Autographa californica Multiple Nucleopolyhedrovirus orf132 Encodes a Nucleocapsid-Associated Protein Required for Budded-Virus and Multiply Enveloped Occlusion-Derived Virus Production

Abstract

Autographa californica multiple nucleopolyhedrovirus orf132 (named ac132) has homologs in all genome-sequenced group I nucleopolyhedroviruses. Its role in the viral replication cycle is unknown. In this study, ac132 was shown to express a protein of around 28 kDa, which was determined to be associated with the nucleocapsids of both occlusion-derived virus and budded virus. Confocal microscopy showed that AC132 protein appeared in central region of the nucleus as early as 12 h postinfection with the virus. It formed a ring zone at the periphery of the nucleus by 24 h postinfection. To investigate its role in virus replication, ac132 was deleted from the viral genome by using a bacmid system. In the Sf9 cell culture transfected by the ac132 knockout bacmid, infection was restricted to single cells, and the titer of infectious budded virus was reduced to an undetectable level. However, viral DNA replication and the expression of late genes vp39 and odv-e25 and a reporter gene under the control of the very late gene p10 promoter were unaffected. Electron microscopy showed that nucleocapsids, virions, and occlusion bodies were synthesized in the cells transfected by an ac132 knockout bacmid, but the formation of the virogenic stroma and occlusion bodies was delayed, the numbers of enveloped nucleocapsids were reduced, and the occlusion bodies contained mainly singly enveloped nucleocapsids. AC132 was found to interact with envelope protein ODV-E18 and the viral DNA-binding protein P6.9. The data from this study suggest that ac132 possibly plays an important role in the assembly and envelopment of nucleocapsids. IMPORTANCETo our knowledge, this is the first report on a functional analysis of ac132. The data presented here demonstrate that ac132 is required for production of the budded virus and multiply enveloped occlusion-derived virus of Autographa californica multiple nucleopolyhedrovirus. This article reveals unique phenotypic changes induced by ac132 deletion on the virus and multiple new findings on ac132.

Proteomic Analysis of Mamestra Brassicae Nucleopolyhedrovirus Progeny Virions from Two Different Hosts

“…Proteins including 49K, GP41, Desmoplakin (AC66) have been reported as ODV tegument proteins and nucleocapsid associated proteins of BV, and are essential for nucleocapsid egress from nucleus to cytoplasm [[ 30 ], S3 Table ]. Additionally, Mabr50 (AC132) [ 26 ], Mabr108 (AC75) [ 31 ] and ODV-E18 [ 32 ] have been demonstrated to be important for the production of infectious BVs.…”

Autographa californica multiple nucleopolyhedrovirus ac75 is required for egress of nucleocapsids from the nucleus and formation of de novo intranuclear membrane microvesicles

“…The anti-GP41 mouse antiserum was raised with GST-tagged GP41. The anti-E25, anti-VP39 and anti-E18 rabbit antisera were separately raised with corresponding His-tagged AcMNPV proteins previously [ 9 , 10 ]. HA tag-specific monoclonal antibody was purchased from Proteintech TM .…”

“…BV and ODV purification and subsequent fractionation into envelope and nucleocapsid was performed as previously described [ 9 , 12 ]. Briefly, Sf9 cells were infected with AcMNPV at an MOI of 0.1, and the cells and medium were harvested separately at 5 days post infection.…”

Baculovirus-induced insect behaviour: from genes to brains

“…In ac132 mutant virus-infected cells, the synthesis of nucleocapsids, ODVs and OBs still occurred, however, virogenic stroma and OB formation were delayed. These data indicate that AC132 plays a role in nucleocapsid envelopment (Yang et al, 2014).…”

“…associates with nucleocapsids of both BVs and ODVs (Yang et al, 2014). During infection, AC132 forms a ring zone at the periphery of the nucleus at 24 hpi.…”