Interactions between molecular chaperone P20 and Cyt2Ba7 toxin inBacillus thuringiensis

P20 or 20-kilodalton protein is a molecular chaperone protein inBacillus thuringiensis(Bt) which can increase yields and facilitates crystal formation of various insecticidal crystal proteins (ICPs). In previous studies, aB. thuringiensisinsecticidal protein gene,cyt2Ba7, was cloned, expressed but its expression level is very low inB. thuringiensis. In this study, various expression vectors were constructed by incorporatingp20 in forward or reverse direction in the upstream ofcyt2Ba7 and transformed into aB. thuringiensisacrystalliferous strain 4Q7. The result showed that in the presence of P20, the expression of Cyt2Ba7 was significantly increased. Especially whenp20 gene was reversely inserted in the upstream ofcyt2Ba7 gene, the expression of Cyt2Ba7 was increased ∼3.2 times meanwhile more and bigger crystals were observed under electron microscopy. By using purified Cyt2Ba7, P20 protein and P20-specific antiserum, immunoblotting and ligand blot analysis demonstrated a strong binding affinity between P20 and Cyt2Ba7. These results reveal that P20 can promote the crystal formation and enhance the expression of Cyt2Ba7 as a molecular chaperone, which can be a powerful tool to boost the ICPs production inB. thuringiensisand help develop more effective insect control strategies.