Identification and sex-specific expression profiles of chemosensory genes from tarsi and antennae in the dead leaf butterfly Kallima inachus

Chemical sensation plays important roles in insect life history, such as host recognition and intraspecific identification, which in turn are key drivers of speciation processes. Kallima butterflies mimic dead leaves to camouflage themselves under shady forest habitat. However, the lack of knowledge about the Kallima chemosensory system has hindered our understanding of how they adapt to host and shady habitat which influence speciation processes. In this study, chemosensory genes of Kallima inachus were identified based on transcriptome data combined with genomic data, including 107 gustatory receptors (GRs), 55 odorant receptors (ORs) and 34 ionotropic receptors (IRs). K. inachus exhibits a higher GR copy number compared to those of other Lepidopteran species, especially for the bitter receptors. Interestingly, among 36 copies in an expanded clade, 17 GRs clustered into a 0.5 Mb window of chromosome 7, suggesting serial tandem duplication events occurred. These GRs such as KinGR14, KinGR39, KinGR42, KinGR45 showed female-specific expression pattern in tarsi, indicating that the duplication events were possibly driven by female-specific biological behaviors such as host recognition and oviposition. One of the ORs in K. inachus (KinOR3) was found to be clustered with Bombyx mori pheromone receptor, and quantitative real-time PCR (qPCR) confirmed its male-biased expression pattern in antennae, which coordinates with expression pattern of moth sex pheromone receptor. Taken together, this study yields a robust dataset of K. inachus chemosensory genes and reveals their expression profile between sexes and organs, providing fundamental insights into host recognition and intraspecific identification in K. inachus and other butterflies.