Expression of mel gene improves the UV resistance of Bacillus thuringiensis

To improve ultraviolet (UV) resistance of Bacillus thuringiensis for increasing the duration of the Bt product applied in the field, a genetically engineered strain Bt TD841 that produced both melanin and Cry1A protein was constructed, and its UV resistance was evaluated in the laboratory.

Melanin quantitative analysis revealed that the recombinant strain Bt TD841 could synthesize 0.15 mg melanin ml(-1) sporulated culture. Atomic force microscopy confirmed the production of diamond crystal and SDS-PAGE results showed the expression of the 130 kDa Cry1A protein. Bioassay results demonstrated that the LC(50) value of Bt TD841 was 3.69 microl ml(-1) against Helicoverpa armigera and the UV resistance of this recombinant was enhanced 9.7-fold compared to its parental strain Bt HC42 after 4-h UV irradiation.

Expression of the mel gene can significantly increase UV resistance of B. thuringiensis.

This is the first report on genetically engineered Bt strain with co-expression of melanin and the insecticidal crystal proteins gene, and the results may offer a practical solution for improving the photoprotection of Bt products in field application.