Possible roles of phytochelatins and glutathione metabolism in cadmium tolerance in chickpea roots

The possible roles of phytochelatin (PC) and glutathione (GSH) in the heavy metal detoxification in plants were examined using two varieties (CSG-8962 and C-235) of chickpea (Cicer arietinum L.). The seedlings were grown for 5 days and the roots were treated with 0–20 μM CdSO₄ for 3 days. The CSG-8962 seedlings exhibited more Cd-tolerant characteristics than did the C-235, where the roots, rather than shoots, suffered from more toxic effects by Cd. Both the seedlings synthesized the large amounts of PCs and homo-phytochelatins (hPCs) in roots, but only a little in shoots in response to Cd. The Cd treatments also caused a marked increase in the levels of GSH and cysteine in both the root and shoot tissues, suggesting that Cd may activate the GSH biosynthesis and, hence, enhance PC synthesis in the plants. Such a Cd-sensitive PC synthesis in chickpea plants does not explain the difference in Cd sensitivity in the varieties, but can be used as a biochemical indicator for Cd contamination in various environments. In the chickpea plants, possible PC-dependent and independent mechanisms for Cd tolerance are discussed. Electronic Publication     

Exposure of silver carp (Hypophthalmichthys molitrix) to environmentally relevant levels of cadmium:hematology,muscle physiology,and implications for stock enhancement in the Xiangjiang River (Hunan,China)

Cadmium is a non-essential metal with a wide distribution that has severe toxic effects on aquatic animals. Changes in hematology and muscle physiology were examined in silver carp (Hypophthalmichthys molitrix) exposed to environmentally relevant levels of cadmium (0.01 mg L-1 ) for 96 h. Cadmium exposure induced significant increases in the red blood cell count, and in the plasma concentrations of cortisol, glucose, and lactate. This suggests that the dose of cadmium was sufficient to cause stress, possibly associated with impaired gas exchange at the gills. There were no changes in hemoglobin concentration or plasma protein concentration. Significant decreases in muscle energy fuels (ATP and glycogen), and increases in muscle lactate persisted until the end of the exposure period, respectively. The changes in muscle lactate and protein in silver carp differed from those observed in response to exposure of fish to cadmium and heavy metals in other studies. The study highlights the importance of selecting unpolluted release sites with suitable water conditions for the survival of newly released individuals for stock enhancement of the Xiangjiang River.     

Mapping QTLs with epistatic effects and QTL×environment interactions for plant height using a doubled haploid population in cultivated wheat

Quantitative trait loci (QTLs) for plant height in wheat (Triticum aestivum L.) were studied using a set of 168 doubled haploid (DH) lines, which were derived from the cross Huapei 3/Yumai 57. A genetic linkage map was constructed using 283 SSR and 22 EST-SSR markers. The DH population and the parents were evaluated for wheat plant height in 2005 and 2006 in Tai’an and 2006 in Suzhou. QTL analyses were performed using the software of QTLNetwork version 2.0 based on the mixed linear model. Four additive QTLs and five pairs of epistatic effects were detected, which were distributed on chromosomes 3A, 4B, 4D, 5A, 6A, 7B, and 7D. Among them, three additive QTLs and three pairs of epistatic QTLs showed QTL×environment interactions (QEs). Two major QTLs, Qph4B and Qph4D, which accounted for 14.51% and 20.22% of the phenotypic variation, were located similar to the reported locations of the dwarfing genes Rht1 and Rht2, respectively. The Qph3A-2 with additive effect was not reported in previous linkage mapping studies. The total QTL effects detected for the plant height explained 85.04% of the phenotypic variation, with additive effects 46.07%, epistatic effects 19.89%, and QEs 19.09%. The results showed that both additive effects and epistatic effects were important genetic bases of wheat plant height, which were subjected to environmental modifications, and caused dramatic changes in phenotypic effects. The information obtained in this study will be useful for manipulating the QTLs for wheat plant height by molecular marker-assisted selection (MAS).     

Effect of Pb pollution on the growth,biomass allocation and photosynthesis of Phragmites australis in flood and drought environment北大核心CSCD

Aims Reed (Phragmites australis) is a typical perennial rhizomatic plant with extensive tolerance to environmental stress. In order to better understand the adaptation and tolerance of reeds subjected to heavy metal pollution in different levels of water, we conducted a study on the effects of Pb pollution on growth, biomass and photosynthesis of reeds in flood and drought environment. This research would provide theoretical basis for application of reeds in wetland restoration and remediation. Methods We conducted a pot experiment with destructive sampling after 90 days of growth. The water treatments were main plot, including two water levels. The Pb treatments were secondary plot (nested within water treatments), including five levels (0, 500, 1 500, 3 000, 4 500 mg·kg–1). There were 10 treatments with 12 replicates per treatment. Important findings In the flood environment, Pb pollution significantly inhibited the growth of buds and rhizomes, but had no significant effect on the number of offspring shoots. The offspring shoots had higher growth rate per day, net photosynthetic rate and biomass compared to the parent shoots. In the drought environment, Pb pollution inhibited the growth of roots, buds and rhizomes, and biomass accumulation of parent and offspring shoots as well as photosynthetic parameters. These parameters were lower under the drought condition than in the flood environment. The Pb was mostly concentrated in roots compared to rhizomes and offspring shoots. In both flood and drought environments, the concentration of Pb in parent shoots was about three times of that in offspring shoots. The Pb concentration in offspring shoots under the flood condition was less than that in the drought environment. Overall, these results indicated that the synergistic effect of Pb and drought significantly inhibited the growth, biomass accumulation and photosynthesis of reeds, which might result in reduced offspring productivity and population density and may lead to population decline. However, the flooded reeds could adopt some strategies of Pb allocation to alleviate the negative effect of Pb on the growth, physiology and clonal propagation, benefiting the population reproduction and stabilization. © 2018 Editorial Office of Chinese Journal of Plant Ecology. All rights reserved.     

无样地法在亚热带常绿阔叶林调查中的应用

 The toxicity of N-503 on wheat appears evidently in the seedling stage and becomes gradually less and little from the jointing stage to the mature stage. However, the symptom of damage is based upon the concentration of N-503 used. The concentration is better to keep below 50ppm. The effect of N-503 on rice is similarly to wheat, but the amount of residue in rice is more apparently than that in wheat. Chlorobenzene in the mixed sewage is also shown some damage symptom to rice.     

Effect of Heavy Metals （Cd, Cu） on the Gametophytes of Laminaria japonica Aresch

Effects of various concentrations of two heavy metals, namely Cd and Cu, on gametophytes of Laminariajaponica Aresch were determined by recording morphological changes of gametophytes, determining pH values and the heavy metal content of the culture solution, calculating the germination rate of sporophytes, and observing heavy metal （Cd） distribution using a fluorescence microscope. The results showed that heavy metals damaged the gametophytes, and were even lethal, and that the higher the concentration of heavy metal ions, the greater the injury to gametophytes. Gametophytes could not survive in culture solutions containing more than 100 mg/L Cd and 50 mg/L Cu and were only able to survive in culture solution containing a mixture of Cd and Cu up to a concentration of 10 mg/L, which indicates that gametophytes have a higher tolerance to Cd than Cu and that multiple heavy metal ions in solution markedly aggravate the damage to gametophytes compared with individual heavy metal ions. With increases in the concentration of the heavy metal, the burgeoning rate of sporophytes decreased acutely, and solutions containing multiple heavy metal ions caused even more marked harm to sporophytes than solutions containing a single heavy metal ion, because most sporophytes died in mixed solutions. The pH value of the culture medium dropped immediately at the beginning （the first day） of treatment, increased over the following days, and then decreased again. The pH of culture media containing multiple heavy metal ions showed greater variation than media containing a single heavy metal ion, with the extent of the decrease in pH of culture media containing multiple ions being greatest during the last period of the experiment. With increases in the concentration of heavy metals, the capacity of gametophytes to accumulate these ions increased. The blue fluorescent light emitted by the Cd-and Cd-binding protein complex existing in gametophytes in media containing different concentrations of Cd showed clearly the distribution of the ion in gametophytes and the results obtained were consistent with distribution determined using other methods. All results of the present study showed that gametophytes of L. japonica play a remarkable role as heavy metal decontaminators, especially with regard to Cd.     

The associated regulators and signal pathway in rIL-16／CD4 mediated growth regulation in Jurkat cells

IL-16 is a ligand and chemotactic factor for CD4 T cells. IL-16 inhibits the CD3 mediated lymphocyte activation and proliferation. The effects of IL-16 on the target cells are dependent on the cell type, the presence of co-activators etc. To understand the regulation function and mechanism of IL-16 on target cells, we used a 130 a.a. recombinant IL-16 to study its effects on the growth of Jurkat T leukemia cells in vitro. We found that the rIL-16 stimulated the proliferation of Jurkat cells at low dose (10^-9M), but inhibited the growth of the cells at higher concentration (10^-5M). Results showed that 10^-5 M of rIL-16 treatment induced an enhanced apoptosis in Jurkat cells. The treatment blocked the expression of FasL, but up-regulated the c-myc and Bid expression in the cells. Pre-treatment of PKC inhibitor or MEK1 inhibitor markedly increased or decreased the rIL-16 induced growth-inhibiting effects on Jurkat cells, respectively.The results suggested that the rIL-16 might be a regulator for the growth or apoptosis of Jurkat cells at a dose-dependent manner. The growth-inhibiting effects of rIL-16 might be Fas/FasL independent, but,associated with the activation of PKC, up-regulated expression of c-Myc and Bid, and the participation of the ERK signal pathway in Jurkat cells.     

The nitrogen cycle, scientific uncertainty and policy relevant science

Much of the research on the nitrogen cycle aims to improving scientific understanding but is not focused specifically on removing or reducing the scientific uncertainties that constrain policy makers in the formulation of appropriate responses to old or emerging environmental problems. Policy makers, for example, commonly find it difficult to assess the spatial or temporal importance of the various risks to human and ecosystem health that stem from man's interference with the natural N cycle. This paper will justify this conclusion by reference to the findings of a recent study on non-point pollution from crop production in China. The findings concern the perceived risks of groundwater nitrate to human health; uncertainties about critical NOX levels and their interactions with other pollutants; various other dimensions of man's impact on the N cycle. The paper will go on to suggest a more systematic process or pathway by which scientists can select and design their research in a manner that could give more effective support to policy makers.     

Effects of Interaction Between Cadmium and Plumbum on Phytochelatins and Glutathione Production in Wheat (Triticum aestivum L.)

Phytochelatins (PCs) may function as a potential biomarker for metal toxicity. However, less attention has been paid to the effects of metal interactions on the production of PCs and glutathione (GSH),the most prominent cellular thiol. In the present study, the effects of interactions between cadmium (Cd) and plumbum (Pb) on the production of PCs and GSH were monitored over a period of 14 d in wheat (Triticum aestivum L.) tissues. The results showed that combination of Cd and Pb led to synergistic growth inhibition in wheat. Exposure to Cd or Pb increased levels of PCs in a concentration-, tissue-, and time-dependent manner. Cadmium was more effective that Pb in increasing PCs production. Compared with the effects of Cd or Pb alone on the production of PCs, the combination of Cd and Pb acted synergistically, resulting in an enhanced production of PCs. Cadmium also stimulated GSH production in a concentration-, tissue-, and time-dependent manner. However, Pb had no obvious effects on GSH levels. The combination of Pb and Cd antagonized GSH production over the course of the growth period. The results of the present study suggest that metal interactions should be considered in the application of PCs and GSH as potential biomarkers for the evaluation of metal toxicity.     

Effects of Interactions Between Cadmium and Lead on Growth, Nitrogen Fixation, Phytochelatin, and Glutathione Production in Mycorrhizal Cajanus cajan (L.) Millsp.

Heavy metals (HM) are a unique class of toxicants because they cannot be broken up into nontoxic forms. Excess HM causes stunted growth, upsets mineral nutrition, and affects membrane structure and permeability. High tolerance to HM toxicity is based on reduced metal uptake or increased internal sequestration in a genotype. Arbuscular mycorrhizal (AM) fungi are important rhizospheric microorganisms that occur in metal-contaminated soils and perhaps detoxify the potential effects of metals. The aim of this work was to study the role of the AM fungus Glomus mosseae in the alleviation of cadmium (Cd) and lead (Pb) toxicities in Cajanus cajan (L.) Millsp. (pigeonpea) genotypes. The effects of interactions between Cd (25 and 50 mg/kg) and Pb (500 and 800 mg/kg) on plant dry mass, nitrogen metabolism, and production of phytochelatins (PCs) and glutathione (GSH) were monitored with and without AM fungus in genotypes Sel-85N (relatively tolerant) and Sel-141-97 (sensitive). Cd treatments were more toxic than Pb, and their combinations led to synergistic inhibitions to growth and nitrogen-fixing potential (acetylene reduction activity [ARA]) in both genotypes. However, the effects were less deleterious in Sel-85N than in Sel-141-97. Exposure to Cd and Pb significantly increased the levels of PCs in a concentration- and genotype-dependent manner, which could be directly correlated with the intensity of mycorrhizal infection (MI). Stimulation of GSH production was observed under Cd treatments, although no obvious effects on GSH levels were observed under Pb treatments. The metal contents (Cd, Pb) were higher in roots and nodules when compared with that in shoots, which was significantly reduced in the presence of AM fungi. The results indicated that PCs and GSH might function as potential biomarkers for metal toxicity, and microbial inoculations showed bioremediation potential by helping pigeonpea plants to grow in multimetal contaminated soils.     

有机酸存在下小麦体内Cd的生物毒性和植物络合素(PCs)合成的关系

采用溶液培养方式 ,研究了有机酸存在下小麦体内 Cd的生物毒性和植物络合素 (PCs)合成的相关关系 ,试图寻求一种与小麦体内 Cd的生物毒性高度相关的评价指标。结果显示 ,Cd胁迫对小麦产生明显的毒害效应并诱导小麦根系内 PCs的大量合成。EDTA、DTPA、柠檬酸、苹果酸和草酸的适量供应可不同程度减轻或消除 Cd的生物毒性 ,其强弱顺序为 EDTA >DTPA 柠檬酸 >苹果酸≈草酸。与此同时 ,小麦根系内 PCs的诱导量也有明显下降 ,与 Cd的生物毒性保持一定的线性关系 ,且在EDTA、DTPA和柠檬酸供应下尤为显著。表明 PCs可以作为一项敏感的生化指标 (biochem ical indicator)用来评价和预测环境中 Cd的污染 ,并有望成为重金属生物有效性评价系统中一种新的补充方法     

PRODUCTION OF PHYTOCHELATINS AND GLUTATHIONE BY MARINE PHYTOPLANKTON IN RESPONSE TO METAL STRESS1

Phytoplankton deal with metal toxicity using a variety of biochemical strategies. One of the strategies involves glutathione (GSH) and phytochelatins (PCs), which are metal‐binding thiol peptides produced by eukaryotes and these compounds have been related to several intracellular functions, including metal detoxification, homeostasis, metal resistance and protection against oxidative stress. This paper assesses our state of knowledge on the production of PCs and GSH by marine phytoplankton in laboratory and field conditions and the possible applications of PCs for environmental purposes. Good relationships have been observed between metal exposure and PC production in phytoplankton in the laboratory with Cd, Pb, and Zn showing the greatest efficacy, thereby indicating that PCs have a potential for application as a biomarker. Fewer studies on PC distributions in particulate material have been undertaken in the field. These studies show that free Cu has a strong relationship with the levels of PC in the particulate material. The reason for this could be because Cu is a common contaminant in coastal waters. However it could also be due to the lack of measurements of other metals and their speciation. GSH shows a more complex relationship to metal levels both in the laboratory and in the field. This is most likely due to its multifunctionality. However, there is evidence that phytoplankton act as an important source of dissolved GSH in marine waters, which may form part of the strong organic ligands that control metal speciation, and hence metal toxicity.     

Effect of mycorrhizal inoculations on heavy metal uptake and stress alleviation of Cajanus cajan (L.) Millsp. genotypes grown in cadmium and lead contaminated soils

The aim of the present study was to evaluate the role of arbuscular mycorrhizal (AM) fungi on metal uptake, oxidative effects and antioxidant defence mechanisms under cadmium (Cd) and lead (Pb) stresses in Cajanus cajan (L.) Millsp. (pigeonpea). Treatments consisted of two concentrations each of Cd (25 and 50 mg/kg of soil) and Pb (500 and 800 mg/kg of soil) singly as well as in combination. Both metals induced oxidative damage through increased lipid peroxidation, electrolyte leakage and hydrogen peroxide levels, but Cd was found to be more toxic than Pb. Compared with the effects of Cd or Pb alone, the combination of Cd and Pb acted synergistically; however, Pb immobilisation in soil controlled the uptake of Cd in plants. There was a direct correlation between the type of genotype, heavy metal content and oxidative damage in concentration dependent manner. Superoxide dismutase (SOD), catalase (CAT) and peroxidase (POX) increased under stress. The toxicity symptoms of the metal stress were significantly higher in Sel-141-97 genotype when compared with Sel-85 N. The high ratio of glutathione to its oxidised form, glutathione disulfide (GSH/GSSG), could be restored by means of higher glutathione reductase (GR) activity and increased GSH synthesis in mycorrhizal stressed plants. AM inoculations with Glomus mosseae significantly arrested uptake of Cd and Pb into the root system and further translocation into the above ground parts and led to decreased lipid peroxidation and electrolyte leakage. Increased activities of SOD, CAT, POX as well as GR were observed in all mycorrhizal stressed plants.     

Effects of cadmium stress upon activities of antioxidative enzymes, photosynthetic rate, and production of phytochelatins in leaves and chloroplasts of wheat cultivars differing in yield potential

We tested the mode of action of Cd on photosynthesis and activities of ATP-sulfurylase (ATP-S), catalase (CAT), superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione reductase (GR), and on contents of phytochelatins (PCs) and glutathione (GSH) in two cultivars of wheat (Triticum aestivum L.) PBW-343 and WH-542 differing in yield potential. Cd treatment increased Cd content and photosynthetic activity in PBW-343 more than in WH-542. The activities of APX, GR, ATP-S, and synthesis of PCs and GSH were also increased by Cd, but the CAT and SOD activities were inhibited in both the cultivars. The efficient functioning of antioxidative enzymes, production of PCs and GSH, helped in counteracting the effects of Cd namely in PBW-343, protected photosynthetic ability, and increased the tolerance to Cd.     

Modulation of Exogenous Glutathione in Phytochelatins and Photosynthetic Performance Against Cd Stress in the Two Rice Genotypes Differing in Cd Tolerance

Greenhouse hydroponic experiments were conducted using Cd-sensitive (Xiushui63) and tolerant (Bing97252) rice genotypes to evaluate genotypic differences in response of photosynthesis and phytochelatins to Cd toxicity in the presence of exogenous glutathione (GSH). Plant height, chlorophyll content, net photosynthetic rate (Pn), and biomass decreased in 5 and 50 μM Cd treatments, and Cd-sensitive genotype showed more severe reduction than the tolerant one. Cadmium stress caused decrease in maximal photochemical efficiency of PSII (Fv/Fm) and effective PSII quantum yield [Y(II)] and increase in quantum yield of regulated energy dissipation [Y(NPQ)], with changes in Cd-sensitive genotype being more evident. Cadmium-induced phytochelatins (PCs), GSH, and cysteine accumulation was observed in roots of both genotypes, with markedly higher level in PCs and GSH on day 5 in Bing97252 compared with that measured in Xiushui63. Exogenous GSH significantly alleviated growth inhibition in Xiushui63 under 5 μM Cd and in both genotypes in 50 μM Cd. External GSH significantly increased chlorophyll content, Pn, Fv/Fm, and Y(II) of plants exposed to Cd, but decreased Y(NPQ) and the coefficient of non-photochemical quenching (qN). GSH addition significantly increased root GSH content in plants under Cd exposure (except day 5 of 50 μM Cd) and induced up-regulation in PCs of 5 μM-Cd-treated Bing97252 throughout the 15-day and Xiushui63 of 5-day exposure. The results suggest that genotypic difference in the tolerance to Cd stress was positively linked to the capacity in elevation of GSH and PCs, and that alleviation of Cd toxicity by GSH is related to significant improvement in chlorophyll content, photosynthetic performance, and root GSH levels.     

Cadmium hyperaccumulation leads to an increase of glutathione rather than phytochelatins in the cadmium hyperaccumulator Sedum alfredii

Sedum alfredii has been reported to be a cadmium (Cd) hyperaccumulator. Phytochelatins (PCs) and other thiol (SH)-containing compounds have been proposed to play an important role in the detoxification and tolerance of some heavy metals, but it is not clear whether PCs are responsible for Cd hyperaccumulation and tolerance in S. alfredii. In this study, two geographically isolated populations of S. alfredii were studied: one population grew on an old Pb/Zn mine site, while the other on a non-mine site. The mine population of this species exhibited a stronger heavy metal tolerance than in the other population. Root-to-shoot transport of Cd was higher in population located at the mine site than at the non-mine site. Considerable amounts of Cd were accumulated in leaves and stems of mine plants, while most Cd was distributed in roots of non-mine plants. Non-protein SH in plant tissues of two populations were further investigated by a HPLC pre-column derivatization system. Upon exposure to Cd, no PCs were detected in all tissues of mine population, while an appreciable amount of glutathione (GSH) was observed in the descending order of stem>root>leaf. The concentrations of GSH consistently increased with the increase of exogenous Cd concentrations and time. On the contrary, Cd exposure strongly induced the production of PCs (mainly PC(2) and PC(3)) and GSH in plant tissues of non-mine population, and the concentrations of GSH showed an initial drop over the duration of 7-d exposure. The present results provided strong evidence that PCs are not involved in Cd transport, hyperaccumulation and tolerance in mine population of S. alfredii.     

Heavy Metal Tolerance and Accumulation in Indian Mustard (Brassica Juncea L.) Expressing Bacterial γ-Glutamylcysteine Synthetase or Glutathione Synthetase

The overexpression of either γ-glutamylcysteine synthetase (γ-ECS) or glutathione synthetase (GS) in Brassica juncea transgenics was shown previously to result in higher accumulation of glutathione (GSH) and phytochelatins (PCs), as well as enhanced Cd tolerance and accumulation. The present study was aimed at analyzing the effects of γ-ECS or GS overexpression on tolerance to and accumulation of other metal/loids supplied individually in agar medium (seedlings) or in hydroponics (mature plants). Also, as pollution in nature generally consists of mixtures of metals, glutamylcysteine synthetase (ECS) and GS seedlings were tested on combinations of metals. Compared to wild-type plants, ECS and GS transgenics exhibited a significantly higher capacity to tolerate and accumulate a variety of metal/loids (particularly As, Cd, and Cr) as well as mixed-metal combinations (As, Cd, Zn/As, Pb, and Zn). This enhanced metal tolerance and accumulation of the ECS and GS transgenics may be attributable to enhanced production of PCs, sustained by a greater availability of GSH as substrate, as suggested by their higher concentrations of GSH, PC2, PC3, and PC4 as compared to wild-type plants. Overexpression of GS and γ-ECS may represent a promising strategy for the development of plants with an enhanced phytoremediation capacity for mixtures of metals.     

环境因子对小麦体内镉的生物毒性和植物络合素合成的影响

采用水培方式,研究了不同环境因子对小麦体内Cd的生物毒性与植物络合素(PCs)合成的影响.结果表明,Cd胁迫对小麦产生明显的毒害效应,并显著诱导根合成PCs;pH、Ca和S对小麦体内Cd的吸收和生物毒性具有不同程度的影响,根中PCs的诱导量与Cd的生物毒性变化表现一致;供磷减轻了Cd胁迫的生物毒性,根中PCs的诱导量也显著降低;镁对Cd胁迫的生物毒性影响甚微,根中PCs的诱导量和Cd的吸收量均未见明显变化.本实验结果证明Cd对PCs的诱导能力与植物体内Cd的毒性之间存在一定的相关关系,可将PCs作为Cd胁迫的生物标记物.