Expression analysis of Bombyx mori parvo-like virus VD2-ORF1 gene encoding a minor structural protein

Bombyx mori parvo-like virus is a small, icosahedral virus containing two single-stranded linear DNA molecules (VD1, VD2). To date, little is known about this virus, how to package. VD2-ORF1 encoded a large viral structural protein with predicted molecular mass of 133 kDa, and this protein was named as P133. It is unusual for 20-22 nm icosahedral viruses to posses so large a structural protein and the function of this protein is still unknown. In this study, the transcription of P133 was examined with quantitative real-time PCR, and the results demonstrated that the mRNA of P133 could be detected from 28 h post inoculation and kept increasing until 72 h post inoculation. P133 C-terminus (P133C) and P133 N-terminus (P133N) were cloned and expressed in E. coli BL21; then the resulting polypeptides were used to produce antibody, respectively. Western blot analysis showed that the protein in virions recognized by anti-P133C and anti-P133N antibody had the same molecular weight, indicating that VD2-ORF1 encoded a viral structural protein without leaky scanning.