Expression of the crylAcl Gene Under the Control of the Native or the $\alpha$-Amylase Promoters in an Acrystalliferous Bacillus thuringiensis Strain

Expression of the crylAcl gene of an acrystalliferous Bacillus thuringiensis strain under the control of the native or $\alpha$-amylase gene promoter was investigated. The crylAcl gene was cloned in a B. thuringiensis - E. coli shutle vector, pHT3101, undder the control of either the native promoter (pProAc) or the $\alpha$-amylase promoter from Bacillus subtilis (pAmyAc). These two recombinant plasmids were successfully expressed in B. thuringiensis subsp. kurstaki Cry B. The first transformant (ProAc/CB), harboring pProAc, expressed an about 130 kDa protein begining 24 hr after inoculations just as in the case of the wild type of B. thuringiensis subsp. kurstaki HD-73. The second pAmyAc-transformant (AmyAc/CB) began to express the gene just 6 hr after inoculation, but Western analysis showed that the activity of the $\alpha$-amylase promoter was relatively weaker than that of the native promoter. As expected, their toxicity against Plutella xylostella larvae was dependent on the amount of Cry1Acl protein expressed.