A genetically modified broad-spectrum strain of Bacillus thuringiensis toxic against Holotrichia parallela, Anomala corpulenta and Holotrichia oblita

Abstract

Cry8Ea1 from Bacillus thuringiensis strain Bt185 has insecticidal activity against Holotrichia parallela. Cry8Ca2 from strain HBF-1 is effective against Anomala corpulenta. Cry8Ga1 from strain HBF-18 is toxic to H. oblita. Given the need to broaden the spectrum of B. thuringiensis, a broad-spectrum coleopteran active strain of B. thuringiensis, BIOT185, engineered to express multiple cry genes, including cry8Ea1, cry8Fa1 and cry8Ca2, was created by homologous recombination introducing the cry8Ca2 into the B. thuringiensis strain Bt185 by Liu et al. (Appl Microbiol Biotechnol 87:243-249, 2010). To further broaden the spectrum, an engineered B. thuringiensis strain BIOT1858G was constructed by introducing the recombinant plasmid pSTK-8G containing cry8Ga1 into the engineered B. thuringiensis strain BIOT185. PCR and Southern blotting demonstrated that the cry8Ga1 gene was transferred to the novel strain BIOT1858G. SDS-PAGE and RT-PCR confirmed the normal expression and transcription of the cry8Ga1 gene in addition to the cry8Ea1, cry8Fa1 and cry8Ca2 genes. Bioassays of BIOT1858G indicated that the recombinant strain broadened the spectrum against not only H. parallela susceptible to the Cry8E protein and A. corpulenta susceptible to the Cry8C protein but also H. oblita susceptible to the Cry8G protein. The pesticide could also decrease the cost of production and field labor.