Increased Bacillus thuringiensis δ-endotoxin Cry3Aa toxicity against longhorned beetle by fusing to peptide specifically binding to beetle Cx-cellulase

Background Bacillus thuringiensis (Bt) Cry toxins have specific toxicity to susceptible insects. They are being used in transgenic plants or spray to control insect pests in agriculture [1, 2, 3]. Cry3A toxins are used extensively for biological control of coleopteran larvae [4, 5]. A Bt886-Cry3Aa gene that exhibited a high activity against Coleoptera insects isolated Our laboratory. Insect bioassay performed on Anoplophora glabripennis Motsch and Apriona germari Hope showed that the mortality of larvae fed with the product of this gene was over 60% [6]. However, both transgenic poplar with native Cry3Aa and withmodified-Cry3Aa by using poplar-prefered codons did little effects on longhorned beetles probably due to its low expression level in poplar.A peptide (LPPNPTK) named PCx that specifically bind to cellulase from midgut of longhorned beetle larvae was screened out from a phage display library previously in our laboratory[7].