The spotted wing drosophila, Drosophila suzukii, is an invasive polyphagous pest endemic to South East Asia. It has recently invaded western countries where it has become a threatening pest for cultivated small fruits. Unlike most others Drosophila species, whose larvae feed on decaying plant, D. suzukii lays its egg on unwounded ripening fruits. Host selection arises from oviposition behaviours of adult females, which detect chemosensory inputs, in the form of plant airborne kairomones, to locate fruits suitable for oviposition. Therefore, it is of great interest to elucidate the molecular basis of olfactory-driven behaviours that D. suzukii has evolved in comparison to Drosophila non-pest species, particularly understanding mechanisms of host fruit selection. The aim of this proposal is the identification and characterisation of olfactory receptors in D. suzukii. The methodology is based on a multidisciplinary approach that combines comparative genomics, transcriptome analysis and functional characterisation of olfactory receptors. D. suzukii gene families encoding olfactory receptors will be compared with those of two non-pest Drosophila species (D. subpulchrella and D. biarmipes, both belonging to the suzukii subgroup) to identify unique D. suzukii genes. Transcriptomic data will be generated to compare the expression profiles of D. suzukii gravid females versus adult males to identify transcripts potentially involved in sex-specific behaviours. Unique D. suzukii genes specifically expressed in gravid females and codifying for odorant receptors (ORs) will be characterized by using the Drosophila melanogaster “empty neuron” system that has proven to be successful in coupling olfactory response to OR genes. With the proposed project, we are confident to gain insight into molecular mechanisms that drive oviposition behaviour of D. suzukii, thus generating valuable information for developing novel control methods based on oviposition disruption.
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