Abstract：We identified for cry7Ab gene by PCR –RFLP from Bacillus thuringiensis HQ40.Then we designed a pair of special primer for full length DNA according to the published sequence of cry7A genes, successfully cloned it into Bt-E.coli shuttle vector pSTK and and transformed into acrystalliferous strain HD73cry-.The Bt engineering bacteria was named HD7Ab4.The gene had been registered in GenBank with accession number EU380678 and designated as the novel gene cry7Ab4 by International Nomenclature Committee of Bt.The SDS-PAGE showed that the cry7Ab gene could be expressed as 130 kD peptide.In addition, rhombohedral crystals was observed.Subsequently,we purified crystal proteins from Bt engineering bacteria HD7Ab4 and wild-type HQ40 respectively,we used the trypsin-activation of pro -endotoxins to do toxicity assay against a series of Orthopteran、 Lepidoptera、Coleoptera.The bioassay results indicated that the cry7Ab4 toxic protein had distinctly insecticidal activity against Colaphellus bowringi Baly.However,it exhibited little toxicity towards Oriental migratory locust ,Plutella xylostella、Spodoptera exigua、Ostrinia furnacalis、Pyrrhalta aenescens、Leptinotarsa decemlineate.
