Life-stage dependent behavior mimics chemosensory repertoire diversity in a belowground, specialist herbivore

Insects rely on the translation of environmental chemical cues into behaviors necessary for survival and reproduction. Specific chemosensory receptors belonging to the odorant and gustatory receptor groups detect odorant and gustatory cues, respectively, making them crucial to these processes. How odorant (OR) and gustatory (GR) receptor expression profiles change in combination with changing life strategies is not well understood. Using genomic and transcriptomic resources, we annotated the OR and GR expression profiles across all life stages of the western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte, a major pest of corn in the United States and Europe. Genomic analyses identified 193 ORs and 189 GRs, of which 125 and 116 were found to be expressed, respectively, in one or more WCR life stages. WCR larvae are subterranean and feed on roots before emerging as adults aboveground. Expression profile analyses revealed first instar larvae possess a unique OR and GR repertoire distinct from other instars and adults, suggesting a role in host plant finding. Similarly, a subset of ORs and GRs differed in their expression levels between adult male and female antennae. By comparing the phylogenetic relationship of ORs and GRs, we identified several receptors with potentially important roles in WCR foraging and reproductive behavior. Together, this study provides support for future investigations into the ecology and evolution of chemoreception in insects.