[Complete nucleotide sequence analysis of Bombyx mori Densonucleosis virus type 3 VD2 (China isolate)].

The genome of Bombyx mori densonucleosis virus type 3 (China isolate) contains two kinds different single-stranded linear DNA molecules (VD1, VD2). The VD2 was purified and cloned into the pUC119 vector, and the complete nucleotide sequence of VD2 was determined. Sequence analysis showed that the VD2 genome sequence consisted of 6022 nts, including inverted terminal repeats (ITRs) of 524 nts. In the viral genome, two major open reading frames (ORF1 and ORF2) in the plus strand and one minor ORF (ORF3) in the complementary strand were identified. Computer analysis suggested the plus stand ORF1 and the minus strand ORF3 most likely encode the major nonstructural protein, while the plus stand ORF2 most likely encodes the major structural protein. Comparing the complete genome sequence of BmDNV-3 VD2 with that of BmDNV-2 VD2 (Yamanashi isolate) demonstrated that they shared 97.7% genome sequence in the VD2 region, with substitutions of 132 nucleotides, deletions of 11 nucleotides and insertions of 2 nucleotides in the VD2 region of BmDNV-3. The results suggested that BmDNV-3 is closely related to BmDNV-2, but with some differences, giving a better understanding about the variation of the viruses and providing clues to their evolution.