title: Bombyx mori nucleopolyhedrovirus ORF56 encodes an occlusion-derived virus protein and is not essential for budded virus production.
abstract: 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.
authors.affiliation: Institute of Insect Science, Zhejiang University, Hangzhou 310029, PR China.
authors.forename: Hai-Jun
authors.initials: HJ
authors.lastname: Xu
authors.affiliation: Institute of Insect Science, Zhejiang University, Hangzhou 310029, PR China.
authors.forename: Zhang-Nv
authors.initials: ZN
authors.lastname: Yang
authors.affiliation: Institute of Insect Science, Zhejiang University, Hangzhou 310029, PR China.
authors.forename: Jin-Fang
authors.initials: JF
authors.lastname: Zhao
authors.affiliation: Institute of Insect Science, Zhejiang University, Hangzhou 310029, PR China.
authors.forename: Cai-Hong
authors.initials: CH
authors.lastname: Tian
authors.affiliation: Institute of Insect Science, Zhejiang University, Hangzhou 310029, PR China.
authors.forename: Jun-Qing
authors.initials: JQ
authors.lastname: Ge
authors.affiliation: Institute of Insect Science, Zhejiang University, Hangzhou 310029, PR China.
authors.forename: Xu-Dong
authors.initials: XD
authors.lastname: Tang
authors.affiliation: Institute of Insect Science, Zhejiang University, Hangzhou 310029, PR China.
authors.forename: Yan-Yuan
authors.initials: YY
authors.lastname: Bao
authors.affiliation: Institute of Insect Science, Zhejiang University, Hangzhou 310029, PR China.
authors.forename: Chuan-Xi
authors.initials: CX
authors.lastname: Zhang
mesh_terms: D000818:Animals; D015153:Blotting, Western; D012831:Bombyx; D002467:Cell Nucleus / Q000737:chemistry; D017353:Gene Deletion; D020869:Gene Expression Profiling; D007814:Larva / Q000821:virology; D018613:Microscopy, Confocal; D009685:Nuclear Envelope / Q000737:chemistry; D017924:Nucleopolyhedroviruses / Q000235:genetics / Q000502:physiology*; D012333:RNA, Messenger / Q000096:biosynthesis; D012367:RNA, Viral / Q000096:biosynthesis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D015678:Viral Structural Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D014779:Virus Replication / Q000235:genetics / Q000502:physiology*
chemical_list: D012333:RNA, Messenger; D012367:RNA, Viral; D015678:Viral Structural Proteins