Functional insights into three pheromone‐binding proteins for detecting Type II sex pheromone component in <i>Thalassodes immissaria</i>

Pheromone-binding proteins (PBPs) play pivotal roles in the moth olfactory system by assisting the neuronal response to pheromone components. Thalassodes immissaria is a major notorious defoliator of lychee orchards in China. In this study, we demonstrated that (3Z,6Z,9Z,12Z)-icosa-3,6,9,12-tetraene (Z3,Z6,Z9,Z12-20:H)-a principal sex pheromone component previously identified in the Japanese population of T. immissaria-elicits significant electroantennogram (EAG) responses and robust behavioral attraction to male moths of the Chinese population. Subsequently, we identified three PBP-encoding genes, among which TimmPBP1 and TimmPBP2 were highly expressed in the antennae of adult male T. immissaria. Further fluorescence competitive binding assays revealed that recombinant TimmPBP1 and TimmPBP2 exhibited strong binding affinities to Z3,Z6,Z9,Z12-20:H. Additionally, the antennae of male moths treated with dsTimmPBP1 or dsTimmPBP2 exhibited significantly reduced EAG responses to Z3,Z6,Z9,Z12-20:H. Finally, the expression profiles of TimmPBP1 and TimmPBP2 exhibited circadian oscillations, which aligned with the diurnal rhythms of T. immissaria mating behavior and the males' EAG responsiveness to Z3,Z6,Z9,Z12-20:H. Our study elucidates the physiological roles of PBPs in the recognition of Type II sex pheromone and offers novel molecular targets for monitoring and sustainable control of T. immissaria in orchard ecosystems.