Caste- and pesticide-specific effects of neonicotinoid pesticide exposure on gene expression in bumblebees
Abstract
Social bees are important insect pollinators of wildflowers and agricultural crops, making their reported declines a global concern. A major factor implicated in these declines is the widespread
use of neonicotinoid pesticides. Indeed, recent research has demonstrated that exposure to low doses of these neurotoxic pesticides impairs bee behaviors important for colony function and survival. However, our understanding of the molecular-genetic pathways that lead to such effects is limited, as is our knowledge of how effects may differ between colony members.
To understand what genes and pathways are affected by exposure of bumblebee workers and
queens to neonicotinoid pesticides, we implemented a transcriptome-wide gene expression
study. We chronically exposed Bombus terrestris colonies to either clothianidin or imidacloprid at
field-realistic concentrations while controlling for factors including colony social environment and
worker age. We reveal that genes involved in important biological processes including
mitochondrial function are differentially expressed in response to neonicotinoid exposure.
Additionally, clothianidin exposure had stronger effects on gene expression amplitude and
alternative splicing than imidacloprid. Finally, exposure affected workers more strongly than
queens. Our work demonstrates how RNA-Seq transcriptome profiling can provide detailed
novel insight on the mechanisms mediating pesticide toxicity to a key insect pollinator.