As a free-living nematode,
C. elegans
is exposed to various pesticides used in agriculture, as well as to persistent organic residues which may contaminate the soil for long periods. Following on ...from our previous study of metal effects on 24 GFP-reporter strains representing four different stress-response pathways in
C. elegans
(Anbalagan et al. Ecotoxicology 21:439–455, 2012), we now present parallel data on the responses of these same strains to several commonly used pesticides. Some of these, like dichlorvos, induced multiple stress genes in a concentration-dependent manner. Unusually, endosulfan induced only one gene (
cyp
-34A9) to very high levels (8–10-fold) even at the lowest test concentration, with a clear plateau at higher doses. Other pesticides, like diuron, did not alter reporter gene expression detectably even at the highest test concentration attainable, while others (such as glyphosate) did so only at very high concentrations. We have also used five responsive GFP reporters to investigate the toxicity of soil pore water from two agricultural sites in south-east Spain, designated P74 (used for cauliflower production, but significantly metal contaminated) and P73 (used for growing lettuce, but with only background levels of metals). Both soil pore water samples induced all five test genes to varying extents, yet artificial mixtures containing all major metals present had essentially no effect on these same transgenes. Soluble organic contaminants present in the pore water were extracted with acetone and dichloromethane, then after evaporation of the solvents, the organic residues were redissolved in ultrapure water to reconstitute the soluble organic components of the original soil pore water. These organic extracts induced transgene expression at similar or higher levels than the original pore water. Addition of the corresponding metal mixtures had either no effect, or reduced transgene expression towards the levels seen with soil pore water only. We conclude that the main toxicants present in these soil pore water samples are organic rather than metallic in nature. Organic extracts from a control standard soil (Lufa 2.2) had negligible effects on expression of these genes, and similarly several pesticides had little effect on the expression of a constitutive
myo
-3::GFP transgene. Both the P73 and P74 sites have been treated regularly with (undisclosed) pesticides, as permitted under EU regulations, though other (e.g. industrial) organic residues may also be present.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Caenorhabditis elegans
strains carrying stress-reporter green fluorescent protein transgenes were used to explore patterns of response to metals. Multiple stress pathways were induced at high doses ...by most metals tested, including members of the heat shock, oxidative stress, metallothionein (mtl) and xenobiotic response gene families. A mathematical model (to be published separately) of the gene regulatory circuit controlling mtl production predicted that chemically similar divalent metals (classic inducers) should show additive effects on
mtl
gene induction, whereas chemically dissimilar metals should show interference. These predictions were verified experimentally; thus cadmium and mercury showed additive effects, whereas ferric iron (a weak inducer) significantly reduced the effect of mercury. We applied a similar battery of tests to diluted samples of soil pore water extracted centrifugally after mixing 20% w/w ultrapure water with air-dried soil from an abandoned lead/zinc mine in the Murcia region of Spain. In addition, metal contents of both soil and soil pore water were determined by ICP-MS, and simplified mixtures of soluble metal salts were tested at equivalent final concentrations. The effects of extracted soil pore water (after tenfold dilution) were closely mimicked by mixtures of its principal component ions, and even by the single most prevalent contaminant (zinc) alone, though other metals modulated its effects both positively and negatively. In general, mixtures containing similar (divalent) metal ions exhibited mainly additive effects, whereas admixture of dissimilar (e.g. trivalent) ions often resulted in interference, reducing overall levels of stress-gene induction. These findings were also consistent with model predictions.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
MicroRNAs are known to regulate gene expression either by repressing translation or by directing sequence-specific degradation of target mRNAs, and are therefore considered to be key regulators of ...gene expression. A gene-regulatory pathway involving heterochronic genes controls the temporal pattern of Caenorhabditis elegans postembryonic cell lineages. Based on experimental data, we propose and analyze a mathematical model of a gene-regulatory module in this nematode involving two heterochronic genes, lin-14 and lin-28 , which are both regulated by lin-4 , encoding a microRNA. The conditions under which the model experiences bifurcations are investigated. We determine the parameter regimes for which the system exhibits monostability and bistability, the latter associated with a biological switch. We observe in particular that bistability occurs without co-operativity, in keeping with knowledge about the regulatory behaviour of lin-14 and lin-28 . The analytical results are confirmed by numerical simulations that illustrate how the microRNA lin-4 plays a crucial role in determining of the qualitative dynamics of the model.
Exposure to microwave radiation enhances the aggregation of bovine serum albumin in vitro in a time- and temperature-dependent manner. Microwave radiation also promotes amyloid fibril formation by ...bovine insulin at 60°C. These alterations in protein conformation are not accompanied by measurable temperature changes, consistent with estimates from field modelling of the specific absorbed radiation (15–20 mW kg
−1). Limited denaturation of cellular proteins could explain our previous observation that modest heat-shock responses are induced by microwave exposure in
Caenorhabditis elegans. We also show that heat-shock responses both to heat and microwaves are suppressed after RNA interference ablating heat-shock factor function.
Full text
Available for:
BFBNIB, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The neural protein α-synuclein aggregates both in vivo and in vitro to form insoluble fibrils that are involved in Parkinson's disease pathogenesis. We have generated α-synuclein/fluorescent-protein ...fusion constructs overexpressed in muscle cells of the nematode, Caenorhabdtis elegans. Green Fluorescent Protein (GFP) variants, Cerulean (C) or Venus (V), were fused to the C-terminus of human α-synuclein (S); the resultant fusion genes were designated SV and SC, plus a CV fusion as well as S, C and V singly. The aggregation behavior of the purified fusion proteins (expressed in E. coli) will be described elsewhere. These constructs were fused to a C. elegans unc-54 myosin promoter, and integrated transgenic lines generated by microinjection, λ-irradiation, and outcrossing of fluorescent progeny. All transgenic lines expressing α- synuclein showed significant reductions (p <0.05) in lifespan, motility and pharyngeal pumping, as compared to wildtype worms or lines expressing CFP and/or YFP only. We showed that CFP and YFP labels colocalised in granular inclusions throughout the body wall in transgenic lines expressing both SC and SV fusions (SC+SV), whereas SV+C worms displayed YFP-labelled inclusions on a diffuse CFP background. These findings implied that the α-synuclein moieties of these fusion proteins still aggregated together in vivo, whereas CFP or YFP moieties alone did not. This in turn suggested that Foerster Resonanace Energy Transfer (FRET) between CFP and YFP labels in α-synuclein aggregates could allow the extent of aggregation to be quantified. Accordingly, we also showed that net FRET signals increased 2- fold between L4 and adult SC+SV worms.
Caenorhabditis elegans is a free-living nematode that is exposed naturally to multiple surfactants contaminating fresh water and soil. Their breakdown products can act as Endocrine Disruptor ...Chemicals (EDCs), which interfere with hormonal signalling in vertebrates and invertebrates. Vitellogenin (yolk protein) synthesis is induced by oestrogens and related hormones in vivo, and is widely utilized as a biomarker for EDCs at sub-lethal concentrations in various test species, including C. elegans. The study shows that C. elegans feeding activity is inhibited at high concentrations of both amphoteric cocamidopropyl betaine (CAPB) and cocamidopropyl hydroxysultaine (CAPHS), and cationic Hyamine 1622 surfactants. Molecular assays measuring induction of stress-responsive Green Fluorescent Protein (GFP) reporter transgenes confirmed the activation of vitellogenin-2 (vit-2) and antioxidant/phase II defences during larval development when using synchronized populations. Among known EDCs, Bisphenol A (BPA) strongly induced vit-2 at 48 and 72 h but had less effect on the stressreporters, whereas 17-Ethinylestradiol (EE2; active ingredient of contraceptive pills) down-regulated vit2 after 24 h but upregulated it dose-dependently after 48 h and 72 h, and also strongly induced sod-4 and gst-1 stress-reporters. CAPB and CAPHS induced vit-2 expression rather weakly at 10-2 mg.l-1 after 48 and 72 h, but had more dramatic effects on stress-reporter expression. Hyamine 1622 at 10-3 mg.l-1 downregulated vit-2 at early time points and also down-regulated the stress-reporters (though gst-1 was upregulated at 24 h). Males are rare in C. elegans populations, but both EDC and surfactant treatments were associated with subtle modifications of male tail morphology.
Caenorhabditis elegans is a free-living nematode that is exposed naturally to multiple surfactants contaminating fresh water and soil. Their breakdown products can act as Endocrine Disruptor ...Chemicals (EDCs), which interfere with hormonal signalling in vertebrates and invertebrates. Vitellogenin (yolk protein) synthesis is induced by oestrogens and related hormones in vivo, and is widely utilized as a biomarker for EDCs at sub-lethal concentrations in various test species, including C. elegans. The study shows that C. elegans feeding activity is inhibited at high concentrations of both amphoteric cocamidopropyl betaine (CAPB) and cocamidopropyl hydroxysultaine (CAPHS), and cationic Hyamine 1622 surfactants. Molecular assays measuring induction of stress-responsive Green Fluorescent Protein (GFP) reporter transgenes confirmed the activation of vitellogenin-2 (vit-2) and antioxidant/phase II defences during larval development when using synchronized populations. Among known EDCs, Bisphenol A (BPA) strongly induced vit-2 at 48 and 72 h but had less effect on the stressreporters, whereas 17-Ethinylestradiol (EE2; active ingredient of contraceptive pills) down-regulated vit2 after 24 h but upregulated it dose-dependently after 48 h and 72 h, and also strongly induced sod-4 and gst-1 stress-reporters. CAPB and CAPHS induced vit-2 expression rather weakly at 10-2 mg.l-1 after 48 and 72 h, but had more dramatic effects on stress-reporter expression. Hyamine 1622 at 10-3 mg.l-1 downregulated vit-2 at early time points and also down-regulated the stress-reporters (though gst-1 was upregulated at 24 h). Males are rare in C. elegans populations, but both EDC and surfactant treatments were associated with subtle modifications of male tail morphology.
PDF
