Exploring the functional evolution of odorant receptors in bark beetles using Drosophila empty-neuron system
Authors: Jibin Johny; Ewald Große-Wilde; Blanka Kalinová; Fredrick Schlyter
Affiliation: Czech University of Life Sciences Prague
Keywords: o. olfaction; u. other (Functional evolution)
Bark beetles (Coleoptera: Curculionidae: Scolytinae) are a highly diverse subfamily of weevils generally considered as economically highly relevant pests of forests. As a natural part of forest ecosystems, they rely on damaged trees, but can switch to healthy hosts during the ‘aggressive’ outbreak phase (Biedermann et al., 2019). Bark beetles employ species-specific aggregation pheromones to attract conspecifics to their host trees (predominantly conifers) for the purposes of mating and resource exploitation. Within the Scolytinae, a clear phylogenetic pattern has been observed in pheromone composition; some components are phylogenetically more conserved than others (Symonds and Elgar, 2004; Symonds and Gitau-Clarke, 2016). The differences in pheromone composition are greater between closely related species than with distantly related species. This indicates a rapid ‘switching on and switching off’ of certain compounds in aggregation pheromone composition (Symonds and Elgar, 2008, 2004). From the evolutionary perspective, we hypothesize a similar level of rapid and heritable switches in olfactory reception at molecular level, i.e. in the structure and expression of pheromone-detecting receptors. We therefore investigate the evolution of chemosensory gene families in closely related Ips species. Species were selected based on niche level differentiation (syntropy), feeding modes and availability in the Czech Republic (Lindgren and Raffa, 2013). An antennal transcriptome and, more recently, the genome of I. typographus have become available (Andersson et al., 2013; Powell et al., 2021) and our research extends this knowledge to other species using both transcriptomes and genomes. For functional analysis we use a Drosophila transgenic expression system (so called “empty neuron”) in conjunction with electrophysiological measurements to characterize receptors by responses (Gonzalez et al., 2016). Overall, this research will provide better understanding of olfactory perception in bark beetles and thereby support development of olfaction-based pest-control strategies.