Bombyx mori nucleopolyhedrovirus ORF9 is a gene involved in the budded virus production and infectivity.
The ORF9 of Bombyx mori nucleopolyhedrovirus (BmNPV) (Bm9) is conserved in all completely sequenced lepidopteran nucleopolyhedroviruses. RT-PCR analysis demonstrated that Bm9 is an early and late transcribed gene that is initiated at 3 h post-infection, and immunofluorescence microscopy showed that Bm9 is localized mainly in the cytoplasm of infected cells. To determine the role of Bm9 during virus infection, Bm9 was knocked out by recombination in a BmNPV genome propagated as a bacmid in Escherichia coli. The budded virus (BV) production of Bm9-deleted bacmids was reduced more than 10-fold compared with wild-type (wt) bacmid; however, the kinetics of viral DNA replication were unaffected. The defect in BV production was recovered by the Bm9 rescue bacmid. In addition, electron microscope observations revealed that polyhedra formation was not affected by the deletion of Bm9. Bioassays showed that the Bm9-deleted bacmid took approximately 14-22 h longer to kill fifth instar B. mori larvae than wt bacmid, and the LD(50) was about 15 times higher than that of the wt bacmid. In conclusion, Bm9 is an important but not essential factor in virus production and infectivity in vivo and in vitro.
Yang
Zhang-Nv
ZN
Institute of Insect Science, Zhejiang University, Kaixuan Road 268, Hangzhou 310029, PR China.
Xu
Hai-Jun
HJ
Thiem
Suzanne M
SM
Xu
Yi-Peng
YP
Ge
Jun-Qing
JQ
Tang
Xu-Dong
XD
Tian
Cai-Hong
CH
Zhang
Chuan-Xi
CX
D000818:Animals; D012831:Bombyx / Q000821:virology*; D002467:Cell Nucleus / Q000821:virology; D004261:DNA Replication; D004279:DNA, Viral / Q000378:metabolism; D055786:Gene Knockout Techniques; D005816:Genetic Complementation Test; D007928:Lethal Dose 50; D046529:Microscopy, Electron, Transmission; D017924:Nucleopolyhedroviruses / Q000235:genetics / Q000472:pathogenicity / Q000502:physiology* / Q000648:ultrastructure; D016019:Survival Analysis; D013997:Time Factors; D014764:Viral Proteins / Q000235:genetics / Q000502:physiology*; D014774:Virulence; D019065:Virus Assembly; D014779:Virus Replication
D004279:DNA, Viral; D014764:Viral Proteins