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

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 enzyme DcTβH and 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 expressing DcOctβ2R regardless of ligand treatment. Combined RNA interference and behavioral assays demonstrated that silencing DcTβH or DcOctβ1R significantly impairs ACP phototactic behavior. These findings revealed that the OA signaling positively regulates phototactic behavior via DcOctβ1R in 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.