Abstract：Bacillus thuringiensis WB9, isolated from Wuyi Mountain of China, showed high insecticidal activity against several agricultural pests and was identified for cry2Ac gene by PCR-RFLP. According to the published sequences of cry2 genes, a pair of primers was designed for full length DNA cloning of cry2Ac gene by PCR using the plasmid DNA of WB9 isolate as the template. Subsequently, the amplified fragment of cry2Ac gene was inserted into Escherichia coli cloning vector pMD18-T and sequenced. The gene had been registered in GenBank with accession number DQ361267 and designated as the novel gene cry2Ac4 by International Nomenclature Committee of Bt. An expression plasmid pHT2Ac was constructed by subcloning the cry2Ac4 gene into shuttle expression vector pHT315. pHT2Ac was transformed into Escherichia coli SCS110 and acrystalliferous Bt HD73 Cry-, respectively. SDS-PAGE analysis showed that the cry2Ac4 gene could be expressed as 70 kD peptide. In addition, square crystal was observed. The bioassay results indicated that the Cry2Ac toxic protein was distinctly insecticidal activity against Bactrocera dorsalis Hendel larvae. However, it exhibited little toxicity towards the larvae of Plutella xylostella and Culex fatlgans.
