Autographa californica multiple nucleopolyhedrovirus ORF 23 null mutant produces occlusion-derived virions with fewer nucleocapsids

• Published in: Journal of general virology Vol. 90; no. 6; pp. 1499 - 1504
• Main Authors: Yu, Ian-Ling, Bray, Doug, Lin, Ying-Chu, Lung, Oliver
• Format: Journal Article
• Language: English
• Published: Reading Soc General Microbiol 01.06.2009; Society for General Microbiology
• Subjects: Animals; Autographa californica; Autographa californica multiple nucleopolyhedrovirus; Baculovirus; Biological and medical sciences; Cell Line; Cell Nucleus - virology; envelope fusion proteins; Fundamental and applied biological sciences. Psychology; fusion proteins; Gene Deletion; Microbiology; mutants; Nuclear polyhedrosis virus; nucleocapsid; Nucleopolyhedroviruses - genetics; Nucleopolyhedroviruses - physiology; occlusion bodies; Replicative cycle, interference, host-virus relations, pathogenicity, miscellaneous strains; Spodoptera; viral proteins; Viral Proteins - genetics; Viral Proteins - physiology; Virology; Virus Assembly; Virus Replication; Nucleopolyhedrovirus; Insecta; Nucleocapsid; Virus replication cycle; Open reading frame; Virus; Baculoviridae; Arthropoda; Autographa californica; Lepidoptera; Null mutation; Noctuidae; Invertebrata
• ISSN: 0022-1317; 1465-2099
• DOI: 10.1099/vir.0.009035-0

Two envelope fusion protein gene homologues have been identified in the baculovirus Autographa californica multiple nucleopolyhedrovirus (AcMNPV). AcMNPV GP64 protein is fusogenic and essential for propagation and pathogenicity. The F homologue (Ac23) is not essential, is fusion-incompetent in standard assays, but contributes to faster host death. Here, we show that occlusion bodies (OBs) from Ac23null mutants and control viruses do not differ significantly in size and the number of occlusion-derived virions (ODVs) contained; however, Ac23null OBs had a much higher percentage of ODVs with a single nucleocapsid (44.6 %) than the near-isogenic control (11.3 %). Infection of Sf9 cells with Ac23–green fluorescent protein (gfp)-expressing recombinant viruses showed Ac23–gfp fluorescence overlapping perinuclear DAPI staining at later times, a pattern not observed with GP64. These results suggest that F proteins have evolved functions beyond envelope fusion and play a different role from that of GP64 in viruses that contain both proteins.