Spodoptera exigua is one of the worldwide distributed agricultural pest insects and has been known to show high resistance to conventional chemical insecticides. Autographa california multiple nucleopolyhedrovirus (AcMNPV) has been used as eco-friendly biological control agent for S. exigua, as it exhibits high level of host specificity, stability and safety. In this study, for formulation of AcMNPV, the optimal conditions for mass-production of AcMNPV polyhedra was established using S. exigua larvae. Mass-produced AcMNPV polyhedra was formulated as wettable powder using microencapsulation method and its control efficacy against S. exigua was evaluated both in laboratory and semi-field experiment. Chinese cabbage treated with the AcMNPV formulation showed significantly reduced damage rates, suggesting that the AcMNPV formulation in this study could be useful for control of S. exigua

ORF78 (ac78) of Autographa californica multiple nucleopolyhedrovirus (AcMNPV) is a baculovirus core gene of unknown function. To determine the role of ac78 in baculovirus life cycle, an ac78-deleted mutant AcMNPV, Ac78KO, was constructed. Quantitative PCR analysis revealed that ac78 is a late gene in the viral life cycle. After transfection into Spodoptera frugiperda cells, Ac78KO produced a single-cell infection phenotype indicating that no infectious budded viruses (BVs) were produced. The defection in BV production was also confirmed by both viral titration and Western blot. However, viral DNA replication is unaffected. Analysis of BV and occlusion derived virus (ODV) revealed that AC78 is associated with both forms of the virions and is a structural protein located to viral envelope. Electron microscopy showed that ac78 also plays an important role in embedding of ODV into occlusion body. This study therefore demonstrates that AC78 is a late virion associated protein and is essential for the viral life cycle.

ORF11 (ac11) of Autographa californica multiple nucleopolyhedrovirus (AcMNPV) is a highly conserved baculovirus gene whose homologs are found in all lepidoteran Group I NPV, but its function is unknown so far. To determine the role of ac11 in baculovirus life cycle, ac11 knock-out mutant, Ac11KO, was constructed using the plasmid capture system (PCS). Real-Time PCR analysis showed that ac11 transcript was first detected at 6 h post-infection (p.i.) and accumulated to maximum at 48 h p.i., indicating that ac11 is belong to late gene. When the genomic DNA of Ac11KO was transfected into Sf9 cells, viral replication was restricted to a cell transfected originally. While viral transmission of the Ac11KO was not observed in Sf9 cells, production of budded virus (BV) in Sf9 cells transfected with Ac11KO was observed by transmission electron microscopy (TEM). These results suggest that the ac11 is essential for AcMNPV to produce infective BV.

Among 154 putative ORFs of Autographa californica multiple nucleopolyhedrovirus (AcMNPV), ac78 and ac79 are highly conserved genes in baculovirus, but their functions in the virus life cycle have been unknown so far. To determine their roles in AcMNPV replication, knockout mutants, ac78KO and ac79KO, were constructed using the plasmid capture system (PCS). Real-Time PCR analysis showed that both of ac78 and ac79 transcripts were first detected at 6 hours post-infection, and accumulated to maximum at 24 hours post-infection, suggesting that both of ac78 and ac79 are belong to late gene. When the genomic DNA of ac78KO was transfected into Sf9 cells, viral replication was restricted to a single cell infection. These results demonstrated that the ac78 play an important role in BV production, and therefore is essential for AcMNPV to mount a successful infection. Whereas Sf9 cells infected with the ac79KO showed normal viral symptoms such as rounding and swelling, OBs were not observed from majority of infected cells. These results suggested that the ac79 might play an important role in OB production.

The polyhedrin is responsible to form polyhedra of nucleopolyhedrovirus(NPV) and highly conserved in most completely sequenced in lepidopteran NPVs. Previously, we have reported that the substitution of polyhedrin of Autographa californica NPV(AcNPV) with that of Spodoptera exigua NPV(SeNPV) or Bombyx mori NPV(BmNPV) result the change of polyhedra morphology. In this study, we investigated the influence of changed polyhedra morphology to the virulence of AcNPV. The recombinant AcNPVs were propagated in Spodoptera frugiperda clone 9, 21 cells and S. exigua larvae. Each collected recombinant polyhedra were used in bioassays using S. exigua larvae. The recombinant AcNPVs show that difference virulence according to the polyhedra morphologies. Internal and external morphological features of each recombinant AcNPV were also compared on the electron microscope. Our results suggest that the morphology of polyhedra influence the virulence of NPV and is well worth considering for the development viral insecticide.

ORF43 (ac43) of Autographa californica multiple nucleopolyhedrovirus (AcMNPV) is a highly conserved baculovirus gene whose function is unknown. To determine the role of ac43 in baculovirus life cycle, we used a new AcMNPV bacmid (bAc-MK) and generated ac43 deletion virus (ac43KO) by using the plasmid capture system (PCS). After transfection into Spodoptera frugiperda cells, ac43KO produced significantly different OBs which with much larger size; and especially had much single nucleocapsids compared to Ac-MK. Furthermore, ac43KO bacmid led to defect in transcription and expression of polyhedrin, which result in less OBs production. However, ac43KO didn't affect BV production since there's no remarkable difference of BV titer in both ac43KO and Ac-MK. These results demonstrate that ac43 play an important role in polyhedrin expression, OB formation, and virion assembly.

Autographa californica nucleopolyhedrovirus (AcMNPV) has a large doublestrand DNA genome of approximately 134 kbp and harbors 156 open reading frames (ORFs). To elucidate DNA replication cascade of AcMNPV, we developed a novel baculovirus genome that can be maintained in Escherichia coli as a plasmid and can infect susceptible lepidopteran insect cells. This genome, named bAc-MK, contains a mini-F replicon and a kanamycin resistance marker. Using a convenient Tn7 transposon-based system, pPCS-S, 55 single ORF-truncated mutants were generated by random insertion into bAc-MK genome. These single ORF-truncated mutants were independently transfected into Sf9 cells, 16 of them were found affecting viral replication since they defected in producing polyhedra. Furthermore, to verify the pathogenicity of the single ORF-truncated mutants, the remaining 39 mutants were subjected to bioassay to Spodoptera exigua 3rd instar larvae. Among them, ac9-, ac49-, ac103- and ac105-knockout mutants showed higher mortality compared to that of bAc-MK. These results suggested that these ORFs could be related to pathogenicity of AcMNPV.

Autographa californica nucleopolyhedrovirus (AcMNPV) has a large doublestrand DNA genome of approximately 134 kbp and comprises 156 open reading frames (ORFs). To elucidate DNA replication cascade of AcMNPV, we developed a novel baculovirus genome that can be maintained in Escherichia coli as a plasmid and can infect susceptible lepidopteran insect cells. This genome, named bAc-MK, contains a mini-F replicon and a kanamycin resistance marker. Using a convenient Tn7 transposon-based system, pPCS-S, which contains an ampicillin resistance gene, 56 single ORF-truncated mutants were generated by random insertion into bAc-MK genome. These single ORF-truncated mutants were independently transfected into Sf9 cells to verify viral replication. Interestingly, both lef-1 and p48 knockout mutants showed normal viral replication in infected cells, which are reported to essential for viral replication. These results suggest that these single ORF-truncated mutants are useful for elucidation of viral replication cascade.

Recently, the genome of Spodoptera litura granulovirus (SlGV) which encodes 133 putative open reading frames (ORFs) was completely sequenced. In this study, to screen novel insecticidal genes of SlGV, we first constructed an advanced plasmid capture system, pPCS-TPI, which contains not only pUC19 ori and ampicillin resistance gene but also Autographa californica nucleopolyhedrovirus (AcMNPV) ORF603 and ORF1629 homologous region between Tn7L and Tn7R. In order to introduce genomic segments of SlGV into the genome of AcMNPV, genomic DNA of SlGV was digested with EcoRI and self-ligated. These self-ligated segments were in vitro transposed with the pPCS-TPI donor by the help of TnsABC* transposase. By this, 10 EcoRI-digested genomic segments of the SlGV were cloned, and these clones were co-transfected with the bApGOZA DNA into sf9 cells to generate corresponding recombinant virus, respectively. The resulting recombinant viruses harboring genomic segments of the SlGV could be used to investigate the insecticidal activity and/or other functions originated from the introduced genomic segments of the SlGV.

The baculovirus Autographa californica nucleopolyhedrovirus (AcMNPV), a large circular double-stranded DNA virus whose genome encodes at least 155 open reading frames (ORFs), is highly pathogenic to a number of lepidopteran insects and widely used to transduce various cells for exogenous gene expression. Although many genes of AcMNPV have been identified, the genome-wide study related to viral replication has not been well announced. In this study, to elucidate DNA replication cascade of AcMNPV, we firstly developed a novel baculovirus genome that can be maintained in Escherichia coli as a plasmid and can infect susceptible lepidopteran insect cells. This genome, named bAc-MK, contains a mini-F replicon and a kanamycin resistance marker. Using a convenient Tn7 transposon-based system, pPCS-S, which contains an ampicillin resistance gene, ORF knock-out mutants were generated by random insertion into bAc-MK genome. These mutants will be suffered DNA microarray to elucidate AcMNPV replication cascade.