Cry3A δ-endotoxin gene mutagenized for enhanced toxicity to spruce bark beetle in a receptor binding loop

Abstract

Bacillus thuringiensis Cry3A gene was redesigned for high expression in Norwegian spruce and the sequence was slightly modified to allow for simple N- and C- terminal deletions and domain II loop 1 exchange for synthetic oligos. Modified Cry3A toxins from 13 variants of the synthetic gene were expressed in Escherichia coli BL21 and their toxicity on spruce bark beetle larvae was tested using spruce bark sandwiches. Mutant toxins with N-terminal deletion and loop 1 duplication showed increased toxicity. Key words : Bacillus thuringiensis , Ips typographus, Picea abies, resistance.