Abstract
General odorant binding proteins (GOBPs) and pheromone binding proteins (PBPs) form a monophyletic subfamily of insect odorant binding proteins (OBPs) specific for Lepidoptera, butterflies and moths. The GOBP/PBP genes include six subgroups (GOBP1–2, PBP-A–D) previously reported to form a complex arrayed in a conserved order in representative moths (superfamily Bombycoidea) and butterflies (Nymphalidae). Although our knowledge of lepidopteran genomes has increased greatly recently, the structure of the GOBP/PBP complex has been studied only for species that represent limited lineages of the highly diverged Ditrysia. To understand the evolution of this functionally important gene complex, we determined 69–149 kb genomic sequences that include GOBP2 and five PBP genes in three Ostrinia moths (Pyraloidea), O. nubilalis, O. furnacalis, and O. latipennis, using bacterial artificial chromosome (BAC) and fosmid clones. The structure of the GOBP2/PBP gene cluster was well conserved despite the different sex pheromone composition utilized by the three moths. Five expressed PBP genes in Ostrinia moths were the result of two duplications of PBP-A genes. Surprisingly, an allele containing a fusion gene between tandemly arrayed PBP-A genes was observed in O. nubilalis. We also revealed duplication and intra-chromosomal translocation of the GOBP1 gene in P. xylostella by fluorescence in situ hybridization (FISH) analysis. Additionally, we compared the structure of the GOBP/PBP gene complex of seventeen species covering six superfamilies and twelve families of the lepidopteran clade, Ditrysia, and found the gene order was basically conserved despite the frequent occurrence of lineage-specific gains, losses, inversions and translocations of these genes, compared with their neighboring genes. Our findings support the hypothesis that the structure of the GOBP/PBP gene complex was already established in the common ancestor of Ditrysia.
Highlights
General odorant binding proteins (GOBPs) and pheromone binding proteins (PBPs) form a subfamily of insect odorant binding proteins (OBPs)
Through similarity search using Kaikobase and MonarchBase, we found that two orthologous coding sequences (CDSs) were located between the GOBP1 and the GOBP2/PBP gene cluster of B. mori and D. plexippus (S3 Table)
Since the Crambidae-specific PBP-A genes are located adjacent to the GOBP2 gene in the Ostrinia moths, it is possible that their expression is controlled more directly by ancestral PBP-A 5’- ciselements compared with those located downstream
Summary
General odorant binding proteins (GOBPs) and pheromone binding proteins (PBPs) form a subfamily of insect odorant binding proteins (OBPs). Insect OBPs are a group of small soluble proteins A PBP was first identified in male antennae of a wild silkmoth, Antheraea polyphemus [3]. GOBP1 and GOBP2 were subsequently defined as conserved non-sex-biased antennal OBPs by sequence comparison among six moth species [4]. The distribution pattern of PBPs and GOBPs in antennae is distinct [5,6]. In three distantly related moths, PBP genes are expressed in supporting cells surrounding male olfactory neurons expressing pheromone receptor genes, in good agreement with the proposed role of PBP [7]. Appropriate combinations of PBPs and pheromone receptors were shown to improve the discrimination ability of pheromone analogs in the striped rice stem borer, Chilo suppressalis [8]
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