Variation in the Transcriptome Response and Detoxification Gene Diversity Drives Pesticide Tolerance in Fishes

Abstract

Pesticides are critical for invasive species management but often have negative effects on nontarget native biota. Tolerance to pesticides should have an evolutionary basis, but this is poorly understood. Invasive sea lamprey (Petromyzon marinus) populations in North America have been controlled with a pesticide lethal to them at lower concentrations than native fishes. We addressed how interspecific variation in gene expression and detoxification gene diversity confer differential pesticide sensitivity in two fish species. We exposed sea lamprey and bluegill (Lepomis macrochirus), a tolerant native species, to 3-trifluoromethyl-4-nitrophenol (TFM), a pesticide commonly used in sea lamprey control. We then used whole-transcriptome sequencing of gill and liver to characterize the cellular response in both species. Comparatively, bluegill exhibited a larger number of detoxification genes expressed and a larger number of responsive transcripts overall, which likely contributes to greater tolerance to TFM. Understanding the genetic and physiological basis for pesticide tolerance is crucial for managing invasive species.

Transcriptomic impacts and potential routes of detoxification in a lampricide-tolerant teleost exposed to TFM and niclosamide

“…The following methodological approach uses the same bluegill exposure series as reported in Lawrence et al (2021) and Lawrence and Grayson et al (2022). Herein, we provide a brief overview of our methods, with further details in the aforementioned works.…”

“…Extraction and sequencing protocols are identical to those outlined in Lawrence and Grayson et al (2022), and they are only briefly outlined here. All extractions were made using a commercial kit (RNeasy Plus Mini Kit; Qiagen, Toronto, ON, Canada) with quality control being determined using a combination of a Nanodrop (260/280 & 260/230 ratios; NanoDrop One Microvolume UV-Vis Spectrophotometer; ThermoFisher, Mississauga, ON), Qubit RNA IQ assay (ThermoFisher, Mississauga, ON, Canada) and a Bioanalyzer (RNA Integrity Number range: 8.5-9.8).…”

“…Using this approach, we could identify broad scale patterns in cellular function arising from lampricide treatment in bluegill. A GO term enrichment analysis approach has already been used to identify effects on detoxification systems and cellular growth/death processes associated with TFM and niclosamide exposures separately in fishes (Lawrence and Grayson et al, 2022;Zhu et al, 2020). As previous work has identified both TFM and niclosamide as targeting oxidative phosphorylation and affecting cell growth and death processes (Borowiec et al, 2022;Lawrence and Grayson et al, 2022), we hypothesized that both niclosamide and a TFM:niclosamide mixture would disrupt cellular energy metabolism and cell cycle processes in bluegill.…”

“…In teleost fishes, the primary means of TFM detoxification is thought to involve phase II pathways, in which glucuronidation through UDP-glucuronosyltransferase (UGT) is proposed to be the primary method of TFM conjugation in fishes (reviewed in Wilkie et al, 2019). Indeed, TFM exposure leads to an accumulation of glucuronidated conjugates (Bussy et al, 2018;Lech, 1974;Vue et al, 2002) and upregulation of several ugt transcripts (Lawrence and Grayson et al, 2022). Additionally, TFM biotransformation also involves sulfotransferases (phase II) and oxidation through cytochrome P450 (Cyp) proteins (phase I; Bussy et al, 2018;Lawrence and Grayson et al 2022;reviewed in Wilkie et al, 2019), although less is known regarding the importance of these particular pathways in lampricide detoxification.…”

“…Indeed, TFM exposure leads to an accumulation of glucuronidated conjugates (Bussy et al, 2018;Lech, 1974;Vue et al, 2002) and upregulation of several ugt transcripts (Lawrence and Grayson et al, 2022). Additionally, TFM biotransformation also involves sulfotransferases (phase II) and oxidation through cytochrome P450 (Cyp) proteins (phase I; Bussy et al, 2018;Lawrence and Grayson et al 2022;reviewed in Wilkie et al, 2019), although less is known regarding the importance of these particular pathways in lampricide detoxification. Due to its phenolic nature, niclosamide detoxification in fishes is predicted to occur through the same general biotransformation pathways as with TFM (Hubert et al, 2005;Statham and Lech, 1975;reviewed in Wilkie et al, 2019).…”