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

Abstract

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.

The sensory neurone membrane protein SNMP1 contributes to the sensitivity of a pheromone detection system

“…This result indicates that SNMP2 cannot functionally substitute SNMP1. This functional difference between SNMP1 and SNMP2 is in line with their different cellular expression; whereas SNMP1 is exclusively found in olfactory neurones, SNMP2 is found in supporting cells (Forstner et al ., ; Zhang et al ., ).…”

“…The visualization of the SNMP1 protein in cell bodies and dendrites of sensory neurones within the long trichoid sensilla of H. virescens , which are responsive to pheromone components (Almaas & Mustaparta, ; Baker et al ., ), confirms and extends the original findings on SNMP1 localization in male antennae of the moth Antheraea polyphemus (Rogers et al ., , ). In addition, it has been shown that SNMP1 is also expressed in OSNs on the antennae of female moths (Rogers et al ., , ; Gu et al ., ; Zhang et al ., ) but the identity of these OSNs is unknown.…”

“…In several moth species a second SNMP‐type (SNMP2) has been identified, which shares about 30% sequence identity with SNMP1 (Rogers et al ., ; Forstner et al ., ; Gu et al ., ; Liu et al ., ; Zhang et al ., ). Interestingly, in situ hybridization studies have shown that SNMP2 is expressed in supporting cells associated with the sensory neurones in pheromone‐responsive sensilla (Forstner et al ., ; Zhang et al ., ). Based on the expression in supporting cells and the functional implication of CD36 proteins in translocation of lipophilic compounds (Martin et al ., ; Valacchi et al ., ), it has been proposed that SNMP2 may play a role in clearance processes within pheromone‐responsive sensilla.…”

Pheromone Reception in Moths

“…Since then, much progress has been achieved in the identification of SNMP1 and SNMP2 in different insect orders. 103,119,[126][127][128][129][130][131][132][133] ApolSNMP1 mRNA expression increased significantly 1-2 days before adult emergence, coinciding with the functional maturation of the olfactory system. The abundant expression of SNMP1 in pheromonespecific olfactory neurons suggests it may be involved in pheromone detection.…”

“…136,137 This was the first demonstration of SNMP functions in vivo. Additionally, it has been reported that SNMPs display wide expression patterns in different tissues, [129][130][131][132][133] suggesting that they may be involved in some functions beyond olfactory detection.…”