Identification and localization of two sensory neuron membrane proteins from Spodoptera litura (Lepidoptera: Noctuidae)

Sensory neuron membrane proteins (SNMPs), which are located on the dendritic membrane of olfactory sensory neurons (OSNs), are proposed to be associated with odor reception in insects. Recent studies have demonstrated that SNMP1 is essential for electrophysiological responses of OSNs to the sex pheromone, cis-vaccenyl acetate (cVA) in Drosophila melanogaster. To investigate the function of Lepidoptera SNMPs, we cloned two SNMP genes, SlituSNMP1 and SltiuSNMP2, from Spodoptera litura (Lepidoptera: Noctuidae). Sequence alignment and phylogenetic analysis showed that both genes bear the general characteristics of SNMPs, including six conserved cysteine residues and two transmembrane domains. Further expression profile experiments showed that SlituSNMP1 is mainly expressed in the antenna, while SlituSNMP2 is broadly expressed in various tissues. By in situ hybridization experiments, it was found that SlituSNMP1 expressing cells are surrounded by the SlituSNMP2 expressing cells in the pheromone sensitive sensilla, suggesting different functions of the two SNMPs in insect olfaction.