochar and urea with Cd. Cd stress alone significantly reduced plant growth indicators such as shoot and root length, fresh and dry biomass, chlorophyll content, and grain yield. However, the supplementation of biochar, urea, or their combination significantly increased shoot length (by 48%, 34%, and 65%), root length (by 73%, 46%, and 70%), and fresh shoot biomass (by 4%, 31%, and 4%), respectively. This improvement is attributed to enhanced soil properties and improved nutrient absorption. The biochar-urea combination also enhanced Cd tolerance by improving total chlorophyll content by 14 %, 13 %, and 16 % compared to the control, respectively. Similaly, these treatments significantly (p < 0.05) boosted the activity of antioxidant enzymes such as catalase, peroxidase, and superoxide dismutase by 51 %, 30 %, and 51 %, respectively, thereby mitigating oxidative stress as a defensive mechanism. The Cd tolerance was improved by biochar, urea, and their combinations, which reduced Cd content in the shoots (by 60.5 %, 38.9 %, and 51.3 %), roots (by 47.5 %, 23.9 %, and 57.6 %), and grains (by 58.1 %, 30.2 %, and 38.3 %) relative to Cd stress alone, respectively. The synergistic effects of biochar and urea are achieved through improved soil properties, nutrient availability, activating antioxidant defense mechanisms, and minimizing the accumulation of metal ions in plant tissues, thereby enhancing plant defenses against Cd stress. Conclusively, converting invasive Parthenium weed into biochar and combining it with urea offers an environmentally friendly solution to manage its spreading while effectively mitigating Cd stress in crops.

Soil application of FeCl3 and Fe2(SO4)3 reduced grain cadmium concentration in Polish wheat (Triticum polonicum L.)

BACKGROUND

Wheat is one of major sources of human cadmium (Cd) intake. Reducing the grain Cd concentrations in wheat is urgently required to ensure food security and human health. In this study, we performed a field experiment at Wenjiang experimental field of Sichuan Agricultural University (Chengdu, China) to reveal the effects of FeCl3 and Fe2(SO4)3 on reducing grain Cd concentrations in dwarf Polish wheat (Triticum polonicum L., 2n = 4x = 28, AABB).

RESULTS

Soil application of FeCl3 and Fe2(SO4)3 (0.04 M Fe3+/m2) significantly reduced grain Cd concentration in DPW at maturity by 19.04% and 33.33%, respectively. They did not reduce Cd uptake or root-to-shoot Cd translocation, but increased Cd distribution in lower leaves, lower internodes, and glumes. Meanwhile, application of FeCl3 and Fe2(SO4)3 up-regulated the expression of TpNRAMP5, TpNRAMP2 and TpYSL15 in roots, and TpYSL15 and TpZIP3 in shoots; they also downregulated the expression of TpZIP1 and TpZIP3 in roots, and TpIRT1 and TpNRAMP5 in shoots.

CONCLUSIONS

The reduction in grain Cd concentration caused by application of FeCl3 and Fe2(SO4)3 was resulted from changes in shoot Cd distribution via regulating the expression of some metal transporter genes. Overall, this study reports the physiological pathways of soil applied Fe fertilizer on grain Cd concentration in wheat, suggests a strategy for reducing grain Cd concentration by altering shoot Cd distribution.

Novel nanocomposite and biochar insights to boost rice growth and alleviation of Cd toxicity

Cadmium (Cd) is an unessential and pervasive contaminant in agricultural soil, eventually affecting the food and instigating health issues. The implication of nanocomposites in agriculture attained significant attention to drive food security. Nanocomposites possess exceptional characteristics to stun the challenges of chemical fertilizers that can enhance plant yield and better nutrient bioavailability. Similarly, biochar has the ability to immobilize Cd in soil by reducing mobility and bioavailability. Rice husk biochar is produced at high temperature pyrolysis under anoxic conditions and a stable carbon-rich material is formed. To strive against this issue, rice plants were subjected to Cd (15, 20 mg kg- 1) stress and treated with alone/combined Ca + Mg (25 mg L- 1) nanocomposite and rice husk biochar. In our study, growth and yield traits showed the nurturing influence of Ca + Mg nanocomposite and biochar to improve rice defence mechanism by reducing Cd stress. Growth parameters root length 28%, shoot length 34%, root fresh weight 19%, shoot fresh weight 16%, root dry weight 9%, shoot dry weight 8%, number of tillers 32%, number of grains 20%, and spike length 17% were improved with combined application of Ca + Mg and biochar, with Cd (20 mg kg- 1), rivalled to alone biochar. Combined Ca + Mg and biochar application increased the SPAD 23%, total chlorophyll 26%, a 19%, b 18%, and carotenoids 15%, with Cd (20 mg kg- 1), rivalled to alone biochar. MDA 15%, H2O2 13%, and EL 10% were significantly regulated in shoots with combined Ca + Mg and biochar application with Cd (20 mg kg- 1) compared to alone biochar. POD 22%, SOD 17%, APX 18%, and CAT 9% were increased in shoots with combined Ca + Mg and biochar application with Cd (20 mg kg- 1) compared to alone biochar. Cd uptake in roots 13%, shoots 14%, and grains 21% were minimized under Cd (20 mg kg- 1) with combined Ca + Mg and B. pumilus application, compared to alone biochar. Subsequently, combined Ca + Mg and biochar application is a sustainable solution to boost crop production under Cd stress.

For aqueous/soil cadmium immobilization under acid attack, does the hydroxyapatite converted from Pseudochrobactrum sp. DL-1 induced vaterite necessarily show higher stability?

Microbial induced carbonate precipitation (MICP) technology was widely applied to immobilize heavy metals, but its long-term stability is tough to maintain, particularly under acid attack. This study successfully converted Pseudochrobactrum sp. DL-1 induced vaterite (a rare crystalline phase of CaCO3) to hydroxyapatite (HAP) at 30 ℃. The predominant conversion mechanism was the dissolution of CdCO3-containing vaterite and the simultaneous recrystallization of Ca4.03Cd0.97(PO4)3(OH)-containing HAP. For aqueous Cd immobilization, stability test at pH 2.0-10.0 showed that the Cd2+ desorption rate of Cd-adsorbed vaterite (3.96-4.35 ‱) were 7.13-20.84 times greater than that of Cd-adsorbed HAP (0.19-0.61 ‱). For soil Cd immobilization under 60 days of acid-rain erosion, the highest immobilization rate (51.00 %) of exchangeable-Cd and the lowest dissolution rate (-0.18 %) of carbonate-Cd were achieved with 2 % vaterite, while the corresponding rates were 16.78 % and 1.31 % with 2 % HAP, respectively. Furthermore, vaterite outperformed HAP in terms of soil ecological thorough evaluation. In conclusion, for Cd immobilization by MICP under acid attack, DL-1 induced vaterite displayed direct application value due to its exceptional stability in soil and water, while the mineral conversion strategy we presented is useful for further enhancing the stability in water.

Cadmium exposure promotes inflammation through the PPAR signaling pathway in the small intestine and colon of Hu sheep

With the increase of cadmium content in the environment, the losses caused by cadmium-induced intestinal diseases to animal husbandry are increasing year by year. However, most of the on-going research activities focus on zoonotic diseases rather than exploring the mechanisms of animal disease occurrence from an anthropogenic environmental perspective. In this study, stressed Hu sheep under cadmium environmental exposure were selected to explore the mechanism of inflammatory bowel disease development. 16 s, untargeted metabolomics and transcriptomic multiomics were used to analyze the changes of their intestinal tract and intestinal contents. The results showed that the beneficial microorganisms (s_Ruminococcus_sp) in the Cd group were significantly decreased and the potentially harmful microorganisms were significantly enriched, and the changes of these microorganisms affected the changes of metabolites (caprylic acid) to a certain extent, resulting in a decrease in fatty acids in the intestine. Due to the combined effect of cadmium ion and fatty acid reduction, the PPAR signaling pathway was inhibited, and the fatty acid transport and binding were further reduced, causing very serious damage to the intestine. We revealed for the first time the mechanism of intestinal injury in Hu sheeps under cadmium environmental exposure and provided new prevention and treatment methods of intestinal diseases under the environmental exposure to trace metals.

Cadmium toxicity promotes hormonal imbalance and induces the expression of genes involved in systemic resistances in barley

Cadmium (Cd) is a widely distributed pollutant that adversely affects plants' metabolism and productivity. Phytohormones play a vital role in the acclimation of plants to metal stress. On the other hand, phytohormones trigger systemic resistances, including systemic acquired resistance (SAR) and induced systemic resistance (ISR), in plants in response to biotic interactions. The present study aimed to investigate the possible induction of SAR and ISR pathways in relation to the hormonal alteration of barley seedlings in response to Cd stress. Barley seedlings were exposed to 1.5 mg g-1 Cd in the soil for three days. The nutrient content, oxidative status, phytohormones profile, and expression of genes involved in SAR and ISR pathways of barley seedlings were examined. Cd accumulation resulted in a reduction in the nutrient content of barley seedlings. The specific activity of superoxide dismutase and the hydrogen peroxide content significantly increased in response to Cd toxicity. Abscisic acid, jasmonic acid, and ethylene content increased under Cd exposure. Cd treatment resulted in the upregulation of NPR1, PR3, and PR13 genes in SAR pathways. The transcripts of PAL1 and LOX2.2 genes in the ISR pathway were also significantly increased in response to Cd treatment. These findings suggest that hormonal-activated systemic resistances are involved in the response of barley to Cd stress.

Integrated physio-biochemistry and RNA-seq revealed the mechanism underlying biochar-mediated alleviation of compound heavy metals (Cd, Pb, As) toxicity in cotton

Biochar has been recognised as an efficacious amendment for the remediation of compound heavy metal contamination in soil. However, the molecular mechanism of biochar-mediated tolerance to compound heavy metal toxicity in cotton is unknown. The objective of this research was to investigate the positive impact of biochar (10 g·kg-1) on reducing damage caused by compound heavy metals (Cd, Pb, and As) in cotton (Gossypium hirsutum L.). The results revealed that biochar reduced Cd concentrations by 24.9 % (roots), and decreased Pb concentrations by 37.1 % (roots) and 59.53 % (stems). Biochar maintained ionic homoeostasis by regulating the expression of metal transporter proteins such as ABC, HIPP, NRAMP3, PCR, and ZIP, and genes related to the carbon skeleton and plasma membrane. Biochar also downregulated genes related to photosynthesis, thereby increasing photosynthesis. Biochar re-established redox homoeostasis in cotton by activating signal transduction, which regulated the activity of the enzymes POD, SOD, and CAT activity; and the expression of related genes. This research revealed the molecular mechanism by which biochar confers resistance to the harmful effects of compound heavy metal toxicity in cotton. The application of biochar as a soil amendment to neutralise the toxicity of compound heavy metals is recommended for cash crop production.

Cadmium in biological samples and site-specific cancer risk and mortality: A systematic review of original articles and meta-analyses

BACKGROUND

Cadmium (Cd) is classified as a class 1 carcinogen by the IARC, yet uncertainty persists regarding the total burden of cancer (incidence and mortality) caused by exposure to it, due to the still limited evidence with regard to its aetiological role in cancer at several body sites.

OBJECTIVES AND METHODS

We searched PubMed and EMBASE for meta-analyses and original articles published by February 1st, 2024, that focused on the link between cadmium measured in biological samples (blood, urine, finger-/toe-nails, and hair) and site-specific cancer risk and mortality.

RESULTS

We included 9 meta-analyses and 57 original articles (of these, the design was retrospective in 38 and prospective in 19, and Cd levels were quantified in blood, n=33, urine, n=19, both blood and urine, n=2, or finger-/toenail, n=3). Current data consistently suggest a causal role of exposure to cadmium in pancreas, lung, and bladder carcinogenesis. Total cancer risk and mortality are also positively correlated with Cd levels in biological samples. The evidence is weak or inconclusive for the remaining cancer sites (including breast and prostate), mostly due to the limited number of studies available to date and/or methodological limitations.

DISCUSSION

Exposure to cadmium poses a risk for increased cancer incidence and mortality. Cadmium-related cancer burden might indeed be currently underestimated, as the amount of available evidence for most cancer sites and types is currently limited, and more research in the field is warranted. Continuing efforts to contain Cd pollution and mitigate associated health risk are also needed.

ATP-binding cassette transporter TaABCG2 contributes to Fusarium head blight resistance by mediating salicylic acid transport in wheat

ATP-binding cassette (ABC) transporters hydrolyse ATP to transport various substrates. Previous studies have shown that ABC transporters are responsible for transporting plant hormones and heavy metals, thus contributing to plant immunity. Herein, we identified a wheat G-type ABC transporter, TaABCG2-5B, that responds to salicylic acid (SA) treatment and is induced by Fusarium graminearum, the primary pathogen causing Fusarium head blight (FHB). The loss-of-function mutation of TaABCG2-5B (ΔTaabcg2-5B) reduced SA accumulation and increased susceptibility to F. graminearum. Conversely, overexpression of TaABCG2-5B (OE-TaABCG2-5B) exerted the opposite effect. Quantification of intracellular SA in ΔTaabcg2-5B and OE-TaABCG2-5B protoplasts revealed that TaABCG2-5B acts as an importer, facilitating the transport of SA into the cytoplasm. This role was further confirmed by Cd2+ absorption experiments in wheat roots, indicating that TaABCG2-5B also participates in Cd2+ transport. Thus, TaABCG2-5B acts as an importer and is crucial for transporting multiple substrates. Notably, the homologous gene TaABCG2-5A also facilitated Cd2+ uptake in wheat roots but did not significantly influence SA accumulation or FHB resistance. Therefore, TaABCG2 could be a valuable target for enhancing wheat tolerance to Cd2+ and improving FHB resistance.

The role of gasotransmitter hydrogen sulfide in plant cadmium stress responses

Cadmium (Cd) is a toxic heavy metal that poses a significant risk to both plant growth and human health. To mitigate or lessen Cd toxicity, plants have evolved a wide range of sensing and defense strategies. The gasotransmitter hydrogen sulfide (H2S) is involved in plant responses to Cd stress and exhibits a crucial role in modulating Cd tolerance through a well-orchestrated interaction with several signaling pathways. Here, we review potential experimental approaches to manipulate H2S signals, concluding that research on another gasotransmitter, namely nitric oxide (NO), serves as a good model for research on H2S. Additionally, we discuss potential strategies to leverage H2S-reguated Cd tolerance to improve plant performance under Cd stress.

How does NaCl enhance Cd tolerance in Inula crithmoides L? Insights into Cd uptake, compartmentalization, and chelation

This study investigated the effect of NaCl on the uptake, translocation, compartmentalization, and chelation of cadmium (Cd) in the halophyte Inula crithmoides. Seedlings were subjected hydroponically for 21 days to 25 and 50 μM Cd applied alone or combined with 100 mM NaCl. Findings revealed that, Cd alone induced intense chlorosis and necrosis and altered plant development resulting in diminished biomass production. However, NaCl alleviated Cd-induced toxicity by increasing biomass accumulation, associated with restoration of photosynthesis activity. At the level of whole plant, NaCl reduced Cd concentration in different organs as well as its translocation toward the shoots. At the cellular level, Na Cl changed the cell-compartmentalization of Cd in the shoots and roots by inducing a preferential accumulation into the soluble fraction (vacuole). NaCl increased the chelation of Cd to chloride and nitrate. As compared to Cd alone, salt addition to Cd-treated plants enhanced significantly succinic acid concentration in the leaves suggesting a possible role of this acid in Cd-chelation. Globally, NaCl alleviated Cd-induced phytotoxicity in this halophyte by reducing Cd absorption, translocation and increased Cd fixation to organic acids as well as through the changes in Cd2+ cell compartmentalization. Obtained data suggested that this fast growing halophyte could be used to rehabilitate Cd polluted saline soils.

Hormetic responses to cadmium exposure in wheat seedlings: insights into morphological, physiological, and biochemical adaptations

Cadmium is commonly recognized as toxic to plant growth, low-level Cd has promoting effects on growth performance, which is so-called hormesis. Although Cd toxicity in wheat has been widely investigated, knowledge of growth response to a broad range of Cd concentrations, especially extremely low concentrations, is still unknown. In this study, the morphological, physiological, and biochemical performance of wheat seedlings to a wide range of Cd concentrations (0-100 µΜ) were explored. Low Cd treatment (0.1-0.5 µM) improved wheat biomass and root development by enhancing the photosynthetic system and antioxidant system ability. Photosynthetic rate (Pn) was improved by 5.72% under lower Cd treatment (1 µΜ), but inhibited by 6.05-49.85% from 5 to 100 µΜ. Excessive Cd accumulation induced oxidative injury manifesting higher MDA content, resulting in lower photosynthetic efficiency, stunted growth, and reduction of biomass. Further, the contents of ascorbate, glutathione, non-protein thiols, and phytochelatins were improved under 5-100 µΜ Cd treatment. The ascorbate peroxidase activity in the leaf showed a hormetic dose-response characteristic. Correlation analysis and partial least squares (PLS) results indicated that antioxidant enzymes and metabolites were closely correlated with Cd tolerance and accumulation. The results of the element network, correlation analysis, and PLS showed a crucial role for exogenous Cd levels in K, Fe, Cu, and Mn uptake and accumulation. These results provided a deeper understanding of the hormetic effect of Cd in wheat, which would be beneficial for improving the quality of hazard and risk assessments.