title: Transcriptomic, cellular and life-history responses of Daphnia magna chronically exposed to benzotriazoles: Endocrine-disrupting potential and molting effects.
abstract: Benzotriazoles (BZTs) are ubiquitous aquatic contaminants used in a wide range of industrial and domestic applications from aircraft deicers to dishwasher tablets. Acute toxicity has been reported in aquatic organisms for some of the BZTs but their mode of action remains unknown. The objectives of this study were to evaluate the transcriptomic response of D. magna exposed to sublethal doses of 1H-benzotriazole (BTR), 5-methyl-1H-benzotriazole (5MeBTR) and 5-chloro-1H-benzotriazole (5ClBTR) using RNA-sequencing and quantitative real-time PCR. Cellular and life-history endpoints (survival, number of neonates, growth) were also investigated. Significant effects on the molting frequency were observed after 21-d exposure to 5MeBTR and 5ClBTR. No effects on molting frequency were observed for BTR but RNA-seq results indicated that this BZT induced the up-regulation of genes coding for cuticular proteins, which could have compensated the molting disruption. Molting in cladocerans is actively controlled by ecdysteroid hormones. Complementary short-term temporal analysis (4- and 8-d exposure) of the transcription of genes related to molting and hormone-mediated processes indicated that the three compounds had specific modes of action. BTR induced the transcription of genes involved in 20-hydroxyecdysone synthesis, which suggests pro-ecdysteroid properties. 5ClBTR exposure induced protein activity and transcriptional levels of chitinase enzymes, associated with an impact on ecdysteroid signaling pathways, which could explain the decrease in molt frequency. Finally, 5MeBTR seemed to increase molt frequency through epigenetic processes. Overall, results suggested that molting effects observed at the physiological level could be linked to endocrine regulation impacts of BZTs at the molecular level.
authors.affiliation: Environment and Climate Change Canada, Aquatic Contaminants Research Division, Water Science and Technology Directorate, Montreal, Québec, Canada.
authors.forename: Maeva
authors.initials: M
authors.lastname: Giraudo
authors.affiliation: Environment and Climate Change Canada, Aquatic Contaminants Research Division, Water Science and Technology Directorate, Montreal, Québec, Canada.
authors.forename: Mélanie
authors.initials: M
authors.lastname: Douville
authors.affiliation: Environment and Climate Change Canada, Aquatic Contaminants Research Division, Water Science and Technology Directorate, Montreal, Québec, Canada.|Université Paris Descartes, Paris, France.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Cottin
authors.affiliation: Environment and Climate Change Canada, Aquatic Contaminants Research Division, Water Science and Technology Directorate, Montreal, Québec, Canada.
authors.forename: Magali
authors.initials: M
authors.lastname: Houde
mesh_terms: D000818:Animals; D059001:Aquatic Organisms / Q000187:drug effects / Q000235:genetics / Q000254:growth & development; D060829:Arthropod Proteins / Q000235:genetics; D003621:Daphnia / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development; D052244:Endocrine Disruptors / Q000633:toxicity; D020869:Gene Expression Profiling / Q000379:methods; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects / Q000235:genetics; D008018:Life Cycle Stages / Q000187:drug effects* / Q000235:genetics; D018978:Molting / Q000187:drug effects* / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017423:Sequence Analysis, RNA; D023382:Toxicity Tests, Acute / Q000379:methods; D036401:Toxicity Tests, Chronic / Q000379:methods; D059467:Transcriptome / Q000187:drug effects* / Q000235:genetics; D014230:Triazoles / Q000633:toxicity*; D014874:Water Pollutants, Chemical / Q000633:toxicity
chemical_list: D060829:Arthropod Proteins; D052244:Endocrine Disruptors; D014230:Triazoles; D014874:Water Pollutants, Chemical; C012771:benzotriazole