A δ-endotoxin encoded in Pseudomonas fluorescens displays a high degree of insecticidal activity

Abstract

The short field-life of Bacillus thuringiensis (Bt) insecticidal crystal protein has limited its use. When the Bt toxin is produced in Pseudomonas fluorescens it can be encapsulated and retain its effectiveness for two to three times longer than other Bt formulations. In order to improve Bt expression, we have synthesized cryIA(c) Bt δ-endotoxin encoding region (GenBank AF537267) according to the usage codon of P. fluorescens and transformed the Bt toxin expression cassette into P. fluorescens strains. T7 RNA polymerase and the T7 promoter system were used to control expression of Bt toxin. SDS-PAGE and Western blotting assay revealed that the δ-endotoxin was expressed as 8% of the total protein in P. fluorescens. In in vitro tests, release of toxin from dead bacteria was demonstrated. Supplementation of diets with Bt toxin-containing Pseudomonas bacterium resulted in high mortality of cabbage butterfly (Pieris brassicae) larvae.