Utilization of a strong promoter combined with the knockout of protease genes to improve the yield of Vip3Aa in Bacillus thuringiensisBMB171

Abstract

Background: Vip3Aa is an insecticidal protein secreted by some Bacillus thuringiensis strains during vegetative growth. It has excellent insecticidal activity, its mechanism of action is different from that of Cry protein, and it can delay the development of pest resistance. To date, Vip3Aa has been widely used in genetically modified Bt crops. However, the secretion of Vip3Aa by industrial production strains is usually very low. Moreover, most of the Vip3Aa in the medium is degraded by proteases, limiting its application as a biopesticide.Results: We report a novel constitutive strong promoter from B. thuringiensis, P rsi , which directs the abundant expression of vip3Aa in B. thuringiensis BMB171. Furthermore, to reduce the degradation of Vip3Aa caused by proteases, we constructed B. thuringiensis mutants in which different protease genes were knocked out. We found that the degradation of Vip3Aa was greatly inhibited and its yield was significantly improved in a mutant that lacked all three protease genes. Conclusion: Our results provide a new strategy to enhance the production of Vip3Aa in B. thuringiensis and have reference value for the research and development of novel bioinsecticides.