Antennal transcriptome analysis of the piercing moth Oraesia emarginata (Lepidoptera: Noctuidae)

Abstract

The piercing fruit moth Oraesia emarginata is an economically significant pest; however, our understanding of its olfactory mechanisms in infestation is limited. The present study conducted antennal transcriptome analysis of olfactory genes using real-time quantitative reverse transcription PCR analysis (RT-qPCR). We identified a total of 104 candidate chemosensory genes from several gene families, including 35 olfactory receptors (ORs), 41 odorant-binding proteins, 20 chemosensory proteins, 6 ionotropic receptors, and 2 sensory neuron membrane proteins. Seven candidate pheromone receptors (PRs) and 3 candidate pheromone-binding proteins (PBPs) for sex pheromone recognition were found. OemaOR29 and OemaPBP1 had the highest fragments per kb per million fragments (FPKM) values in all ORs and OBPs, respectively. Eighteen olfactory genes were upregulated in females, including 5 candidate PRs, and 20 olfactory genes were upregulated in males, including 2 candidate PRs (OemaOR29 and 4) and 2 PBPs (OemaPBP1 and 3). These genes may have roles in mediating sex-specific behaviors. Most candidate olfactory genes of sex pheromone recognition (except OemaOR29 and OemaPBP3) in O. emarginata were not clustered with those of studied noctuid species (type I pheromone). In addition, OemaOR29 was belonged to cluster PRIII, which comprise proteins that recognize type II pheromones instead of type I pheromones. The structure and function of olfactory genes that encode sex pheromones in O. emarginata might thus differ from those of other studied noctuids. The findings of the present study may help explain the molecular mechanism underlying olfaction and the evolution of olfactory genes encoding sex pheromones in O. emarginata.

Fig 1. Life cycle of O. emarginata.

Fig 2. Phylogenetic analysis of putative OR gene sequences of O. emarginata (black circle).

The tree was rooted with Orco lineage (pink color). Bootstrap values < 50% are not shown. Color legend: Orange = PR group, yellow = OR18 group, green = OemaORs group, and blue = other general OR groups. Adis, Athetis dissimilis, Aips, A. ipsilon, Bmor, B. mori, Hvir, H. virescens, Msex, M. sexta, Oema, O. emarginata, Ofur, O. furnacalis, Slitu, S. litura.

Fig 3. Phylogenetic analysis of putative OBP gene sequences of O. emarginata (black circle), other moth species (black lines), and Dipteran species (green lines).

The tree was rooted with the Lepidopteran GOBP-PBP group (green color). Bootstrap values < 50% are not shown. Color legend: Orange = conserved OBP groups, pink = expanded OemaOBPs group, green = Lepidopteran GOBP-PBP group, and blue = other general OBP groups. Adis, A. dissimilis, Agam, Anopheles gambiae, Aips, A. ipsilon, Bmor, B. mori, Cpun, Conogethes punctiferalis, Dmel, Drosophila melanogaster, Dple, D. plexippus, Gmol, Grapholita molesta, Harm, H. armigera, Hvir, H. virescens, Msex, M. sexta, Ofur, O. furnacalis, Oema, O. emarginata, Sexi, S. exigua, Slit, S. littoralis, Slitu, S. litura.

Fig 4. Aligned putative full ORF of OBP gene sequences of O. emarginata.

Six conserved cysteines are highlighted in blue.

Fig 5. Phylogenetic analysis of putative CSP gene sequences of O. emarginata (black circles), other moth species (black lines) and Dipteran species (green lines).

Bootstrap values < 50% are not shown. Agam, A. gambiae, Aips, A. ipsilon, Bmor, B. mori, Dmel, D. melanogaster, Gmol, G. molesta, Oema, O. emarginata, Slit, S. littoralis, Slitu, S. litura.

Fig 6. Aligned putative full ORF of CSP gene sequences of O. emarginata.

Four conserved cysteines are highlighted in blue.

Fig 7. Phylogenetic analysis of putative IR gene sequences of O. emarginata (black circles).

The tree is rooted with IR25a and IR8a lineages. Bootstrap values < 50% are not shown. Bmor, B. mori, Dmel, D. melanogaster, Harm, H. armigera, Msex, M. sexta, Oema, O. emarginata, Slitu, S. litura.

Fig 8. Phylogenetic analysis of putative SNMP gene sequences of O. emarginata (black circles), D. melanogaster (black lines), other moth species (purple lines), and Hymenopteran species (green lines).

Bootstrap values < 50% are not shown. Amel, Apis mellifera, Apol, Antheraea polyphemus, Bmor, B. mori, Dmel, D. melanogaster, Harm, H. armigera, Hvir, H. virescens, Mbra, M. brassicae, Msex, M. sexta, Nvit, Nasonia vitripennis, Oema, O. emarginata, Scyn, Samia ricini, Slitu, S. litura.

Fig 9. Expression levels of olfactory genes in male and female antennae as measured by RT-qPCR analysis.

Gene expression was calculated relative to the reference genes, UCCR and AK. The expression in female antennae was arbitrarily defined as 1 for all genes and was used in the normalization of gene expression of the male antennae. A, Expression levels of CSP, IR, and SNMP genes. B, Expression levels of the OBP genes. C, Expression levels of OR genes.

Fig 10. The phylogeny of Lepidopteran PRs.

The tree was rooted with Orco lineage (yellow color). Bootstrap values < 50% are not shown. Genes of O. emarginata, O. brumata, and other noctuid species are indicated by black circles, black triangles, and diamonds, respectively. Clusters PRI—PRIV for type I pheromones are indicated in red, green, purple, and blue, respectively. Aseg, A. segetum, Atra, Amyelois transitella, Bmor, B. mori, Harm, H. armigera, Hvir, H. virescens, Obru, O. brumata, Oema, O. emarginata, Onub, O. nubilalis, Pxyl, P. xylostella, Sexi, S. exigua, Slit, S. litura.

Fig 11. The phylogeny of Lepidopteran PBPs.

The tree was rooted with GOBP lineage. Bootstrap values < 50% are not shown. Genes of O. emarginata, other species with type II pheromones, and the other noctuid species are indicated by black circles, black triangles, and diamonds, respectively. Clusters PBPI—PBPIII are indicated by orange, purple, and blue colors, respectively. Acon, Argyresthia conjugella, Aips, A. ipsilon, Apol, A. polyphemus, Asel, Ascotis selenaria cretacea, Bmor, B. mori, Cpun, C. punctiferalis, Csup, C. suppressalis, Ehip, Eogystia hippophaecolus, Harm, H. armigera, Hass, H. assulta, Gmol, G. molesta, Ldis, Lymantria dispar, Msex, M. sexta, Obru, O. brumata, Oema, O. emarginata, Ofur, O. furnacalis, Onub, O. nubilalis, Pxyl, P. xylostella, Sexi, S. exigua, Sinf, S. inferens, Slit, S. litura.