Search Results (54)

Cadmium (Cd) contamination in agricultural soils severely threatens rice production and food safety. To address this issue, this study developed transgenic rice lines co-expressing three Vitis vinifera genes: the ABCC transporter Vvmrp1 and metallothioneins Vvmt1 and Vvmt2. AlphaFold computational modeling confirmed the conserved ABCC-type transporter domain in VvMRP1. Under hydroponic conditions, transgenic rice showed remarkable Cd tolerance, surviving 30 mM Cd (lethal to wildtype, WT) without growth penalties, and exhibited 62.5% survival at 1 mM Cd vs. complete wild-type mortality. Field-relevant Cd exposure (1 mM) reduced Cd accumulation to 35.8% in roots, 83% in stems, and 76.8% in grains compared to WT. Mechanistic analyses revealed that Vvmrp1 mediates cellular Cd efflux while Vvmt1 and 2 chelate free Cd ions, synergistically inhibiting Cd translocation. Transgenic plants also maintained better Fe, P, and Mg homeostasis under Cd stress. This study pioneers the co-expression of a transporter with metallothioneins in rice, demonstrating their complementary roles in Cd detoxification without pleiotropic effects from endogenous gene modification. The findings provide an effective genetic strategy for cultivating low-Cd rice in contaminated soils, offering significant implications for food safety and sustainable agriculture. Full article

Heavy metals such as Cu and Cd are important pollutants. Quillay (Quillaja saponaria) is a tree species endemic to Chile that is of worldwide commercial interest due to its saponins. It can grow on contaminated sites. However, the biological mechanisms underlying its defensive responses remain elusive. This study aimed to characterize Quillay plants under Cu and Cd stress and identify mechanisms controlling their interaction with these metals. We subjected six-month-old plants to Cu (75, 150, and 300 μM) and Cd (20, 40, and 80 μM) in hydroponics for a week and assessed growth, metal accumulation, saponin production, and the expression of a suite of stress-induced genes. Those genes are related to phytochelatins (PCS) and metallothioneins (MT), the antioxidant system (GS and GR), and metal transporters (COPT1). The results indicated that both metals were accumulated mainly in roots, with 339.9 and 433.8 mg/kg DW, for Cd and Cu, respectively, exhibiting a metal excluder pattern. Cd increased the length of the principal root. Higher doses of Cd and Cu augmented the saponin content (62.8% and 41.2% compared to control, respectively). The genes GS, GR, and COPT1 modified their transcriptional levels depending on the metal and organ evaluated. These results provide evidence of specific defensive responses of this species against heavy metal stress, which is helpful to guide new research efforts and support the development of strategies for using Quillay for phytoremediation. Full article

It remains an open question whether violets use universal mechanisms, such as the production of metallothioneins, phytochelatins, and organic acids and/or rely on specific mechanisms like the production of antimicrobial cyclic peptides (cyclotides) for heavy metal tolerance. To contribute to the understanding of the role of cyclotides, we used seed-derived plants from metallicolous (M) and non-metallicolous (NM) populations of Viola tricolor, a pseudometallophyte tolerant to Zn and Pb. Eight- to ten-week-old plants were treated with 1000 μM of Zn or Pb for 3 or 7 days and subsequently measured for cyclotides and heavy metal content using MALDI-MS and Atomic Absorption Spectrometry (AAS), respectively. Individuals from the M population accumulated a similar amount of Zn but occasionally more Pb in comparison with the NM population. Of the 18 different cyclotides included in the analysis, some showed statistically significant changes under the heavy metal treatment. In general, a decrease was observed in the M population, whereas an increase was observed in the NM population (except for the 3-day treatment with Zn). The day of treatment and dose of metal and their interaction played a crucial role in the explained variance for cyclotides produced by the M individuals but not for the NM plants. This unravels the importance of this antimicrobial compound in heavy metal tolerance and indicates that, in V. tricolor, cyclotides are involved in heavy metal tolerance, but specimens from two populations have developed different strategies and tolerance mechanisms involving cyclotides to mitigate heavy metal stress. Full article

Background/Objectives: Plant metallothioneins (MTs) are low-molecular-weight proteins involved in heavy metal binding and response to stress conditions. This work aimed to analyse canola (Brassica napus L.) MTs (BnMT1-4) response to salinity and plant interaction with bacteria. Methods: (1) We tested germination and canola growth and development in the presence of sodium chloride and bacteria Serratia plymuthica; (2) We analysed phytohormones content using LC-MS/MS; (3) We identified in silico cis-regulatory elements in promoters of BnMT1-4 genes; and (4) we investigated BnMT1-4 genes’ expression in B. napus. Results: Under saline conditions, canola germination and plant growth were notably inhibited, whereas inoculation of seeds with S. plymuthica significantly stimulated the analysed physiological traits of B. napus. The content of auxin, abscisic acid, jasmonates, gibberellins, and salicylic acid in B. napus was significantly affected by salinity and modulated by S. plymuthica presence. The promoter regions of the BnMT1-4 genes contain numerous regulatory elements controlled by light, hormones, and various stresses. Interestingly, the expression of BnMT1-3 genes was down-regulated under salt stress, while BnMT4 transcript levels increased strongly at the highest salt concentrations with and without S. plymuthica present. Conclusions: The results show that BnMT genes are differently affected by salinity and bacteria S. plymuthica and significantly correlate with particular phytohormones content in canola tissues, confirming the diversified functions of MTs in plant responses to changing environment. Full article

Metallothioneins (MTs) and phytochelatins (PCs) are small Cys-rich proteins with low molecular mass responsible for detoxifying heavy metals in cells. Arabidopsis thaliana expresses eight metallothionein genes and two types of PCS; however, there is still a need to acquire more knowledge regarding their individual responses to some heavy metals. Thus, it was intended to study the expression of AtMT- and AtPCS1-encoding genes in response to high levels of nickel in wild-type A. thaliana. Seeds of A. thaliana were placed in MS medium supplemented with increasing concentrations of Ni—0 mg L⁻¹, 2.5 mg L⁻¹, 5 mg L⁻¹, 7.5 mg L⁻¹, and 10 mg L⁻¹. After 21 days of exposure, the expression of the AtMTs (1A, 1B, 1C, 2A, 2B, and 3) and AtPCS1 was analysed through RT-qPCR in different plant organs: roots, young leaves, and mature leaves. The concentrations of photosynthetic pigments, hydrogen peroxide, and reduced glutathione were also evaluated, but no significant changes were observed. The gene expression analysis showed that the seven genes reacted differentially to the varying concentrations of Ni and in an organ-specific way. It was noted that in roots, the expression of AtMT1A, AtMT1C, and AtMT3 increased starting with the 2.5 mg L⁻¹ treatment. At the same time, the response in the leaves fluctuated more as AtMT1B and AtMT1C increased in young leaves with concentrations higher than 7.5 and 2.5 mg L⁻¹, respectively, with the remaining genes analysed having their expressions decreased starting with 7.5 mg L⁻¹ of Ni. In mature leaves, AtMT1A increased, while AtMT2A, AtMT2B, and AtPCS1 decreased with Ni concentrations starting from 7.5 mg L⁻¹. These results strongly suggest that the increase in the expression of AtMT1B, AtMT1C, and AtMT3 in the roots significantly reduced Ni toxicity, contributing to its local accumulation and buffering its translocation to the shoots. The overall reduction in the expression of MTs and PCS1 in leaves may be linked to the active participation of MT1A in mature leaves, while young leaves depended on the increased production of MT1B and MT1C to deal with the high amount of Ni present therein. These results contribute further knowledge to the understanding of the defence mechanisms of plants against high levels of Ni regarding the participation of MTs and PCS1. Full article

Heavy metal pollution from industrial activities and poor waste disposal poses significant environmental and health threats to humans and animals. This calls for sustainable approaches to the cleanup of heavy metals. This review explores metal tolerance mechanisms of bacteria such as the formation of biofilms, efflux systems, and enzymatic detoxification. These mechanisms allow bacteria communities to adapt and survive in contaminated environments. These adaptations are enhanced by mutations in the bacteria genes and by horizontal gene transfers, enabling bacteria species to survive under environmental stress while simultaneously contributing to nutrient cycling and the decomposition of organic matter. This review further explores the symbiotic interactions between bacteria, plants, and animals. These relationships enhance the metal tolerance ability of the different living organisms involved and are also very important in the bioremediation and phytoremediation of heavy metals. Plant growth-promoting rhizobacteria, Rhizobium, and Bacillus species are very important contributors to phytoremediation; they improve heavy metal uptake, improve the growth of roots, and plants resilience to stress. Moreover, this review highlights the importance of genetically engineered bacteria in closed-loop systems for optimized metal recovery. This offers environmentally friendly and sustainable options to the traditional remediation methods. Engineered Cupriavidus metallidurans CH34 and Pseudomonas putida strain 15420352 overexpressing metallothioneins have shown enhanced metal-binding capabilities, which makes them very effective in the treatment of industrial wastewaters and in biosorption applications. The use of engineered bacteria for the cleanup of heavy metals in closed-loop systems promotes the idea of a circular economy by recycling metals, thus reducing environmental waste. Multidisciplinary research that integrates synthetic biology, microbial ecology, and environmental science is very important for the advancement of metal bioremediation technologies. This review’s analysis on bacterial metal tolerance, symbiosis, and bioengineering strategies offers a pathway to effective bioremediation options, for the reclamation of heavy metal-polluted environments while promoting sustainable environmental practices. Full article

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. Full article

Industrial waste and sewage deposit heavy metals into the soil, where they can remain for long periods. Although there are several methods to manage heavy metals in agricultural soil, microorganisms present a promising and effective solution for their detoxification. We isolated a rhizofungus, Aspergillus terreus (GenBank Acc. No. KT310979.1), from Parthenium hysterophorus L., and investigated its growth-promoting and metal detoxification capabilities. The isolated fungus was evaluated for its ability to mitigate lead (25 and 75 ppm) and copper (100 and 200 ppm) toxicity in Triticum aestivum L. seedlings. The experiment utilized a completely randomized design with three replicates for each treatment. A. terreus successfully colonized the roots of wheat seedlings, even in the presence of heavy metals, and significantly enhanced plant growth. The isolate effectively alleviates lead and copper stress in wheat seedlings, as evidenced by increases in shoot length (142%), root length (98%), fresh weight (24%), dry weight (73%), protein content (31%), and sugar content (40%). It was observed that wheat seedlings possess a basic defense system against stress, but it was insufficient to support normal growth. Fungal inoculation strengthened the host’s defense system and reduced its exposure to toxic heavy metals. In treated seedlings, exposure to heavy metals significantly upregulated MT1 gene expression, which aided in metal detoxification, enhanced antioxidant defenses, and maintained metal homeostasis. A reduction in metal exposure was observed in several areas, including normalizing the activities of antioxidant enzymes that had been elevated by up to 67% following exposure to Pb (75 mg/kg) and Cu (200 mg/kg). Heavy metal exposure elevated antioxidant levels but also increased ROS levels by 86%. However, with Aspergillus terreus colonization, ROS levels stayed within normal ranges. This decrease in ROS was associated with reduced malondialdehyde (MDA) levels, enhanced membrane stability, and restored root architecture. In conclusion, rhizofungal colonization improved metal tolerance in seedlings by decreasing metal uptake and increasing the levels of metal-binding metallothionein proteins. Full article

Pollution of arable land with heavy metals is a worldwide problem. Cadmium (Cd) is a toxic metal that poses a severe threat to humans’ and animals’ health and lives. Plants can easily absorb Cd from the soil, and plant-based food is the main means of exposure to this hazardous element for humans and animals. Phytoremediation is a promising plant-based approach to removing heavy metals from the soil, and plant growth-promoting micro-organisms such as the fungi Trichoderma can enhance the ability of plants to accumulate metals. Inoculation of Avena sativa L. (oat) with Trichoderma viride enhances germination and seedling growth in the presence of Cd and, in this study, the growth of 6-month-old oat plants in Cd-contaminated soil was not increased by inoculation with T. viride, but a 1.7-fold increase in yield was observed. The content of Cd in oat shoots depended on the Cd content in the soil. Still, it was unaffected by the inoculation with T. viride. A. sativa metallothioneins (AsMTs) participate in plant–fungi interaction, however, their role in this study depended on MT type and Cd concentration. The inoculation of A. sativa with T. viride could be a promising approach to obtaining a high yield in Cd-contaminated soil without increasing the Cd content in the plant. Full article

Metallothioneins (MTs) are non-enzymatic metal-binding proteins widely found in animals, plants, and microorganisms and are regulated by metal-responsive transcription factor 1 (MTF1). MT and MTF1 play crucial roles in detoxification, antioxidation, and anti-apoptosis. Therefore, they are key factors allowing organisms to endure the toxicity of heavy metal pollution. Phascolosoma esculenta is a marine invertebrate that inhabits intertidal zones and has a high tolerance to heavy metal stress. In this study, we cloned and identified MT and MTF1 genes from P. esculenta (designated as PeMT and PeMTF1). PeMT and PeMTF1 were widely expressed in all tissues and highly expressed in the intestine. When exposed to 16.8, 33.6, and 84 mg/L of zinc ions, the expression levels of PeMT and PeMTF1 in the intestine increased first and then decreased, peaking at 12 and 6 h, respectively, indicating that both PeMT and PeMTF1 rapidly responded to Zn stress. The recombinant pGEX-6p-1-MT protein enhanced the Zn tolerance of Escherichia coli and showed a dose-dependent ABTS free radical scavenging ability. After RNA interference (RNAi) with PeMT and 24 h of Zn stress, the oxidative stress indices (MDA content, SOD activity, and GSH content) and the apoptosis indices (Caspase 3, Caspase 8, and Caspase 9 activities) were significantly increased, implying that PeMT plays an important role in Zn detoxification, antioxidation, and anti-apoptosis. Moreover, the expression level of PeMT in the intestine was significantly decreased after RNAi with PeMTF1 and 24 h of Zn stress, which preliminarily proved that PeMTF1 has a regulatory effect on PeMT. Our data suggest that PeMT and PeMTF1 play important roles in the resistance of P. esculenta to Zn stress and are the key factors allowing P. esculenta to endure the toxicity of Zn. Full article

Fish infectious diseases are one of the main constraints of the aquaculture sector. The use of medicinal plants provides a sustainable way of protection using safe, eco-friendly compounds in a more cost-effective way of treatment, compared to antibiotics. The aim of the present study is the assessment of Artemisia arborescens (AA) feed-supplementation effects on gilthead seabream (Sparus aurata). Fish with an average initial body weight of 109.43 ± 3.81 g, were divided into two groups based on AA feed composition (A25 and A50). Following two months of ad libitum feeding, the effect of diets on fish weight and length were measured. Fish serum and mucus were analyzed for non-specific immune parameters (nitric oxide, lysozyme, myeloperoxidase, protease-/anti-protease activity, and complement), antibody responses, oxidative stress (cytochrome P450 1A1, metallothionein), and metabolism markers (total protein, alkaline phosphatase, and glucose). Expression levels of antioxidants (sod1, gpx1), cytokines (il-1b, il-10, tfgb1, and tnfa), hepcidin, and heat shock protein grp75 genes were measured in spleen samples. A results analysis indicated that A. arborescens use as a feed supplement has a compromised positive effect on the growth performance, immune response, and blood parameters of gilthead seabream. Overall, the suitability of A. arborescens as an efficient food supplement for gilthead seabream health improvement was investigated, setting the basis for its application assessment in Mediterranean aquaculture. Full article

Plant glycine-rich RNA-binding proteins (GRPs) play crucial roles in the response to environmental stresses. However, the functions of AtGRP7 in plants under heavy metal stress remain unclear. In the present study, in Arabidopsis, the transcript level of AtGRP7 was markedly increased by Ni but was decreased by Pb. AtGRP7-overexpressing plants improved Ni tolerance, whereas the knockout mutant (grp7) was more susceptible than the wild type to Ni. In addition, grp7 showed greatly enhanced Pb tolerance, whereas overexpression lines showed high Pb sensitivity. Ni accumulation was reduced in overexpression lines but increased in grp7, whereas Pb accumulation in grp7 was lower than that in overexpression lines. Ni induced glutathione synthase genes GS1 and GS2 in overexpression lines, whereas Pb increased metallothionein genes MT4a and MT4b and phytochelatin synthase genes PCS1 and PCS2 in grp7. Furthermore, Ni increased CuSOD1 and GR1 in grp7, whereas Pb significantly induced FeSOD1 and FeSOD2 in overexpression lines. The mRNA stability of GS2 and PCS1 was directly regulated by AtGRP7 under Ni and Pb, respectively. Collectively, these results indicate that AtGRP7 plays a crucial role in Ni and Pb tolerance by reducing Ni and Pb accumulation and the direct or indirect post-transcriptional regulation of genes related to heavy metal chelators and antioxidant enzymes. Full article

In this study, canola (Brassica napus L.) seedlings were treated with individual and combined salinity and lithium (Li) stress, with and without acetic acid (AA) or nitric acid (NO), to investigate their possible roles against these stresses. Salinity intensified Li-induced damage, and the principal component analysis revealed that this was primarily driven by increased oxidative stress, deregulation of sodium and potassium accumulation, and an imbalance in tissue water content. However, pretreatment with AA and NO prompted growth, re-established sodium and potassium homeostasis, and enhanced the defense system against oxidative and nitrosative damage by triggering the antioxidant capacity. Combined stress negatively impacted phenylalanine ammonia lyase activity, affecting flavonoids, carotenoids, and anthocyanin levels, which were then restored in canola plants primed with AA and NO. Additionally, AA and NO helped to maintain osmotic balance by increasing trehalose and proline levels and upregulating signaling molecules such as hydrogen sulfide, γ-aminobutyric acid, and salicylic acid. Both AA and NO improved Li detoxification by increasing phytochelatins and metallothioneins, and reducing glutathione contents. Comparatively, AA exerted more effective protection against the detrimental effects of combined stress than NO. Our findings offer novel perspectives on the impacts of combining salt and Li stress. Full article

Plastic-based contamination has become a major cause of concern as it pervades many environments such as air, water, sediments, and soils. This study sought to examine the presence of microplastics (MPs) and nanoplastics (NPs) in freshwater mussels placed at rainfall/street runoff overflows, downstream (15 km) of the city centre of Montréal, and 8 km downstream of a municipal effluent dispersion plume. MPs and NPs were determined using flow cytometry and size exclusion chromatography using fluorescence detection. Following 3 months of exposure during the summer season, mussels contained elevated amounts of both MPs and NPs. The rainfall overflow and downstream of the city centre were the most contaminated sites. Lipid peroxidation, metallothioneins, and protein aggregates (amyloids) were significantly increased at the most contaminated sites and were significantly correlated with NPs in tissues. Based on the levels of MPs and NPs in mussels exposed to municipal effluent, wastewater treatment plants appear to mitigate plastic contamination albeit not completely. In conclusion, the data support the hypothesis that mussels placed in urbanized areas are more contaminated by plastics, which are associated with oxidative damage. The highest responses observed at the overflow site suggest that tire wear and/or asphalt (road) erosion MPs/NPs represent important sources of contamination for the aquatic biota. Full article

Soil co-contamination with cadmium (Cd) and arsenic (As) occurs frequently and has caused increasing concern. This study aimed to explore the transfer characteristics and the chemical forms, subcellular distribution of Cd and As, as well as the synthesis of phytochelatins (PCs) and other chelates in peanut (Arachis hypogaea L.) plants grown in a Cd and As co-contaminated soil, shedding light on the mechanisms involved. Compared with the single Cd contamination, Cd–As co-contamination led to a higher accumulation of Cd in peanut plants. Conversely, compared to the single As contamination, the As content increased in peanut shoots but decreased in roots and grains under Cd–As co-contamination. Furthermore, the Cd–As interaction resulted in notable changes in peanut plants’ physiological and biochemical responses. In the roots and shoots, there was an 81.8% and 60.0% increase in water-soluble Cd. In the roots, metallothioneins (MTs) content increased by 50%, while PCs increased by 6.4% in the shoots. These changes promoted the translocation of Cd from roots to grains. The Cd–As interaction also influenced the synthesis of MTs in the roots, showing a 41.2% increase, and facilitated the transfer of As to the shoots. In peanut shoots, Cd increased the cell wall fraction of As by 34.5%, decreased the proportion of water-soluble As by 31.8%, and increased PCs content by 6.9%. These changes inhibited the migration of As from shoots to grains. Overall, Cd–As co-contamination increased Cd in peanut grains by increasing water-soluble forms and MTs in roots, while Cd–As co-contamination decreased As in peanut grains by increasing cell wall fractions and PCs in shoots. These findings provide a theoretical basis for understanding Cd–As interactions in soil–peanut systems. Full article