Transcriptome-Based Identification of Genes Responding to the Organophosphate Pesticide Phosmet in Danio rerio

Abstract

Organophosphate pesticides (OPPs) are one of the most widely used insecticides. OPPs exert their neurotoxic effects by inhibiting acetylcholine esterase (AChE). Most of the gross developmental abnormalities observed in OPP-treated fish, on the other hand, may not be explained solely by AChE inhibition. To understand the overall molecular mechanisms involved in OPP toxicity, we used the zebrafish (ZF) model. We exposed ZF embryos to an OPP, phosmet, for 96 h, and then analyzed developmental abnormalities and performed whole transcriptome analysis. Phenotypic abnormalities, such as bradycardia, spine curvature, and growth retardation, were observed in phosmet-treated ZF (PTZF). Whole transcriptome analysis revealed 2190 differentially expressed genes (DEGs), with 822 and 1368 significantly up-and downregulated genes, respectively. System process and sensory and visual perception were among the top biological pathways affected by phosmet toxicity. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed significant enrichment of metabolic pathways, calcium signaling pathway, regulation of actin cytoskeleton, cardiac muscle contraction, drug metabolism–other enzymes, and phototransduction. Quantitative real-time PCR results of six DEGs agreed with the sequencing data expression profile trend. Our findings provide insights into the consequences of phosmet exposure in ZF, as well as an estimate of the potential risk of OPPs to off-target species.

Developmental Toxic Effects of Thiram on Developing Zebrafish (Danio rerio) Embryos

“…Hatching failures could be caused by disruption of protease secretion necessary for chorion digestion [ 35 ]. Morphological abnormalities, such as tail malformations and spine curves, may limit the embryo’s ability to break the chorion since ZF larvae with tail abnormalities showed hatching defects [ 23 , 28 , 29 ]. Disruption of mitochondrial bioenergetics is possibly responsible for hatching delays in ZF embryos treated with DTC [ 8 ].…”

“…Spinal curvature anomalies significantly impact aquatic life, as fish with curved spines experience swimming difficulties [ 23 , 28 , 29 ] that may interfere with feeding and predatory behaviors. Spinal abnormalities, such as scoliosis, kyphosis, and lordosis, were observed in thiram-treated ZF ( Figure S1 ).…”

“…In accordance with Park et al (2021), propineb, a DTC fungicide, causes ocular toxicity in ZFs and leads to the reduction in eye size [ 5 ]. Moreover, pesticides cause decreased retinal pigmentation [ 29 ] and alter many biological processes relevant to visual system development and perception [ 23 ].…”

“…Other DTCs, such as propineb and maneb, have demonstrated similar effects on ZF development, correlating with these findings [ 5 , 8 ]. At the molecular level, pesticides affect a wide spectrum of gene expression and biological processes in ZF [ 23 ]. Therefore, the overall growth suppression is possibly caused by multiple perturbed molecular mechanisms occurring in response to thiram.…”

“…ZF are excellent model organisms in terms of size, economy, and ease of husbandry, and several aspects of their development are used in toxicity studies [ 22 ]. Moreover, their easy genetic modification, the possibility of omics-level analysis, and the availability of existing sequenced genomes make them ideal models for investigating toxicity mechanisms [ 23 ]. ZF produce large clutches, their embryos develop ex vivo, all major body systems form within 72 h post fertilization (hpf), and the embryos are transparent at early developmental stages; these factors result in xenobiotic exposure and simple deformity scoring [ 22 ].…”