Screening of Cd tolerant genotypes and isolation of metallothionein genes in alfalfa (Medicago sativa L.)

In order to evaluate Cd tolerance in wide-ranging sources of alfalfa (Medicago sativa) and to identify Cd tolerant genotypes which may potentially be useful for restoring Cd-contaminated environments, thirty-six accessions of alfalfa were screened under hydroponic culture. Our results showed that the relative root growth rate varied from 0.48 to 1.0, which indicated that different alfalfa accessions had various responses to Cd stress. The candidate fragments derived from differentially expressed metallothionein (MT) genes were cloned from leaves of two Cd tolerant genotypes, YE and LZ. DNA sequence and the deduced protein sequence showed that MsMT2a and MsMT2b had high similarity to those in leguminous plants. DDRT-PCR analysis showed that MsMT2a expressed in both YE and LZ plants under control and Cd stress treatment, but MsMT2b only expressed under Cd stress treatment. This suggested that MsMT2a was universally expressed in leaves of alfalfa but expression of MsMT2b was Cadmium (Cd) inducible.     

The arbuscular mycorrhizal fungus Glomus mosseae can enhance arsenic tolerance in Medicago truncatula by increasing plant phosphorus status and restricting arsenate uptake

A pot experiment examined the biomass and As uptake of Medicago truncatula colonized by the arbuscular mycorrhizal (AM) fungus Glomus mosseae in low-P soil experimentally contaminated with different levels of arsenate. The biomass of G. mosseae external mycelium was unaffected by the highest addition level of As studied (200 mg kg⁻¹) but shoot and root biomass declined in both mycorrhizal and non-mycorrhizal plants, indicating that the AM fungus was more tolerant than M. truncatula to arsenate. Mycorrhizal inoculation increased shoot and root dry weights by enhancing host plant P nutrition and lowering shoot and root As concentrations compared with uninoculated plants. The AM fungus may have been highly tolerant to As and conferred enhanced tolerance to arsenate on the host plant by enhancing P nutrition and restricting root As uptake.     

Arsenic tolerances in rice (Oryza sativa) have a predominant role in transcriptional regulation of a set of genes including sulphur assimilation pathway and antioxidant system

World wide arsenic (As) contamination of rice has raised much concern as it is the staple crop for millions. Four most commonly cultivated rice cultivars, Triguna, IR-36, PNR-519 and IET-4786, of the West Bengal region were taken for a hydroponic study to examine the effect of arsenate (As^V) and arsenite (As^III) on growth response, expression of genes and antioxidants vis-à-vis As accumulation. The rice genotypes responded differentially under As^V and As^III stress in terms of gene expression and antioxidant defences. Some of the transporters were up-regulated in all rice cultivars at lower doses of As species, except IET-4786. Phytochelatin synthase, GST and γ-ECS showed considerable variation in their expression pattern in all genotypes, however in IET-4786 they were generally down-regulated in higher As^III stress. Similarly, most of antioxidants such as superoxide dismutase (SOD), ascorbate peroxidase (APX), guaiacol peroxidase (GPX), catalase (CAT), monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR) increased significantly in Triguna, IR-36 and PNR-519 and decreased in IET-4786. Our study suggests that Triguna, IR-36 and PNR-519 are tolerant rice cultivars accumulating higher arsenic; however IET-4786 is susceptible to As-stress and accumulates less arsenic than other cultivars.     

Oxidative stress in the kidney injury of mice following exposure to lanthanides trichloride

Environmental pollution from lanthanides (Ln) has been recognized as a major problem due to a grab exploitation of Ln mine in China. Exposure to Ln has been demonstrated to cause the nephrotoxicity, very little is known about the mechanism of oxidative damage to kidney in animals. In order to understand Ln-induced nephrotoxicity, various biochemical and chemical parameters were assayed in mouse kidney. Intragastric exposures of LaCl₃, CeCl₃, and NdCl₃ at doses of 2, 5, and 10 mg kg⁻¹ BW for 90 consecutive days caused nephritis or epithelial cell necrosis and oxidative stress to kidney. An increase in coefficients of the kidney, La, Ce, and Nd accumulation and histopathological changes in the kidney could be observed, followed by increased reactive oxygen species production and peroxidation levels of lipid, protein and DNA, and decreased activities of superoxide dismutase, catalase, glutathione-S-transferase and glutathione reductase as well as antioxidants such as glutathione, ascorbic acid and thiol contents. Furthermore, La, Ce, and Nd significantly suppressed expression of genes and proteins of these antioxidative enzymes in mouse kidney. In addition, kidney functions were disrupted, including an increase of the creatinine, and reductions of uric acid, urea nitrogen, calcium and phosphonium. These findings suggest that nephritis generation or epithelial cell necrosis in mice following exposure to Ln is closely associated with oxidative stress. Of these damages, the most severe was in the Ce³⁺-exposed kidneys, next in the Nd³⁺-exposed kidneys, and the least in the La³⁺-exposed kidneys, which may be attributed to the 4f electron of Ln.     

Enhanced antioxidant capacity and upregulated transporter genes contribute to the UV-B-induced increase in blinin in Conyza blinii

Environmental Science and Pollution Research - Conyza blinii (C. blinii) is a traditional Chinese medicinal plant mainly grown in Sichuan, China. C. blinii is suitable for studying the mechanism of...     

Relationship between foliar injury and changes in antioxidant levels in red and Norway spruce exposed to acidic mists

Elevated levels of total glutathione and enhanced activities of glutathione reductase and ascorbate peroxidase were found in needles of red spruce which had been exposed to acidic mists. Reduced levels of ascorbate were also detected. Such observations suggest that oxidative stress is involved in processes which resist foliar injury caused by acidic misting. Different ionic compositions of the acidic mists applied had pronounced effects on the levels of these antioxidants and the activities of related enzymes. Sulphate was found to be most effective in causing increases in glutathione, while additions of ammonium and/or nitrate mitigated the effects of sulphuric acid. Moreover, it is the composition of ions in the applied mists, rather than the levels of acidity, that determines the extent of the overall response of red spruce. By contrast, although acidic mists caused similar increases in glutathione content of Norway spruce needles, no statistically significant changes of ascorbate or related enzymic activities were found.     

Cloning of a river pufferfish (Takifugu obscurus) metallothionein cDNA and study of its induction profile in cadmium-exposed fish

We report here the full-length cDNA sequence of metallothionein (MT) gene from an anadromous river pufferfish, Takifugu obscurus (order: Tetradotiformes; family: Tetradontidae). Phylogenetic relationship analysis revealed that the identified MT has high sequence similarity with many Perciformes fish species. The tissue distribution and concentration- and time-dependent expression of MT mRNA were studied in fish exposed to cadmium. Liver showed the highest level of MT gene expression followed by other tissues (brain, gill and kidney) in response to cadmium exposure. Muscle showed a weak expression response of MT gene. Time-course study revealed highest early phase (at 6h) expression in the brain and late persistence of induction in the intestine. MT mRNA expression showed a concentration-dependent expression in all the tissues. However, induction in brain and liver occurred at much lower concentrations as compared to other tissues. Our results demonstrate that MT in T. obscurus is induced by cadmium exposure which indicates that it plays a functionally conserved function of metal detoxification.     

Oxidative stress status,antioxidant metabolism and polypeptide patterns in Juncus maritimus shoots exhibiting differential mercury burdens in Ria de Aveiro coastal lagoon (Portugal)

This study assessed the oxidative stress status, antioxidant metabolism and polypeptide patterns in salt marsh macrophyte Juncus maritimus shoots exhibiting differential mercury burdens in Ria de Aveiro coastal lagoon at reference and the sites with highest, moderate and the lowest mercury contamination. In order to achieve these goals, shoot-mercury burden and the responses of representative oxidative stress indices, and the components of both non-glutathione- and glutathione-based H₂O₂-metabolizing systems were analyzed and cross-talked with shoot-polypeptide patterns. Compared to the reference site, significant elevations in J. maritimus shoot mercury and the oxidative stress indices such as H₂O₂, lipid peroxidation, electrolyte leakage and reactive carbonyls were maximum at the site with highest followed by moderate and the lowest mercury contamination. Significantly elevated activity of non-glutathione-based H₂O₂-metabolizing enzymes such as ascorbate peroxidase and catalase accompanied the studied damage-endpoint responses, whereas the activity of glutathione-based H₂O₂-scavenging enzymes glutathione peroxidase and glutathione sulfo-transferase was inhibited. Concomitantly, significantly enhanced glutathione reductase activity and the contents of both reduced and oxidized glutathione were perceptible in high mercury-exhibiting shoots. It is inferred that high mercury-accrued elevations in oxidative stress indices were obvious, where non-glutathione-based H₂O₂-decomposing enzyme system was dominant over the glutathione-based H₂O₂-scavenging enzyme system. In particular, the glutathione-based H₂O₂-scavenging system failed to coordinate with elevated glutathione reductase which in turn resulted into increased pool of oxidized glutathione and the ratio of oxidized glutathione-to-reduced glutathione. The substantiation of the studied oxidative stress indices and antioxidant metabolism with approximately 53-kDa polypeptide warrants further studies.     

Lead and zinc accumulation and tolerance in populations of six wetland plants

Wetland plants such as Typha latifolia and Phragmites australis have been indicated to show a lack of evolution of metal tolerance in metal-contaminated populations. The aim of the present study is to verify whether other common wetland plants such as Alternanthera philoxeroides and Beckmannia syzigachne, also possess the same characteristics. Lead and zinc tolerances in populations of six species collected from contaminated and clean sites were examined by hydroponics. In general, the contaminated populations did not show higher metal tolerance and accumulation than the controls. Similar growth responses and tolerance indices in the same metal treatment solution between contaminated and control populations suggest that metal tolerance in wetland plants are generally not further evolved by contaminated environment. The reasons may be related to the special root anatomy in wetland plants, the alleviated metal toxicity by the reduced rooting conditions and the relatively high innate metal tolerance in some species.     

Subcellular distribution and chemical form of Cd and Cd-Zn interaction in different barley genotypes

A hydroponic experiment was carried out to study the genotypic difference in subcellular distribution and chemical form of Cd and Zn uptake and their interaction in four barley genotypes. Increased Cd level in the medium caused a significant increase of Cd concentration in all fractions of roots/shoots, with most accumulation in FI (cell wall) and FIV (soluble). In root, the greatest amount of Cd was found in extraction solution of 2% HAC or 0.6M HCl, followed by 1M NaCl (20%), and lowest in extraction of 80% ethanol or d-H2O. While in shoot, the highest value of Cd accumulation was recorded in the fractions extracted by 1M NaCl and 2% HAC, followed by 0.6M HCl or d-H2O, and least in 80% ethanol extraction solution. There was a distinct difference among genotypes in Cd concentration in subcellular and chemical forms and it was found that the Cd-sensitive genotype Wumaoliuling, in comparison with the other three Cd-resistant genotypes, had higher Cd concentration in chloroplast-shoot/trophoplast-root (FII), membrane and organelle (FIII) and in inorganic and water-soluble Cd of roots, while lower in FI, FIV and pectates/protein integrated Cd. After 48 h of Cd treatment, the plants were replaced into Cd-free nutrient solution and grown for 72 h, a significant decrease in Cd concentration of root FI was observed, with less Cd reduction in Wumaoliuling. In comparison with control (no Cd), addition of Cd significantly increased Zn accumulation in chloroplast (FII), with least increase in Wumaoliuling. The Zn content in the other 3 fractions decreased significantly with addition of Cd, especially in roots, while Wumaoliuling was the most severely affected genotype. Moreover, it could be suggested Zn supplement could significantly reduce Cd concentration in root trophoplast and in shoot soluble fraction of Cd-treated plants.     

Culturability and concentration of indoor and outdoor airborne fungi in six single-family homes

In this study, the culturability of indoor and outdoor airborne fungi was determined through long-term sampling (24-h) using a Button Personal Inhalable Aerosol Sampler. The air samples were collected during three seasons in six Cincinnati area homes that were free from moisture damage or visible mold. Cultivation and total microscopic enumeration methods were employed for the sample analysis. The geometric means of indoor and outdoor culturable fungal concentrations were 88 and 102 colony-forming units (CFU) m(-3), respectively, with a geometric mean of the I/O ratio equal to 0.66. Overall, 26 genera of culturable fungi were recovered from the indoor and outdoor samples. For total fungal spores, the indoor and outdoor geometric means were 211 and 605 spores m(-3), respectively, with a geometric mean of I/O ratio equal to 0.32. The identification revealed 37 fungal genera from indoor and outdoor samples based on the total spore analysis. Indoor and outdoor concentrations of culturable and total fungal spores showed significant correlations (r = 0.655, p<0.0001 and r = 0.633, p<0.0001, respectively). The indoor and outdoor median viabilities of fungi were 55% and 25%, respectively, which indicates that indoor environment provides more favorable survival conditions for the aerosolized fungi. Among the seasons, the highest indoor and outdoor culturability of fungi was observed in the fall. Cladosporium had a highest median value of culturability (38% and 33% for indoor and outdoor, respectively) followed by Aspergillus/Penicillium (9% and 2%) among predominant genera of fungi. Increased culturability of fungi inside the homes may have important implications because of the potential increase in the release of allergens from viable spores and pathogenicity of viable fungi on immunocompromised individuals.     

鸡粪有机肥对土壤中抗生素抗性基因和整合酶基因的影响

为探究施用有机肥对土壤中抗性基因和整合酶基因分布的影响及其与土壤环境因子的相关关系,利用高通量PCR技术监测了鸡粪有机肥施用120 d后土壤中四环素类抗性基因、大环内酯类抗性基因、整合酶基因和土壤理化性质的变化情况。研究结果表明,施肥土壤的电导率、pH、有机质含量均明显增加,而土壤氧化还原电位由217.27 mV降低到154.47 mV。施肥土壤中钾、氮、磷、铅、铜和锌含量均上升。施加鸡粪有机肥120 d后,土壤中tetM、tetQ、tetW、tetG和tetX 5种四环素类抗性基因相对丰度分别增加了2.90、0.97、6.80、0.98和0.94倍,而erm35、ermB、ermT、ermX和ermF 5种大环内酯类抗性基因相对丰度分别增加了0.98、136.68、0.95、2.89和2.89倍;但erm36相对丰度降低了0.75倍,其中施肥后土壤中ermB丰度最高而erm36丰度最低。施用鸡粪有机肥后,土壤中intI1和intI3的丰度分别降低了4.71 × 10-5和2.57 × 10-7,而intI2的丰度增加了3.74 × 10-6。Network分析发现intI3与除ermB外的基因均呈显著负相关关系(R=-1.00,P<0.05)。     

Fenton试剂和活化过硫酸钠氧化降解土壤中的二氯酚和三氯酚

氯酚类物质（chlorophenols, CPs）在环境介质中广泛存在且具有很强环境毒性。为探究化学氧化修复场地氯酚类污染的可行性,通过室内实验、模拟搅拌实验、现场中试,开展应用Fenton试剂和活化过硫酸钠氧化降解土壤CPs的研究。结果表明,化学氧化可有效降解土壤中的CPs,在氧化剂用量和CPs总量摩尔比为15:1时,CaO活化Na2S2O8能高效降解土壤中的二氯酚（2,4-DCP）和三氯酚（2,4,6-TCP）,室内实验和现场中试的去除率均达90%以上,处理后的2,4-DCP和2,4,6-TCP浓度均低于《展览会用地土壤环境质量评价标准》（HJ 350-2007）A类标准限值。Fenton试剂在室内实验中降解率达90%以上,但现场中试对2,4-DCP和2,4,6-TCP的降解率仅为66.1%、23.8%,处理后2,4-DCP浓度仍超过A类标准限值1倍以上。此外,在修复过程中,约70%的2,4-DCP、2,4,6-TCP会向液相转移,因此,需要关注修复系统引入水后污染物向液相中的转移可能造成的二次污染。研究结果可为氯酚类污染土壤的修复提供新思路,并为实际工程应用提供理论依据。     

Correlations between cadmium and mineral nutrients in absorption and accumulation in various genotypes of rice under cadmium stress

The absorption and accumulation of Cd2+, Fe3+, Zn2+, Mn2+, Cu2+ and Mg2+ in the roots and leaves of 20 rice cultivars (Oryza sativa L.) with different genotypes under cadmium (Cd) stress were investigated with pot experiments. The results showed that there existed significant differences among the rice cultivars in the contents of six mineral elements in both roots and leaves at both heading and ripening periods. The statistical analysis showed that, for their contents in roots, significant and positive correlations between Cd2+ and Fe3+, Cd2+ and Zn2+, Cd2+ and Mn2+, Cd2+ and Cu2+ existed, but no significant correlation between Cd2+ and Mg2+, at the two periods. In the leaves, Cd also showed significant and positive correlations with Fe3+, Zn2+ and Cu2+ at the both periods, but a significant and negative correlation with Mn2+ and no significant correlation with Mg2+ at heading, a significant and positive correlation with Mg2+ and no significant correlation with Mn2+ at ripening. These results suggested that there were cooperative absorption between Cd2+ and Fe3+, Mn2+, Cu2+, Mn2+ in rice plants. Genotypic differences in Cd uptake and translocation among the rice cultivars suggested that paddy field of some rice cultivars may be irrigated with partially treated sewage water.     

Fractionation analysis and health risk assessment of heavy metals in six traditional Chinese medicines

Environmental Science and Pollution Research - Traditional Chinese medicines (TCMs) are widely used to treat various diseases in China and some countries, and TCM products are becoming increasingly...     

ALAD genotypes and blood lead levels of neonates and children from e-waste exposure in Guiyu,China

Extensive e-waste recycling activity in Guiyu, China, has been conducted using primitive techniques for the last 20 years, resulting in serious heavy metal environmental contamination. A polymorphic variant of the δ-aminolevulinic acid dehydratase (ALAD) gene has been found to influence lead uptake and, thus, may influence an individual’s susceptibility to lead toxicity. We therefore explored whether the ALAD gene polymorphism affects blood lead levels of newborns and children in Guiyu. A total of 273 newborns and 504 children, and a combination of 2004/2005 and 2006 independent recruitments were used for this study. Umbilical cord blood from newborns (Guiyu/exposed group 189 vs. Chaonan/reference group 84) and venous blood from children (exposed group, 319 vs. Chendian/reference group 185) were collected. Blood lead levels (BLLs) were measured via graphite furnace atomic absorption spectrometry (GFAAS) for all samples, while ALAD genotyping was performed using PCR-RFLP for 273 neonate cord blood and 246 children’s blood. The median BBLs of neonates in exposed group vs. the reference group were 10.50 (2.36–40.78) vs. 7.79 (0.8–19.51) for 2004/2005 and 9.41 (9.28–47.60) vs. 5.49 (0.35–18.68) for 2006, while child mean BLLs were 15.31?±?5.79 vs. 9.94?±?4.05 for 2004/2005 and 13.17?±?5.98 vs. 10.04?±?4.85 for 2006. The genotype frequencies in newborns were 98.90 % for the ALAD-1/ALAD-1 homozygote and 1.10 % for the ALAD-1/ALAD-2 heterozygotes, while the values were 95.93 and 4.07 %, respectively, in children. The allele frequencies of the ALAD-1 and ALAD-2 were 99.45 and 0.55 % for newborns, but 97.97 and 2.03 % for children, respectively. No significant differences in blood lead levels were found between ALAD-1/ALAD-1 and ALAD-1/ALAD-2 either in newborns or in children. The frequency distribution of the ALAD-2 allele in newborns from the exposed group was lower than that of the reference group. There were no significant differences, between the two different ALAD genotypes in the lead load of newborns and children. The frequency distribution of ALAD gene does not influence the blood lead levels of newborns and children in this case, which means that the higher lead burden in the exposed children was possibly influenced by e-waste recycling, but not ALAD genotypes.     

Dissipation and sorption of six commonly used pesticides in two contrasting soils of New Zealand

We investigated dissipation and sorption of atrazine, terbuthylazine, bromacil, diazinon, hexazinone and procymidone in two contrasting New Zealand soils (0–10 cm and 40–50 cm) under controlled laboratory conditions. The six pesticides showed marked differences in their degradation rates in both top- and subsoils, and the estimated DT₅₀ values for the compounds were: 19–120 (atrazine), 10–36 (terbuthylazine), 12–46 (bromacil), 7–25 (diazinon), 8–92 (hexazinone) and 13–60 days for procymidone. Diazinon had the lowest range for DT₅₀ values, while bromacil and hexazinone gave the highest DT₅₀ values under any given condition on any soil type. Batch derived effective distribution coefficient (K _d ^eff) values for the pesticides varied markedly with bromacil and hexazinone exhibiting low sorption affinity for the soils at either depth, while diazinon gave high sorption values. Comparison of pesticide degradation in sterile and non-sterile soils suggests that microbial degradation was the major dissipation pathway for all six compounds, although little influence of abiotic degradation was noticeable for diazinon and procymidone.     

Oxidative damage induced in hearts, kidneys and spleens of mice by landfill leachate

The effects of the Xingou landfill leachate on levels of thiobarbituric acid reactive substances (TBARS) and the activities of Cu, Zn-superoxide dismutase (Cu, Zn-SOD), Se-dependent glutathione peroxidase (Se-dependent GPx) and catalase (CAT) were investigated in hearts, kidneys and spleens of Kunming albino mice of both sexes. Exposure to leachate caused significant increases of TBARS levels in the organs tested from mice of both sexes. For hearts, Cu, Zn-SOD, Se-dependent GPx and CAT activities were significantly increased at high concentrations for male mice, but the activities of these antioxidant enzymes were significantly increased at low concentration and decreased at high concentrations for female mice. For kidneys, Cu, Zn-SOD and Se-dependent GPx activities were significantly increased at high concentrations for male mice, but the activities were significantly increased at low concentrations and the ratio of increase was reduced with the increasing of concentration for female mice; CAT activities remained unchanged for male mice and were significantly increased at all concentrations tested for female mice. For spleens, Cu, Zn-SOD and Se-dependent GPx activities were significantly increased at high concentrations for male mice, but the activities were significantly increased at low concentrations and decreased at high concentrations for female mice; CAT activities remained unchanged for male mice and were significantly increased at high concentrations for female mice. The results suggest that leachate exposure can cause oxidative damage on hearts, kidneys and spleens of mice, and there were sex difference and organ difference in the response of antioxidant status.