Abstract: Expression of cry2Ac4 Gene from Bacillus thuringiensis (Bt) in Escherichia coli. The cry2Ac4 gene from Bt WB9 was amplified by PCR using plasmid DNA of pMD2Ac as the template and ET-F/ET-R as the specific primers. Subsequently, the amplified fragment of cry2Ac4 gene was inserted into a prokaryotic expression vector pET-29a. A recombinant expression vector pET-29a-cry2Ac4 was constructed and then transformed into Escherichia coli JM109. The plasmid of pET-29a-cry2Ac4 was recovered from the positive transformant, and further transformed into E. coli BL21 (DE3) pLysS to express the Cry2Ac4 protein by the induction of IPTG. SDS-PAGE showed that the molecular weight of the expressed product was about 70kDa.