| Popis: |
Three kinds of Bacillus thuringiensis serotype-subsp. Leesis(H33) strain YBT-833, subsp. Aizawai(H7) strain YBT-1416 and subsp. Kurstaki(H3ab) strain YBT-1535, which were isolated by our lab, are chosen as original strain to clone vegetative insecticidal protein gene. Southern hybridization showed that vip genes are all localized at roughly 4-5 kb size-fractionated XbaI fragments of total DNA from YBT-833, YBT-1416 and YBT-1535. Three subgenomic libraries containing the vip gene fragment, were constructed with pUC19 as vector. Then, three vegetative insecticidal protein gene vip83, vip14 and vip15 are obtained from the libraries through the methods of colony-blot-in-situ screening and enzyme-cut detection. Comparision of DNA sequence made out that only vip83 gene exist five different base pairs with known vip genes. Because the sequences of vip14 and vip15 are the same, two of the three genes, vip83 and vip14, were subcloned to shuttle vehicle pHT315 to get recombinant plasmids pBMB8901 and pBMB8902 in turn. The plasmids were separately transformed into vip Bt. receptors BMB171 and 4Q7 to obtain four engineered strains BMB8901-171, BMB8902-171, BMB8901-4Q7 and BMB8902-4Q7. SDS-PAGE results indicated that all recombinant strains express 88 kD vegetative insecticidal protein. Bioassay also showed that the proteins of genes vip83 and vip14 both have certain toxicity to Lepidopteran insect larvae such as Heliochis armigera, Spodotera exigua and Plutella xylostella. While the toxicity of vip protein from four engineered strains to Plutella xylostellas are highest, whose LC50 value is 28.6, 31.6, 45.4 and 37.6 microL/mL respectively. This study will contributed to construct high efficacy and wide spectrum engineered strains on theory and reality. |
