Identification, expression, and insecticidal activity analysis of a novel cry toxin gene from Bacillus thuringiensis...

Bacillus thuringiensis (Bt) is a widely used biological control agent in agriculture, known for its insecticidal crystal proteins (Cry toxins) that act specifically against target insect pests. In this study, a wild-type Bt strain, Gxun777-1, was isolated from soil samples collected in Wuzhishan, Hainan Province, China. Microscopic observations revealed that the strain produces diverse parasporal crystal morphologies.Bioassays showed that the total protein preparation from Bt Gxun777-1 exhibited clear toxicity against second-instar Ostrinia furnacalis larvae, with an LC₅₀ of 148.64 µg/mg (95% CI: 117.72-183.59 µg/mg). Whole-genome sequencing and database alignment identified two putative cry-type toxin genes. Among them, p1G_81 shared only 24.4% amino acid identity with Cry1Na2. Functional validation through gene cloning and heterologous expression demonstrated that the recombinant P1G_81 protein exhibited high toxicity against O. furnacalis, with an LC₅₀ of 0.852 µg/mg in the soluble fraction. Bioinformatic analysis indicated that P1G_81 possesses a typical three-domain Cry toxin architecture and shows structural similarity to Cry7Ca1. These findings expand the diversity of Bt pesticidal genes and provide candidates for Bt biopesticide development and insect resistance management.