Transcriptome Responses of Rainbow Trout and Chinook Salmon to Sub-Lethal Exposures to Zinc
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In the environment, fish are often exposed to cationic metals from mining activities, roadway runoff, and other sources. Data are needed on the influence of taxonomic relatedness regarding the molecular impacts from metal exposures among closely related taxa to help inform decisions on the potential use of surrogate species in toxicity risk assessments. Thus, we compared transcriptome changes in fin, gill, and liver of juvenile rainbow trout (Oncorhynchus mykiss) and Chinook salmon (Oncorhynchus tshawytscha) exposed to zinc (Zn) in control laboratory waters, and at 17%, or 50% of available 96-hour LC50 concentrations for 24 or 96 hours (N=6 per experimental group). Trimmed Illumina RNA-Seq reads from trout and salmon were aligned to GCF_002163495_1_Omyk_1.0_rna and GCF_018296145.1_Otsh_v2.0_rna templates respectively. Expression levels compared to controls were normalized with DESeq2 and differentially expressed genes (DEGs) were identified (i.e., ≥2-fold change, corrected P ≤0.05 and signal ≥10). Enrichment of KEGG and Reactome pathways by DEGs was tested by Fisher’s Exact Test (corrected FDR = 0.05). Rainbow trout had 1632 DEGs across all groups, while there were 10809 in Chinook salmon. For both species, the majority of DEGs came from gill tissue (58% and 96%, respectively). There were 89 significantly enriched pathways for trout and 212 for salmon with 22 shared between the species. For both species there were proportional increases of impacted pathways associated with higher Zn concentration and longer exposure duration. The top hierarchical categories for the shared pathways were cell cycle, cellular responses to stimuli, environmental information processing, extracellular matrix organization, genetic information processing, hemostasis, immune system, metabolism, metabolism of RNA, organismal systems, and signal transduction. The results suggest that a diverse core of salmonid-specific transcriptome responses to Zn exposure is present within the broader changes seen in each species. Investigations are underway to identify the extent to which these pathways are also affected by Zn in more distantly related fish including zebrafish (Danio rerio) and medaka (Oryzias latipes). In addition, we are checking for relationships between salmonid transcriptome changes and metabolomic shifts.