Comparative toxicology and transcriptomic response of age-matched honey bee queens and workers

Queen failure is frequently cited as a major cause of honey bee colony loss, yet our understanding of basic honey bee queen biology remains poor in comparison to workers. This is particularly evident when evaluating the toxicological response of queens to commonly applied insecticides, as most studies examining agrochemicals and queen health have focused on larval instead of adult exposures. Here, we generated foundational LD₅₀s of two commonly applied insecticides, lambda-cyhalothrin and imidacloprid, in honey bee queens and age-matched workers and compared their transcriptomic responses across caste, chemical type, and dose intensity using RT-qPCR and tissue-specific RNA-seq. Queens produced LD₅₀s between 4-18 times greater than that of workers for both insecticides even after accounting for body mass, indicating that additional physiological mechanisms may be responsible for this outsized difference. Targeted examinations of specific P450 genes suggest that queens may be able to selectively upregulate their detoxification gene expression in response to agrochemical exposure. We predict that the RNA-seq results will show queens and workers having similar baseline vitellogenin and detoxification expression, but that queens will have a much higher expression ceiling, when presented with increasing insecticide concentrations. Taken collectively, these results can help establish key aspects of basic honey bee queen biology and serve as valuable data for studying other aspects of queen health, such as sequestration ability or resource allocation.