Sex pheromones and olfactory proteins in Antheraea moths: A. pernyi and A. polyphemus (Lepidoptera: Saturniidae)

Olfaction is essential for regulating the physiological and behavioral actions of insects with specific recognition of various odors. Antheraea moths (Lepidoptera: Saturniidae) possess relatively large bodies and antennae so that they are good subjects for exploring molecular aspects of insect olfaction. Current knowledge of the molecular aspects of Antheraea olfaction is focused on the Chinese tussah silkmoth A. pernyi Guérin-Méneville and another species A. polyphemus (Cramer) in their pheromones, odorant-binding proteins (OBPs), odorant receptors (ORs), odorant receptor coreceptors (ORCOs), sensory neuron membrane proteins (SNMPs), and odorant-degrading enzymes (ODEs). The first insect OBP, SNMP, and ODE were identified from A. polyphemus. This review summarizes the principal findings associated with the olfactory physiology and its molecular components in the two Antheraea species. Three types of olfactory neurons may have specific ORs for three respective sex-pheromone components, with the functional sensitivity and specificity mediated by three respective OBPs. SNMPs and ODEs are likely to play important roles in sex-pheromone detection, inactivation, and degradation. Identification and functional analysis of the olfactory molecules remain to be further performed in A. pernyi, A. polyphemus, and other Antheraea species.     

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.     

棉铃虫普通气味受体基因HarmOR9和HarmOR29的克隆和组织表达分析

【目的】对棉铃虫Helicoverpa armigera 2个普通气味受体基因的cDNA全长进行分析,明确这两个普通气味受体基因在不同组织中的表达分布,为进一步的功能研究奠定基础。【方法】利用PCR结合RACE技术克隆棉铃虫两条普通气味受体基因的cDNA全长;利用不同的生物信息学软件对序列进行结构预测、序列比对和进化树分析;利用半定量RT-PCR检测其在棉铃虫成虫不同组织中的表达。【结果】获得两条棉铃虫气味受体基因的全长序列,并命名为HarmOR9和HarmOR29（GenBank登录号分别为KJ188252和KJ188253）。序列分析显示,HarmOR9全长1 206 bp,编码401个氨基酸;HarmOR29全长1 188 bp,编码395个氨基酸。选择已报道的鳞翅目昆虫烟青虫Heliothis assulta、家蚕Bombyx mori、烟芽夜蛾Heliothis virescens和棉铃虫的气味受体与本实验克隆得到的两个气味受体基因的编码产物进行序列比对和进化树分析,结果显示这两个气味受体与性信息素受体区别明显,并与其他普通气味受体聚类在一起。半定量RT-PCR的结果显示HarmOR9与HarmOR29都主要在触角中高表达且无雌雄间差异,HarmOR29在其他组织中均不表达;而HarmOR9在雄虫下唇须中有微量表达,在其他组织中均不表达。【结论】本研究从棉铃虫中克隆得到2个气味受体基因HarmOR9和HarmOR29的cDNA全长,其编码产物具有气味受体的典型特征并且属于普通气味受体。明确了这两个气味受体基因都在棉铃虫成虫的触角中高表达,且无雌雄差异,推测其可能参与了棉铃虫普通气味的识别过程。     

Has gene expression neofunctionalization in the fire ant antennae contributed to queen discrimination behavior?

Queen discrimination behavior in the fire ant Solenopsis invicta maintains its two types of societies: colonies with one (monogyne) or many (polygyne) queens, yet the underlying genetic mechanism is poorly understood. This behavior is controlled by two supergene alleles, SB and Sb, with ~600 genes. Polygyne workers, having either the SB/SB or SB/Sb genotype, accept additional SB/Sb queens into their colonies but kill SB/SB queens. In contrast, monogyne workers, all SB/SB, reject all additional queens regardless of genotype. Because the SB and Sb alleles have suppressed recombination, determining which genes within the supergene mediate this differential worker behavior is difficult. We hypothesized that the alternate worker genotypes sense queens differently because of the evolution of differential expression of key genes in their main sensory organ, the antennae. To identify such genes, we sequenced RNA from four replicates of pooled antennae from three classes of workers: monogyne SB/SB, polygyne SB/SB, and polygyne SB/Sb. We identified 81 differentially expressed protein‐coding genes with 13 encoding potential chemical metabolism or perception proteins. We focused on the two odorant perception genes: an odorant receptor SiOR463 and an odorant‐binding protein SiOBP12. We found that SiOR463 has been lost in the Sb genome. In contrast, SiOBP12 has an Sb‐specific duplication, SiOBP12b′, which is expressed in the SB/Sb worker antennae, while both paralogs are expressed in the body. Comparisons with another fire ant species revealed that SiOBP12b′ antennal expression is specific to S. invicta and suggests that queen discrimination may have evolved, in part, through expression neofunctionalization.