Enantioselective Neurotoxicity of Pydiflumetofen in Zebrafish Embryos: <i>R</i> -Enantiomer Disrupts Neurodevelopment via Suppression of Wnt/β-Catenin Signaling

As the share of chiral pesticides rises annually, conducting enantiomer-specific toxicology can promote single-isomer application, helping to reduce pesticide use and environmental risks. Pydiflumetofen (PYD) is a chiral fungicide with a long half-life; however, its enantioselective neurotoxicity remains poorly understood. This study revealed the toxic risks of PYD and its isomers, demonstrating that PYD induces neurodevelopmental toxicity in zebrafish embryos, with the toxic effects primarily attributed to R -PYD. The results showed that PYD exposure caused morphological abnormalities, reduced spontaneous movement, brain tissue damage, and decreased numbers of central and motor neurons. Mechanistically, PYD suppressed the Wnt/β-catenin pathway by upregulating wif1 and downregulating axin2, β- catenin, lef1, myc a, and cyclin d1 . Notably, cotreatment with the pathway agonist TWS119 significantly attenuated R -PYD-induced neurotoxicity, strongly indicating that the Wnt/β-catenin pathway is a key target of R -PYD. Overall, PYD impairs zebrafish neurodevelopment by inhibiting the Wnt/β- catenin pathway, with R -PYD being the most toxic enantiomer.