Induction of sister chromatid exchanges by heavy metal salts in root meristem cells ofAllium cepa L.

Four heavy metal salts, nickel sulphate, mercuric chloride, cadmium sulphate and zinc sulphate, were tested for induction of sister chromatid exchange (SCE) in root meristem cells ofAllium cepa. A simple modified Feulgen staining procedure was employed for SCE-analysis. Maleic hydrazide and paraquat were included for comparison. An evaluation of genotoxicity of the above test chemicals made on the basis of SCE-assay was found positive for all the test chemicals with exception of zinc sulphate which gave a weak positive result.     

Effect of heavy metals on nitrate and protein metabolism in sugar beet

Nitrate content, activities of nitrate reductase and glutamine synthetase, soluble protein content, and proportion of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) protein in total proteins were measured in leaves of Beta vulgaris L. plants affected by nickel, cadmium, and molybdenum in concentrations of 10^-4, 10^-2, and 1 mM. The most harmful effect on the above mentioned parameters had Cd, less harmful Ni, whereas Mo stimulated the investigated parameters. The proportion of RuBPCO protein showed a high tolerance to heavy metals. This revised version was published online in July 2006 with corrections to the Cover Date.     

Lateral plasma membrane compartmentalization links protein function and turnover

Biological membranes organize their proteins and lipids into nano‐ and microscale patterns. In the yeast plasma membrane (PM), constituents segregate into a large number of distinct domains. However, whether and how this intricate patchwork contributes to biological functions at the PM is still poorly understood. Here, we reveal an elaborate interplay between PM compartmentalization, physiological function, and endocytic turnover. Using the methionine permease Mup1 as model system, we demonstrate that this transporter segregates into PM clusters. Clustering requires sphingolipids, the tetraspanner protein Nce102, and signaling through TORC2. Importantly, we show that during substrate transport, a simple conformational change in Mup1 mediates rapid relocation into a unique disperse network at the PM. Clustered Mup1 is protected from turnover, whereas relocated Mup1 actively recruits the endocytic machinery thereby initiating its own turnover. Our findings suggest that lateral compartmentalization provides an important regulatory link between function and turnover of PM proteins.     

Evaluation of the phytoremediation potential of Arundo donax L. for nickel-contaminated soil

This study investigates the accumulation and distribution of nickel in Arundo donax L. parts to assess the potential use of this plant in phytoremediation of Ni-contaminated soils. The effect of ethylene diamine tetra-acetic acid (EDTA) and nutrient solution containing NPK on the plant was proped. A 35-day pot experiment was performed in the laboratory and the pots were irrigated with Ni-contaminated solution combined or not with EDTA and NPK. The growth of plants was evaluated at the end of the experiment. The accumulation of Ni was analyzed by atomic absorption spectroscopy (AAS). The obtained results indicate that the plant was able to survive with high Ni content. The growth and the concentrations of Ni in the plant tissues were less affected. In the absence of the amendments, Ni was accumulated in the stems and leaves. However, the addition of NPK significantly reduced Ni concentration in the stems and leaves. The application of EDTA enhanced Ni uptake in roots. The translocation factor (TF) was greater than 1, which categorizes A. donax L. as a great candidate for Ni phytoextraction. A. donax L. is suitable for phytoremediation of Ni. This investigation contributes to the studies on the potential of phytoremediation technologies in Algeria.     

Effects of Bacterial Inoculation to Immobilize Nickel in Wheat Grown on Ni-Contaminated Soil

Abstract

Plant growth stimulating bacteria are very effective in immobilization of metals and reducing their translocation in plants through precipitation, and adsorption. A pot experiment was conducted to investigate the effectiveness of chitosan- and hematite-modified biochar and bacterial inoculations on the immobilization of nickel (Ni) in polluted soil under wheat cultivation. Application of modified biochars and inoculation with Pseudomonas putida significantly increased both wheat root and shoot dry matter yields but decreased Ni phytoextraction efficiency. The Ni concentration, translocation factor and uptake in wheat shoot and root significantly decreased the application of either modified or unmodified biochars. Bacterial inoculation significantly decreased mean translocation factor and also root and shoot concentration and the uptake Ni in the shoot. Chitosan-modified biochar was the most influential treatment in decreasing Ni uptake by wheat followed by P. putida inoculation treatment. The results demonstrated positive effects of chitosan modified biochar and inoculation with P. putida in increasing dry matter yield and decreasing Ni uptake in wheat grown on Ni-contaminated soil. According to the results of present study, modified biochars application and bacterial inoculation are influential treatments which prevent Ni toxicity probably.     

Recovery of copepod, but not cladoceran, zooplankton from severe and chronic effects of multiple stressors

In the mid‐twentieth century, many lakes near Sudbury, Canada, were severely contaminated by acid and metal emissions from local smelters. For example, in the early 1970s, Middle Lake had pH of 4.2, and Cu and Ni levels both >0.5 mg L^?1 . To determine if crustacean zooplankton could recover from such severe and chronic damage, Middle Lake was neutralized in 1973. A comparison of its zooplankton with that of 22 reference (pH > 6) lakes indicates that the planktonic Copepoda completely recovered by 2001. In contrast, the cladoceran assemblage improved but did not recover. Colonist sources existed – Cladocera and Copepoda occurred with equal frequency in area lakes – but six separate colonizations by cladoceran species failed. We argue that local factors, metal toxicity and predation by yellow perch, have, to date, prevented cladoceran recovery. Nonetheless, the complete copepod recovery is encouraging, given the severity and duration of pre‐neutralization stress.     

Relative contributions of nine genes in the pathway of histidine biosynthesis to the control of free histidine concentrations in Arabidopsis thaliana

Despite the functional importance of histidine (His) as an essential amino acid in proteins and as a metal-coordinating ligand, comparatively little is known about the regulation of its biosynthesis in plants and the potential for metabolic engineering of this pathway. To investigate the contribution of different steps in the pathway to overall control of His biosynthesis, nine His biosynthetic genes were individually over-expressed in Arabidopsis thaliana to determine their effects on free amino acid pools. Constitutive, CaMV 35S -driven over-expression of the cDNAs encoding either isoform of ATP-phosphoribosyltransferase (ATP-PRT), the first enzyme in the pathway, was sufficient to increase the pool of free His by up to 42-fold in shoot tissue of Arabidopsis , with negligible effect on any other amino acid. In contrast, over-expression of cDNAs for seven other enzymes in the biosynthetic pathway had no effect on His content, suggesting that control of the pool of free His resides largely with ATP-PRT activity. Over-expression of ATP-PRT and increased His content had a negative pleiotropic effect on plant biomass production in 35S:PRT1 lines, but this effect was not observed in 35S:PRT2 lines. In the presence of 100 µM Ni, which was inhibitory to wild-type plants, a strong positive correlation was observed between free His content and biomass production, indicating that the metabolic cost of His overproduction was outweighed by the benefit of increased tolerance to Ni. His-overproducing plants also displayed somewhat elevated tolerance to Co and Zn, but not to Cd or Cu, indicating chemical selectivity in intracellular metal binding by His.