The agrochemical fungicide triadimefon induces abnormalities in Xenopus laevis embryos

The dysmorphogenic activity of the triazole fungicide triadimefon (FON) has been evaluated using Xenopus laevis development. Embryos, exposed to 500. μM FON during early neurulation phases (stages 13-17, Nieuwkoop and Faber), were allowed to develop until stage 47. Larvae revealed serious craniofacial defects, bent forebrain, and abnormal hindbrain segmentation. CRABP and CYP26 (markers related to retinoic acid homeostasis) gene and protein expression and protein distribution have been evaluated at stage 17 and at the end of the branchial arch morphogenesis (stage 27) by real-time PCR, western blot and whole-mount immunostaining. A significant increase of CYP26 transcript has been observed at both embryonic stages. A co-localization of the two markers has been observed at the cephalic region. Embryos exposed to FON showed abnormal distribution of positive tissues. Due to the strict similarity of these results with those previously described in rodents, a FON-related alteration of mechanism conserved during vertebrate evolution is suggested.