Abstract: 【Aim】 fruitless (fru) is the key gene for courtship and mating behaviors in insects, but its specific role in Bactrocera dorsalis is still unclear. The aim of this study is to characterize the role of fru in courtship and mating behaviors in B. dorsalis and to further clarify its biological significance. 【Methods】 Primers were designed based on the fru sequence of B. dorsalis from NCBI, the full-length cDNA of fru gene was cloned from the head of the mated 10-day-old adults of B. dorsalis, and the structural domain of its encoded protein was predicted. The variations of gene expression levels in B. dorsalis adults before and after mating were analyzed by real-time fluorescent quantitative PCR (RT-qPCR). The fru dsRNA was synthesized, and injected into the abdomen of the 9-day-old adults. The relative expression level of fru was examined at 48 and 72 h after injection. At 72 h after injection, the courtship and mating behaviors including the mating frequency and duration were examined. 【Results】 The full-length cDNA of B. dorsalis fru obtained by cloning is 2 865 bp in length, encoding 954 amino acids with the predicted molecular weight of 104.1 kD and pI of 6.01. The encoded protein has unique domains including one BTB domain and two zinc finger domains. The RT-qPCR results revealed that the expression level of fru in the head of male adults of B. dorsalis was significantly higher after mating than before mating. B. dorsalis male adults in the RNAi group injected with dsfru engaged significantly longer time (25-35 min longer) in the courtship behavior and had the mating frequency decreased by 17%-22% as compared to the male adults in the blank control group (injected with DEPC water) and the negative control group (injected with dsGFP), suggesting that fru plays important roles in regulating courtship and mating behaviors of male B. dorsalis. 【Conclusion】 The results of this study provide a theoretical basis for clarifying the role of fru in the non-model insect B. dorsalis and further studying courtship and mating behaviors in B. dorsalis.

Key words: Bactrocera dorsalis; fruitless, expression profile, courtship behavior, mating frequency, RNAi