Screening of Bacillus thuringiensis Strains with High Toxicity against Spodoptera exigua and Identification of a New cry2Ah5 Gene

doi:10.16409/j.cnki.2095-039x.2016.03.018

Abstract

Abstract: According to the results of bioassay, five Bacillus thuringiensis strains with high toxicity against Spodoptera exigua were obtained. The median lethal concentrations (LC₅₀) of these strains ranged from 0.556 to 0.914 mg/mL spores and crystals mixture, and the strain GS3 had the highest toxicity with a LC₅₀of 0.556 mg/mL. These strains contained cry1Aa, cry1Ab, cry1La, cry1Ia, cry1Ib, cry2Ab, cry2Ad, cry2Ah, cry7Ab and cry9Ba genes, forming globular or bipyramidal in different sizes crystals. All of them expressed 60 kD and 130-150 kD proteins, and two of them also lowly expressed 80 kD proteins. A new cry2A gene identified from the strain GS3 with an accession number of KT692984 was designated cry2Ah5 by the International Nomenclature Committee of Bt δ-endotoxin genes. Sequence analysis showed that cry2Ah5 contained a 1899 bp open reading frame, which encoded a 70.8 kD protein composing of 632 amino acids. The pI of this protein was 8.18. The Cry2Ah5 protein showed 97%-99% sequence identity with other Cry2Ah. The cry2Ah5 gene expressed a 70 kD protein in Escherichia coli BL21 (DE3) corresponding to the predict molecular weight. Our research provided more strains and genetic resources for the biological control of S. exigua.

Key words: Bacillus thuringiensis, Spodoptera exigua, cry gene, cry2Ah5

CLC Number:

S433
S476.11

ZHANG Yakun, ZHAO Dan, GUO Wei, WANG Wei, LU Xiujun, LI Ruijun. Screening of Bacillus thuringiensis Strains with High Toxicity against Spodoptera exigua and Identification of a New cry2Ah5 Gene[J]. journal1, 2016, 32(3): 414-420.

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