Olfactory Gene Families in Scopula subpunctaria and Candidates for Type-II Sex Pheromone Detection. Scopula subpunctaria

Scopula subpunctaria, an abundant pest in tea gardens, produce type-II sex pheromone components, which are critical for communication and reproduction. However, genes encoding proteins involved in the detection of type-II sex pheromone components have rarely been documented in moths. In the present study, we sequenced the transcriptomes of the male and female S. subpunctaria antennae. A total of 150 candidate chemoreception genes, including 58 odorant receptors (SsubORs), 26 ionotropic receptors (SsubIRs), 24 chemosensory proteins (SsubCSPs), 40 odorant-binding proteins (SsubOBPs), and 2 sensory neuron membrane proteins (SsubSNMPs) were identified in S. subpunctaria. Phylogenetic analysis, qPCR, and mRNA abundance analysis results suggested that SsubOR46 may be the Orco (non-traditional odorant receptor, a subfamily of ORs) of S. subpunctaria. SsubOR9, 51, 53, and 55 belonged to the pheromone receptor (PR) clades with higher male antennae abundance. Interestingly, SsubOR44 was uniquely expressed in antennae, with higher expression levels in males than in females. SsubOBP25, 27, and 28 were clustered into the moth pheromone-binding proteins (PBP) sub-family and uniquely expressed in the antennae, with greater abundance in the antennae of males than in those of females. SsubOBP19, a member of the GOBP2 group, is the most antenna-abundant OBPs. This indicates that these olfactory genes, including five candidate PRs, three candidate PBPs, and a candidate GOBP2, may be involved in type II sex pheromone detection. Beyond these genes, most of the remaining SsubORs and all SsubIRs showed much higher expression levels in the female antennae than in the male antennae. Several of these, such as SsubOR40, 42, 43, and SsubIR26, were more abundant in female antennae. These olfactory and ionotropic receptors may be related to the detection of the host plant volatiles. The results of the present study provide a basis for exploring the olfaction mechanisms in S. subpunctaria, focusing on the genes involved in type II sex pheromones. The evolutionary analyses in our study provide new insights into the differentiation and evolution of lepidopteran PRs.