EXPRESSION OF THE INSECTICIDAL CRYSTAL PROTEIN GENE FROM A GRAM-POSITIVE BACILLUS-THURINGIENSIS IN A GRAM-NEGATIVE PSEUDOMONAS-FLUORESCENS MEDIATED BY PROTOPLAST FUSION

Protoplast fusion between a Gram-negative strain Pseudomonas fluoresce ns having plant growth promoting activities and a Gram-positive Bacill us thuringiensis var, kurstaki HD 73 possessing insecticidal activity, was carried out to generate P.fluorescens hybrids possessing insectic idal activity. The antibiotic resistance markers of P. fluorescens (ri f(r), nal(r)) and the immunoreactivity to the antiserum raised against the crystal proteins of B. thuringiensis var. galleriae were used as selection markers for the hybrids. The hybrids exhibited lethal but di fferential activity in Heliothis armigera and in Spodoptera a litura w hen compared to the parental B. thuringiensis strain. The anti-feedant activity which is characteristic of B. thuringiensis toxin was not ob served in the hybrids. Although the presence of sequences homologous t o the cloned insecticidal gene of B. thuringiensis was demonstrated, t he Western blot analysis of cell extract of the hybrid (PK 105) showed that only low molecular mass crystal proteins (less than 40 kDa) coul d be detected under denaturing conditions. It indicates that the high molecular mass toxin peptide may be degraded by proteolysis. Besides t his, a clear separation of lethal and anti-feedant activity of the B. thuringiensis toxin has been observed by this study.