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Volume 36 Number 3 Volume 36 Number 4 Volume 37 Number 1

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Research articles

ScienceAsia 36 (2010): 271-279 |doi: 10.2306/scienceasia1513-1874.2010.36.271

Analysis of the insecticidal crystal gene type 1 of Bacillus thuringiensis isolates affecting lepidopterans

Benjawan Lertwiriyawonga, Krit Pinthonga, Jariya Chanpaisaengb, Panapa Saksoonga, Pattana Srifah Huehnea,c,*

ABSTRACT:     The novel δ-endotoxin from Bacillus thuringiensis (Bt) is one of the alternative measures for lepidopteran pest control. A survey of 31 Bt isolates, obtained from Thailand and previously screened for their toxicity to lepidopterans, was conducted to determine the presence of cry1-type genes, using polymerase chain reaction - restriction fragment length polymorphism analysis. Seven distinct types of cry1 genes: cry1Aa, cry1B, cry1C, cry1Cb, cry1D, cry1E, and cry1F, were identified. The most common of the cry1-type genes was cry1Cb, followed by cry1C and cry1D, which covered 64.6, 48.4, and 25.8%, respectively. Besides cry1C and cry1Cb, two candidate cry genes, cry1E and cry1D, of isolate JC 190 (harbouring cry1C/1E), with cotton bollworm toxin specificity, showed 99% amino acid sequence identity to Cry1Ea of B. thuringiensis subsp. kenyae, while isolate JC 291 (containing cry1C/1Cb/1D), with Asian corn borer toxin specificity, harboured Cry1Dc, which exhibited only 84% amino acid sequence identity to Cry1Da of B. thuringiensis subsp. aizawai. The C-terminus of the JC291Cry1Dc possessed a unique sequence, 812-NVPIIPIISPW-822. Furthermore, the major differences between the 3D structure of Cry1Dc and Cry1Aa were confined to Domain II as three loop structures.

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a Department of Genetics, Faculty of Science, Kasetsart University, Bangkok 10900, Thailand
b Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok 10900, Thailand
c Laboratory of Biotechnology, Chulabhorn Research Institute, Bangkok 10210, Thailand

* Corresponding author, E-mail: fscipns@ku.ac.th

Received 2 Mar 2010, Accepted 30 Sep 2010