Growth rates and the evolution of heavy metals concentrations in segments of different ages of the terrestrial moss Pseudoscleropodium purum

Ecología, Facultad de Biología, Universidad de Santiago de Compostela

Phytoremediation by poplar: polyphenols polyamines and oxidative damage in the response to heavy metals in in vitro and in hydroponic cultures.

Poplar is considered a good candidate for phytoremediation, but its tolerance to heavy metals has not been fully investigated yet. In the present work, two different culture systems (in vitro and aeroponic/hydroponic) and two different stress tolerant clones of Populus alba (AL22 and Villafranca) were investigated for their total polyphenol and flavonoid content, individual phenolic compounds, polyamine, lipid peroxidation and hydrogen peroxide levels in response to Cu. In AL22 poplar plants cultured in vitro in the presence or absence of 50 μM Cu, total leaves polyphenol and flavonoid content was higher in treated samples than in controls but unaltered in the roots. Equally the same clone, grown under aeroponic conditions and hydroponically treated for 72 h with 100 μM Cu, displayed increased amount of polyphenols and flavonoids in the leaves, in particular chlorogenic acid and quercetin, and no differences in the roots. In exudates from treated roots total polyphenols and flavonoids, in particular catechin and epicatechin, were more abundant than in controls. Polyamine levels show an increase in conjugated putrescine (Put) and spermidine (Spd) was found. In the Villafranca clone, treated with 100 μM Cu for 6, 24 and 72 h, the pattern of polyphenol and flavonoid accumulation was the same as in AL22; in Cu-treated roots these compounds decreased compared with controls while they increased in root exudates. Free polyamine levels rose at 24 and 72 h while only conjugated Put increased at 24 h. Cu-treated Villafranca plants exhibited a higher malondialdehyde production than controls indicative of membrane lipid peroxidation and, therefore, oxidative stress. An in vitro experiment was carried to investigate the antioxidant effect of the polyamine spermidine (Spd). Exogenous Spd, supplied together with 100 μM Cu, reduced the accumulation of polyphenols and flavonoids, MDA and hydrogen peroxide induced by Cu.

Heavy Metals in Crop Plants: Transport and Redistribution Processes on the Whole Plant Level

Copper, zinc, manganese, iron, nickel and molybdenum are essential micronutrients for plants. However, when present in excess they may damage the plant or decrease the quality of harvested plant products. Some other heavy metals such as cadmium, lead or mercury are not needed by plants and represent pollutants. The uptake into the roots, the loading into the xylem, the acropetal transport to the shoot with the transpiration stream and the further redistribution in the phloem are crucial for the distribution in aerial plant parts. This review is focused on long-distance transport of heavy metals via xylem and phloem and on interactions between the two transport systems. Phloem transport is the basis for the redistribution within the shoot and for the accumulation in fruits and seeds. Solutes may be transferred from the xylem to the phloem (e.g., in the small bundles in stems of cereals, in minor leaf veins). Nickel is highly phloem-mobile and directed to expanding plant parts. Zinc and to a lesser degree also cadmium are also mobile in the phloem and accumulate in meristems (root tips, shoot apex, axillary buds). Iron and manganese are characterized by poor phloem mobility and are retained in older leaves.

Human DNA ligase and DNA polymerase as molecular targets for heavy metals and anticancer drugs

DNA ligase and DNA polymerase play important roles in DNA replication, repair, and recombination. Frequencies of spontaneous and chemical- and physical-induced mutations are correlated to the fidelity of DNA replication. This dissertation elucidates the mechanisms of the DNA ligation reaction by DNA ligases and demonstrates that human DNA ligase I and DNA polymerase $\alpha$ are the molecular targets for two metal ions, Zn$\sp{2+}$ and Cd$\sp{2+},$ and an anticancer drug, F-ara-ATP.^ Human DNA ligases were purified to homogeneity and their AMP binding domains were mapped. Although their AMP-binding domains are similar, there could be difference between the two ligases in their DNA binding domains.^ The formation of the AMP-DNA intermediate and the successive ligation reaction by human DNA ligases were analyzed. Both reactions showed their substrate specificity for ligases I and II, required Mg2+, and were inhibited by ATP.^ A protein inhibitor from HeLa cells and specific for human DNA ligase I but not ligase II and T4 ligase was discovered. It reversibly inhibited DNA ligation activity but not the AMP-binding activity due to the formation of a reversible ligase I-inhibitor complex.^ F-ara-ATP inhibited human DNA ligase I activity by competing with ATP for the AMP-binding site of DNA ligase I, forming a ligase I-F-ara-AMP complex, as well as when it was incorporated at 3$\sp\prime$-terminus of DNA nick by DNA polymerase $\alpha.$^ All steps of the DNA ligation reaction were inhibited by Zn$\sp{2+}$ and Cd$\sp{2+}$ in a concentration-dependent manner. Both ions did not show the ability to change the fidelity of DNA ligation reaction catalyzed by human DNA ligase I. However, Zn$\sp{2+}$ and Cd$\sp{2+}$ showed their contradictory effects on the fidelity of the reaction by human DNA polymerase $\alpha.$ Zn$\sp{2+}$ decreased the frequency of misinsertion but less affected that of mispair extension. On the contrary, Cd$\sp{2+}$ increased the frequencies of both misinsertion and mispair extension at very low concentration. Our data provided strong evidence in the molecular mechanisms for the mutagenicity of zinc and cadmium, and were comparable with the results previously reported. ^

Lead and cadmium in the Weser Estuary and the German Bight: Correlations between bacteria populations, heavy metals and organic carbon

Organic carbon, lead and cadmium contents of 20 sediments were determined and compared with the colony counts of anaerobic heterotrophic, anaerobic nitrogen fixing, chitinoclastic and cellulolytic bacteria. Organic carbon content, which is dependent on the sediment type, was positively correlated with lead and cadmium as well as with colony counts of all 4 physiological groups of bacteria. Even the sediments with the highest concentrations of 251.7 ppm Pb and 3.1 ppm Cd showed no reduction in their colony counts. From 2 different sediment sampIes with lead contents of 140 ppm and 21 ppm lead tolerance of the aerobic heterotrophic bacteria was investigated. However, no significant difference in lead tolerance of the 2 heterotrophic populations was found. Water from 6 stations was analysed for dissolved and particulate organic carbon, lead and cadmium. Dissolved lead concentrations were in the range of 0.2-0.5 µg/l and the particulate lead contents were between 0.05 and 4.3 µg/l. The concentrations of total lead for the stations off-shore were only one order of magnitude from the concentrations of the near-shore stations. The same phenomenon was observed for dissolved cadmium (0.02 - 0.25 µg/l) and particulate cadmium (0.003 - 0.15 µg/I) concentrations. Correlations between dissolved (1.6 - 10.8 mg/I) and particulate organic carbon (0.25 - 1.53 mg/I) with dissolved and particulate lead or cadmium were not found.

Concentrations of dissolved and particulate heavy metals in waters above the northwestern slope of the Paramushir Island (Sea of Okhotsk)

Distributions of Mn, Fe, Cu, Cd, Cr, Co and Ni in sea water are investigated (42 samples, dissolved and particulate forms) in the vicinity of the underwater gas vent field on the northwestern slope of the Paramushir Island. While regular background distributions of the elements occur in the shore zone, there is a column of elevated concentrations of particulate matter, particulate Mn, and dissolved Mn, Fe, Cu, Cd, Cr, Co and Ni that coincides with location of the gas plume. This column can be traced as high as 780 m above the bottom. High metal concentrations in water of the plume are attributable to physico-chemical concentration at the phase interface; the source of elevated mineral concentrations is obviously flux of dissolved minerals from interstitial waters, which extends to considerable distances in vertical direction.