The Neuropeptide Neuroparsin-A Regulates the Establishment of Dominance Hierarchy in Bumblebees

The regulation of reproductive division of labor in eusocial insects is pivotal for the evolution and maintenance of social organization. In <i>Bombus terrestris</i>, dominance hierarchies emerge among orphan workers through repeated agonistic interactions, forming distinct behavioral ranks. To explore the neural basis of this process, we combined behavioral assays with single-nucleus RNA sequencing to profile brain-wide gene expression across α-, β-, and γ-bumblebee workers. Our analyses revealed pronounced transcriptional divergence among Kenyon cells, which exhibited enrichment in synaptic, insulin, and MAPK signaling pathways. Among the neuropeptides examined, Neuroparsin-A was markedly upregulated in the Kenyon cells and glial cells of dominant workers, while its receptor, OR1, showed strong expression within Kenyon populations, suggesting a conserved neuropeptide-receptor axis in social Hymenoptera. Gene regulatory network inference further identified ecdysone-responsive transcription factors, including <i>br</i>, <i>Eip74EF</i>, <i>Hr38</i>, <i>Hr3</i> and <i>Hr4</i>, as key regulators linked to neural plasticity and behavioral differentiation. Together, our findings uncover a neuroendocrine mechanism in which Neuroparsin-A signaling coordinates brain transcriptional programs associated with dominance hierarchy formation in queenless bumblebee societies, offering new insights into the molecular underpinnings of eusocial behavior.