Anna Tukendorf

Changes in glutathione and phytochelatins in roots of maize seedlings exposed to cadmium

Abstract The effects of excess Cd on the contents of free cysteine, total glutathione and phytochelatin (PC) were measured in roots of intact maize seedlings. Exposure to 3 /tmM Cd for 15 min caused PCs to appe substrates for formation of longer PCs. Total glutathione levels declined with PC synthesis, free cysteine contents changed little. The reactions to excess Cd differed along the length of roots. In the 1 cm apical region a high production of PCs occurred with a moderate loss of total glutathione. In the mature region, PC content was 2.5-fold less than in apices, several unidentified thiols accumulated, and total glutathione levels declined drastically. Exposure to 0.05 μM Cd for 24 h induced PCs, the contents rose as Cd concentrations were increased. The roots produced PCs in excess of that required to chelate the Cd present, as if some PCs were compartmentalized or had not yet formed Cd-PC complexes. Phytochelatin formation was stimulated most effectively by Cd, less by Zn and Cu and negligibly by Ni. Total glutathione declined with Cd and Zn exposure, however, with excess Cu the roots contained 45% more total glutathione than did the controls.

Characteristics of the Photosynthetic Apparatus of Copper Non-tolerant Spinach Exposed to Excess Copper

Summary Individual spinach plants ( Spinacia oleracea L., c.v. Matador) sensitive to excess copper were grown on a nutrient medium containing toxic amounts of the metal, and the characteristics of its photosynthetic apparatus were examined. In chloroplasts isolated from Cu-treated plants the accumulation of plastid pigments and lipoquinones was lower than in controls and it decreased with the increase of copper toxicity. The loss of photochemical activity of photosystem I and photosystem II was observed at the late stage of leaf degradation (the leaves turned yellow). The loss of photosystem II activity was faster than that of photosystem I. Consequently, changes in chlorophyll distribution of light harvesting chlorophyll-protein complexes were observed. The CPa level, being the presumable reaction center of photosystem II, decreased significantly. The fine structure of chloroplasts revealed degradation of grana stacks and stroma lamellae depending on the stage of their degeneration, an increase in the number and size of plastoglobuli and intrathylakoidal inclusions. The results obtained have been discussed with regard to direct or indirect effects of copper in chloroplasts of plants sensitive to excess copper.

Age-dependent response of maize leaf segments to cadmium treatment: Effect on chlorophyll fluorescence and phytochelatin accumulation

The relationship between the age of leaf tissue and response of the photosynthetic apparatus and phytochelatin accumulation to Cd treatment was studied. Studies were carried out with seedlings of Zea mays L. cv. Hidosil grown in the presence of 100-200 mumol/L Cd for 14 days under low light conditions. The third leaf was divided into 3 segments of equal length differing in the stage of tissue maturity and used for measurements of chlorophyll content, chlorophyll fluorescence, glutathione and phytochelatin content and Cd accumulation. A close relationship between the age of leaf tissue and response of the photosynthetic apparatus to Cd was shown. Cadmium (200 mumol/L) reduced photochemical processes more in older than younger leaf segments as seen in the Chl fluorescence parameters Fv/F0, and t1/2, while the chlorophyll fluorescence decrease ratio (Rfd) was inhibited more strongly in younger ones. Fv/Fm was slightly affected. Cd-induced enhancement of GSH content was correlated with higher phytochelatin accumulation to a greater extent in younger than in older leaf segments. Phytochelatin level corresponded to changes of photochemical processes in older leaves. The peptide thiol:Cd molar ratio for the phytochelatins varied depending on Cd concentration and age of leaf segments. The protective role of phytochelatins for the photosynthetic apparatus is discussed.

The effect of copper deficiency on the photosynthetic apparatus of higher plants

Summary The effect of copper deficiency on the photochemical reactions, plastid pigments and lipoquinones of oat and spinach chloroplasts was investigated. The synthesis of all thylakoid prenyl lipids as well as of chlorophylls was lower during copper deficiency. The inhibition was observed to a different degree for the individual lipids. The formation of plastoquinones (C45-chain) was much more strongly inhibited than that of phytol derivatives and carotenoids. The rates of photosynthesis, expressed as O2 evolved per leaf area, were lower in the deficient than in the control plants. On the basis of chlorophyll, the O2-evolution was slightly higher in deficient plants. The Photosystem I activity of deficient chloroplasts measured in terms of O2-uptake and the photoreduction of NADP from water was much lower than that of the control ones. Cyclic photophosphorylation was inhibited to the same degree. Photosystem II activity was affected to a lesser extent. Plastocyanin and total copper content in deficient chloroplasts decreased over 50% in comparison with control chloroplasts. The effect of copper deficiency on electron transport was discussed with regard to the plastocyanin content of the chloroplasts.

Homophytochelatin accumulation in Cd-treated runner bean plants is related to their growth stage

Abstract Runner bean plants (Phaseolus coccineus L. cv. Piekny Jaś) grown hydroponically in Knop solution were treated with 25 μM Cd at three different stages of primary leaf growth. After 1, 3, 8, 10 and 1, 4, 8, 12 days of the metal treatment the contents of homophytochelatins in roots and in primary leaves, respectively were investigated. A high level of accumulation of Cd homophytochelatins was found in the primary leaves and roots of plants exposed to Cd at the early growth stage. The capacity to accumulate homophytochelatins both in roots and primary leaves of plants treated with Cd at later stages of development was greatly decreased. The rate of synthesis and accumulation of homophytochelatins in roots and leaves seems to be related to the growth stage of plants in which Cd was applied to the nutrient solution and to the duration of the treatment.

Copper binding proteins in spinach tolerant to excess copper

Cu-complexes were isolated from cytosol of roots and leaves of spinach plants surviving in a medium containing a high concentration of copper without showing any symptoms of toxicity and possessing an efficiently acting photosynthetic apparatus. Most of the copper in cytosol is assumed to be bound to low molecular weight proteins. Two Cu-binding fractions, at a molecular weight of 12,500 and 9,500 respectively, were isolated from the roots. However, in the cytosol of the leaves only one fraction, at a molecular weight of 8,500, was isolated. It has been suggested that Cu-complexes are formed due to copper binding by preexisting proteins in cytosol and their synthesis seems to be stimulated by excess copper. They would be able to protect, among other things, the photosynthetic apparatus against the toxic effect of copper ions.

Partial Purification and Characterization of Copper-binding Protein from Roots of Avena sativa Grown on Excess Copper

Summary During the growth of oat seedlings in a nutrient solution containing excess copper great amounts of the metal appear in the roots in the form of complexes with low molecular weight proteins. Cytosol, the major copper containing fraction of the cells, was isolated from the roots and purified by chromatography, first on Sephadex G-75 and next on DEAE-Sephadex A-25. Partially purified protein copper-complexes had apparent molecular weights of 8,000 and 11,000, obtained during molecular sieving. They bound 0.56 and 2 g atoms copper/mol protein, respectively. Proteins of cytosol from roots of control plants which had the same molecular weights bound 0.16 and 0.65 g atoms copper/mol protein, respectively. Amino acid composition of copper-proteins did not reveal a high cysteine content. The total content of protein sulfhydryl group of copper-treated plants was 2 and 7 times lower, respectively, than that of control plants. Copper-binding proteins produced by roots of oats exposed to excess copper do not seem to be metal thioneine-like substances.

Dietary factors in women with dysplasia colli uteri associated with human papillomavirus infection

The studies were carried out in a group of 228 female patients with normal cytological smear and 324 patients with cervical intraepithelial neoplasia (CIN). The applied method of human papillomavirus (HPV) identification, i.e., the HPV digene hybrid capture system, made it possible to select a control group consisting of 168 HPV-negative patients with normal Papanicolaou smears, as well as a group of 228 HPV-positive female patients with CIN. By examining the diet of the patients, it was shown that women with cervical dysplasia associated with high oncogenic risk of HPV infections consumed a smaller quantity of foods containing vitamin C, beta-carotene, and folacin. Our studies indicate a relationship between nutritional habits and the development of CIN associated with HPV infection.

Copper Binding in Roots by Cytosol Proteins in vitro

Summary Copper-binding proteins were isolated from roots of spinach cultivated hydroponically at a copper dose of 20mgl -1 . Two low-molecular Cu-proteins of molecular weight 1.5 and 1.9kD were isolated by ion-exchange chromatography on DEAE-Sephadex A-25 and gel filtration on Sephadex G-75. Similar copper-bound proteins were also isolated from root preparations of control plants incubated with copper in experiments in vitro .

Content of α-tocopherol in blood serum of human Papillomavirus-infected women with cervical dysplasias

The studies were carried out in a group of 228 female patients with normal cytological smear and 324 patients with cervical intraepithelial neoplasia. The applied method of identification, i.e., the human Papillomavirus (HPV) digene hybrid capture system, made it possible to select a control group consisting of 168 HPV-negative patients with normal Pap smear, as well as a group of 228 HPV-positive patients with cervical intraepithelial neoplasia. The high-performance liquid chromatography method was employed to evaluate the level of alpha-tocopherol in the blood serum of the patients who were examined. A statistically significantly lower level of alpha-tocopherol was observed in the blood serum of HPV-positive patients with cervical intraepithelial neoplasia. The risk of dysplasia was four times higher for an alpha-tocopherol level < 7.95 mumol/l.