Genes for Protease Inhibitors - In cowpea (Vigna unguiculata), trypsin inhibitor (CpTI) level was shown to be responsible for its resistance to attack by the major storage pest of its seeds (i.e. bruchid beetle = Callosobruchus maculatus). CpTI was latet shown to be toxic to a variety of insects but cowpea seeds with high level of CpTI are not toxic to humans.

It was, thereforoe, considered desirable to transfer gene(s) for CpTI for production of transgenic insect resistant plants. A number of binary vectors were developed using Ti plasmid, where CpTI gene was joined with CaMV 35S promoter, and one or more marker genes.