Molecular and Biological Characterization of Chinese Sacbrood Virus LN Isolate

Chinese sacbrood virus (CSBV) was purified from diseased insects, and its genome was cloned and sequenced. The genomic RNA of CSBV is 8863 nucleotides in length and contains a single large open reading frame encoding a 319.614 kDa polyprotein. The coding sequence is flanked by a 178-nucleotide 5′ nontranslated leader sequence and a 142-nucleotide 3′ nontranslated region, followed a poly(A) tail. Four major structural proteins, VP1,VP2, VP3 and VP4, were predicted in the N-teminal of the polyprotein. The C-terminal part of the polyprotein contains sequence motifs which is a typical and well-characterized picornavirus nonstructural proteins: an RNA helicase, a chymotrypsin-like 3C protease, and an RNA-dependent RNA polymerase. Genetic analysis shows that the CSBV-LN had a 13-amino-acid deletion at amino acid positions 710–719 and 727–729 in comparison with CSBV-GZ and SBV-UK, and the SBV-UK had a 7-amino-acid deletion at amino acid positions 2124–2132 in comparison with CSBV-GZ and CSBV-LN, and the CSBV-GZ and CSBV-LN had a 6-amino-acid deletion at amino acid positions 2143–2150 in comparison with SBV-UK. Phylogenetic analysis using RdRp of selected picorna-like viruses shows that CSBV/SBV and Deformed Wing Virus (DWV) tend to group together, which possesses an RNA of similar size and gene order.