Abstract: 【Aim】 Junonia coenia densovirus (JcDV) encodes four viral structural proteins, namely VP1, VP2, VP3 and VP4 via leaky scanning. This study aims to explore the expression characteristics of four viral structural protein genes (vp1-4) of JcDV in Spodoptera frugiperda larvae, so as to provide the basis for further studying on the function of the virus structural proteins VP1-4 and the mechanism of their assembly. 【Methods】 The subcellular localization of VP1-4 within Hi5 cells transfected with pJcDV plasmid was detected by immunofluorescence. The expression levels of vp1-4 in the 2nd instar larvae of S. frugiperda at 0, 3, 6, 12, 24, 48, 72, 96 and 120 h after infection by JcDV were analyzed through RT-PCR. The expression levels of VP1-4 in the 2nd instar larvae of S. frugiperda at 0, 24, 48, 72, 96 and 120 h after infection by JcDV were detected by Western blot. Immunohistochemistry was adopted to detect the tissue expression characteristics of VP1-4 in the 2nd instar larvae of S. frugiperda at 0, 24 and 96 h after infection by JcDV. 【Results】 VP1-4 were mainly located in the cytoplasm of Hi5 cells and only distributed in small amounts in the nucleus in the form of polymers. The transcription of vp1-4 could be detected in the 2nd instar larvae of S. frugiperda at 3 h after infection by JcDV, and stably extended to at least 120 h. VP1-4 were expressed at 24－120 h after infection by JcDV. The expression of VP1-4 was detected in the cuticle and trachea of the 2nd instar larvae of S. frugiperda at 96 h after infection by JcDV, however, there were no obvious expression signals in the muscle and fat body. 【Conclusion】 The transcription and translation of the viral structural protein genes vp1-4 could be detected in the 2nd instar larvae of S. frugiperda at 3 and 24 h, respectively, after infection by JcDV, indicating that VP1-4 might play an important role in the early stages of infection. JcDV could infect the cuticle and trachea of S. frugiperda larvae, which might be one of the causes accounting for their death.

Key words: Spodoptera frugiperda; Junonia coenia densovirus, structural protein gene, transcriptional phase, expression phase