Odorant receptor sequences of Hyles lineata and Hyles vespertilio

In insects, odorant receptors (ORs) are required for the detection of most olfactory cues. Gene duplications leading to OR clade expansions may indicate chemosensory adaptations to ecological niches. Here, we investigated a clade of four intact duplicated ORs in the hawkmoth Manduca sexta. We tested these paralogs with 80 odorants and found that they encode broadly tuned receptors with overlapping but distinct response spectra. Two paralogs, which arose after divergence from related lineages, show high sensitivity to floral esters released by a nectar-rich plant frequently visited by M. sexta. Functional imaging in mutant moths lacking one of the paralogs suggests that olfactory sensory neurons expressing this OR target a previously identified feeding-associated glomerulus in the primary olfactory center of the brain. However, only the response of this glomerulus to the single ligand unique to the mutant OR disappeared, suggesting co-expression of the paralogs. Our results suggest a link between OR expansion and enhanced detection of odors emitted by valuable nectar sources in M. sexta.

Methods
The OR tandem arrays of two Hyles species were annotated in previously published genome assemblies (Godfrey et al. 2023; Pippel et al. (2020) )using a semi-automated pipeline developed for the annotation of multi-gene chemosensory gene families (Brand and Ramírez 2017).

Godfrey, R.K., Britton, S.E., Mishra, S., Goldberg, J.K., and Kawahara, A.Y. (2023). A high-quality, long-read genome assembly of the whitelined sphinx moth (Lepidoptera: Sphingidae: Hyles lineata) shows highly conserved melanin synthesis pathway genes. G3-Genes Genomes Genetics 13. 10.1093/g3journal/jkad090.

Pippel, M., Jebb, D., Patzold, F., Winkler, S., Vogel, H., Myers, G., Hiller, M., and Hundsdoerfer, A.K. (2020). A highly contiguous genome assembly of the bat hawkmoth Hyles vespertilio (Lepidoptera: Sphingidae). Gigascience 9, giaa001. 10.1093/gigascience/giaa001.

Brand, P., and Ramírez, S.R. (2017). The evolutionary dynamics of the odorant receptor gene family in corbiculate bees. Genome Biology and Evolution 9, 2023-2036. 10.1093/gbe/evx149.