Effects of the 20kDa Protein Gene on Expression of Pesticidal Crystal Protein Gene in Wild-type Bt Strains

摘要

To know the effect of 20kDa protein from Bti on expression of pesticidal crystal protein and pesticidal activity in wild-type Bt strains, the recombinant vector, pBMB20 and pBMB82 containing 20kDa protein gene were constructed and transformed by electroporation into both wild-type Bt strains YBT-1520 and YBT803-1. The transformants, BMB20-4 and BMB21882 were respectively obtained. The protein analysis showed that the expression of BMB20-4 was two-fold higher than that of wild-type strains. Continuous accumulation of protein (130kDa protein) was observed in transformants BMB21882 containing 20kDa protein encoding gene during the whole sporulation stage, whease the yield of protein increased steeply before t_4 and then decreased quickly in wild strain YBT1520. At the end of the sporulation, about 1/3 protein was almost degraded in wild-type strain, which resulted from intracellular protease activity. It suggested that the 20kDa protein protected degration of protoxin from intracellular protease. In addition, bioassay showed that the toxicity of the transformants BMB20-4 and BMB21882 to P. xylostalla increased by 26.7% and 14% of recipient strains YBT803-1 and YBT1520 respectively.