Narrow tuning and sensitivity of the pheromone-specific olfactory neuron in male European grapevine moth (Lobesia botrana)

The European grapevine moth (Lobesia botrana, Lepidoptera: Tortricidae) is a serious pest of grapevine. Understanding male peripheral detection of the female-produced sex pheromone is essential for improving pest management strategies. Yet, despite its importance, the functional properties and specificity of the pheromone-sensitive olfactory sensory neurons (OSNs), housed in sensilla trichodea in this species, remain incompletely characterized. Here, we used single sensillum recording (SSR) to systematically test the responses of male OSNs to 24 pheromone stimuli. The OSNs gave the most specific response to the major pheromone component, (E,Z)-7,9-dodecadienyl acetate (E7,Z9-12Ac), but (Z,Z)-7,9-dodecadienyl acetate (Z7,Z9-12Ac) also significantly excited the neuron in higher doses. The OSNs also responded to two other compounds, (Z)-9-dodecenyl acetate (Z9-12Ac) and (Z)-9-undecenyl acetate (Z9-11Ac), at the highest dose. The other two stereoisomers of the major pheromone component, E7,E9-12Ac and Z7,E9-12Ac did not elicit any response. Cross-adaptation experiments and electron microscopic study of sensillar morphology confirmed that only one neuron per sensillum mediates these responses, indicating narrow ligand specificity rather than strict, high specificity. In contrast, electroantennaography (EAG) recordings of whole antennal responses demonstrated a broadening of pheromone tuning specificity, suggesting that the integration of responses from different OSN types may contribute to this phenomenon.