The crystal proteins, or 5-endotoxins, of Bacillus thuringiensis are
specifically lethal to Lepidopteran insects. We utilized a truncated and
modified portion of a cloned crystal protein gene to construct a chimeric
gene capable of expression in plant cells. Using an Agrobacterium
tumefaciens binary vector system, we then transferred the chimeric toxin
gene into tobacco (Nicotiana tabacum cv Havana 425) cells and regenerated
recombinant plants. One to several copies per cell of the toxin
gene are routinely present in the recombinant plants. Hybridization
experiments demonstrated that these plants had a new RNA species of
the size expected for the truncated toxin mRNA, and a polypeptide
having the mobility expected for the truncated toxin was detected by
immunoblotting. Significant variation was found in the levels of toxinspecific
RNA expression between different recombinants, but the levels
of hybridizing RNA in transformants correlated with the level of toxicity
demonstrated against Manduca sexta (tobacco hornworm), and other
Lepidopteran insects. The recombinant genes were transmitted to progeny
and resistance to insects was maintained, thus demonstrating that the
introduction of toxin genes into plants may be a practical method of
providing protection against certain insect pests.