Copper elicits an increase in cytosolic free calcium in cultured tobacco cells

Recent advances on environmental behavior of Cu-based nanomaterials in soil-plant system: A review

In recent years, copper-based nanomaterials (Cu-based NMs) have shown great potential in promoting agriculture development due to their special physicochemical characteristics. With the mass production and overuse of Cu-based NMs, there are potential effects on the soil-plant environment. Soil organisms, especially soil microorganisms, play a significant part in terrestrial or soil ecosystems; plants, as indirect organisms with soil-related Cu-based NMs, may affect human health through plant agricultural products. Understanding the accumulation and transformation of Cu-based NMs in soil-plant systems, as well as their ecotoxicological effects and potential mechanisms, is a prerequisite for the scientific assessment of environmental risks and safe application. Therefore, based on the current literature, this review: (i) introduces the accumulation and transformation behaviors of Cu-based NMs in soil and plant systems; (ii) focuses on the ecotoxicological effects of Cu-based NMs on a variety of organisms (microorganisms, invertebrates, and plants); (iii) reveals their corresponding toxicity mechanisms. It appears from studies hitherto made that both Cu-based NMs and released Cu2+ may be the main reasons for toxicity. When Cu-based NMs enter the soil-plant environment, their intrinsic physicochemical properties, along with various environmental factors, could also affect their transport, transformation, and biotoxicity. Therefore, we should push for intensifying the multi-approach research that focuses on the behaviors of Cu-based NMs in terrestrial exposure environments, and mitigates their toxicity to ensure the promotion of Cu-based NMs.

Prevention of copper-induced cell death by GC-rich DNA oligomers in murine macrophage-like RAW264.7 cells

Impact of redox active transition metals on activation of cell death signaling in plant cells have been documented to date. We have recently reported that GC-rich DNA oligomers with high affinity for binding of copper and catalytic activity for removal of ROS as novel plant cell-protecting agents. Here, we show that similar DNA oligomers protect the mouse macrophage-like RAW264.7 cells from copper-induced cell death, suggesting that the phenomenon firstly observed in plant model can be expanded to a wider range of cells and/or organisms including mammalian cells.

Mitigation of copper toxicity by DNA oligomers in green paramecia

Impact of transition metals which catalyze the generation of reactive oxygen species (ROS), on activation of cell death signaling in plant cells have been documented to date. Similarly in green paramecia (Paramecium bursaria), an aquatic protozoan species harboring symbiotic green algae in the cytoplasm, toxicities of various metallic ions have been documented. We have recently examined the effects of double-stranded GC-rich DNA fragments with copper-binding nature and ROS removal catalytic activity as novel plant cell-protecting agents, using the suspension-cultured tobacco cells. Here, we show that above DNA oligomers protect the cells of green paramecia from copper-induced cell death, suggesting that the phenomenon firstly observed in tobacco cells is not limited only within higher plants but it could be universally observable in wider range of organisms.

Protection of tobacco cells from oxidative copper toxicity by catalytically active metal-binding DNA oligomers

The impact of copper ions on the oxidative and calcium signal transductions, leading to cell death in plant cells, have been documented. Copper induces a series of biological and chemical reactions in plant cells including the oxidative burst reflecting the production of reactive oxygen species and the stimulation of calcium channel opening allowing a transient increase in cytosolic calcium concentrations. These early events, completed within a few minutes after the contact with copper, are known to trigger the development of cell death. The effects of DNA fragments with copper-binding motifs as novel plant cell-protecting agents were assessed using cell suspension cultures of transgenic tobacco (Nicotiana tabacum L., cell line BY-2) expressing the aequorin gene. The addition of GC-rich double-stranded DNA fragments, prior to the addition of copper ions, effectively blocked both the copper-induced calcium influx and cell death. In addition, the DNA-Cu complex examined was shown to possess superoxide-scavenging catalytic activity, suggesting that DNA-mediated protection of the cells from copper toxicity is due to the removal of superoxide. Lastly, a possible mechanism of DNA-Cu interaction and future applications of these DNA fragments in the protection of plant roots from metal toxicity or in aid of phyto-remediation processes are discussed.

Subcellular distribution and toxicity of cadmium in Potamogeton crispus L

The submerged macrophyte Potamogeton crispus L. was subjected to varying doses of cadmium (0, 20, 40, 60 and 80 μM) for 7 d, and the plants were analyzed for subcellular distribution of Cd, accumulation of mineral nutrients, photosynthesis, oxidative stress, protein content, and ultrastructural distribution of calcium (Ca). Leaf fractionation by differential centrifugation indicated that 48-69% of Cd was accumulated in the cell wall. At all doses of Cd, the levels of Ca and B rose and the level of Mn fell; the levels of Fe, Mg, Zn, Cu, Mo, and P rose initially only to decline later. Exposure to Cd caused oxidative stress as evident by increased content of malondialdehyde and decreased contents of chlorophyll and protein. Photosynthetic efficiency, as indicated by the quenching of chlorophyll a fluorescence (Fv/Fm, Fo and Fm), decreased significantly, the extent of decrease being directly proportional to the concentration of Cd. Increased amounts of precipitates of calcium were noticed in the treated plants, located either outside the cell membrane or in chloroplasts, mitochondria, the nucleus, and the cytoplasm whereas control plants showed small deposits of the precipitates around surface of the vacuole membrane and in the intercellular space but rarely in the cytoplasm. Photosynthetic efficiency and oxidative stress could be used as indicators of physiological end-points in determining the extent of Cd phytotoxicity.

Co-occurring increases of calcium and organellar reactive oxygen species determine differential activation of antioxidant and defense enzymes in Ulva compressa (Chlorophyta) exposed to copper excess

In order to analyse copper-induced calcium release and (reactive oxygen species) ROS accumulation and their role in antioxidant and defense enzymes activation, the marine alga Ulva compressa was exposed to 10 µM copper for 7 d. The level of calcium, extracellular hydrogen peroxide (eHP), intracellular hydrogen peroxide (iHP) and superoxide anions (SA) as well as the activities of ascorbate peroxidase (AP), glutathione reductase (GR), glutathione-S-transferase (GST), phenylalanine ammonia lyase (PAL) and lipoxygenase (LOX) were determined. Calcium release showed a triphasic pattern with peaks at 2, 3 and 12 h. The second peak was coincident with increases in eHP and iHP and the third peak with the second increase of iHP. A delayed wave of SA occurred after day 3 and was not accompanied by calcium release. The accumulation of iHP and SA was mainly inhibited by organellar electron transport chains inhibitors (OETCI), whereas calcium release was inhibited by ryanodine. AP activation ceased almost completely after the use of OETCI. On the other hand, GR and GST activities were partially inhibited, whereas defense enzymes were not inhibited. In contrast, PAL and LOX were inhibited by ryanodine, whereas AP was not inhibited. Thus, copper stress induces calcium release and organellar ROS accumulation that determine the differential activation of antioxidant and defense enzymes.

Physiological roles of nonselective cation channels in plants: from salt stress to signalling and development

Nonselective cation channels (NSCCs) catalyse passive fluxes of cations through plant membranes. NSCCs do not, or only to a small extent, select between monovalent cations, and several are also permeable to divalent cations. Although a number of NSCC genes has been identified in plant genomes, a direct correlation between gene products and in vivo observed currents is still largely absent for most NSCCs. In this review, physiological functions and molecular properties of NSCCs are critically discussed. Recent studies have demonstrated that NSCCs are directly involved in a multitude of stress responses, growth and development, uptake of nutrients and calcium signalling. NSCCs can also function in the perception of external stimuli and as signal transducers for reactive oxygen species, pathogen elicitors, cyclic nucleotides, membrane stretch, amino acids and purines.