RNA-seq analysis of workers’ brain reveals that queen and brood affect bumble bee worker reproduction via similar genetic pathways

Worker reproduction in social insects is often regulated by the queen’s presence but can be regulated by other colony members, such as the brood and nestmates. Adults and brood may induce the same outcomes in subordinates but may use different mechanisms. Here, we compared gene expression patterns in bumble bee workers (Bombus impatiens) in response to the queen, the brood, both or none. RNA‐seq analysis of workers’ brain identified 27 differentially expressed genes regulated by the queen and the brood. Expression levels of 8 candidate genes were re-tested using qRT-PCR in worker brain and fat body. Our results show that the brood’s effect on gene expression is substantially weaker than the queen, and a greater impact on gene expression was caused by the combined presence of the queen and the brood. All the genes that were explained by the brood presence were also regulated by the queen presence. A significant amount of the variation in gene expression was explained by the queen, that regulated the expression of key regulators of reproduction and brood care across insects, such as neuroparsin and vitellogenin. A comparison of the data with similar datasets in the honeybee and the raider ant revealed that neuroparsin is the only differentially expressed gene shared by all species. These data highlight the need to consider components other than the queen when examining mechanisms regulating worker sterility and provide information on key genes regulating reproduction that are likely to play an important role in the evolution of sociality.