Bombyx mori nucleopolyhedrovirus ORF56 (Bm56) is a baculovirus core gene that is highly conserved in all baculoviruses that have had their genomes sequenced to date. Its transcripts in BmNPV-infected cells could be detected from 12 h post-infection (p.i.) and the encoded protein could be detected at 16 h p.i. by using a polyclonal antibody against glutathione S-transferase-Bm56 fusion protein. Western blot analysis showed that Bm56 is a structural component of the occlusion-derived virus nucleocapsid. Subsequent confocal microscopy revealed that Bm56 was distributed in the outer nuclear membrane and the intranuclear region of infected cells. To investigate the role of Bm56 in virus replication, a Bm56-knockout bacmid of BmNPV was constructed via homologous recombination in Escherichia coli. The Bm56 deletion had no effect on budded virus (BV) production in cultured cells; however, the deletion affected occlusion-body morphogenesis. A larval bioassay demonstrated that the Bm56 deletion did not reduce infectivity, whereas it resulted in a 50 % lethal time that was 16-18 h longer than that of the wild-type bacmid at every dose used in this study. These results indicate that Bm56 facilitates efficient virus production in vivo; however, it is not essential for BV production in vitro.

The outbreak of porcine epidemic diarrhea virus (PEDV) has been a big problem of swine industry in China in recent years. In this study, we investigated molecular diversity, phylogenetic relationships, and protein characterization of Fujian field samples with other PEDV reference strains. Sequence analysis of the S1 and sM genes showed that each sample had unique characteristics, and the sample P55 may be differentiated from the others by the unique deletions and insertions of sM gene. Phylogenetic analysis based on S1 or sM gene, which have high levels of variations, indicated that each sample was related to the specific reference strain, and this finding was consistent with the protein characterization prediction analysis. The study is useful to better understand the prevalence of PEDV and its prevention and control in Fujian.

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