Cadmium-induced changes in glutathione and phenolics of Thlaspi and Noccaea species differing in Cd accumulation (original) (raw)
Related papers
Morphological, physiological and biochemical responses of different plant species to Cd stress
Naturally plants exposed with many adverse environmental conditions like biotic and a biotic stress. Despite all others stresses heavy metal stress is one of great importance which has a notable adverse effects on crop productivity and growth, heavy metal stress triggers different responses in plants, ranging from biochemical responses to crop yield. Understanding the biochemical and molecular responses to Cd stress is essential for a holistic opinion of plant resistance mechanisms to heavy metal stress. This review illustrates some aspects of Cd stress that make changes in morphological, physiological and biochemical changes of plants. Cd stress gradually declines photosynthetic rate due to limited access of CO2 which decrease gas exchange results triggers in reduction of plant growth and productivity. It also reduce leaf size, stems extension and root proliferation and decrease water absorption and transportation by causing turgor loss through decreasing the cell wall elasticity. Exposure to Cd stress increase reactive oxygen species (ROS) production which is harmful for the cell components and toxicity of cadmium is responsible for alterations in the antioxidant systems and increase of lipid peroxidation can be strongly limited at both production and consumption level by increasing antioxidative systems. This review focuses on the ability and strategies of higher plants to respond adapt and overcome the Cd stress.
Intraspecific variation of physiological and molecular response to cadmium stress in Populus nigra L
Tree Physiology, 2011
Little is known about the variability of response to heavy metal stress within tree species, although it could be a key for a better understanding of tolerance mechanisms and for breeding. The aim of the present study was to characterize the natural variation of response to cadmium (Cd) in Populus nigra L. in order to understand the mechanisms of Cd tolerance. For that, two P. nigra genotypes, originating from contrasting environments in northern (genotype 58-861) and southern (genotype Poli) Italy, were exposed to Cd stress in hydroponics for 3 weeks. The effect of stress was estimated by measuring biomass production, photosynthetic performance and accumulation and translocation of Cd at the end of the experiment. To better understand the mechanisms of Cd tolerance, the expression of some candidate genes involved in the ascorbate-glutathione cycle (ascorbate peroxidase, glutathione reductase, glutathione S-transferase) and in metal sequestration (metallothioneins) was analyzed in leaves. Biomass production and photosynthesis were affected by the treatment in both clones but the southern clone was markedly more tolerant to Cd stress than the other. Nevertheless, the Cd content in leaves was not significantly different between the two clones and was quite low compared to other species. The content of thiols and phytochelatins (PCs), associated with the transcription profile of the glutathione S-transferase gene, indicated relevant differences in the use of the PCs pathway under Cd stress, which could explain the different tolerance to Cd. The northern clone accumulated thiols but down-regulated the GST gene, whereas the southern clone accumulated PCs and up-regulated the GST gene, which can be useful to complex and detoxify Cd. These results suggest that the glutathione pathway is involved in the differential Cd tolerance of the two genotypes. The natural germplasm of P. nigra represents a valuable resource for understanding tolerance to Cd and for selection of plant material for phytoremediation.
2015
Background and Aims Cadmium (Cd) is a non-essential trace element that elicits oxidative stress. Plants respond to Cd toxicity via increasing their Cd-chelating and antioxidative capacities. They predominantly chelate Cd via glutathione (GSH) and phytochelatins (PCs), while antioxidative defence is mainly based on the use and recycling of both GSH and ascorbate (AsA), complemented by superoxide dismutase (SOD) and catalase (CAT). In addition, both metabolites act as a substrate for the regeneration of other essential antioxidants, which neutralize and regulate reactive oxygen species (ROS). Together, these functions influence the concentration and cellular redox state of GSH and AsA. In this study, these two parameters were examined in plants of Arabidopsis thaliana exposed to sublethal Cd concentrations. Methods Wild-type plants and mutant arabidopsis plants containing 30-45 % of wild-type levels of GSH (cad2-1) or 40-50 % of AsA (vtc1-1), together with the double-mutant (cad2-1 vtc1-1) were cultivated in a hydroponic system and exposed to sub-lethal Cd concentrations. Cadmium detoxification was investigated at different levels including gene expression and metabolite concentrations. Key Results In comparison with wild-type plants, elevated basal thiol levels and enhanced PC synthesis upon exposure to Cd efficiently compensated AsA deficiency in vtc1-1 plants and contributed to decreased sensitivity towards Cd. Glutathione-deficient (cad2-1 and cad2-1 vtc1-1) mutants, however, showed a more oxidized GSH redox state, resulting in initial oxidative stress and a higher sensitivity to Cd. In order to cope with the Cd stress to which they were exposed, GSH-deficient mutants activated multiple alternative pathways. Conclusions Our observations indicate that GSH and AsA deficiency differentially alter plant GSH homeostasis, resulting in opposite Cd sensitivities relative to wild-type plants. Upon Cd exposure, GSH-deficient mutants were hampered in chelation. They experienced phenotypic disturbances and even more oxidative stress, and therefore activated multiple alternative pathways such as SOD, CAT and ascorbate peroxidase, indicating a higher Cd sensitivity. Ascorbate deficiency, however, was associated with enhanced PC synthesis in comparison with wild-type plants after Cd exposure, which contributed to decreased sensitivity towards Cd.
Cadmium (Cd) is a widespread environmental contaminant, strongly mutagenic and known to cause DNA damage in plants. In this work, flow cytometry (FCM) was applied to determine if in vivo exposure to Cd would induce genotoxic effects at the genome level. The hyper-accumulator Thlaspi caerulescens (J. & C. Presl), the related non-accumulator Thlaspi arvense L. and the accumulator crop species Lactuca sativa L. were germinated in distilled water and grown in modified Hoagland's medium with increasing concentrations of Cd(NO 3 ) 2 (0, 1, 10 and 100 mM). After 28 days of exposure, shoot and root growth was recorded and the tissues were harvested for Cd and FCM analysis. In general, roots from treated plants contained higher content of Cd than leaves and growth inhibition was observed in the treated plants. Nuclear DNA content was estimated and the G 0 /G 1 full peak coefficient of variation (FPCV), as an indicator of clastogenic damage, was recorded. In T. arvense and T. caerulescens no significant differences were detected between control and exposed plants. Leaves of L. sativa exposed to 10 mM Cd presented a statistically significant increase in FPCV values in comparison with the control group. Furthermore, roots exposed to 100 mM Cd presented a reduction in nuclear DNA content and an increase in FPCV when compared to the control. FCM data indicates that no major DNA damage was induced on both Cd-exposed Thlaspi species and L. sativa leaves. On the contrary, results obtained with L. sativa roots suggests clastogenic damage in these organs exposed to 100 mM of Cd.
Genotypic variation of the response to cadmium toxicity in Pisum sativum L
Journal of Experimental Botany, 2004
This work evaluates the (cor-)relations between selected biochemical responses to toxic Cd and the degree of Cd sensitivity in a set of pea genotypes. Ten genotypes were analysed that differ in their growth response to Cd when expressed as root or shoot tolerance indices (TIs). Concentrations of non-protein thiols (NPTs) and malondialdehyde (MDA), activity of chitinase, peroxidase (POX), and catalase significantly increased in all pea genotypes treated with Cd. Cdsensitivity of genotypes was correlated with relative increases in MDA concentration as well as activities of chitinase and POX, suggesting similar Cd stress effects. Activities of ascorbate peroxidase (APX) decreased, but concentrations of glutathione (GSH) increased in the less Cd-sensitive genotypes. Differences in root and leaf contents of Cd revealed no correlation with TI, metabolic parameters, and enzyme activities in Cd-treated plants, respectively, except that shoot Cd concentration positively correlated with shoot chitinase activity. Toxic Cd levels inhibited uptake of nutrient elements such as P, K, S, Ca, Zn, Mn, and B by plants in an organ-and genotype-specific manner. Cd-sensitivity was significantly correlated with decreased root Zn concentrations. The results show both similarities, as well as distinct features, in Cd toxicity expression in genotypes of one species, suggesting that independent and multi-factorial reactions modulate Cd sensitivity on the low-tolerance level of plants. The study illustrates the biochemical basis of earlier detected genotypic variation in Cd response. by guest on January 5, 2016 http://jxb.oxfordjournals.org/ Downloaded from Fig. 3. Contents of non-protein thiols (NPTs) (A, B) and glutatione (GSH) (C, D) in roots of pea genotypes grown in hydroponics culture with or without Cd. Data in (A) and (C) correspond to control (open squares) and Cd-treatment (filled squares), 6SE (box) and 6SD (bars) from 12 determinations of two experiments. The percentage changes between treatment and control are given in (B) and (D).
How cadmium affects the fitness and the glucosinolate content of oilseed rape plantlets
Environmental and Experimental Botany
Secondary metabolites such as glucosinolates (GSLs) are involved in plant response to biotic stress but can be significantly influenced by abiotic factors as well. Oilseed rape (Brassica napus L.) produces large quantities of several GSLs both in seeds and at the vegetative stage. These sulfur-containing compounds are known to play an important role in cadmium stress tolerance within the Brassicaceae family probably due to specific cross-talk between the S primary and secondary metabolism. Sulfur assimilation is in the middle of multiple metabolic pathways including Cd stress responses at physiological level. Our research focused on the assessment of GSL profiles and content in the roots and shoots of 28-day-old winter oilseed rape plantlets. The study was conducted under in vitro sterile conditions using concentration gradients of 0, 5, 15 and 45 μM of cadmium. A phenotypic analysis was carried out at the end of this experiment in order to evaluate the plantlets' fitness. Our results described hormetic growth curves for root elongation, root biomass and shoot biomass at Cd concentrations of 5 μM and 15 μM respectively. Our experiment shows that a concentration of 5 μM can be considered as non-toxic, while one of 45 μM represents a lethal dose. Strong relationships were found between Cd accumulated in roots or translocated to shoots and the total sulfur accumulation in the plantlets' different organs. A decrease of both indole and aliphatic GSL content associated with an increase of Cd accumulation and an increase of total sulfur accumulation was observed in the roots and shoots of the plantlets. It was also further demonstrated that Cd stress has a highly significant effect on roots' and shoots' GSL content bringing new insights into GSL's possible role in the priming of Cd stress.
Pedosphere, 2012
Knowledge of cellular metal homeostasis will provide a better understanding of the mechanisms involved in metal tolerance and hyperaccumulation in metal-hyperaccumulating plants. Energy dispersive X-ray spectrometry (EDS) was used to determine the localization of cadmium (Cd) in leaves of the Zn/Cd hyperaccumulator Picris divaricata which had a shoot Cd concentration of 565 mg kg −1 after 2 weeks of growth in solution culture supplying 10 μmol L −1 CdCl 2 . The results indicated that Cd was distributed mainly in the trichomes, upper and lower epidermis and bundle sheath cells, with a relatively low level of Cd in mesophyll cells. Mesophyll protoplasts isolated from leaves remained viable after 24 h exposure to CdCl 2 at a concentration up to 1 mmol L −1 , indicating their high tolerance to Cd. The intracellular Cd was visualized by staining with Leadmium Green dye, a cellular permeable Cd fluorescence probe. The results showed that the majority of protoplasts (> 82%) did not accumulate Cd, with only a minority (< 18%) showing Cd accumulation. In the Cd-accumulating protoplasts, Cd accumulation was depressed by the addition of Fe 2+ , Mn 2+ and the metabolic inhibitor carbonyl cyanide m-chlorophenylhydrazone (CCCP), but not by Ca 2+ or Zn 2+ . Furthermore, the entire process of Cd uptake from external solution into the cytoplasm and subsequent sequestration into vacuoles was successfully recorded by confocal images. These results suggested that reduced cellular Cd accumulation and efficient Cd vacuolar sequestration in mesophyll cells might be responsible for cellular Cd tolerance and distribution in the leaves of P. divaricata.
Journal of Hazardous Materials, 2008
Plant growth, ultrastructural and antioxidant adaptations and glutathione biosynthesis in Cd-hyperaccumulating ecotype Sedum alfredii Hance (HE) countering high Cd environment were investigated and compared with its non Cd-hyperaccumulating ecotype (NHE). Cadmium exposure resulted in significant ultrastructural changes in root meristem and leaf mesophyll cells of S. alfredii, but damage was more pronounced in NHE even when Cd concentrations were one-tenth of those applied to HE. Cadmium stress damaged chloroplasts causing imbalanced lamellae formation coupled with early leaf senescence. Histochemical results revealed that glutathione (GSH) biosynthesis inhibition led to overproduction of hydrogen peroxide (H 2 O 2) and superoxide radical (O 2 •−) in HE but not in NHE. Differences were noted in both HE and NHE for catalase (CAT), guaiacol peroxidase (GPX), ascorbate peroxidase (APX) and glutathione reductase (GR) activities under various Cd stress levels. No relationship was found between antioxidative defense capacity including activities of superoxide dismutase (SOD), CAT, GPX, APX and GR as well as ascorbic acid (AsA) contents and Cd tolerance in the two ecotypes of S. alfredii. The GSH biosynthesis induction in root and shoot exposed to elevated Cd conditions may be involved in Cd tolerance and hyperaccumulation in HE of S. alfredii H.
Ecological Engineering, 2012
The aim of this study was to examine the phytotoxicity of cadmium (Cd) on commonly measured physiological parameters [root and shoot growth inhibition, dry mass (DM) and fresh mass (FM) production, water content (WC), Cd accumulation] and biochemical parameters [photosynthetic pigments (chlorophyll a, b, total carotenoids), proteins, thiobarbituric acid reactive substances (TBARS), and protein sulfhydryl group content] using regression analyses. Biochemical parameters were evaluated to estimate oxidative stress in seedlings. For all parameters, the sensitivity of Hordeum vulgare L. and Sinapis alba L. plants was studied as representative of widely cultivated crop plants. Cd showed a greater inhibitory effect on root than shoot growth, predominantly in S. alba. In addition to growth inhibition, Cd reduced biomass production (FM, DM), mainly in the shoots. Although Cd was accumulated chiefly in the roots, the accumulation of Cd in S. alba shoots exceeded that in H. vulgare. While Cd resulted a greater reduction of chlorophyll b than chlorophyll a, carotenoids content in S. alba increased when metal concentration reached 71 and 143 mg Cd l −1 . The adverse effect of Cd was also confirmed by a significant reduction in protein sulfhydryl groups. In a regression analysis, positive correlations were observed between proteins and sulfhydryl groups in shoots of S. alba and TBARS and sulfhydryl groups in H. vulgare, while negative correlations were found between Cd concentrations in S. alba roots and proteins, TBARS, and WC contents. Cd concentration in H. vulgare roots was also negatively correlated with TBARS and shoot length. (M. Molnárová), fargasova@fns.uniba.sk (A. Fargašová). 1 Tel.: +421 2 602 96 575; fax: +421 2 602 96 704. 0925-8574/$ -see front matter
Journal of Al-Nahrain University-Science
An experiment was carried out to study cadmium tolerance at the tissue culture and whole plant levels of Helianthus annuus. Callus was initiated and maintained on Murashige and Skoog medium (MS) supplemented with 0.2 mg.L-1 Kinetin (KIN), 0.4 mg.L-1 Naphthalene acetic acid (NAA) and 0.5 mg.L-1 2,4-dichlorophenoxy acetic acid (2,4-D) using hypocotyls explants for callus induction. Different concentrations of cadmium were added directly to the culture medium as a contaminants. Selected tolerant cell lines were subjected to regeneration. The concentration of cadmium accumulated in callus tissues recorded 18 ppm at 2.0 mg.L-1 of Cd. The study included the effect of the cytokinin Benzyl adenine (BA) and the auxin NAA on the number of regenerated shoots percentage from tolerant callus to Cd. Results exhibited that 71% of callus tolerant to Cd, when the combination of 1.0 mg.L-1 BA and 0.5 mg.L-1 NAA was supplemented to the medium. The effect of NAA on rooting of shoots showed that the concentration 2.0 mg.L-1 of NAA gave rooting percentage mounted to 66%. The study also included measurement of plant height and fresh weight. Maximum Cd accumulation reached 12.2 ppm in the shoots. Tolerance to Cd seems to express in the plant shoots according to the current study.