Jong Bin Park

Genomic sequence analysis of granulovirus isolated from the tobacco cutworm, Spodoptera litura.

Background Spodoptera litura is a noctuid moth that is considered an agricultural pest. The larvae feed on a wide range of plants and have been recorded on plants from 40 plant families (mostly dicotyledons). It is a major pest of many crops. To better understand Spodoptera litura granulovirus (SpliGV), the nucleotide sequence of the SpliGV DNA genome was determined and analyzed. Methodology/Principal Findings The genome of the SpliGV was completely sequenced. The nucleotide sequence of the SpliGV genome was 124,121 bp long with 61.2% A+T content and contained 133 putative open reading frames (ORFs) of 150 or more nucleotides. The 133 putative ORFs covered 86.3% of the genome. Among these, 31 ORFs were conserved in most completely sequenced baculovirus genomes, 38 were granulovirus (GV)-specific, and 64 were present in some nucleopolyhedroviruses (NPVs) and/or GVs. We proved that 9 of the ORFs were SpliGV specific. Conclusions/Significance The genome of SpliGV is 124,121 bp in size. One hundred thirty-three ORFs that putatively encode proteins of 50 or more amino acid residues with minimal overlap were determined. No chitinase or cathepsin genes, which are involved in the liquefaction of the infected host, were found in the SpliGV genome, explaining why SpliGV-infected insects do not degrade in a typical manner. The DNA photolyase gene was first found in the genus Granulovirus. When phylogenic relationships were analyzed, the SpliGV was most closely related to Trichoplusia ni granulovirus (TnGV) and Xestia c-nigrum granulovirus (XecnGV), which belong to the Type I-granuloviruses (Type I-GV).

Bumblebee Venom Serine Protease Increases Fungal Insecticidal Virulence by Inducing Insect Melanization

Insect-killing (entomopathogenic) fungi have high potential for controlling agriculturally harmful pests. However, their pathogenicity is slow, and this is one reason for their poor acceptance as a fungal insecticide. The expression of bumblebee, Bombus ignitus, venom serine protease (VSP) by Beauveria bassiana (ERL1170) induced melanization of yellow spotted longicorn beetles (Psacothea hilaris) as an over-reactive immune response, and caused substantially earlier mortality in beet armyworm (Spodopetra exigua) larvae when compared to the wild type. No fungal outgrowth or sporulation was observed on the melanized insects, thus suggesting a self-restriction of the dispersal of the genetically modified fungus in the environment. The research is the first use of a multi-functional bumblebee VSP to significantly increase the speed of fungal pathogenicity, while minimizing the dispersal of the fungal transformant in the environment.

Functional Characterization of Autographa californica Multiple Nucleopolyhedrovirus ORF43 and Phenotypic Changes of ORF43-Knockout Mutant

ORF43 (ac43) of Autographa californica multiple nucleopolyhedrovirus (AcMNPV) is a highly conserved baculovirus gene of unknown function. To investigate the role of ac43 in the baculovirus lifecycle, we constructed an ac43-deleted mutant AcMNPV, Ac43KO. After transfection into Spodoptera frugiperda cells, Ac43KO produced polyhedra much larger in size than those of wild-type AcMNPV. Interestingly, some of the nucleocapsids were singly enveloped in the polyhedrin matrix while the nucleocapsids of AcMNPV are known to be multiply enveloped. Furthermore, Ac43KO led to a defect in the transcription and expression of polyhedrin, which resulted in reduced occlusion body production. However, Ac43KO did not affect production of budded virus as there was no remarkable difference in budded virus titer. These results suggest that ac43 plays an important role in the expression of polyhedrin, the morphogenesis of occlusion body, and the assembly of virions occluded in occlusion bodies.

Existence of lysogenic bacteriophages in Bacillus thuringiensis type strains

We screened the existence of bacteriophages in 67 Bacillus thuringiensis type strains by phage DNA extraction and PCR using phage terminase small subunit (TerS)-specific primers to the supernatants and the precipitated pellets of Bt cultures, and by transmission electron microscopy. The various bacteriophages were observed from the supernatants of 22 type strains. Ten type strains showed the extracted phage DNAs and the amplified fragment by TerS PCR but 12 type strains showed only the phage DNAs. Their morphological characteristic suggests that they belong to Family Siphoviridae which had a long tail and symmetrical head.