A highly conserved baculovirus gene p48 (ac103) is essential for BV production and ODV envelopment

Autographa californica multiple nucleopolyhedrovirus (AcMNPV) p48 (ac103) is a highly conserved baculovirus gene of unknown function. In the present study, we generated a knockout of the p48 gene in an AcMNPV bacmid and investigated the role of P48 in baculovirus life cycle. The p48-null Bacmid vAcP48-KO-PH-GFP was unable to propagate in cell culture, while a ‘repair’ Bacmid vAcP48-REP-PH-GFP was able to replicate in a manner similar to a wild-type Bacmid vAcPH-GFP. Titration assays and Western blotting confirmed that vAcP48-KO-PH-GFP was unable to produce budded viruses (BVs). qPCR analysis showed that p48 deletion did not affect viral DNA replication. Electron microscopy indicated that P48 was required for nucleocapsid envelopment to form occlusion-derived viruses (ODVs) and their subsequent occlusion. Confocal analysis showed that P48 prominently condensed in the centre of the nucleus. Our results demonstrate that P48 plays an essential role in BV production and ODV envelopment in the AcMNPV life cycle.