Non-essential Toxic Heavy Metal Research Articles

OsPDR20 is an ABCG metal transporter regulating cadmium accumulation in rice

Cadmium (Cd) is a non-essential toxic heavy metal, seriously posing high environmental risks to human health. Digging genetic resources relevant to functional genes is important for understanding the metal absorption and accumulation in crops and bioremediation of Cd-polluted environments. This study investigated a functionally uncharacterized ATP binding cassette transporter G family (ABCG) gene encoding a Pleiotropic Drug Resistance 20 (PDR20) type metal transporter which is localized to the plasma membrane of rice. OsPDR20 was transcriptionally expressed in almost all tissues and organs in lifespan and was strongly induced in roots and shoots of young rice under Cd stress. Ectopic expression of OsPDR20 in a yeast mutant ycf1 sensitive to Cd conferred cellular tolerance with less Cd accumulation. Knockdown of OsPDR20 by RNA interference (RNAi) moderately attenuated root/shoot elongation and biomass, with reduced chlorophylls in rice grown under hydroponic medium with 2 and 10 µmol/L Cd, but led to more Cd accumulation. A field trial of rice grown in a realistic Cd-contaminated soil (0.40 mg/kg) showed that RNAi plants growth and development were also compromised compared to wild-type (WT), with smaller panicles and lower spikelet fertility but little effect on yield of grains. However, OsPDR20 suppression resulted in unexpectedly higher levels of Cd accumulation in rice straw including lower leaves and culm and grain. These results suggest that OsPDR20 is actively involved in Cd accumulation and homeostasis in rice crops. The increased Cd accumulation in the RNAi plants has the potential application in phytoremediation of Cd-polluted wetland soils.

Evaluation of Cd2+ stress tolerance in transgenic rice overexpressing PgGPx gene that maintains cellular ion and reactive oxygen species homeostasis.

Non-essential toxic heavy metal like cadmium (Cd2+) interferes with the plant growth and development in many ways. Cd2+ travels via plant transportation system, specifically through xylem and may integrate into the food chain causing unfavorable condition in human health. Therefore, strategies to develop Cd2+ tolerance and less accumulation in the plant system require urgent attention. Peroxidase gene family is known for metal ions transportation including Cd2+ and thus plays an important role in ion homeostasis. Previously, we have reported the presence of a Cd2+ dependent functional peroxiredoxin from Pennisetum glaucum (PgGPx). The present study elucidates the role of this PgGPx against Cd2+ stress in rice. The transcript levels of PgGPx were found to be highly upregulated in response to exogenous Cd2+. Moreover, recombinant PgGPx protein showed significant glutathione S-transferase activity in vitro. Ectopically expressed PgGPx in transgenic rice plants showed tolerance towards Cd2+ stress as demonstrated by several physiological indices including shoot and root length, biomass, chlorophyll, and hydrogen peroxide content. Moreover, these transgenic plants also showed enhanced capability to cope up with oxidative stress by enhancing the activity of different antioxidant enzymes including Superoxide dismutase, Catalase, Ascorbate peroxidase, Glutathione peroxidase, Glutathione reductase) in response to Cd2+. Hence, maintenance of cellular ion homeostasis and modulation of reactive oxygen species-scavenging pathway are found to be improved by overexpression of PgGPx under Cd2+ stress. These results will pave the way to develop strategies for engineering Cd2+ stress tolerance in economically important crop plants.

Dietary fiber ameliorates lead-induced gut microbiota disturbance and alleviates neuroinflammation.

Dietary fiber (DF) is a carbohydrate from the edible part of plants and has the functions of promoting gastrointestinal motility, regulating gut microbiota (GM) and improving health. Lead is a non-essential toxic heavy metal that can accumulate in the environment over time and enter the body through the respiratory tract, skin and gastrointestinal tract. Lead not only causes disturbances in GM but also leads to loss of homeostasis of immune functions, causes neuronal damage and results in neuroinflammation. The scientific literature has reported that DF had anti-inflammatory activity as a natural product. This review highlights the role of DF and its metabolic products in alleviating lead-induced neuroinflammation by inducing changes in the species and quantity of GM and regulating the immune system, providing a potential dietary protective strategy for lead-induced disease. © 2022 Society of Chemical Industry.

A Mini Review on Arsenic and Cadmium Ion Detection Using Fluorescent-Colorimetric Sensors

Heavy metals with high atomic numbers, mass, and density are five times greater than water. They are naturally occurring elements and widely distributed in the environment due to their numerous applications like agricultural, industrial, domestic, technological, and medical fields increasing issues about their potential impact on the environment and human health. In this mini review, we focused on cadmium and arsenic metals. Cadmium is also the non-essential toxic heavy metal element found naturally in the earth's crust, and it is easily affected by plants’ movements through the food cycle and also causes harm to live beings. Arsenic is a common element found in low amounts in almost all environmental compartments. Chemosensors play a pivotal role in environmental and analytical chemistry. Chemosensors can detect enzymes, anions, and hazardous heavy metal ions with excellent selectivity and sensitivity at a low cost. Colorimetric chemosensors are instruments that convert chemical data into analytically relevant signals that can be viewed with the naked eye. Fluorescent-based chemosensors for cations, anions, and neutral analytes have been used in a wide range of applications.

Hematological, Biochemical and Immunological Responses of Estuarine Catfish Mystus gulio (Hamilton 1822) After Exposure to Lead (Pb)

Due to increased industrialization in developing countries some of the toxic substances are being increased in day-to-day life. Living organisms need some trace amounts of metals like copper, manganese, zinc etc. but some of the non-essential toxic heavy metals are also accumulated in the body of living organisms which may cause damages to the immune organs of the organism. The present study investigated the impacts of sublethal dosage of inorganic Lead acetate on the hematological, biochemical and immunological responses of the brackish water fish Mystus gulio. The LC50 at 96 h was determined by the Probit method. The experiment was performed for 30 days of exposure of lead acetate (4 mg/l) to the fish Mystus gulio. After exposure to lead nitrate hematological (hemoglobin, RBC, WBC, PCV, neutrophil, eosinophil and platelet), biochemical (glucose, protein, albumin and globulin) and immunological (IgM) parameters were analyzed. A decrease was seen in the RBC count, hemoglobin, PCV, MCV, MCH, MCHC, protein, albumin and globulin whereas an increase was seen in WBC count, neutrophils, eosinophils, ESR, platelet count, glucose and Immunoglobulin (IgM).

Towards on-Site Detection of Cadmium in Human Urine

Cadmium (Cd) is a non-essential toxic heavy metal. Human exposure to Cd occurs from multiple sources, including diet, tobacco smoke, fossil fuel combustion, and variously contaminated environments. This work reports a rapid method for Cd 2+ detection in simulated urine samples containing glucose (GLC) and actual human urine using the electrochemical technique of square wave anodic stripping voltammetry (ASV). Electrochemical techniques for onsite analysis and detection are preferred for their quick response time, application simplicity, inexpensive instrumentation, and potential portability. This approach is a step forward towards Cd 2+ detection in biological fluids, despite their composition complexity due to possible interference of its constituents. Application of a simple, well controlled, and uniform carbon nanotube (CNT) thin film generated through spinnable CNT arrays enabled us to increase the surface area of traditional glassy carbon electrodes and made possible the detection of nanomolar concentration of Cd ions in urine samples. Employing 120s deposition time on anodic stripping voltammetry led to 1.9 nM and 324 nM limit of detection (LOD) in simulated urine and human samples, respectively. The developed method would facilitate high throughput screening of human urine samples for assessing Cd exposure in future studies.

Soil nutrients and heavy metal availability under long-term combined application of swine manure and synthetic fertilizers in acidic paddy soil

Fertilization is a vital approach to increase the crop yield by enhancing soil fertility, but some of the fertilizer sources such as pig manure contain non-essential toxic heavy metals, which can produce the environmental and public health risk. Therefore, the purpose of this study was to investigate the soil fertility and heavy metal pollution risk under long-term fertilization in acidic paddy soil. Fertilizer treatments that were arranged in randomized complete block design (RCBD) included CK (no fertilization), NK (inorganic nitrogen and potassium fertilization), NPK (inorganic NK and phosphorus fertilization), NPKM1 (70% of NPK and 30% pig manure application), NPKM2 (50% of NPK and 50% of pig manure application), and NPKM3 (30% of NPK and 70% of pig manure application). The rice grain yield and soil nutrient contents were highest under NPKM3 treatment. Long-term addition of manure significantly (P ≤ 0.05) increased soil pH and SOC content compared to the NPK fertilization. Soil available and total Cr, Cd, and Hg contents were highest under NPKM3 treatments, while soil total and available Pb content was significantly (P ≤ 0.05) higher under NPK treatment. Highest ecological risk (IR) was (1904) under NPK treatment and highest pollution load index (PLI) was 1.5 under NPKM3 treatment. Cd concentration in rice grain exceeded the maximum permissible limit of 0.1 mg kg−1 under combined application of manure and inorganic fertilization treatments. Grain Cr, Hg, and Pb contents were within safe limits of their concentration in all treatments. Moreover, biological accumulation coefficients of Cr, Cd, Hg, Pb, Zn, and Cu were highest under NPK treatment. Redundancy analysis (RDA) showed that soil pH and nutrient contents showed significant correlation with heavy metal concentrations in soil. Soil pH showed significant (P ≤ 0.05) positive effect on Cd accumulation in rice grain. Heavy metals in pig manure should be monitored before application to the field to reduce the risk of heavy metal pollution in soil and plant. Furthermore, combined application at the rate of 70% inorganic fertilization and 30% of manure could be better strategy to produce high crop yield with minimum risk of heavy metal contamination in soil and food crops.

Towards on-site detection of cadmium in human urine

Cadmium (Cd) is a non-essential toxic heavy metal. Human exposure to Cd occurs from multiple sources, including diet, tobacco smoke, fossil fuel combustion, and various contaminated sources. This work reports a rapid method for Cd2+ detection in simulated urine samples containing glucose (GLC) and human urine using the electrochemical technique of square wave anodic stripping voltammetry (ASV). Electrochemical techniques for onsite analysis and detection are preferred for their quick response time, application simplicity, inexpensive instrumentation, and potential portability. This approach is a step forward towards Cd2+ detection in biological fluids, despite their composition complexity due to possible interference of its constituents. Application of a simple, well controlled, and uniform carbon nanotube (CNT) thin film generated through spinnable CNT arrays enabled us to increase the surface area of traditional glassy carbon electrodes and made possible the detection of nanomolar concentration of Cd ions in urine samples. This voltammetric technique led to 1.9 nM limit of detection (LOD) in simulated urine, and 5.85 nM (female) and 324 nM (male) LOD in human urine. The developed method would facilitate high throughput screening of human urine samples for assessing Cd exposure in future studies.

The Role of Spirulina (Arthrospira) in the Mitigation of Heavy-Metal Toxicity: An Appraisal

Heavy-metal toxicity imposes a potential worldwide threat to the environment and humans. Cadmium, mercury, lead, and arsenic are nonessential toxic heavy metals that are most frequently involved in environmental and health hazards. Conventional chelating agents are unsuitable for subchronic and chronic heavy-metal toxicities. Scientific literature reveals that Spirulina (Arthrospira), a photosynthetic filamentous cyanobacterium that is generally known as blue-green algae, alleviates experimentally induced heavy-metal toxicity. The present review attempts to summarize such studies regarding cadmium, mercury, lead, and arsenic toxicity. A total of 58 preclinical studies demonstrate the alleviative effect of Spirulina against experimental arsenic, cadmium, lead, and mercury toxicities. Five clinical studies reported protective effects of Spirulina against arsenic toxicity in humans. Clinical studies against three heavy metals were not found in the literature. The present literature study appears to show that Spirulina possesses promising heavy-metal toxicity-ameliorative effects that are mainly attributed to its intrinsic antioxidant activity.

Cadmium toxicity: effects on human reproduction and fertility.

Background Cadmium (Cd) is a non-essential toxic heavy metal, an environmental toxicant, and toxic at a low concentration, and it has no known beneficial role in the human body. Its exposure induces various health impairments including hostile reproductive health. Objective The present review discusses the information on exposure to Cd and human reproductive health impairments including pregnancy or its outcome with respect to environmental and occupational exposure. Methods The present review provides current information on the reproductive toxic potential of Cd in humans. The data were collected using various websites and consulting books, reports, etc. We have included recent data which were published from 2000 onward in this review. Results Cd exposure affects human male reproductive organs/system and deteriorates spermatogenesis, semen quality especially sperm motility and hormonal synthesis/release. Based on experimental and human studies, it also impairs female reproduction and reproductive hormonal balance and affects menstrual cycles. Based on the literature, it might be concluded that exposure to Cd at low doses has adverse effects on both human male and female reproduction and affects pregnancy or its outcome. Further, maternal prenatal Cd exposure might have a differential effect on male and female offspring especially affecting more female offspring. Hence, efforts must be made to prevent exposure to Cd. Conclusion Cd affects both male and female reproduction, impairs hormone synthesis/regulation and deteriorates pregnancy rate or its outcome even at lower doses.

Cadmium-induced neurodegeneration and activation of noncanonical sonic hedgehog pathway in rat cerebellum.

Cadmium is a nonessential toxic heavy metal, which enters the body easily and damages the cellular system. The sonic hedgehog (Shh) signaling pathway is one of the key regulatory pathways, which define neural growth and development. This study aimed to explore how cadmium exposure affects neural activities, Shh signaling cascade, and its downstream target genes. Total 18 male Wistar rats were randomly divided into two groups, control and test groups. Test rats were administered with 3 mg cadmium/kg body weight, while the control rats were treated with vehicle continuously for 28 days. Thereafter, rats were killed and the isolated brain samples were examined using oxidative stress assessment, histological and immunohistological behavioral assessment, polymerase chain reaction (PCR), and the comet assay. A disturbed oxidative balance, DNA damage, and an upregulated Shh signaling pathway were observed in cadmium-treated samples. Loss of structural integrity in cerebellum and loss of motor activity were observed in cadmium-treated rats.

Maize Cd-tolerant ZmVTE4 encoding γ-tocopherol-methyl-transferase alleviated Cd-toxicity through its product α-tocopherol

Cadmium (Cd) is a widespread non-essential toxic heavy metal and usually arouses oxidative stress which impairs plant growth. The key lipophilic antioxidant α-tocopherol is synthesized from γ-tocopherol by γ- tocopherol-methyl-transferase (γ-TMT encoded by VTE4) in response to a variety of abiotic stresses.The main purpose of this study was to characterize the Cd-tolerant maize ZmVTE4 which was obtained through high-throughput survival screening in the presence of Cd. Further heterologous expression of a ZmVTE4 enhanced Cd tolerance in yeast as well in tobacco. Moreover, Cd treatment induced the increment of tocopherols in maize leaves. Similarly, transient overexpressing ZmVTE4 increased the content of γ-tocopherol and α-tocopherol thus enhancing the Cd tolerance in tobacco leaves. Visualized fluorescence indicated that ZmVTE4 was localized in chloroplasts, where tocopherols were synthesized. These results collectively implicated that ZmVTE4-mediated α-tocopherol generation facilitated plant tolerance to Cd.

Inorganic mercury and cadmium induce rigidity in eukaryotic lipid extracts while mercury also ruptures red blood cells

Hg and Cd are non-essential toxic heavy metals that bioaccumulate in the tissues of living systems but less is known about their interactions with Eukaryotic lipid bilayers. Microscopy experiments showed that Hg and Cd changed the cell morphology of rabbit erythrocytes while Hg also induced cell rupture. As membranes are one of the first available targets, our study aimed to better understand metal-lipid interactions that could lead to toxic effects. Fluorescence spectroscopy (Laurdan Generalized Polarization) and dynamic light scattering were used to analyze metal-induced changes in membrane fluidity and the size of liposomes composed of Brain (Porcine), Liver (Bovine), Heart (Bovine) and Yeast (S. cerevisiae) lipid extracts. Under physiological chloride and pH levels, Hg irreversibly cleaves plasmalogens resulting in an increase in membrane rigidity. These lipids are enriched in Brain, Heart and Erythrocyte membranes and are important in signalling and the protection against oxidative stress. Interestingly, Hg had a heavily reduced effect on the plasmalogen-free Yeast extract membrane. In contrast, Cd induced rigidity by targeting negatively charged phosphatidic acid, phosphatidylserine, phosphatidylinositol, phosphatidylglycerol and cardiolipin in these extracts. Metal-induced liposome aggregation depended on the proportion of negatively charged lipids/plasmalogen and even the order of metal addition. Our results show that data from model systems correlate with trends observed in complex biological extracts and red blood cells and serve as a predictive tool for analyzing metal-lipid interactions. The determination of the specific lipid targets for Hg and Cd provides new insights how these metals exert toxic effects on cell membranes.

Decoding the role of hypothetical protein All3255 of Anabaena PCC7120 in heavy metal stress management in Escherichia coli.

Cadmium is a non-essential toxic heavy metal for organisms, including plants and cyanobacteria. Cadmium resistance transporters involved in resistance of cells against various toxicants such as drugs and effluxes cytotoxic compounds from cells. However, cadmium resistance-associated protein (CadD) has never been reported from a diazotrophic cyanobacterium Anabaena sp. To test whether the hypothetical protein All3255 of Anabaena sp. PCC7120 a homolog of cadmium resistance-associated protein (CadD) involved in cadmium or heavy metal resistance or not, cloning and heterologous expression analysis of all3255 performed in Escherichia coli BL21 (DE3). Our results revealed that the strain transformed with pGEX-5X-2 + all3255 showed resistant towards not only to cadmium but also other heavy metals such as nickel, copper, zinc, lead and cobalt in addition to arsenic than those of transformed with empty vector (pGEX-5X-2). Furthermore, the results of metal accumulation analysis of these cells unveil a lower accumulation of tested heavy metals in all3255-overexpressing E. coli cells than those transformed with empty vector. This study strongly supports the role of All3255 of Anabaena sp. PCC7120 as a CadD efflux pump of heavy metals in E.coli.

Melatonin promotes the proliferation of GC-1 spg cells by inducing metallothionein-2 expression through ERK1/2 signaling pathway activation.

Synthesized by the pineal gland, melatonin is a neurohormone implicated in diverse physiological functions via several mechanisms. However, the role of melatonin in spermatogenesis and its underlying mechanisms have yet to be completely understood. In the present study, transcriptome sequencing was performed to characterize the mechanism of melatonin-induced GC-1 spg proliferation. Gene ontology (GO) enrichment and pathway analyses were also conducted to identify the signaling pathways and biological processes involved in differential mRNA expression. Results revealed 28 differential genes. Of these genes, 11 were upregulated and 17 were downregulated. Melatonin increased the expression of metallothionein-2 (Mt2), a gene that acts as a protector to sequester nonessential toxic heavy metals. Functional investigations demonstrated that Mt2 overexpression promoted the proliferation of GC-1 spg cells, but Mt2 knockdown significantly suppressed their proliferation and increased their apoptosis. Mechanistic analysis indicated that the extracellular-signal-regulated kinase 1/2 (ERK1/2) pathway participated in melatonin-promoted proliferation of GC-1 spg cells. Therefore, melatonin induces the proliferation of GC-spg 1 cells by stimulating Mt2 expression, and this process is mediated by the ERK1/2 signaling pathway.

Zinc fertilisation increases grain zinc and reduces grain lead and cadmium concentrations more in zinc-biofortified than standard wheat cultivar

Given that plant uptake and transport systems for metals have some similarities, zinc (Zn)-biofortified cultivars may concurrently accumulate non-essential toxic heavy metals in grains. However, Zn-biofortified cultivars have never been tested for heavy metal accumulation in grains. In a pot experiment, we compared Zn-biofortified wheat (Zincol-2016) with a standard wheat (Faisalabad-2008) cultivar on heavy-metal-contaminated soils for yield response and grain accumulation of Zn, lead (Pb) and cadmium (Cd), without or with Zn fertilisation (8mgZnkg−1). The soils, collected from agricultural fields in (i) industrial zone and (ii) peri-urban area, had been receiving industrial and city effluents for >20years. In the two soils, Zn fertilisation significantly (P≤0.05) increased grain yield of both cultivars. Zinc fertilisation increased grain Zn concentration of Zincol-2016 and Faisalabad-2008 by respectively 32 and 18% in industrial-zone soil, and by 15 and 2% in peri-urban soil. Averaged across Zn rates, Zincol-2016 accumulated in grains more than double the Zn amount than Faisalabad-2008 in industrial-zone soil. At 0mgZnkg−1, grain Pb and Cd concentrations were respectively 26 and 33% greater in Zincol-2016 than Faisalabad-2008 in industrial-zone soil, and 86 and 50% greater in Zincol-2016 than Faisalabad-2008 in peri-urban soil. Zinc fertilisation significantly (P≤0.05) decreased concentration of Pb and Cd in grains of both cultivars. In industrial-zone soil, a toxic level of Pb in grains (0.24mgkg−1) was attained at control rate of Zn by Zincol-2016, and was decreased to a safe level (0.07mgkg−1) by application of 8mgZnkg−1. Therefore, biofortified cultivars should not be grown in contaminated soils, and/or sufficient Zn must be applied, to decrease accumulation of non-essential toxic heavy metals in grains. Moreover, future breeding efforts should be directed toward selection of biofortified cultivars that would selectively accumulate Zn in grains, but not the contaminants.

Bioaccumulation and health risks of heavy metals associated with consumption of rice grains from croplands in Northern India

ABSTRACTThe present study focused on micronutrients and nonessential toxic heavy metals quantification and their bio-concentration in soil–rice system in Haryana, India. Composite samples of rice grains and paddy fields' soil were collected, processed and analyzed for heavy metals. Nutrient and heavy metals' content of paddy fields' soil varied over a wide range, having highest Fe content followed by Cu > Cr > Pb > Ni > Zn > Co > Cd. Most of the metals viz. Fe, Zn, Cu and Co found profusely in rice grains were essential micronutrients. Bio-concentration factors (BCFs) in rice grains were in the following order: Zn (0.11) > Co (0.10) > Cu (0.08) = Cr (0.08) > Ni (0.02) > Pb (0.011) > Cd (0.009) > Fe (0.003), indicating higher accumulation of micronutrients than non-essential toxic heavy metals. Principal component analysis revealed three factors accounting for 70% of the total variance which supported correlation among electrical conductivity (EC)-Na, EC-cation exchange capacity (CEC), CEC-Na, pH-TOC, and BCFCu-BCFZn. Health risk indices anticipated that the grains are safe for consumption as non-carcinogenic hazard quotients were less than unity for all the studied heavy metals.

Carbon nanotubes and graphenes as adsorbents for adsorption of lead ions from water: a review

Nanomaterials have wide applications as sorbents for water purification as they have high selectivity as well as capacity for organic/inorganic pollutants and contaminants in aqueous solutions. Non-essential toxic heavy metals present in water have become a major cause of many diseases, ageing, and genetic problems. Carbon-based nanomaterials have generated great interest in their use as sorbent materials for removal of heavy metals from water/wastewater as they are stable, have limited reactivity, wide surface area, and are strong antioxidants. This study explored the possibility of ranking different carbon-based nanomaterials for efficient removal of lead ions from water which are routinely detected in water samples. Lead may be introduced in water because of its intensive use in many products. The adsorbents based on graphenes and carbon nanotubes have been analyzed on the basis of adsorption capacity, reusability, toxicity/biocompatibility, and cost. The effects of surface area of sorbent, pH of water, thermodynamics/kinetic studies have also been analyzed to evaluate the efficiency of sorbents. The information can be utilized to select the appropriate, most efficient and safe sorbents for removal of lead ions from water.

OsACA6, a P-type 2B Ca(2+) ATPase functions in cadmium stress tolerance in tobacco by reducing the oxidative stress load.

The present study demonstrates the first direct evidence of the novel role of OsACA6 in providing Cd (2+) stress tolerance in transgenic tobacco by maintaining cellular ion homeostasis and modulating ROS-scavenging pathway. Cadmium, a non-essential toxic heavy metal, interferes with the plant growth and development. It reaches the leaves through xylem and may become part of the food chain, thus causing detrimental effects to human health. Therefore, there is an urgent need to develop strategies for engineering plants for Cd(2+) tolerance and less accumulation. The members of P-type ATPases family transport metal ions including Cd(2+), and thus play important role an ion homeostasis. The present study elucidates the role of P-type 2B Ca(2+) ATPase (OsACA6) in Cd(2+) stress tolerance. The transcript levels of OsACA6 were up-regulated upon Cd(2+), Zn(2+) and Mn(2+) exposure. Transgenic tobacco expressing OsACA6 showed tolerance towards Cd(2+) stress as demonstrated by several physiological indices including root length, biomass, chlorophyll, malondialdehyde and hydrogen peroxide content. The roots of the transgenic lines accumulated more Cd(2+) as compared to shoot. Further, confocal laser scanning microscopy showed that Cd(2+) exposure altered Ca(2+) uptake in OsACA6 transgenic plants. OsACA6 expression in tobacco also protected the transgenic plants from oxidative stress by enhancing the activity of enzymatic (SOD, CAT, APX, GR) and non-enzymatic (GSH and AsA) antioxidant machinery. Transgenic lines also tolerated Zn(2+) and Mn(2+) stress; however, tolerance for these ions was not as significant as observed for Cd(2+) exposure. Thus, overexpression of OsACA6 confers Cd(2+) stress tolerance in transgenic lines by maintaining cellular ion homeostasis and modulating reactive oxygen species (ROS)-scavenging pathway. The results of the present study will help to develop strategies for engineering Cd(2+) stress tolerance in economically important crop plants.

Cadmium determinant 1 is a putative heavy‐metal transporter in Arabidopsis thaliana (617.4)

Cadmium (Cd) is a non‐essential toxic heavy metal for most organisms. Accumulation of Cd is toxic to plants, and it also causes serious health concerns in humans as plants are the major staples in human diet. In A. thaliana, cadmium is mainly accumulated in the roots suggesting that root‐to‐shoot Cd translocation is restricted at the xylem loading. Up to date, two members of HEAVY METAL P1B‐ATPase (HMA) family of transporters, namely HMA2 and HMA4, and some YSL transporters have been shown to be responsible for Cd loading into the xylem. Here we present data suggesting CADMIUM DETERMINANT 1 (CDM1) as a previously uncharacterized putative heavy‐metal transporter in plants. Expression of CDM1 was induced under Cd treatment in wild‐type seedling roots. Elemental analysis of two alleles of cdm1 mutant by ICP‐MS showed that the mutants accumulated less Cd and Zn both in shoots and roots after Cd treatment. In addition, root growth of cdm1 mutants showed higher tolerance to Cd toxicity. These data suggest that CADMIUM DETERMINANT 1 (CDM1) functions in Cd distribution in plants. Interestingly, preliminary confocal microscopy analyses of seedlings overexpressing CDM1:GFP indicated that CDM1 localized to the plastids. Further characterization of CDM1:GUS and CDM1 overexpression lines are in progress.Grant Funding Source: Supported by NSF‐MCB 0950459