Project description:To determine toxicant specific effects of Ordnance Related Compound (ORC) exposure we performed microarray hybridizations with RNA isolated from Daphnia magna following different ORC exposures at the 1/10 LC50. The gene expression profiles revealed toxicant specific gene expression profiles allowed for the identification of specific biomarkers of exposure. Keywords: ecotoxicogenomic exposure study We exposed Daphnia magna the 1/10 LC50 of different Ordnance Related Compounds (Cu, Zn, Pb, WO4, RDX, TNT, 2-ADNT, 2-ADNT, TNB, DNB, 2,4-DNT, and 2,6-DNT) for 24 hours. For each exposure condition, we performed 3 exposures and 2 technical replicates (as dye swap) for each exposure (6 microarrays total, except TNT and Cu). All exposures were compared to a unexposed laboratory control (MHRW media).
Project description:A reduced level of DNA methylation has recently been described in both Zn-exposed and non-exposed offspring of Daphnia magna exposed to Zn. The hypothesis examined in this study is that DNA hypomethylation has an effect on gene transcription. A second hypothesis is that accumulative epigenetic effects can affect gene transcription in non-exposed offspring from parents with an exposure history of more than one generation. Transcriptional gene regulation was studied with a cDNA microarray. In the exposed and non-exposed hypomethylated daphnids, a large proportion of common genes were similarly up- or downregulated, indicating a possible effect of the DNA hypomethylation. Two of these genes can be mechanistically involved in DNA methylation reduction. The similar transcriptional regulation of two and three genes in the F0 and F1 exposed daphnids on one hand and their non-exposed offspring on the other hand, could be the result of a one-generation temporary transgenerational epigenetic effect, which was not accumulative.
Project description:To determine dose-dependent effects of metal exposure we performed microarray hybridizations with RNA isolated from Daphnia magna following Cu, Cd, and Zn exposures over a range of concentrations that included a tolerated concentration, a sublethal concentration, and a highly toxic concentration. The gene expression profiles revealed effects to digestion related genes, immune related genes, metallothioneins, and oxidative stress genes at the higher concentrations. We also observed that the highest concentrations produced less specific gene expression profiles than the lower concentrations suggesting a more general stress response at the higher concentrations. The lowest concentration tested, representing tolerated concentrations of the metals, caused differential expression of only a few genes and were distinct from the expression profiles of the higher concentrations. This result provides support for the presence of a No Observed Transcriptional Effect Level (NOTEL) for metal exposure in D. magna and suggests that gene expression analysis may offer a strategy for distinguishing between toxic and nontoxic concentrations of metals in the environment. Keywords: ecotoxicogenomic exposure study
Project description:This SuperSeries is composed of the following subset Series: GSE29854: Daphnia magna exposed to narcotics and polar narcotics - aniline GSE29856: Daphnia magna exposed to narcotics and polar narcotics - 4-chloroaniline GSE29857: Daphnia magna exposed to narcotics and polar narcotics - 3,5-dichloroaniline GSE29858: Daphnia magna exposed to narcotics and polar narcotics - 2,3,4-trichloroaniline GSE29862: Daphnia magna exposed to narcotics and polar narcotics - ethanol GSE29864: Daphnia magna exposed to narcotics and polar narcotics - isopropanol GSE29867: Daphnia magna exposed to narcotics and polar narcotics - methanol Refer to individual Series
Project description:A reduced level of DNA methylation has recently been described in both Zn-exposed and non-exposed offspring of Daphnia magna exposed to Zn. The hypothesis examined in this study is that DNA hypomethylation has an effect on gene transcription. A second hypothesis is that accumulative epigenetic effects can affect gene transcription in non-exposed offspring from parents with an exposure history of more than one generation. Transcriptional gene regulation was studied with a cDNA microarray. In the exposed and non-exposed hypomethylated daphnids, a large proportion of common genes were similarly up- or downregulated, indicating a possible effect of the DNA hypomethylation. Two of these genes can be mechanistically involved in DNA methylation reduction. The similar transcriptional regulation of two and three genes in the F0 and F1 exposed daphnids on one hand and their non-exposed offspring on the other hand, could be the result of a one-generation temporary transgenerational epigenetic effect, which was not accumulative. The experimental design used in the current study is as follows. A set of neonates (0-24h) taken from the laboratory culture was divided into two batches. One batch was transferred to modified standard M4 medium (Elendt and Bias, 1990) and cultured for three generations (CtrlF0–CtrlF2). A second batch of neonates was transferred into the same medium, with the Zn concentration adjusted to 388 µg/L. A group of F1 neonates born from this ZnF0 generation was then cultured in this Zn-contaminated medium [Zn(+)F1]. Another group of these F1 neonates was transferred back to the control medium [Zn(-)F1]. In this way, Zn(-)F1 daphnids were only briefly exposed to Zn during the first hours of their life-cycle. Offspring of the F1Zn(-) organisms were also cultured in the control medium [Zn(-/-)F2, which were named F2Zn(-) in Vandegehuchte et al. (2009))]. Offspring of the Zn(+)F1 daphnids were in turn divided in a similar manner into two batches, one of which was cultured further in Zn-contaminated medium [Zn(+)F2] while the other one was transferred to the control medium [Zn(+/-)F2]. Each combination of generation and exposure history is termed a ‘treatment’. Three replicates of ten adult daphnids each per treatment were sampled for RNA extraction on the day the next generation was started. In general, a universal reference design was used in which the reference sample was a pool composed of differently aged daphnids cultured in aerated carbon-filtered tap water, enriched with selenium (1 µg/L) and vitamins (7.5 mg/L thiamine, 100 µg/L cyanocobalamin and 75 µg/L biotin). Dye-bias effects were accounted for by regularly swapping Cy3 and Cy5 for labelling treatments/reference pool samples.
Project description:In the past years, the research focus on the effects of microplastics (MP) on aquatic organisms extended from marine systems towards freshwater systems. An important freshwater model organism in the MP field is the cladoceran Daphnia, which plays a central role in lacustrine ecosystems and has been established as a test organism in ecotoxicology. To investigate the effects of MP on Daphnia magna, we performed a chronic exposure experiment with polystyrene MP under strictly standardized conditions. Chronic exposure of D. magna to PS microparticles led to a significant reduction in body length and number of offspring. To shed light on underlying molecular mechanisms induced by microplastic ingestion in D. magna, we assessed the effects of PS-MP at the proteomic level.
Project description:To determine toxicant specific effects of Ordnance Related Compound (ORC) exposure we performed microarray hybridizations with RNA isolated from Daphnia magna following different ORC exposures at the 1/10 LC50. The gene expression profiles revealed toxicant specific gene expression profiles allowed for the identification of specific biomarkers of exposure. Keywords: ecotoxicogenomic exposure study
Project description:Epigenetic mechanisms have been found to play important roles in environmental stress response and regulation. These can, theoretically, be transmitted to future unexposed generations, yet few studies have shown persisting stress-induced transgenerational effects, particularly in invertebrates. Here, we focus on the aquatic microcrustacean Daphnia, a parthenogenetic model species, and its response to salinity stress. Salinity is a serious threat to freshwater ecosystems and a relevant form of environmental perturbation affecting freshwater ecosystems. We exposed one generation of D. magna to high levels of salinity (F0) and found that the exposure provoked specific methylation patterns that were transferred to the three consequent non-exposed generations (F1, F2 and F3). This was the case for the hypomethylation of six protein-coding genes with important roles in the organisms’ response to environmental change: DNA damage repair, cytoskeleton organization and protein synthesis. This suggests that epigenetic changes in Daphnia are particularly targeted to genes involved in coping with general cellular stress responses. Our results highlight that epigenetic marks are affected by environmental stressors and can be transferred to subsequent unexposed generations. Epigenetic marks could therefore prove to be useful indicators of past or historic pollution in this parthenogenetic model system. Furthermore, no life history costs seem to be associated with the maintenance of hypomethylation of across unexposed generations in Daphnia following a single stress exposure.
Project description:Zinc Oxide nanoparticles (ZnO NPs) are being rapidly developed for use in consumer products, wastewater treatment and chemotherapy providing several possible routes for ZnO NP exposure to humans and aquatic organisms. Recent studies have shown that ZnO NPs undergo rapid dissolution to Zn+2, but the relative contribution of Zn+2 to ZnO NP bioavailability and toxicity is not clear. Gene expression profiling of D. magna exposed to ZnO NPs or ZnSO4 at equitoxic concentrations demonstrated that the particles cause toxicity through a distinct mechanism compared with Zn+2. D. magna were also exposed to a SiO NPs as a particle control at equimolar concentrations. The SiO NPs resulted in few differentially expressed genes and there was very little overlap between the genes affected by the ZnO NPs and the SiO NPs, suggesting that ZnO NPs cause a distinct pattern of differentially expressed genes. In the ZnO NP exposures, effects were observed to genes involved in cytoskeletal transport, cellular respiration and reproduction. Three biomarker genes including a multi-cystatin, ferritin and a C1q containing gene were confirmed as differentially expressed in a specific pattern by ZnO NP and provide a suite of biomarkers for identifying environmental exposure to ZnO NP and differentiating between NP and ionic exposure. We exposed Daphnia magna to the 1/10 LC50 and LC25 of ZnO nanoparticles and Zn++ as ZnSO4 for 24-h. For each exposure condition, we performed 3 exposures and 2 technical replicates (as dye swap) for each exposure (6 microarrays total). All exposures were compared to a unexposed laboratory control
Project description:Phenotypic plasticity, the ability of one genotype to express different phenotypes in response to changing environmental conditions, is one of the most common phenomena characterising the living world and is not only relevant for the ecology but also for the evolution of species. Daphnia, the waterflea, is a textbook example for predator induced phenotypic plastic defences including changes in life-history, behaviour and morphology. However, the analysis of molecular mechanisms underlying these inducible defences is still in its early stages.<br><br>We exposed Daphnia magna to chemical cues of the predator Triops cancriformis to identify key processes underlying plastic defensive trait formation. D. magna is known to develop an array of morphological changes in the presence of T. cancriformis including changes of carapace morphology and cuticle hardening. To get a more comprehensive idea of this phenomenon, we studied four different genotypes originating from habitats with different predation history, reaching from predator-free to temporary habitats containing T. cancriformis.<br><br>We analysed the morphologies as well as proteomes of predator-exposed and control animals. Three genotypes showed morphological changes when the predator was present. Using a high-throughput proteomics approach, we found 294 proteins which were significantly altered in their abundance after predator exposure in a general or genotype dependant manner. Proteins connected to genotype dependant responses were related to the cuticle, protein synthesis and calcium binding whereas the yolk protein vitellogenin increased in abundance in all genotypes, indicating their involvement in a more general response. Furthermore, genotype dependant responses at the proteome level correlated well with local adaptation to Triops predation.<br><br>Altogether, our study provides new insights concerning genotype dependant and general molecular processes involved in predator-induced phenotypic plasticity in D. magna.