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Research article - Peer-reviewed, 2022

Chemosensory Receptors in the Larval Maxilla of Papilio hospiton

Crava, Cristina M.; Bobkov, Yuriy V.; Sollai, Giorgia; Anfora, Gianfranco; Crnjar, Roberto; Cattaneo, Alberto Maria


Among the butterflies of the genus Papilio (Lepidoptera: Papilionidae), Papilio hospiton (Gene) has a geographical distribution limited to the Mediterranean islands of Sardinia (Italy) and Corsica (France). This is mainly due to the host range that includes only a few plant species of Apiaceae and Rutaceae growing on these islands. In a previous electrophysiological investigation conducted on the maxillary gustatory system of larvae of P. hospiton and its closely phylogenetically related species Papilio machaon, a significantly higher spike activity was shown for the gustatory neurons of lateral and medial styloconic sensilla in P. hospiton when bitter compounds were tested. This effect was possibly correlated to the limited host choice range for P. hospiton. To shed light on the molecular aspects of this phenomenon, we investigated the expression pattern of sensory-related sequences by conducting a transcriptomic analysis from total RNA isolates of P. hospiton larval maxillae. We identified several transcripts that may be involved in taste (one gustatory receptor, one divergent ionotropic receptor, and several transient receptor potential channels, TRPs) as well as transcripts supporting an olfactory function for this appendage, including odorant receptors (ORs), antennal ionotropic receptors (A-IRs), sensory neuron membrane proteins (SNMPs), and odorant-binding proteins (OBPs). We used Human Embryonic Kidney (HEK293A) cells to heterologously express two of the identified receptors, PhospOR1 and PhospPain, together with their orthologs from P. machaon, for functional characterization. While our data suggest no activation of these two receptors by the ligands known so far to activate the electrophysiological response in larval maxillary neurons of Papilio species, nor temperature activation of both Papilio TRPA-channel Painless, they represent the first attempt in connecting neuronal activity with their molecular bases to unravel diet specialization between closely related Papilio species.


papilionid butterflies; larval maxilla; RNA-seq analysis; odorant receptors; transient receptor potential (TRP) channels; heterologous expression; human embryonic kidney cells

Published in

Frontiers in Ecology and Evolution
2022, volume: 9, article number: 795994

Authors' information

Crava, Cristina M.
University of Valencia
Crava, Cristina M.
Fondazione Edmund Mach
Bobkov, Yuriy V.
University of Florida
Sollai, Giorgia
University of Cagliari
Anfora, Gianfranco
Fondazione Edmund Mach
Anfora, Gianfranco
University of Trento
Crnjar, Roberto
University of Cagliari
Edmund Mach Foundation
University of Florida
University of Cagliari
Swedish University of Agricultural Sciences, Department of Plant Protection Biology
University of Lausanne

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