A strain of Bacillus thuringiensis, named Bt 1-3, was isolated from Korean soil sample and it showed high insecticidal activity against Plutella xylostella. Bt 1-3 was deterimined to belong to ssp. aizawai (H7) by an H antiserum agglutination test and produced bipyramidal-shaped crystal proteins. PCR analysis with specific cry gene primers showed that Bt 1-3 contained cry1Aa, cry1Ab, cry1C, cry1D and cry2Ab genes. In addition, this isolate showed high uptake rate of foreign plasmid by electroporation. Based on these characteristics of Bt 1-3, we tried to construct a spore-free Bt 1-3 mutant by knock-out sigG gene, which is known as a key transcription factor during sporulation. First, we constructed a basal vector, named pDST, consisting of erythromycin resistant gene (EmR), partial polyhedrin gene and temperature sensitive origin of replication gene (Orits). Subsequently, according to the chromosomal DNA sequence of Bt subsp. konkukian 97-27, we amplifed upstream and downstream regions of Bt 1-3 sigG, and cloned into pDST (pDST-G). So far, several EmR colonies were obtained by electroporating into the wildtype Bt 1-3 and crossover by homologous recombination is going on.

The complete genomic nucleotide sequence of the Spodoptera litura multicapsid nucleopolyhedrovirus (SlMNPV) isolated in Korea, SlMNPV-K1, was determined. It was 137,435 bp long, with a 55.4 % A+T content and contained 132 putative open reading frames (ORFs) of 150 nucleotides or larger that showed minimal overlap. The 132 putative ORFs covered 87.7% of the genome. Among these, 131 ORFs were are homologous to genes identified in previously reported SlMNPV genome which consisted 139,342 bp and contained 141 putative ORFs. However, arrangement of some ORFs were somewhat different from each other. Even though the SlMNPV-K1 genome is smaller than that of previously reported SlMNPV genome and had lesser predicted ORFs, the main functional genes were all conserved. When the phylogenic relationship was analyzed using the nucleotide sequence of polyhedrin gene, SlMNPV-K1 was most closely related to Lymantria dispar multicapsid nucleopolyhedrovirus (LdMNPV) which were belonged to Group Ⅱ nucleopolyhedrovirus.

To develop an improved baculovirus insecticide with additional advantages, a novel recombinant baculovirus, AcB5B-AaIT was constructed. B. thuringiensis crystal protein gene (cry1-5) and insect-specific neurotoxin gene (AaIT) were introduced into Autographa californica nucleopolyhedrovirus genome by fusion of polyhedrin-cry1-5-polyhedrin under the control of polyhedrin (polh) gene promoter, and AaIT under the control of early promoter of ORF3004 from Cotesia plutellae bracovirus, respectively. About 150 kDa of Polyhedrin-Cry1-5-Polyhedrin fusion protein expressed by AcB5B-AaIT was occluded into the polyhedra produced by the recombinant virus, and activated as about 65 kDa of crystal protein when treated with gut-juice of Bombyx mori. The AcB5B-AaIT showed about 50% reduced LT50 value compared to that of the recombinant virus, Ap1Ac, expressing Cry1Ac against Plutella xylostella larvae. In addition, Spodoptera exigua larvae fed the recombinant polyhedra of AcB5B-AaIT showed about 4 fold higher refusing diet effect compared S. exigua larvae fed the recombinant polyhedra of the recombinant virus, Ap1C, expressing Cry1C. AcB5B-AaIT could be transferred to wild-type baculovirus along with serial passage by the homologous recombination between two polyhedrin genes contained in polh-cry1-5-polh fusion protein gene. These results suggested that the novel recombinant baculovirus, AcB5B-AaIT, could be applied as advanced viral insecticide.