Proteinaceous insecticidal proteins, Cry proteins, from Bacillus thuringiensis (Bt) are insecticidal proteins that are highly active against several species of Lepidoptera. Thus, cry genes encoding these Cry proteins have been widely applied for construction of transgenic crops resistant to pest insects. In this study, through the 3D structure prediction and accompanying mutagenesis study for the Mod-Cry1Ac, 7 and 16 amino acid residues from domain I and II, respectively, responsible for its insecticidal activity against larvae of Spodoptera exigua and Ostrinia furnacalis were identified. We used site-directed mutagenesis to improve the insecticidal activity of Mod-Cry1Ac, resulted 31 mutant cry genes. These mutant cry genes encodes potent insecticidal proteins in the form of crystalline protoxins of 95 kDa. SDS-PAGE analysis of the recombinant polyhedra revealed that expressed Cry proteins was occluded into polyhedra and activated stably to 65 kDa by trypsin. When the insecticidal activities of these mutant Cry proteins against to larvae of P. xylostella, S. exigua and O. furnacalis were assayed, they showed higher or similar insecticidal activity compared to those of Cry1Ac and Cry1C. Especially, Mutant-N16 is considered to have the potential for the efficacious biological insecticide since it showed the highest insecticidal activity.

Crystals of proteinaceous insecticidal proteins, Cry proteins, produced by Bacillus thuringiensis (Bt) have been generally used to control insect pests. In this study, through the 3D structure prediction and accompanying mutagenesis study for the Mod-Cry1Ac, 7 and 16 amino acid residues from domain I and II, respectively, responsible for its insecticidal activity against larvae of Spodoptera exigua and Ostrinia furnacalis were identified. To construct novel cry genes with enhanced insecticidal activity, we randomly mutated these 23 amino acid sequences by in vitro muti site-directed mutagenesis, resulting in totally 24 mutant cry genes. For further characterization, these mutant cry genes were expressed as a fusion protein with polyhedrin using baculovirus expression system. SDS-PAGE analysis of the recombinant polyhedra revealed that expressed Cry proteins was occluded into polyhedra and activated stably to 65 kDa by trypsin. When the insecticidal activities of these mutant Cry proteins against to larvae of P. xylostella and S. exigua were assayed, they showed higher or similar insecticidal activity compared to those of Cry1Ac and Cry1C. Especially, among them Mutant-N16 showed the highest insecticidal activity against to both of P. xylostella and S. exigua. Therefore, Mutant-N16 is considered to have the potential for the efficacious biological insecticide.

Varieties of Bacillus thuringiensis (Bt) crystal proteins, Cry proteins, have so far been found as one of the most successful biological control agents which are safe to natural environments for a long time. Recently, cry genes encoding these Cry proteins have been widely applied for construction of transgenic crops resistant to pest insects. In this study, through the 3D structure prediction and accompanying mutagenesis study for the Mod-Cry1Ac, 7 and 16 amino acid residues from domain I and II, respectively, responsible for its insecticidal activity against larvae of Spodoptera exigua and Ostrinia furnacalis were identified. To construct novel cry genes with improved insecticidal activity, we randomly mutated these 23 amino acid sequences by in vitro muti site-directed mutagenesis, resulting in totally 24 mutant cry genes. For further characterization, these mutant cry genes were expressed as a fusion protein with polyhedrin using baculovirus expression system. SDS-PAGE analysis of the recombinant polyhedra revealed that expressed Cry proteins was occluded into polyhedra and activated stably to 65 kDa by trypsin. In the further study, we plan to investigate their insecticidal activity against Plutella xylostella, S. exigua and O. furnacalis larvae.

Background : This study was carried out to provide the basic data for selection of excellent resources and true seeds of southern medicinal plant (Camellia japonica). Methods and Results : Camellia japonica seedlings (measure in October, seeding in May) were 7.4 leaves, 1.0 g leaf dry weight, 6.7 ㎝ stem length, 2.9 ㎜ stem diameter, 0.3 g stem dry weight, 17.3 ㎝ root length, 1.0 g root dry weight, 2.0 g plant dry weight and 1.4. T/R ratio. Leaf number, leaf dry weight, stem diameter and root dry weight were higher than average after 1.21 g of seed weight. Stem length was higher than average after 1.01 g of seed weight, plant dry weight was higher than average after 0.81 g of seed weight, and stem dry weight was higher than average after 0.61 g of seed weight. Seedling growth was good when the seeds were heavy, and T/R ratio tended to decrease when the seeds were heavy. Conclusions : In order to mass-produce of seedlings using Camellia japonica seeds, it was necessary to specify the weight and size of the seeds.

Background : This study was carried out to provide the basic data for selection of excellent resources and true seeds of southern medicinal plant (Camellia japonica). Methods and Results : The germination rate at room temperature and 4℃ dry storage did not show a tendency according to seed weight. The germination rate of 4℃ wet sand storage increased with seed weight but showed very low germination rate at 120 days of storage. The germination rate at 4℃ wet filter paper storage was higher than 80% in 60 days, 90 days and 120 days storage, and there was no difference in germination rate with seed weight. The mean number of germination days was about 30 days in average at room temperature and 4℃ dry storage, but wet storage (sand, filter paper) was short as about 13 days. Conclusions : The seeding of Camellia japonica seeds (last autumn harvest) in the spring of the next year was evaluated as the most efficient way to 4℃ wet filter paper storage