Project description:Environmental risk assessment relies heavily on the use of bioassays to assess the environmental impact of chemicals. Gene expression is gaining acceptance as a valuable mechanistic endpoint in bioassays and effect-based screening. Data analysis and its results however, are often complex and not directly applicable in risk assessment. Classifier analysis is a promising method to turn complex gene expression analysis results into answers suitable for risk assessment. We have assembled a large gene expression dataset assembled from multiple studies and experiments in the springtail Folsomia candida, with the aim of selecting a set of genes that can be trained to classify general toxic stress. By performing differential expression analysis prior to classification we were able to select a set of 135 genes which was enriched in stress related processes. This set was then used to classify two test sets comprised of chemical spiked soils, polluted soils and clean soils and compared to another, more traditional feature selection for classification. The gene set presented here outperformed the more traditionally selected gene set. This gene set has the potential to be used as a biomarker to test for adverse effects caused by chemicals in springtails to provide endpoints in environmental risk assessment.
Project description:Environmental risk assessment relies heavily on the use of bioassays to assess the environmental impact of chemicals. Gene expression is gaining acceptance as a valuable mechanistic endpoint in bioassays and effect-based screening. Data analysis and its results however, are often complex and not directly applicable in risk assessment. Classifier analysis is a promising method to turn complex gene expression analysis results into answers suitable for risk assessment. We have assembled a large gene expression dataset assembled from multiple studies and experiments in the springtail Folsomia candida, with the aim of selecting a set of genes that can be trained to classify general toxic stress. By performing differential expression analysis prior to classification we were able to select a set of 135 genes which was enriched in stress related processes. This set was then used to classify two test sets comprised of chemical spiked soils, polluted soils and clean soils and compared to another, more traditional feature selection for classification. The gene set presented here outperformed the more traditionally selected gene set. This gene set has the potential to be used as a biomarker to test for adverse effects caused by chemicals in springtails to provide endpoints in environmental risk assessment. The data presented in our manuscript is part of a larger experiment which was performed in single, large loop design. Only the samples used in the study presented here are named while the other samples will remain unnamed. All the data can still be used for normalization after which the analysis presented in the manuscript can be replicated. A single channel, interwoven loop design was used to test animals exposed to a control and to 5 concentrations of cadmium and phenanthrene (cadmium concentrations are: cad_1 till cad_5: 5.8, 14.5, 28.9, 57.9 and 115.8 mg/Kg respectively and phenanthrene concentrations are: phe_1 till Phe_5: 0, 4.6, 11.4, 22.9, 45.8 and 91.6 mg/Kg soil respectively). Exposures lasted for 2 days and used 4 biological replicates per condition each containing 30 grams soil and 30 individuals.
Project description:Pentachlorophenol (PCP) as a widely used pesticide is also considered to be an endocrine disruptor. Molecular effects of chemicals with endocrine disrupting potential on soil invertebrates are largely unknown. Collembola (Folsomia candida) has been used as a model organism in ecotoxicity and in this study we explored the transcriptional expression changes of Folsomia candida in response to PCP contamination. A total of 92 genes were significantly differentially expressed at all exposure time and majority of them were found to be down-regulated. In addition to the transcripts encoding cytochrome P450s and transferase enzymes, chitin-binding protein was also identified in the list of common differentially genes. Analyses of Gene Ontology (GO) annotation and enrichment revealed that cell cycle related transcripts were significantly induced by PCP, indicating it can stimulated the cell proliferation in springtail as reported in human breast cancer cells. We also observed enrichment of functional terms related to steroid receptor and particularly twenty significant differential expressed genes involved in Chitin metabolism in response to PCP exposure. Combined with the confirmation by qPCR, our results appears that the adverse effects on reproduction of springtails after exposure to PCP can be attributed to a chemical-induced delay in the molting cycle and molting associated genes may serve as possible biomarkers for toxicological effects. In general, analysis of changes in the gene expression profiles of springtails in response to PCP exposure is useful for obtaining information on endocrine disruptor exposure of soil invertebrate and may contribute to the classification and risk assessment of relative chemicals.
Project description:Increasing concern about pollution of our environment calls for advanced and rapid methods to estimate ecological toxicity. The use of gene expression microarrays in environmental studies can potentially meet this challenge. We present a novel method to examine soil toxicity. We exposed the collembolan Folsomia candida to soil containing an ecologically relevant cadmium concentration, and found a cumulative total of 1586 differentially expressed transcripts across three exposure durations, including transcripts involved in stress response, detoxification, and hypoxia. Additional enrichment analysis of gene ontology (GO) terms revealed that antibiotic biosynthesis is important at all time points examined. Interestingly, genes involved in the "penicillin and cephalosporin biosynthesis pathway" have never been identified in animals before, but are expressed in F. candida’s tissue. The synthesis of antibiotics can possibly be a response to increased cadmium-induced susceptibility to invading pathogens, which might be caused by repression of genes involved in the immune-system (C-type lectins and Toll receptor). This study presents a first global view on the environmental stress response of an arthropod species exposed to contaminated soil,and provides a mechanistic basis for the development of a gene expression soil quality test. Keywords: cadmium, soil, Collembola, environmental genomics
Project description:In a recent study, we showed that the springtail Folsomia candida was quite sensitive the neonicotinoid insecticides imidacloprid and thiacloprid. This study aimed at determining the toxicity of both compounds to F. candida following exposure over three generations, in natural LUFA 2.2 standard soil. In the first generation, imidacloprid was more toxic than thiacloprid, with LC50s of 0.44 and 9.0 mg/kg dry soil, respectively and EC50s of 0.29 and 1.5 mg/kg dry soil, respectively. The higher LC50/EC50 ratio suggests that thiacloprid has more effects on reproduction, while imidacloprid shows lethal toxicity to the springtails. In the multigeneration tests, using soil spiked at the start of the first generation exposures, imidacloprid had a consistent effect on survival and reproduction in all three generations, with LC50s and EC50s of 0.21-0.44 and 0.12-0.29 mg/kg dry soil, respectively, while thiacloprid-exposed animals showed clear recovery in the second and third generations (LC50 and EC50 > 3.33 mg/kg dry soil). The latter finding is in agreement with the persistence of imidacloprid and the fast degradation of thiacloprid in the test soil.