EXPRESSION OF BACILLUS-THURINGIENSIS INSECTICIDAL PROTEIN GENES IN TRANSGENIC CROP PLANTS

The crystals and spores of Bacillus thuringiensis (Bt) have been used for many years as microbially produced insecticides with mixed success . Many of the problems of using Bt as a spray, such as environmental i nactivation of the proteins or poor crop coverage, can be circumvented by modem genetic engineering techniques. These can now be used to tra nsfer the genes for the toxic Bt crystal proteins from the bacteria in to crop plants and so protect them from attack by economically importa nt insect pests. For many years, the two major obstacles limiting the potential commercial use of transgenic plants expressing these insecti cidal Bt proteins were the introduction of Bt genes into important agr icultural species and having them expressed at sufficiently high level s to achieve insect control. Many of the technical limitations have no w been overcome and the first commercial releases of transgenic insect resistant crops, like cotton are now, or soon will be, in the hands o f regulatory bodies. Transgenic seed should hopefully come on the mark et over the next 4 or 5 years if general approval is given. One of the major considerations that might delay commercialisation is the possib ility that insects may become resistant to the Bt proteins expressed i n transgenic plants. Considerable research into the deployment of tran sgenic Bt plants on farms and/or in the production of multiply resista nt transgenic plants will still be needed to ensure the effective use of this valuable agricultural resource.