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Autographa californica multiple nucleopolyhedrovirus core gene ac96 encodes a per Os infectivity factor (PIF-4)

Minggang Fang1, Yingchao Nie, Stephanie Harris

  • 1Pacific Agri-Food Research Centre, Agriculture and Agri-Food Canada, Summerland, British Columbia,Canada.

Journal of Virology
|September 18, 2009
PubMed

Insights

Autographa californica multiple nucleopolyhedrovirus ac96 gene is essential for oral infection of Trichoplusia ni larvae. Deleting this gene, encoding per os infectivity factor 4 (PIF-4), prevents midgut infection but not virus replication or budded virus production.

Area of Science:

  • Virology
  • Molecular Biology
  • Insect Pathology

Background:

  • Autographa californica multiple nucleopolyhedrovirus (AcMNPV) is a significant pathogen of Lepidoptera.
  • The function of the core gene ac96 in the AcMNPV life cycle remains largely uncharacterized.

Purpose of the Study:

  • To elucidate the role of the AcMNPV ac96 gene in viral replication and insect infection.
  • To identify potential functions of the AC96 protein during the baculovirus life cycle.

Main Methods:

  • Generation of an ac96-null AcMNPV mutant (vAc(96)(null)) using the bacmid system.
  • Analysis of viral DNA replication and budded virus (BV) production in infected Sf9 cells.
  • Western blotting and confocal immunofluorescence to determine AC96 protein localization.
  • Larval infection assays via injection and per os inoculation in Trichoplusia ni.

Main Results:

  • The absence of ac96 did not impact viral DNA replication or BV production in vitro.
  • AC96 protein localizes to the cytoplasm, nucleus, and viral envelopes (BV and occlusion-derived virus).
  • vAc(96)(null) efficiently killed T. ni larvae when injected, but failed to infect the midgut via oral inoculation.

Conclusions:

  • The AcMNPV ac96 gene is dispensable for viral replication in cell culture and systemic infection following injection.
  • Ac96 encodes a novel per os infectivity factor, designated PIF-4, crucial for initiating infection through oral ingestion in Trichoplusia ni larvae.

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