Lepidopteran-active variable-region sequence imparts coleopteran activity in eCry3.1Ab, an engineered Bacillus thuringiensis hybrid insecticidal protein.

A unique, coleopteran-active protein, termed eCry3.1Ab, was generated following variable-region exchange of a Bacillus thuringiensis lepidopteran-active protein, Cry1Ab, with a Cry3A region. Our results support the hypothesis that this variable-region exchange is responsible for imparting strong bioactivity against the larvae of western corn rootworm (WCR) (Diabrotica virgifera virgifera LeConte), a pest species which is not susceptible to either parent protein sequence.

The mode of action of the Bacillus thuringiensis vegetative insecticidal protein Vip3A differs from that of Cry1Ab delta-endotoxin.

The Vip3A protein, secreted by Bacillus spp. during the vegetative stage of growth, represents a new family of insecticidal proteins. In our investigation of the mode of action of Vip3A, the 88-kDa Vip3A full-length toxin (Vip3A-F) was proteolytically activated to an approximately 62-kDa core toxin either by trypsin (Vip3A-T) or lepidopteran gut juice extracts (Vip3A-G).