Octopamine Signaling Regulates Phototactic Behavior via a β-Adrenergic-like Receptor in Diaphorina citri

Simple SummaryThe Asian citrus psyllid (Diaphorina citri) is the primary vector of citrus huanglongbing, a destructive disease that causes severe losses to citrus production worldwide.D. citriexhibits positive phototaxis, the innate tendency to move toward light. However, the molecular mechanisms that control this key behavioral trait remain poorly understood. In this study, we investigated the role of octopamine, a core neuromodulator that governs multiple behaviors in insects, in regulatingD. citriphototactic behavior. We identified three key genes in the octopamine signaling pathway, analyzed their expression patterns, characterized the pharmacological response of receptors, and validated their behavioral functions via RNA interference. Our results show that the octopamine positively regulates phototactic behavior viaDcOctβ1RinD. citri. These findings deepen our understanding of the molecular basis of insect behavior.The Asian citrus psyllid (Diaphorina citri, ACP) is the primary vector of citrus huanglongbing and exhibits positive phototactic behavior. Octopamine (OA) is a critical neuromodulator of diverse insect behaviors, yet its regulatory mechanism in ACP phototactic behavior remains largely uncharacterized. In this study, three core genes of the OA signaling pathway in ACP were identified and characterized: the biosynthetic enzymeDcTβHand two β-adrenergic-like OA receptors (DcOctβ1R,DcOctβ2R). All three genes exhibited a U-shaped developmental expression pattern and high transcript abundance in the head, suggesting potential involvement in the early nymphal and adult stages and essential roles in central nervous system. Pharmacology assays revealed that DcOctβ1R activation by OA and tyramine induced cyclic adenosine monophosphate (cAMP) accumulation, with agonists and antagonists exerting differential effects on its activity. In contrast, no cAMP response was observed in cells expressingDcOctβ2R regardless of ligand treatment. Combined RNA interference and behavioral assays demonstrated that silencingDcTβHorDcOctβ1Rsignificantly impairs ACP phototactic behavior. These findings revealed that the OA signaling positively regulates phototactic behavior viaDcOctβ1Rin ACP. This study enhances the understanding of OA-mediated phototactic behavior in agricultural pests and lays a foundation for exploring the molecular mechanisms of insect behaviors.