title: Autographa californica Multiple Nucleopolyhedrovirus AC83 is aPer OsInfectivity Factor (PIF) Protein Required for Occlusion-Derived Virus (ODV) and Budded Virus Nucleocapsid Assembly as well as Assembly of the PIF Complex in ODV Envelopes.
abstract: Baculovirus occlusion-derived virus (ODV) initiates infection of lepidopteran larval hosts by binding to the midgut epithelia, which is mediated byper osinfectivity factors (PIFs). Autographa californica multiple nucleopolyhedrovirus (AcMNPV) encodes seven PIF proteins, of which PIF1 to PIF4 form a core complex in ODV envelopes to which PIF0 and PIF6 loosely associate. Deletion of anypifgene results in ODV being unable to bind or enter midgut cells. AC83 also associates with the PIF complex, and this study further analyzed its role in oral infectivity to determine if it is a PIF protein. It had been proposed that AC83 possesses a chitin binding domain that enables transit through the peritrophic matrix; however, no chitin binding activity has ever been demonstrated. AC83 has been reported to be found only in the ODV envelopes, but in contrast, the Orgyia pseudotsugata MNPV AC83 homolog is associated with both ODV nucleocapsids and envelopes. In addition, unlike knownpifgenes, deletion ofac83eliminates nucleocapsid formation. We propose a new model for AC83 function and show AC83 is associated with both ODV nucleocapsids and envelopes. We also further define the domain required for nucleocapsid assembly. The cysteine-rich region of AC83 is also shown not to be a chitin binding domain but a zinc finger domain required for the recruitment or assembly of the PIF complex to ODV envelopes. As such, AC83 has all the properties of a PIF protein and should be considered PIF8. In addition,pif7(ac110) is reported as the 38th baculovirus core gene.IMPORTANCEODV is essential for theper osinfectivity of the baculovirus AcMNPV. To initiate infection, ODV binds to microvilli of lepidopteran midgut cells, a process which requires a group of seven virion envelope proteins called PIFs. In this study, we reexamined the function of AC83, a protein that copurifies with the ODV PIFs, to determine its role in the oral infection process. A zinc finger domain was identified and a new model for AC83 function was proposed. In contrast to previous studies, AC83 was found to be physically located in both the envelope and nucleocapsid of ODV. By deletion analysis, the AC83 domain required for nucleocapsid assembly was more finely delineated. We show that AC83 is required for PIF complex formation and conclude that it is a trueper osinfectivity factor and should be called PIF8.
authors.affiliation: Saskatoon Research and Development Centre, Agriculture and Agri-Food Canada, Saskatoon, Saskatchewan, Canada.
authors.forename: Muhammad Afzal
authors.initials: MA
authors.lastname: Javed
authors.affiliation: Plant Science Program, Faculty of Land and Food Systems, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Siddhartha
authors.initials: S
authors.lastname: Biswas
authors.affiliation: Summerland Research and Development Centre, Agriculture and Agri-Food Canada, Summerland, British Columbia, Canada.
authors.forename: Leslie G
authors.initials: LG
authors.lastname: Willis
authors.affiliation: Saskatoon Research and Development Centre, Agriculture and Agri-Food Canada, Saskatoon, Saskatchewan, Canada.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Harris
authors.affiliation: Summerland Research and Development Centre, Agriculture and Agri-Food Canada, Summerland, British Columbia, Canada.
authors.forename: Caitlin
authors.initials: C
authors.lastname: Pritchard
authors.affiliation: Laboratory of Virology, Wageningen University, Wageningen, The Netherlands.
authors.forename: Monique M
authors.initials: MM
authors.lastname: van Oers
authors.affiliation: London Research and Development Centre, Agriculture and Agri-Food Canada, London, Ontario, Canada.
authors.forename: B Cameron
authors.initials: BC
authors.lastname: Donly
authors.affiliation: Saskatoon Research and Development Centre, Agriculture and Agri-Food Canada, Saskatoon, Saskatchewan, Canada.
authors.forename: Martin A
authors.initials: MA
authors.lastname: Erlandson
authors.affiliation: Saskatoon Research and Development Centre, Agriculture and Agri-Food Canada, Saskatoon, Saskatchewan, Canada dwayne.hegedus@agr.gc.ca david.theilmann@agr.gc.ca.
authors.forename: Dwayne D
authors.initials: DD
authors.lastname: Hegedus
authors.affiliation: Plant Science Program, Faculty of Land and Food Systems, University of British Columbia, Vancouver, British Columbia, Canada dwayne.hegedus@agr.gc.ca david.theilmann@agr.gc.ca.|Summerland Research and Development Centre, Agriculture and Agri-Food Canada, Summerland, British Columbia, Canada.
authors.forename: David A
authors.initials: DA
authors.lastname: Theilmann
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D036022:Capsid Proteins / Q000502:physiology*; D017124:Conserved Sequence; D019251:Nucleocapsid / Q000378:metabolism*; D017924:Nucleopolyhedroviruses / Q000502:physiology*; D054730:Protein Interaction Domains and Motifs; D055503:Protein Multimerization; D061987:Sf9 Cells; D018411:Spodoptera; D019065:Virus Assembly; D014779:Virus Replication
chemical_list: D036022:Capsid Proteins
keywords: AC83; AcMNPV; PIF; PIF complex; ZF domain; baculovirus; chitin binding domain; fluorescence microscopy; nucleocapsid assembly; occlusion-derived virus; per os infection; zinc finger proteins