Pollen diet mediates how pesticide exposure impacts brain gene expression in nest-founding bumble bee queens

A primary goal in biology is to understand the effects of multiple, interacting environmental stressors on organisms. Wild and domesticated bees are exposed to a wide variety of interacting biotic and abiotic stressors, with widespread declines in floral resources and agrochemical exposure being two of the most important. In this study, we used examinations of brain gene expression to explore the sublethal consequences of neonicotinoid pesticide exposure and pollen diet composition in nest-founding bumble bee queens. We demonstrate for the first time that pollen diet composition can influence the strength of bumble bee queen responses to pesticide exposure at the molecular level. Specifically, one pollen mixture in our study appeared to buffer bumble bee queens entirely against the effects of pesticide exposure, with respect to brain gene expression. Additionally, we detected unique effects of pollen diet and sustained (versus more temporary) pesticide exposure on queen gene expression. Our findings support the hypothesis that nutritional status can help buffer animals against the harmful effects of other stressors, including pesticides, and highlight the importance of using molecular approaches to explore sublethal consequences of stressors.

Methods
Brain gene expression - RNAseq

Read counts table was generated using featureCount v1.5.0-p3 (Liao et al. 2014), wherein it determines the number of reads uniquely mapping to exons and summed at the gene level using gene features annotated in the B. impatiens OGSv1.0.

Pollen diet - Metabolomic data
Pollen samples were examined through untargeted liquid chromatography-mass spectrometry (LC-MS) metabolomics.