Silencing the odorant coreceptor (Orco) disrupts sex pheromonal communication and feeding responses in Blattella germanica: toward an alternative target for controlling insect-transmitted human diseases.

Abstract

The German cockroach, Blattella germanica, is one of the most severe pests of urban and rural areas. High-throughput genetic screening approaches indicate that the olfactory system of this pest is extremely powerful because it has an extensive array of olfactory receptor genes compared with many other insect species. Several of these genes have been identified previously, but their functions have not yet been characterized. This study describes the sequence of five transcriptomes of B. germanica adult male antennae, female antennae, maxillary palps, legs, and fifth-instar nymph antennae to investigate expression patterns of odorant receptors (ORs). Approximately 90% of ORs were found to be the most highly expressed genes in adult or nymph antennae. Additionally, every OR requires an odorant co-receptor (Orco) to become fully functional, and this was selected and successfully inhibited by injection of the corresponding double-stranded (ds)RNA targeting the Orco. A strong RNA interference (RNAi) effect was observed in which > 75% of Orco messenger RNA (mRNA) was clearly suppressed after 72 h of treatment. Olfactory behavioral assays showed that Orco-impaired B. germanica respond more slowly and show less attraction to one volatile sex pheromone and food resources compared with a control group. The results show that Orco plays a pivotal role in both sex pheromone and food-seeking olfactory processes, and provide an alternative genetic technique for controlling this urban pest species by olfactory disruption. © 2020 Society of Chemical Industry.