RT Journal Article SR Electronic(1) A1 Shen, Yunwang A1 Feng, Min A1 Wu, XiaofengYR 2018 T1 Bombyx mori nucleopolyhedrovirus ORF40 is essential for budded virus production and occlusion-derived virus envelopment JF Journal of General Virology, VO 99 IS 6 SP 837 OP 850 DO https://doi.org/10.1099/jgv.0.001066 PB Microbiology Society, SN 1465-2099, AB ORF40 (bm40) of the Bombyx mori nucleopolyhedrovirus (BmNPV) encodes a homologue of Autographa californica multiple nucleopolyhedrovirus (AcMNPV) AC51 and is a highly conserved gene in sequenced alphabaculoviruses. To investigate the role of bm40 in the baculovirus infection cycle, a bm40 knockout BmNPV bacmid was constructed via homologous recombination in Escherichia coli. Western blotting analysis revealed that bm40 is a late gene during virus infection. Compared with wild-type and repair viruses, the knockout virus exhibited a single-cell infection phenotype. Titration assays confirmed that no infectious budded viruses (BVs) were produced due to the bm40 deletion, while there was no effect on viral DNA replication. Electron microscopy revealed that Bm40 is required for nucleocapsid egress from the nucleus to the cytoplasm, nucleocapsid envelopment to form occlusion-derived viruses (ODVs) and subsequent embedding of ODVs into polyhedra. Confocal microscopy showed that Bm40 was predominantly localized in the nuclei from 48 h post-infection and subsequently condensed on the nuclear membrane and polyhedra at the late phase of infection. Taken together, these results demonstrate that Bm40 plays an essential role in BV production and ODV envelopment in the BmNPV infection cycle., UL https://www.microbiologyresearch.org/content/journal/jgv/10.1099/jgv.0.001066