A new cry1Ab-type gene, cry1Ab17, was cloned from Bacillus thuringiensis WB9 by PCR. Nucleotide sequenceindicated that the open reading frames (ORFs) consists of 3471 bases and encodes a protein of 1156 residueswith a calculated molecular weight of 130.5 kDa and an pI value of 5.04. Homology comparison revealed thatthe deduced amino acid sequence of Cry1Ab17 had 95.4% to 99.7% identity with those of the known Cry1Abproteins. The Cry1Ab17 was one residue longer than the known Cry1Ab (except for Cry1Ab2). Domain I (Tyr33 toArg253), II (Arg265 to Phe462), III (Asn464 to Thr610) of the Cry1Ab17 were 96.8%, 68.2% and 100% identical tothe corresponding domains of Cry1Aa. Additionally, the cry1Ab17 gene was expressed in Escherichia coli BL21under the control of T7 promoter and the Cry1Ab17 isolated from the culture medium was toxic to 3rd instarPlutella xylostella larvae.

In order to better understand the fundamental biology of Bacillus thuringiensis, a single oligonucleotide primer (50-CATSSCCATCAASYTAAVR-30) was used to investigate the distribution pattern of IS231 elements in B. thuringiensis by PCR. Theresults indicated that IS231 elements appeared in 20 standard strains and 107 of 111 China isolates. Three novel IS231, IS231J,IS231O and IS231Q, five variants and a mobile insertion cassette MICBth4 were cloned from eight standard strains of B. thuringiensis,respectively. Interestingly, BLAST analysis revealed that the 50 end of novel IS231J shared 99% identity in 495-bp with aDNA segment adjacent to the 30 end of B. thuringiensis vip1Ac gene (GenBank Accession No. AY245547). Two phylogenetic treesof IS231 elements were constructed and analyzed by neighbor-joining and UPGMA methods from PHYLIP 3.6b program,respectively.