A moth odorant receptor highly expressed in the ovipositor is involved in detecting host-plant volatiles.

Abstract

Antennae are often considered to be the nostrils of insects. Here, we sequenced the transcriptome of the pheromone gland-ovipositor complex of <i>Helicoverpa assulta</i> and discovered that an odorant receptor (OR) gene, <i>HassOR31</i>, had much higher expression in the ovipositor than in antennae or other tissues. To determine whether the ovipositor was involved in odorant detection, we co-expressed <i>HassOR31</i> and its co-receptor, <i>HassORco</i>, in a <i>Xenopus</i> oocyte model system, and demonstrated that the OR was responsive to 12 plant odorants, especially Z-3-hexenyl butyrate. These odorants elicited electrophysiological responses of some sensilla in the ovipositor, and <i>HassOR31</i> and <i>HassORco</i> were co-expressed within ovipositor sensilla. Two oviposition preference experiments showed that female moths lacking antennae still preferentially selected oviposition sites containing plant volatiles. We suggest that the expression of <i>HassOR31</i> in the ovipositor of <i>H. assulta</i> helps females to determine precise egg-laying sites in host plants.