Bacillus thuringiensis 1-3 (Bt 1-3) which was isolated from a Korean soil sample showed high insecticidal activity against Aedes aegypti as well as Plutella xylostella. The isolate was determined to belong to ssp. aizawai (H7) type by an H antiserum agglutination test and produced bipyramidal-shaped crystal proteins with a molecular weight of 130 kDa. PCR analysis with cry gene specific primers showed that Bt 1-3 contained cry1Aa, cry1Ab, cry1C, cry1D and cry2A gene, differing from spp. aizawai (reference strain) which contains cry1Aa, cry1Ab, cry1C and cry1D. We modified the plasmid capture system (PCS) to clone plasmid from Bt 1-3 through in vitro transposition. Fifty-three clones were acquired and their sizes were approximately 10 kb. Based on the sequence analysis, they were classified according to similarities with four known Bt plasmids, pGI3, pBMB175, pGI1 and pGI2, respectively. One of pGI3-like clones, named as pBt1-3, was fully sequenced and its 20 putative open reading frames (ORFs), Rep-protein, double-strand origin of replication (dso), single-strand origin of replication (sso), have been identified. The structure of pBt1-3 showed high similarity with pGI3 which is one of rolling-circle replication (RCR) group VI family.

Through an application of plasmid capture system (PCS) to Bacillus thuringiensis plasmid DNAs, we acquired 21 polymorphic clones of putative genomic DNA of bacteriophage. The genome size of phage 1-3 (PhBT1-3) was determined to be 46,517 base pairs (bp) with 35.43% G + C content and 83% coding region. Sixty-five putative open reading frames (ORFs) with more than 50 codons were found in the new phage genome. In accordance with this genome finding, the phage particles and its DNA were confirmed from the supernatant of B. thuringiensis 1-3. Morphological characterization and infectivity assay demonstrated that PhBT1-3 belongs to the family Siphoviridae and it showed infectivity to three B. thuringiensis type strains, galleriae, entomocidus, and morrisoni. Based on these results, we screened the existence of phages in B. thuringiensis type strains by PCR with terminase small subunit-specific primers. Ten of 67 type strains showed PCR products and the similarity of those putative amino acids was more than 70%. Furthermore, we verified the existence of various shaped phages from the supernatants of 10 B. thuringiensis type cultures. In conclusion, we characterized a putative genome of phage, PhBT1-3 from B. thuringiensis 1-3, and confirmed the distribution of phages in the group of 67 B. thuringiensis type strains.

A new Bacillus thuringiensis isolate 19-22 (Bt 19-22) exhibited high anti-fungal activity against barley powdery mildew (Blumeria graminis f. sp. hordei). The cry gene content of Bt 19-22 comprised cry1Aa, cry1Ab, cry1Ac and cry1D which have high insecticidal activity against lepidopteran larvae. We tried to confer a dipteran insecticidal activity to Bt 19-22 for constructing a recombinant strain which has multiple functions, anti-fungal and dual insecticidal activity. The insecticidal cry11Aa gene of B. thuringiensis was constructed under cry1Ac promoter in an E. coli-B. thuringiensis shuttle vector (pPro11A). The plasmid, pPro11A was introduced into Bt 19-22 isolate by electroporation and four transformants which had different cry gene contents were identified by PCR with cry11Aa and cry1-type specific primers. Among them, a Bt 19-22 transformant (11A/19-22 No. 7) expressed Cry11A protein (approximately 70 kDa) successfully without change of its inherent characteristics such as Cry protein expression and antifungal activity. The insecticidal activity of 11A/19-22 No. 7 was checked against Plutella xylostella and Culex pipiens. These results suggests that the recombinant strain shows dual insecticidal activity against lepidopteran and dipteran larvae as well as antifungal activity.

This study was conducted to investigate the insecticidal capacity of several recombinant baculoviruses to P. xylostella and S. exigua larvae. NeuroBactrus was constructed as follows: the cry1-5 of Bacillus thuringiensis 2385-1 was inserted into Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV) genome by fusion of polyhedrin-cry1-5-polyhedrin under the control of polyhedrin gene promoter, and insect-specific neurotoxin from the scorpion Androctonus australis (AaIT) under the control of early promoter from Cotesia plutellae bracovirus was introduced by fusion of orf603 partial fragment in the opposite direction of polyhedrin gene, respectively. Other recombinant baculoviruses derived from the NeuroBactrus - NBt-DelA (deleted AaIT), NBt-Del5 (deleted cry1-5), and NBt-DelA5 (deleted AaIT and cry 1-5) - were manufactured in serial passages in vitro. The data were analyzed by SPSS. The value of LC50 was lower when P. xylostella larvae fed on cabbage coated with NeuroBactrus (4068.4) than when it fed on cabbage coated with AcMNPV (4.5x106). Survival time (ST50) of P. xylostella larvae (2.54days) was shorter when it fed on cabbage coated with NeuroBactrus than when it fed on cabbage coated with other recombinant baculoviruses (7.54days, 7.68days, and 8.26days) and AcMNPV (9.67days). S. exigua larvae presented the same results.

Bacillus thuringiensis 1-3 (Bt 1-3), belonging to subsp. aizawai (H7), showed different characteristics in plasmid profiles from type strain and had cry2A gene in addition to cry1Aa, cry1Ab, cry1C and cry1D. To clone its plasmids and construct E.coli-Bt shuttle vector, we constructed the plasmid capture system (PCS) by inserting attB sites including lacZ between transposable elements (designated as pPCS-Troy). Through in vitro transposition with total plasmids DNA of Bt 1-3, 53 clones were acquired and their sizes were approximately 10 kb. Based on the sequence analysis, they were classified in four groups showing similarities with four known Bt plasmids, pGI3, pBMB175, pGI1 and pGI2, respectively. One of pGI3-like clones, named as pBt1-3, was fully sequenced and its putative open reading frames (ORFs), Rep-protein, double-strand origin of replication (dso), single-strand origin of replication (sso), have been identified. The structure of pBt1-3 showed high similarity with pGI3 which is one of rolling-circle replication (RCR) group VI family. As a donor for construction of shuttle vector, pDonr-attPEm vector harboring erythromycin resistant gene between attP sites was constructed. Through BP recombination with pPCS-Troy-cloned Bt plasmids and pDonr-attPEm, erythromycin resistant gene was transposed to Bt plasmids. This scheme proposes that in vitro transposition using pPCS-Troy and BP recombination using pDonr-attPEm can easily clone Bt plasmids and construct novel shuttle vectors.

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.

Plasmid capture systems (PCS) facilitate cloning and manipulation of circular double-stranded DNA. We recently developed an improved PCS (PCS-LZ) to clone relatively large DNA molecules of 30-150 kb. The PCS-LZ donor consists of a mini-F replicon and a kanamycin resistance marker between Tn7 left and Tn7 right ends. Both the replicon and marker gene of the PCS-LZ donor are transferred into target plasmid DNAs by in vitro transposition, followed by replication in E. coli. Colonies are tested for lacZ expression by blue/white screening. Circular DNAs were obtained from plasmids of Bacillus thuringiensis, genome segments of Cotesia glomerata bracovirus and polymorphic genomes of Autographa californica nucleopolyhedrovirus. PCS-LZ is a powerful tool for use in genomic analysis and mutagenesis in invertebrate pathology, and we are extending its application to include vertebrate research.

Previously, we found that expression by translational fusion of the polyhedrin (Polh)-green fluorescence protein (GFP) led to the formation of granular structures and these fluorescent granules were easily precipitated by high-speed centrifugation. Here, we developed an easy, fast, and mass purification system using this baculovirus expression system (BES). An enhanced GFP (EGFP) fused with Polh gene at the N-terminus including an adaptor and enterokinase (EK) site between Polh and EGFP was expressed in Sf9 cells. The cells infected by AcPolhEKA-EGFP produced fluorescent granules. The EGFP fusion protein was purified from granule-containing cells according to three steps; cell harvest, sonication and EK digestion. Through the final enterokinase digestion, EGFP was presented mainly in the supernatant (93.3%) and the supernatant also showed a pure EGFP band. These results suggest that the combined procedure of Polh fusion expression and enterokinase digestion can used for the rapid and easy purification of other proteins.

Bacillus thuringiensis, an entomopathogenic bacterium belonging to the B. cereus group, harbors numerous extra-chromosomal DNA molecules whose sizes range from 2 to 250 kb. In this study, we used a plasmid capture system (PCS) to clone three small plasmids from B. thuringiensis subsp. kurstaki K1 using PCS which were not found in B. thuringiensis subsp. kurstaki HD-1, and determined the complete nucleotide sequence of plasmid pK1S-1 (5.5 kb). Of the six putative open reading frames (ORF2-ORF7) in pK1S-1, ORF2 (MobK1) showed approximately 90% aa identity with the Mob-proteins of pGI2 and pTX14-2, which are rolling circle replicating group VII (RCR group VII) plasmids from B. thuringiensis. In addition, a putative origin of transfer (oriT) showed 95.8% identity with those of pGI2 and pTX14-2. ORF3 (RepK1) showed relatively low aa identity (17.8-25.2%) with the Rep protein coded by RCR plasmids, however. The putative double-strand origin of replication (dso) and single-strand origin of replication (sso) of pK1S-1 exhibited approximately 70% and 64% identities with those of pGI2 and pTX14-2. ORF6 and 7 showed greater than 50% similarities with alkaline serine protease, which belongs to the subtilase family. The other 2 ORFs were identified as hypothetical proteins. To determine the replicon of pK1S-1, seven subclones were contructed in the B. t huringiensis ori-negative pHT1K vector and were electroporated into a plasmid cured B. thuringiensis strain. The 1.6 kb region that included the putative ORF3 (Rep1K), dso and ORF4, exhibited replication ability. These findings identified pK1S-1 as a new RCR group VII plasmid, and determined its replication region.

Bacillus thuringiensis 1-3 (Bt 1-3), belonging to subsp. aizawai (H7), showed different characteristics in plasmid profiles and had cry2A gene in addition to cry1Aa, cry1Ab, cry1C and cry1D. This strain exhibited dual insecticidal activity against Aedes aegypti as well as Plutella xylostella. Recently, we improved the donor-s of plasmid capture system (PCS) by inserting attB sites including lacZ between transposable elements (designated as pPCS-Troy), to construct E.coli-Bt shuttle vector. Through in vitro transposition with total plasmids DNA of Bt 1-3, 53 clones were acquired and their range of sizes were approximately 10 kb. Based on the sequence analysis, they were classified in 4 groups showing similarity with 4 known plasmids, pGI1, pGI2, pGI3 and pBMB175, respectively. One of pGI3-like clones was fully sequenced and its open reading frames were analyzed. As a donor for construction of shuttle vector, pDonr-attPEm vector harboring erythromycin resistant gene between attP sites was constructed. Through BP recombination with pPCS-Troy-cloned Bt plasmids and pDonr-attPEm, erythromycin resistant gene was transposed to Bt plasmids. This scheme proposes that in vitro transposition using pPCS-Troy and BP recombination using pDonr-attPEm can easily construct novel shuttle vectors with any Bt plasmids and this combined procedure can introduce foreign gengs into various circular DNA molecular.

A novel recombinant baculovirus, NeuroBactrus, was constructed to develop an improved baculovirus insecticide with additional beneficial properties such as higher insecticidal activity and recovery to wild-type baculovirus. For this, Bacillus thuringiensis crystal protein gene (cry1-5) was introduced into Autographa californica nucleopolyhedrovirus (AcMNPV) genome by fusion of polyhedrincry1- 5-polyhedrin under the control of poyhedrin gene promoter. In the opposite direction of this fusion gene, an insect-specific neurotoxin gene (AaIT) under the control of early promoter from Cotesia plutellae bracovirus was introduced by fusion of orf603 partial fragment. Western hybridization and confocal microscopy revealed that AaIT neurotoxin and Polyhedrin-Cry1-5-Polyhedrin fusion protein expressed by the NeuroBactrus and that the fusion protein occluded into the polyhedra. In addition, the fusion protein was activated as about 65 kDa of crystal protein when treated with trypsin. The NeuroBactrus showed high level of insecticidal activity against Plutella xylostella larvae and significant reduction in median lethal time (LT50) against Spodoptera exigua larvae compared to those of wild-type AcMNPV. Re-recombinants derived from the NeuroBactrus, NBt-Del5 (deleted cry1-5), NBt-DelA (deleted AaIT) and NBt-Del5A (deleted cry1-5 and AaIT; wild-type baculovirus) were generated in serial passages in vitro and in vivo. These results suggested that the NeuroBactrus could be transferred to wild-type baculovirus along with serial passages by the homologous recombination between two polyhedrin genes and two partial orf603 fragments.

Plasmid capture system (PCS) was developed for easy cloning and manipulation of circular double-stranded DNA from various sources. Recently, we improved PCS system (named PCS-LZ) to clone relatively large-sized DNA molecules (30-150 kb). PCS-LZ donor consists of a Mini-F replicon and a kanamycin resistance marker between Tn7L and Tn7R regions. Both replicon and marker gene of PCS-LZ donor are transferred into target plasmid DNAs by in vitro transposition and the transposed DNAs can replicate in E. coli cells by transformation. White/blue screening by LacZ expression is also available to avoid backgrounds. Up to now, we acquired various circular DNA clones from four sources such as plasmids of B. thuringiensis, bacteriophage genome isolated from B. thuringiensis, genome segments of Cotesia glomerata bracovirus, and polymorphic genomes of Autographa californica nucleopolyhedrovirus. Among them, interestingly, the genome clones of bacteriphage (Ph1-3) were screened from the PCS transposition with plasmids of B. thuringiensis 1-3 strain. The genome of Ph1-3 was fully sequenced (46517 bp) and open reading frames were analyzed. In accordance with this genome finding, the phage particles and its DNA were confirmed from the supernatant of B. thuringiensis 1-3. Ph1-3 showed infectivity to B. thuringiensis type strains such as subsp. galleriae, entomocidus, and morrisoni. Based on these results, we screened the existence of phage in B. thuringiensis type strains by PCR with terminase small subunit-specific primers. Ten of 67 type strains showed PCR products and their sequence similarity was more than 70%. Conclusively, we expect this PCS-LZ system would be a powerful tool for genomic analysis and mutagenesis study at the area of invertebrate pathology and further its application will be enlarged to the vertebrate pathology area.

Bacillus thuringiensis 1-3 (Bt 1-3), isolated from Korean soil sample, showed high insecticidal activity against Plutella xylostella. Recently, we improved plasmid capture system donor-s (PCS-S) by inserting attB sites including lacZ between transposable elements (designated as pTroy), to reduce background and construct E. coli-Bt shuttle vector. Through in vitro transposition with total plasmid DNA of Bt 1-3, at least 6 different size plasmids of Bt 1-3 were cloned. Among them, 47 clones which have approximately 10 kb plasmid in size were sequenced and 5 contigs were assembled. These contigs showed partial similarity with two known plasmids, pGI3 or pBMB175, separately. These cloned plasmids will acquire erythromycin resistance by BP recombination reaction with pDonrattPEm vector. After transformation into Bt cells, final erythromycin resistant Bt cell might contain novel E. coli-Bt shuttle vector. This scheme proposes that pTroy and pDonr-attPEm system can easily construct new shuttle vector by in vitro transposition, BP reaction, and erythromycin selection with any Bt plasmids.

Recently, we constructed a novel recombinant baculovirus genome, bEasyBac, enabling easy and fast generation of pure recombinant baculovirus without any purification step. In the bEasyBac, bacteriophage lambda site-specific attachment (att) sites were introduced to facilitate the generation of recombinant viral genome by in vitro transposition. Moreover, extracellular RNase gene from Bacillus amyloliquefaciens, barnase, was expressed under the control of Cotesia plutellae bracovirus (CpBV) ORF3005 early promoter to negatively select against non-recombinant background. The bEasyBac could replicate in host insect cells only when the barnase gene was replaced to gene of interest by in vitro transposition. When the bEasyBac was transposed with pDualBac-EGFP and the EGFP expression efficiency along passage was investigated, the resulting recombinant virus, EasyBac-EGFP, showed comparable level of EGFP expression efficiency with the plaque-purified recombinant virus, AcEGFP, which was constructed using bAcGOZA system, whereas, the non-purified AcEGFP showed quite reduced level of EGFP along passages. Moreover, no non-recombinant backgrounds were detected from unpurified EasyBac-EGFP stocks. Based on these results, high-throughput condition for generation of multiple recombinant viruses in a time was established. These results suggest that the bEasyBac has an effective benefit enabling for high-throughput baculovirus expression vector without purifying recombinant virus.

The nucleotide sequence of the Spodoptera litura granulovirus (SlGV) genome was determined and analysed. It was 124,121 bp long, with a 61.2% A+T content and contained 133 putative open reading frames (ORFs) of 150 nucleotides or larger. The 133 putative ORFs covered 86.3% of the genome. Among these, 29 ORFs were conserved in most completely sequenced baculovirus genomes, 44 were granuloviruses (GVs)-specific, 4 were nucleopolyhedroviruses (NPVs)-specific, and 56 were present in some NPVs and/or GVs. Especially, we proved that there were 9 SlGV-specific ORFs in 44 GV-specific ORFs by RT-PCR. Chitinase and cathepsin genes involved in the liquefaction of the infected hostwere not found in the SlGV genome, which explains why SlGV-infected insects do not degrade in a typical manner. When the phylogenic relationship was analyzed using the nucleotide sequence of granulin gene, SlGV was most closely related to Trichoplusia ni granulovirus (TnGV) and Xestia c-nigrum granulovirus (XcGV) which were belonged to TypeI granulovirus.

Bt crystal proteins, encoded by cry genes, are a group of insecticidal proteins unique in the Gram-positive and spore-forming bacterium, Bacillus thuringiensis. These cry genes are widely applied as one of the most successful candidates for constructing transgenic crops resistant to pest insects. In our previous report, we found Cry1-5 had high insecticidal activity against Spodoptera larvae although its amino acid sequences showed high similarity (95.6%) to those of Cry1Ac which had low activity. In comparison with Cry1Ac, Cry1-5 had 12 different residues on domain I and II. In order to convert these residues to Cry1-5 randomly, 10 mutagenic primers were designed. Through multi site-directed mutagenesis, we mutated the modified cry1Ac gene by plant codon usage in pOBI-Modcry1Ac based on cry1-5 and constructed 63 mutant cry genes. Among them, 10 mutant cry genes on domain II were selected and their recombinant proteins were expressed by baculovirus expression system. From bioassay results to P. xylostella and S. exigua, we found some mutants have high insecticidal activities to be applicable to transgenic crops.

To develop an advanced baculovirus insecticide with additional advantages, such as higher toxicity and recovering to wild-type baculovirus, a novel recombinant baculovirus, NeuroBactrus was constructed. Bacillus thuringiensis crystal protein gene (cry1-5) and an insect-specific neurotoxin gene (AaIT) were introduced into Autographa californica nucleopolyhedrovirus genome by fusion of polyhedrin-cry1-5-polyhedrin under the control of poyhedrin gene promoter, and by fusion of orf603 partial genes and AaIT under the control of early promoter of ORF3006 from Cotesia plutellae bracovirus. About 150 kDa of Polyhedrin-Cry1-5-Polyhedrin fusion protein expressed by NeuroBactrus was occluded into the polyhedra, and activated as about 65 kDa of crystal protein when treated with trypsin. RT-PCR analysis indicated that transcription of AaIT gene occurs by 2 h postinfection (p.i.) and increased at 16 h p.i.. NeuroBactrus showed high toxicity against Plutella xylostella larvae and significant reduction in median lethal time (LT50) against Spodoptera exigua larvae compared to those of wild-type AcNPV. Re-recombinants derived from NeuroBactrus, NBt-Del5 (deleted cry1-5), NBt-DelA (deleted AaIT) and NBt-Del5A (deleted cry1-5 and AaIT; wild-type baculovirus) were generated in serial passages in vitro. This result showed that the NeuroBactrus could be transferred to wild-type baculovirus along with serial passages by the homologous recombination between two polyhedrin genes and two partial orf603 genes.

A new Bacillus subtilis isolate showed high anti-fungal activities (more than 80% control efficacy) against several plant diseases such as rice blast (Magnaporthe grisea), tomato gray mold (Botrytis cinerea), tomato late blight (Phytophthora infestans) and wheat leaf rust (Puccinia recondita). We tried to confer an insecticidal activity to this B. subtilis isolate for constructing a recombinant strain which has dual functions, anti-fungal and insecticidal activity. The insecticidal cry1Ac gene of B. thuringiensis was constructed under its own promoter in a minimal E. coli-B. thuringiensis shuttle vector (pHT1K-1Ac). The plasmid, pHT1K-1Ac was introduced into B. subtilis isolate by electroporation and the transformant was confirmed by PCR with cry1Ac specific primers. B. subtilis transformant produced a parasporal inclusion in the cells as in B. thuringiensis and the size of that protein was appox. 130 kDa. The insecticidal activity of the transformant was checked against lepidopteran pest, Plutella xylostella. This result suggests that this recombinant B. subtilis strain shows the possibility of controlling harmful insect pests as well as plant fungal diseases simultaneously at one crop, and both culture broth and harvested cells of this strain can be used as individual biological control agents separately for integrated crop protection.

Bt crystal proteins, encoded by cry genes, are a group of insecticidal proteins unique in the Gram-positive and spore-forming bacterium, Bacillus thuringiensis. These cry genes are widely applied as one of the most successful candidates for constructing transgenic plants resistant to pest insects. In our previous report, we found Cry1-5 had high insecticidal activity against Spodoptera larvae although its amino acid sequences showed high similarity (97.9%) to those of Cry1Ab which had low activity. In comparison with Cry1Ac, Cry1-5 had 12 different residues in domain Ⅰ and domain Ⅱ, and we focused on domain Ⅰand domain Ⅱ regions and designed 10 mutagenic primers to change 12 residues. Through multi site-directed mutagenesis, we mutated the modified cry1Ac gene by plant codon usage in pOBⅠ-Mod-cry1Ac based on cry1-5 and constructed 63 various mutant cry genes. In the further study, we will express those mutant proteins as a fusion form with polyhedrin using baculovirus expression system and subsequently do bioassay to Spodoptera larvae.