Expression of the cry11A gene of Bacillus thuringiensis ssp. israelensis in Saccharomyces cerevisiae

The complete cry11A region gene of Bacillus thuringiensis ssp. israelensis was fused in frame to the 3' end of the GST gene under the control of the Saccharomyces cerevisiae HXK1 promoter. The fusion protein GST-cry11A was expressed in S. cerevisiae strain AMW13C+. The fusion gene GST-cry11A was expressed when yeast cells were grown on galactose and a nonfermentable medium containing ethanol as carbon and energy source. When the cells were grown in glucose, mannose, fructose, or glycerol as carbon sources, the GST-cry11A gene was repressed. Thus, a regulated expression in accordance with the regulatory activity of the HXK1 gene promoter has been detected. The GST-cry11A fusion protein was detected in the transformed yeasts as a soluble protein. The fusion protein was purified by affinity chromatography using glutathione-Sepharose beads. Cell-free extracts from transformed yeasts grown in ethanol-containing culture media showed insecticidal activity against third-instar Aedes aegypti larvae. This insecticidal activity was increased about 4-fold when the purified fusion protein was assayed.