A toxicogenomics approach reveals characteristics supporting the honey bee (Apis mellifera L.) safety profile of the butenolide insecticide flupyradifurone

Flupyradifurone, a novel butenolide insecticide, selectively targets insect nicotinic acetylcholine receptors (nAChRs), comparable to structurally different insecticidal chemotypes such as neonicotinoids and sulfoximines. However, flupyradifurone was shown in acute toxicity tests be several orders of magnitude less toxic western honey bee (Apis mellifera L.) than many other insecticides targeting nAChRs. The underlying reasons for this difference remains unknown were investigated here. Pharmacokinetic studies after contact application [14C]flupyradifurone bees revealed slow uptake, with internalized compound degraded into few metabolites that are all practically non-toxic both oral bioassays. Furthermore, receptor binding lack high-affinity these Screening library 27 heterologously expressed cytochrome P450 enzymes (P450s) identified three P450s involved the detoxification flupyradifurone: CYP6AQ1, CYP9Q2 CYP9Q3. Transgenic Drosophila lines ectopically expressing CYP9Q3 significantly susceptible when compared control flies, confirming importance metabolism bees. Biochemical assays using fluorescent probe substrate 7-benzyloxymethoxy-4-(trifluoromethyl)-coumarin (BOMFC) indicated weak, non-competitive inhibition BOMFC by flupyradifurone. In contrast, azole fungicides prochloraz propiconazole strong nanomolar inhibitors metabolizing P450s, explaining their highly synergistic effects combination demonstrated laboratory adult Interestingly, fungicide prothioconazole is only slightly - an observation supported molecular assays. Such have value prediction potential risks posed mixture partners under applied conditions. Quantitative PCR confirmed expression genes life-stages, highest levels observed late larvae adults, suggesting capacity metabolize across life-stages. These findings provide biochemical explanation low intrinsic offer new, more holistic approach support pollinator risk assessment means.