Effects of Azole Fungicides on Secreted Metabolomes of Botrytis cinerea

Botrytis cinerea, gray mold, is one of the most notorious phytopathgens, causing serious economic loss in the agricultural industry. The phytotoxic effects are mainly derived from secreted virulence proteins and terpenoid-type secondary metabolites. Azole fungicides are commonly used to manage the disease. However, their biochemical effects other than sterol biosynthesis were not documented, especially toxic secreted metabolites. In this study, six azole fungicides were treated with in vitro and in vivo conditions. Comprehensive profiles of primary and secondary metabolites in culture media were evaluated to assess the fungal metabolomes under pesticide-stressed conditions. The results indicated that extensive metabolic differentiation was induced by azole fungicides. Epoxiconazole clearly reduced the extracellular phytotoxin concentrations, while the level of indole-3-acetic acid was increased. In addition, significant differentiation of primary metabolism could be deduced from secreted metabolite profiles, including the tricarboxylic acid cycle and aromatic amino acid catabolism. Cellular lipid profiles, including fatty acids and sterol, have been altered drastically by azoles, which indicate extensive changes of cellular lipid metabolism. These system-wide metabolic alterations resulted in reduced plant damages, proven by the in vivo assay with tomato. Overall, azole fungicides induced significant changes of endo- and exometabolomes and could reduce the fungal infection. The experimental results will provide a more detailed understanding of physiological changes of phytopathogens under pesticide treatment and information for new pesticide development.