An integrative omics approach to unravel toxicity mechanisms of environmental chemicals: effects of a formulated herbicide

Abstract

The use of integrative molecular approaches can aid in a comprehensive understanding of the effects of toxicants at different levels of biological organization, also supporting risk assessment. The present study aims to unravel the toxicity mechanisms of a widely used herbicide to the arthropod Folsomia candida exposed in a natural soil, by linking effects on reproduction, proteomics and genome-wide gene expression. The EC50 effects on reproduction over 4 weeks was 4.63 mg glyphosate/kg of soil. The formulation included a polyethoxylated tallowamine as an adjuvant, which at 50% effect on reproduction had an estimated concentration of 0.87-1.49 mg/kg of soil. No effects were observed on survival and reproduction when using the isolated active substance, pointing the toxicity of the formulated product to the co-formulant instead of the active ingredient, glyphosate. RNA sequencing and shotgun proteomics were applied to assess differential transcript and protein expressions between exposed and control organisms in time, respectively. Specific functional categories at protein and transcriptome levels were concordant with each other, despite overall limited correlations between datasets. The exposure to this formulation affected normal cellular respiration and lipid metabolism, inducing oxidative stress and leading to impairment in biological life cycle mechanisms such as molting and reproduction.

Figure 1

Categorization of all differential F. candida gene expression and protein levels classified by GO-term (Biological Process) after exposure to the herbicide formulation during 4, 7 and 10 days. Results are expressed in percentage (%). Blast2GO software (version 4.0) and UniProt database (www.uniprot.org) were used to group both differential transcript expression and protein levels into the GO categories, according to the major biological processes involved.

Figure 2

Gene interaction analysis [co-expression (purple), co-localization (light blue), physical interactions (orange), genetic interactions (green) and consolidated pathways (grey)] performed with F. candida’s differentially expressed transcripts after exposure to the herbicide formulation for 10 days. Protein domain attributes and genes related to query genes are presented in grey nodes and query genes presented in black nodes. Interaction analysis was performed with the list of Drosophila melanogaster genome homologous genes to F. candida, using GeneMANIA plugin from Cytoscape software (version 3.4.0).