XB-ART-39643Int J Biol Sci January 1, 2009; 5 (4): 319-30.
A male-specific odorant receptor conserved through the evolution of sex pheromones in Ostrinia moth species.
In many moths, mate-finding communication is mediated by the female sex pheromones. Since differentiation of sex pheromones is often associated with speciation, it is intriguing to know how the changes in female sex pheromone have been tracked by the pheromone recognition system of the males. A male-specific odorant receptor was found to have been conserved through the evolution of sex pheromone communication systems in the genus Ostrinia (Lepidoptera: Crambidae). In an effort to characterize pheromone receptors of O. scapulalis, which uses a mixture of (E)-11- and (Z)-11-tetradecenyl acetates as a sex pheromone, we cloned a gene (OscaOR1) encoding a male-specific odorant receptor. In addition, we cloned a gene of the Or83b family (OscaOR2). Functional assays using Xenopus oocytes co-expressing OscaOR1 and OscaOR2 have shown that OscaOR1 is, unexpectedly, a receptor of (E)-11-tetradecenol (E11-14:OH), a single pheromone component of a congener O. latipennis. Subsequent studies on O. latipennis showed that this species indeed has a gene orthologous to OscaOR1 (OlatOR1), a functional assay of which confirmed it to be a gene encoding the receptor of E11-14:OH. Furthermore, investigations of six other Ostrinia species have revealed that all of them have a gene orthologous to OscaOR1, although none of these species, except O. ovalipennis, a species most closely related to O. latipennis, uses E11-14:OH as the pheromone component. The present findings suggest that the male-specific receptor of E11-14:OH was acquired before the divergence of the genus Ostrinia, and functionally retained through the evolution of this genus.
PubMed ID: 19421342
PMC ID: PMC2677733
Article link: Int J Biol Sci
Species referenced: Xenopus
Genes referenced: cox2
Article Images: [+] show captions
|Figure 1. Phylogenetic relationships (left) and sex pheromone blends (right) of Ostrinia species examined in this study. The phylogenetic tree was constructed based on the mitochondrial COII gene sequences. The numbers near branches indicate bootstrap values. The size of circles represents rough blend ratio, and × denotes that the compound works as behavioral antagonist. * not tested for behavioral antagonism.|
|Figure 2. Nucleotide and deduced amino acid sequences of OscaOR1. A, full nucleotide sequences and deduced amino acid sequence of OscaOR1. Arrows indicate primers using RT-PCR. B, aligned amino acid sequences of OscaOR1 and sex pheromone receptors of Bombyx mori and Heliothis virescens.|
|Figure 3. Nucleotide and deduced amino acid sequences of OscaOR2. A, full nucleotide sequence and deduced amino acid sequence of OscaOR2. Arrows indicate primers using RT-PCR. B, Aligned amino acid sequences of OscaOR2 and Or83b family proteins. OscaOR2 (Ostrinia scapulalis, present study), DmOr83b (Drosophila melanogaster), AgOR7 (Anopheles gambiae), HvOR2 (H. virescens), BmOR2 (B. mori), TcOr1 (Tribolium castaneum), and AmOr2 (Apis mellifera).|
|Figure 4. Expression of OR1 and OR2 genes in different tissues. Expression of OscaOR1 and OscaOR2 in different tissues was tested by RT-PCR using specific primers for each gene. A, antenna; FL, foreleg; L, midleg and hindleg; P, proboscis; T, testis; H, head; F, fat body; M, midgut.|
|Figure 5. Expression of OscaOR1 and OscaOR2 genes in adult male antenna. Longitudinal sections of antennae were hybridized with antisense or sense probes for OscaOR2 (A, B and C). Longitudinal sections of antennae were hybridized with antisense or sense probes for OscaOR1 (D, E and F). Magnification of the boxed area in A (C) and D (F). Arrowheads indicate the cell bodies stained. Arrows indicate sensilla coeloconica. Scale bar in A = 10 µm (the same scale applies to A, B, D and E). Scale bar in C = 2 µm (the same scale applies to C and F).|
|Figure 6. Responses of oocytes co-expressing OR1 and OR2 to the pheromone components and analogs. A, responses of oocytes co-expressing OscaOR1/OscaOR2. B, dose-response curves of four compounds to which the oocytes showed significant responses. C, responses of oocytes co-expressing OlatOR1 and OlatOR2, orthologs of OscaOR1 and OscaOR2 in O. latipennis, respectively. The concentrations of pheromone components in A and C were10 µM.|
|Figure 7. Aligned amino acid sequences of OR1 orthologs in the genus Ostrinia. The gray boxes show positions where a substitution of the amino acid residue was found between OscaOR1 and OlatOR1.|
|Figure 8. Phylogenetic tree of odorant receptor proteins of Ostrinia and other lepidopteran species. The numbers near branches indicate bootstrap values. Values of < 70% are not shown.|
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