Characterization of a Novel Insecticidal Protein Cry9Cb1 from Bacillus thuringiensis

In recent decades, there have been increasing reports of insect resistance in Bacillus thuringiensis (Bt) crops. Alternative use of Cry toxins, with high insecticidal activity and different mechanisms of action, may be an important strategy to manage this resistance. Cry9 protein, with high toxicity to the lepidopteran pests and no cross-resistance with commercial Cry1 proteins, is a valuable relevant resource. A novel insecticidal protein, MP1489, subsequently named as Cry9Cb1, with 88% amino acid sequence identity with Cry9Ca1, was identified from Bt strain SP663; it exhibited high insecticidal activity against Plutella xylostella, Ostrinia furnacalis, and Chilo suppressalis and no cross-resistance with Cry1Fa in Ostrinia furnacalis. Its minimal active fragments against Plutella xylostella and Ostrinia furnacalis were identified to be 72(T)-657(V) and 68(D)-655(A), respectively; food-safety assessment showed no sequence homology with any known allergen and rapid degradation and inactivation by both heat and the gastrointestinal environment. Therefore, Cry9Cb1 is proposed to have a brilliant prospect as an insecticidal protein in agriculture.