Embryonic exposure to fenbuconazole inhibits gametogenesis in adult zebrafish by targeting gonads not brain

Fenbuconazole (FBZ) is widely used in agriculture. The current study was conducted to evaluate the influence of embryonic exposure to FBZ on reproduction in adult zebrafish. Embryos were exposed to 5, 50 and 500 ng/L FBZ for 72 h and then raised in clean water until adulthood. The result showed that the percentage of mature gametes was significantly reduced in adult zebrafish. The fertilization rate and survival rate of F1 embryos were decreased when the exposed fish were mated with untreated fish. The transcription of brain gnrh3, fshβ and lhγ in adult fish was upregulated, while the levels of 17β-estradiol and testosterone were not significantly changed in all treated groups, indicating that the reproduction-related genes in brain was not responsible for the reduced reproductive ability. The downregulated transcription of fshr, lhr, ar and esr2 in the gonads indicated the dysfunction of Sertoli and Leydig cells. Notably, downregulated transcription and upregulated methylation levels of genes related to germ cells were observed in treated F0 larvae and adult gonads. The elevated methylation levels of piwil1 and dnmt6 in the testes and vasa and dazl in the ovary were matched with the alterations in the expression of these genes, suggesting that germ cells are the main targets of FBZ. These results provide new mechanism underlying reproductive toxicity in fish caused by chemicals, and give potential retroactive biomarkers for monitoring reproductive toxic pollutants.