Abstract: Bacillus thuringiensis strain Ly30, isolated from Lianyungang, Jiangsu Province, was highly toxic to several kinds of insect pests. Results of CAPS (cleaved amplified polymorphic sequences) analysis indicated that Ly30 contained the cry1Aa gene. According to the 5' and 3' end nucletiode sequence of the known cry1Aa gene, one pair of primers was designed and the full-length cry1Aa gene (3.5 kb) was thereby obtained by PCR amplification from strain Ly30. Sequencing analysis showed that this cry1Aa gene contained one open reading frame of 3 531 bp, and encoded 1 176 amino acid residues deduced from its nucletiode sequence with molecular mass of 133.2 kD. This gene was registered in GenBank (Accession number is AF384211) and designated as cry1Aa12, a novel cry gene, by the international Nomenclature Committee of Bt δ-endotoxin genes. Expression of cry1Aa12 had been performed by inserted it into E. coli expression vector Pkk233.2, and a 133.2 kD protein band could be easily detected by SDS-PAGE. Results of bioassays proved that the expression products of cry1Aa12 gene had high toxicity against two Plutella xylostella colonies,with LC₅₀ of 0.203 μg/mL，0.554 μg/mL respectively.

Key words: Bacillus thuringiensis Ly30, cry1Aa gene, clone, expression, pesticidal activity