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Transcriptomic and Metabolomic Responses of Two Ecotoxicological Test Species to Trifluralin Exposure
Citation:
Lavelle, C., W. Henderson, J. Awkerman, B. Hemmer, P. Harris, D. Glinksi, C. Lilavois, N. Zielinski, E. Moso, AND S. Raimondo. Transcriptomic and Metabolomic Responses of Two Ecotoxicological Test Species to Trifluralin Exposure. PRIMO 20th International Symposium, Charleston, South Carolina, May 19 - 22, 2019.
Impact/Purpose:
An early life stage study of the comparative toxicity of the herbicide trifluralin was conducted with a model fish and frog species. This is part of a larger project to evaluate the use of fish as a surrogate species for amphibians in risk assessments and develop tools to translate laboratory effects into population models for native species. This research will be of interest to the eco-toxicology scientific community as well as to environmental risk assessors and managers.
Description:
Omics approaches incorporated into standard toxicity tests can provide valuable information that can be used to inform the ecological risk assessment process. Specifically, the field of toxicogenomics, and its subdisciplines of transcriptomics, proteomics and metabolomics, can be used to identify the biological pathways perturbed by sub-lethal chemical exposure. These sublethal biological pathways can include metabolic processes, immune system suppression, and endocrine disruption among others, which can ultimately contribute to deleterious population level effects. Our research focuses on identifying differences in species sensitivity to contaminant exposure across multiple molecular pathways to reduce uncertainty in extrapolation and improve predictive toxicology. In this study, we used transcriptomics and metabolomics to characterize the toxicity pathways of the widely used herbicide, trifluralin (TR), on zebrafish, Danio rerio, and the African clawed frog, Xenopus laevis. Aqueous TR early life stage exposures were conducted for 30 and 70 days for D. rerio and X. laevis, respectively. Zebrafish had high levels of mortality (LC50 of 17.356 ± 0.70 μg/L) and exhibited reduced growth with increasing dose. Growth measurements in X. laevis at metamorphosis were not correlated with exposure; however, time to metamorphosis was delayed relative to TR concentration. Tissues collected from exposed individuals were used to compare differential gene expression on targets related to the thyroid axis, stress response, mitochondrial function, and apoptosis. Species-specific gene expression patterns suggest that different biological pathways in D. rerio and X. laevis are perturbed by TR exposure. Non-targeted metabolomics identified a subset of metabolites that were dose-responsive in both species following exposure suggesting that omic approaches can complement apical endpoints. Integration of the molecular and biochemical responses highlight the species-specific alterations of biological pathways, informing the utility of using toxicity data from putative representative species in risk assessment.