Abstract: 【Aim】 The objective of this study is to clone the gene of a general odorant receptor (OR) OR20 of the oriental fruit moth, Grapholita molesta, and to investigate its expression profiles in different developmental stages and adult tissues of the moth, so as to provide a theoretical basis for further functional study of the odorant receptor gene. 【Methods】 According to the antennal transcriptome of female adults of G. molesta, the open reading frame (ORF) of OR20 gene of G. molesta was cloned by PCR. The expression levels of this gene at different developmental stages (egg, 1-5 instar larva, pupa, and female and male adults), in different adult tissues (antenna, head with antenna removed, thorax, abdomen, leg and wing), and in antennae of adults of different age (1, 3, 5 and 7 day-old) were detected by qRT-PCR. 【Results】 The cDNA sequence of GmolOR20 gene (GenBank accession no.: MH898864) in G. molesta was obtained. Its complete ORF is 1 284 bp in length, encoding 427 amino acids with the predicted molecular weight of 49.83 kD, the isoelectric point of 8.57, and seven transmembrane domains. Multiple sequence alignment and phylogenetic tree analyses revealed that GmolOR20 is closely related with CpomOR15 of Cydia pomonella and CnigOR15 of Cydia nigricana, with the amino acid sequence identity of 87% and 84%, respectively. Developmental stage-specific expression results revealed that GmolOR20 was expressed in various developmental stages of G. molesta, and its expression levels in female and male adults were significantly higher than those in other developmental stages (P<0.05), but showed no significant difference between female and male adults. Tissue expression profiles revealed that GmolOR20 was highly expressed in the antenna of adults, with extremely significantly higher expression level in the antenna of female adult than in the antenna of male adult (P<0.01). GmolOR20 was also expressed in antennae of adults of different day-old, with significantly higher expression levels in antennae of the 1 and 3 day-old adults than in antennae of other day-old adults (P<0.05). 【Conclusion】 Based on the profiling results of GmolOR20, we infer that GmolOR20 may be involved in the recognition of plant volatiles and pheromones in G. molesta.

Key words: Grapholita molesta, general odorant receptor, gene cloning, sequence analysis, expression profile