The cry1Ac gene of Bacillus thuringiensis ZQ-89 encodes a toxin against long-horned beetle adult

Aims: Bacillus thuringiensis is toxic to many insects including Coleopteran pests. However, there is no report that B. thuringiensis is toxic to the adults of long-horned beetle, Batocera horsfieldi, a pest of poplar trees. This work aims to select a B. thuringiensis strain toxic towards the adults of Asian long-horned beetle. Methods and Results: A total of 504 B. thuringiensis strains were tested for the insecticidal activity to B. horsfieldi adults by artificial feeding. A strain of ZQ-89 was found with a high toxicity to B. horsfieldi adults. The rectified lethal rate of ZQ-89 to beetle was 55·33%. Additionally, the body weight and egg-hatching rate of beetle, respectively, decreased by 2·22 and 19·62% after being fed with ZQ-89. Further investigation found that the pure parasporal crystal had high toxicity to beetle adults. The ZQ-89 crystal protein was purified and analysed by peptide-mapping fingerprint and found it was highly homologous to Cry1Ac protein. The crystal protein gene was cloned and named cry1Ac89. The cry1Ac89 gene and its promoter were inserted into the plasmid pHT304 and then transformed into B. thuringiensis acrystalliferous strain BMB171. SDS-PAGE analysis showed the BMB171-Cry1Ac89 recombinant strain successfully expresses a 133-kDa recombinant crystal protein with highly lethal activity to B. horsfieldi adults. Conclusions: The strain of ZQ-89 is highly toxic to the adults of long-horned beetle, and the crystal protein mainly contributes to the antipest role of this strain. The cry1Ac89 gene is a good candidate to be used for making transgenic trees or develop environment-friendly bioinsecticides against long-horned beetles such as B. horsfieldi in the future. Significance and Impact of the Study: It is the first report of a B. thuringiensis strain toxic to the adults of Asian long-horned beetle, and the Cry1Ac protein is also firstly reported to be toxic to Coleopteran pests.