Unveiling sensory mechanisms for the control of two insect pests: from behaviour to molecular interactions

Pest control strategies targeting insect olfaction represent a promising venue for control of tortricid insects (Lepidoptera: Tortricidae). Among tortricids, the grapevine moth Lobesia botrana (Denis and Schiffermüller) and the codling moth Cydia pomonella (L.) are serious pests for worldwide production of fruit crops. We employed several approaches to the olfactory system, from electrophysiological and behavioral studies in the grapevine moth, to bioinformatic and molecular studies of olfactory sensory proteins in the codling moth. At the receptor level, we studied both the Olfactory Receptors (ORs), the most common class of sensory proteins mediating detection of odors in insect antennae, and the Transient Receptor Potential (TRP) channels, a novel family of receptor, that recently were also found in the antennae of lepidopterous species. We demonstrated electrophysiological and behavioral responses of the grapevine moth to volatiles emitted by a non-host, Perilla frutescens, previously known to activate TRPs in the rat, Rattus norvegicus. In the codling moth, we characterized a novel TRP channel (TRPA pyrexia-like) and we confirmed activation of its human orthologue to the same non-host compounds active on the olfactory system of the grapevine moth. ORs were heterologously expressed in vivo and in vitro, for identification of their ligands among host and non-host plant volatiles and pheromones (deorphanization). Among several ORs of codling moth, we deorphanized a candidate pheromone receptor (PR) to plant synergists, an OR to non-host volatiles and another PR candidate to a pheromone antagonist of the insect. Our study thus opens for refinement of existing pest control, or novel applications. The behavioral response of the grapevine moth to volatiles from a nonhost plant, and the identification of a novel TRP channel in the codling moth may have perspectives for application in agriculture, targeting the somatosensory system of these tortricids. The evolutionary implications of the responses of the human orthologue of TRPA pyrexia-like to volatiles active on the grapevine moth olfactory system could imply a large degree of conservation of the receptor function. In the codling moth, identification of synergist and antagonist ligands for candidate PRs and deorphanization of an OR to non-host plant volatiles suggest a possible role of these receptors in reproductive and ecological isolation. This could lead to further refinement of existing semiochemicalbased control techniques, by enabling a better understanding of mate- and host-finding in this species.