Identification,Sequence Characteristics,and Expression Pattern Analysis Of Olfactory-related Genes From Galleria Mellonella

The greater wax moth,Galleria mellonella,is one of the most important insect pests of apiculture.The olfactory system is essential for insects in localization of hosts,mates,and oviposition sites.Thus,revealing of the function of the olfactory-related genes could provide a theoretical basis for developing new behavioral control agents such as attractants and repellents for management of G.mellonella.To date,it s well-accepted that several gene families are involved in the olfaction pathways in insects.These genes include odorant-binding proteins(OBPs),chenmosensory proteins(CSPs),odorant receptors(ORs),ionotropic receptors(IRs),sensory neuron membrane proteins(SNMPs),and odorant-degrading enzymes(ODEs).However,the information regarding the sequences and expression profiles of olfactory-related genes in G.mellonella is still unclear.In this study,we reported the transcriptome sequencing on the antennae of male and female adults of G.mellonella,and the identification of olfactory-related genes from this insect species.Furthermore,we analyzed the expression patterns of a subset of genes.The results are as follows:1.Antennal transcriptome sequencing of G.mellonellaAntennal transcriptome sequencing was performed on the male and female adults of G.mellonella,and 73.8 Mb and 73.9 Mb raw reads were obtained from the male and female transcriptome,respectively.The data have been submitted to NCBI SRA database under accession numbers SRR8307568 and SRR8307567.A total of 42544 unigenes were obtained by assembling the transcriptomes.Of these,14481 unigenes(34% of the total unigenes)showed homology with genes of other species in the NCBI non-redundant(NR)database.Moreover,8887 unigenes(20.9% of the total unigenes)could be annotated to at least one term in Gene Ontology(GO)database.2.Identification and sequence analysis of olfactory-related genes in G.mellonellaBy using a homology searching method,we identified a total of 105 olfactory-related genes from the unigene dataset of the antennal transcriptome of G.mellonella.These genes are: 21 OBPs,18 CSPs,43 ORs,18 IRs,two SNMPs and three AOXs.Based on these results,we analyzed the sequence characteristics,phylogenetic relationships,motif patterns,and expression profiles of the olfactory-related genes in G.mellonella by using multiple bioinformatical softwares and programs.3.Tissue-specific expression profiles of olfactory-related genes in G.mellonellaThe expression profiles of fourteen olfactory-related genes in different tissues of male and female adults of G.mellonella were determined using real-time quntitative PCR.The results showed that the expression levels of Gmel OBP18,Gmel OBP20,Gmel OR48,Gmel OR49,Gmel IR50 and Gme IR1.2 in female antennae were higher than those in male antennae,while the expression levels of Gmel OBP19,Gmel OBP21,Gmel OR46,Gmel OR47 and Gme IR64 a in male antennae were higher than those in female antennae.We also observed that,among the three AOX genes,Gmel AOX2 was highly expressed in the antennae of adults,and the transcription level of this gene in antennae was significantly higher than those in other tissues,suggesting that Gmel AOX2 might encode an odorant-degrading enzyme involved in the aldehyde degradation.By contrast,the expression of Gmel AOX1 and Gmel AOX3 was not tissue-specific.