Submitted to: Journal of General Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/19/2009
Publication Date: 5/1/2010
Publication URL: http://hdl.handle.net/10113/42096
Citation: Harrison, R.L., Sparks, W.O., Bonning, B.C. 2010. The autographa californica multiple nucleopolyhedrovirus ODV-E56 envelope protein is required for oral infectivity and can be functionally substituted by rachiplusia ou multiple nucleopolyhedrovirus ODV-E56. Journal of General Virology. 91:1173-1182. Interpretive Summary: Insect pests cause billions of dollars of damage to crops each year. The use of chemical insecticides to control insect pests can have negative ecological, environmental, and health consequences. Baculoviruses are a group of insect viruses that can be used to infect and kill insect pests without the problems of chemical insecticides. A more complete understanding of the genetic factors regulating baculovirus insecticidal activity is necessary for improving their scope and performance as biopesticides. In this study, a baculovirus gene was discovered that encodes a protein needed by baculoviruses to infect and kill insects. The information in this study contributes to the knowledge of how baculoviruses infect and kill insect pests that is needed in order to identify or develop baculovirus strains with enhanced insecticidal activity. Baculoviruses have a wide range of applications in addition to their use as biopesticides, and this study will be of interest to scientists in academia, government, and industry who work with this group of viruses.
Technical Abstract: The Autographa californica multiple nucleopolyhedrovirus (AcMNPV) odv-e56 gene encodes an occlusion-derived virus (ODV)-specific envelope protein, ODV-E56. In a previous analysis, the odv-e56 gene was found to be under positive selection pressure, suggesting that it may be a determinant of viral host range. To assess the role of ODV-E56 in oral infectivity and host range, we constructed recombinant AcMNPV clones (Ac69GFP-e56lacZ and AcIEGFP-e56lacZ) in which ODV-E56 protein synthesis was eliminated by inserting a beta-galactosidase (lacZ) expression cassette into the odv-e56 open reading frame. We also constructed a recombinant virus, Ac69GFP-Roe56, in which the native AcMNPV odv-e56 coding sequence was replaced with that of Rachiplusia ou multiple nucleopolyhedrovirus (RoMNPV). RoMNPV is genetically very similar to AcMNPV, but differs significantly in its virulence towards individual host species. The odv-e56 recombinant viruses exhibited no alterations in polyhedra production and morphogenesis or in the production of infectious budded virus in cell culture. In bioassays against three lepidopteran host species, the oral infectivities of the odv-e56 mutant viruses Ac69GFP-e56lacZ and AcIEGFP-e56lacZ were profoundly impaired compared to those of wild-type and marker-rescued viruses. Oral infectivity was fully restored by marker-rescue of the odv-e56 mutant viruses with either the AcMNPV or the RoMNPV odv-e56 gene. In bioassays against two host species that are more susceptible to RoMNPV than AcMNPV, Ac69GFP-Roe56 killed larvae with LC50 values similar to those of recombinant viruses expressing AcMNPV ODV-E56. This result suggested that replacement of the AcMNPV odv-e56 gene with the RoMNPV orthologue did not alter virulence against these two species.