http://science.sciencemag.org/content/sci/201/4359/899.2.full.pdf

Phenomenology of perception.

▪ Abstract Among the heavy metal-binding ligands in plant cells the phytochelatins (PCs) and metallothioneins (MTs) are the best characterized. PCs and MTs are different classes of cysteine-rich, heavy metal-binding protein molecules. PCs are enzymatically synthesized peptides, whereas MTs are gene-encoded polypeptides. Recently, genes encoding the enzyme PC synthase have been identified in plants and other species while the completion of the Arabidopsis genome sequence has allowed the identification of the entire suite of MT genes in a higher plant. Recent advances in understanding the regulation of PC biosynthesis and MT gene expression and the possible roles of PCs and MTs in heavy metal detoxification and homeostasis are reviewed.

PHYTOCHELATINS AND METALLOTHIONEINS: Roles in Heavy Metal Detoxification and Homeostasis

The Tact of Teaching: The Meaning of Pedagogical Thoughtfulness.

http://eportfolio.lib.ksu.edu.tw/user/G/9/G980N004/repository/PAPER/es10.pdf

Biochemical biomarkers in algae and marine pollution: a review.

Phytoremediation is an eco friendly approach for remediation of contaminated soil and water using plants. Phytoremediation is comprised of two components, one by the root colonizing microbes and the other by plants themselves, which degrade the toxic compounds to further non-toxic metabolites. Various compounds, viz. organic compounds, xenobiotics, pesticides and heavy metals, are among the contaminants that can be effectively remediated by plants. Plant cell cultures, hairy roots and algae have been studied for their ability to degrade a number of contaminants. They exhibit various enzymatic activities for degradation of xenobiotics, viz. dehalogenation, denitrification leading to breakdown of complex compounds to simple and non-toxic products. Plants and algae also have the ability to hyper accumulate various heavy metals by the action of phytochelatins and metallothioneins forming complexes with heavy metals and translocate them into vacuoles. Molecular cloning and expression of heavy metal accumulator genes and xenobiotic degrading enzyme coding genes resulted in enhanced remediation rates, which will be helpful in making the process for large-scale application to remediate vast areas of contaminated soils. A few companies worldwide are also working on this aspect of bioremediation, mainly by transgenic plants to replace expensive physical or chemical remediation techniques. Selection and testing multiple hyperaccumulator plants, protein engineering ofphytochelatin and membrane transporter genes and their expression would enhance the rate of phytoremediation, making this process a successful one for bioremediation of environmental contamination. Recent years have seen major investments in the R&D, which have also resulted in competition of filing patents by several companies for economic gains. The details of science & technology related to phytoremediation have been discussed with a focus on future trends and prospects of global relevance.

Phytoremediation—A Novel and Promising Approach for Environmental Clean-up

A cDNA library was constructed from macroalgae adapted to prolonged elevated environmental copper levels. To investigate the possible existence of a metallothionein (MT) gene, the library was screened with degenerate probes designed using plant MT cysteine-rich motifs. A gene was identified (1229 bp) with a putative open reading frame (204 bp) encoding a 67-amino-acid protein exhibiting several characteristic features of MT proteins, including 16 cysteine residues (24%) and only one aromatic residue. Although the protein sequence showed high identity with plant and invertebrate MTs, it contained a unique 'linker' region (14 amino acid residues) between the two putative metal-binding domains which contained no cysteine residues. This extended linker is larger than the tripeptide found in archetypal vertebrate MTs, but does not conform either with the 40-amino-acid linkers commonly found in plant MT sequences. An S-peptide Fucus MT fusion protein expressed in Escherichia coli exhibited a relative molecular mass of approximately 14 kDa. The recombinant fusion bound seven Cd ions, of which 50% were dissociated at pH 4.1. Under anaerobic conditions, the Cd ions were displaced by Cu(I), which associated with the protein at a ratio of 13:1. Laboratory exposure of F. vesiculosus to elevated copper resulted in induction of the MT gene. Thus this paper describes, for the first time, an MT gene identified from macroalgae which is induced by copper exposure and whose encoded protein product binds cadmium and copper.

Identification and characterization of a recombinant metallothionein protein from a marine alga, Fucus vesiculosus.

We have investigated the response dynamics of the estrogen-dependent genes vitellogenin (VTG) and the vitelline envelope proteins (VEPs) as well as circulating VTG in immature female rainbow trout (Oncorhynchus mykiss) exposed to 17β-estradiol (E2) and 17α-efhinylestradiol (EE2) for periods of 7 and 14 d. Gene responses were quantified by measurement of messenger RNA (mRNA) in liver extracts using a chemiluminescent hybridization protection assay. Circulating VTG was measured by a homologous enzyme-linked immunosorbent assay. Exposure to both E2 and EE2 induced concentration-dependent increases in all biomarkers. The data presented indicate that VEP genes may be more sensitive to estrogens than the VTG gene. The biomarker lowest-observed-effect concentrations (biomarkerLOEC) in the 14-d study with E2 were 14 ng/L (VTG protein, VTG mRNA, VEPβ, and VEPγ) or 4.8 ng/L (VEPα). The EE2 was 5- to 66-fold more potent depending on the biomarker studied. In the 7-d study, all biomarkers were elevated after 48-h exposure to E2, with biomarkerLOECs of 30 ng/L (VTG protein, VTG mRNA, and VEPγ) or 9.7 ng/L (VEPα and VEPβ). Vitellogenin mRNA was induced up to 1,000-fold above baseline, and this translated into an increase of approximately 50,000-fold in circulating VTG. In conclusion, all biomarkers responded to estrogen exposure at environmentally relevant concentrations.

Dynamics of estrogen biomarker responses in rainbow trout exposed to 17β-estradiol and 17α-ethinylestradiol

We describe a whole-mount RNA in situ hybridization (ISH) method optimized for detection of the cellular and subcellular distributions of specific mRNA within Drosophila testes and male genital tract. Digoxygenin (dig)-labeled antisense RNA probes are in vitro transcribed from a template synthesized by (RT)-PCR; the probe length is reduced by hydrolysis. Testes and male genital tracts are dissected from adult flies, fixed and processed for hybridization. Both probe and fixed testes can be stored before use. Extensive post-hybridization washing reduces the background. Detection is through alkaline phosphatase-conjugated anti-dig antibodies followed by a color reaction. This protocol is suitable for low-medium throughput applications with parallel processing of 2–48 samples, and takes 4–5 d to complete. We have used this protocol, which is similar to other RNA ISH protocols, but optimized for whole-mount Drosophila testes, to document the expression of about 1,000 genes in Drosophila melanogaster male genital tract.

Determination of gene expression patterns using in situ hybridization to Drosophila testes

Phytochelatins are small cysteine-rich non-ribosomal peptides that chelate soft metal and metalloid ions, such as cadmium and arsenic. They are widely produced by plants and microbes; phytochelatin synthase genes are also present in animal species from several different phyla, but there is still little known about whether these genes are functional in animals, and if so, whether they are metal-responsive. We analysed phytochelatin production by direct chemical analysis in Lumbricus rubellus earthworms exposed to arsenic for a 28 day period, and found that arsenic clearly induced phytochelatin production in a dose-dependent manner. It was necessary to measure the phytochelatin metabolite concentrations directly, as there was no upregulation of phytochelatin synthase gene expression after 28 days: phytochelatin synthesis appears not to be transcriptionally regulated in animals. A further untargetted metabolomic analysis also found changes in metabolites associated with the transsulfuration pathway, which channels sulfur flux from methionine for phytochelatin synthesis. There was no evidence of biological transformation of arsenic (e.g. into methylated species) as a result of laboratory arsenic exposure. Finally, we compared wild populations of earthworms sampled from the field, and found that both arsenic-contaminated and cadmium-contaminated mine site worms had elevated phytochelatin concentrations.

/pdf/earthworms-produce-phytochelatins-in-response-to-arsenic-3b9be9rn58.pdf

Earthworms Produce phytochelatins in Response to Arsenic

https://uwe-repository.worktribe.com/preview/908829/1-s2.0-S2214166915000284-main.pdf

Ceri A. Morris

Papers

Identification and characterization of a recombinant metallothionein protein from a marine alga, Fucus vesiculosus.

Dynamics of estrogen biomarker responses in rainbow trout exposed to 17β-estradiol and 17α-ethinylestradiol

Determination of gene expression patterns using in situ hybridization to Drosophila testes

Earthworms Produce phytochelatins in Response to Arsenic

Evaluation of the swirl characteristics of a tidal stream turbine wake