Chlorantraniliprole detoxification in honey bees, Apis mellifera – another job for the catalytically promiscuous CYP9Q subfamily?

Almond orchards in California are dependent on pollination services provided by more than a million honey bee hives every year. Reports of bee die-offs and a high amount of colony losses after almond pollination have fueled the investigation of frequently used pesticides in almond orchards regarding their potential involvement in this phenomenon. Diamide insecticides targeting the insect ryanodine receptor such as chlorantraniliprole have become increasingly important for the control of pest species occurring during almond bloom. Recent findings showing synergism between the azole fungicide propiconazole and chlorantraniliprole in larval and adult laboratory experiments suggest cytochrome P450s as an integral part of chlorantraniliprole detoxification in honey bees. Especially enzymes from the CYP9Q family have been previously linked to the metabolism of several insecticidal chemotypes providing evidence for their general role in xenobiotic detoxification. Here, we investigated the potential role of CYP9Q2 and CYP9Q3 in chlorantraniliprole detoxification by employing recombinantly expressed proteins as well as transgenic Drosophila lines ectopically expressing the honey bee enzymes. Furthermore, we tested the inhibitory potential of other frequently applied fungicides towards the CYP9Q enzymes with a recently described in-vitro assay developed for the fast identification of high-risk synergistic pesticide mixtures. Here we provide another example for the utility of such molecular approaches for honey bee pesticide risk assessment in an agricultural environment highly dependent on chemical crop protection.