Expression of squash bee cytochrome P450 detoxification enzymes in response to neonicotinoid insecticide exposure

Hoary squash bees (Xenoglossa pruinosa) are important pollinators of cucurbit crops such as squash, pumpkin, and zucchini. These crops are members of the Cucurbita genus, on which squash bees specialize, and are the only host plants available to the bees in most of their range. This close association with crops virtually guarantees that squash bees will be exposed to pesticides. Honey bees (Apis mellifera) use cytochrome P450 monooxygenase enzymes in the CYP9 family to detoxify insecticides such as neonicotinoids and pyrethroids. We searched the recently published squash bee genome for sequences similar to honey bee CYP9 amino acid sequences using tblastn on NCBI and found eleven candidates. We performed an acute contact bioassay on adult squash bees by applying pesticide active ingredients dissolved in acetone to each bee’s thorax with a micro-applicator. Bees were treated with either the neonicotinoid insecticide acetamiprid, the sterol biosynthesis inhibitor fungicide triflumizole, a combination of both pesticides, or an acetone control. The bees were then euthanized, and RT-qPCR was performed on their abdomens to quantify the expression of the newly identified detoxification genes.