Insecticidal Activity of a Vip3Ab1 Chimera Is Conferred by Improved Protein Stability in the Midgut of Spodoptera eridania

• Published in: Toxins 2019-05, Vol.11 (5), p.276
• Main Authors: Bowling, Andrew J, Sopko, Megan S, Tan, Sek Yee, Larsen, Cory M, Pence, Heather E, Zack, Marc D
• Format: Article
• Language: English
• Subjects: Amino acids; Animals; Bacillus thuringiensis; Bacterial Proteins - chemistry; Bacterial Proteins - toxicity; Benzamidines - chemistry; Binding sites; Biocompatibility; C-Terminus; Chromatography; Digestive enzymes; Fluids; Gastrointestinal Tract - chemistry; Gastrointestinal Tract - drug effects; immunolocalization; insect histopathology; Insecticides - toxicity; Insects; Larva - drug effects; lepidoptera; Midgut; Pest control; Pest Control, Biological; Pests; Protease inhibitors; Protease Inhibitors - chemistry; Protein Stability; Proteinase inhibitors; Proteins; Serine; Soybeans; spodoptera; Spodoptera - drug effects; Spodoptera eridania; Spodoptera frugiperda; Stability; Toxicity; Vip3A
• ISSN: 2072-6651; 2072-6651
• DOI: 10.3390/toxins11050276

Vip3A proteins are important for the control of spodopteran pests in crops, including (fall armyworm). Native Vip3Ab1 controls , but it is ineffective against (southern armyworm), a major pest of soybean in South America. Recently, a Vip3Ab1 chimera with a modified C-terminus was described, Vip3Ab1-740, which has increased potency against while maintaining activity against . As and are differentially susceptible to Vip3Ab1, experiments were conducted to identify and understand the mechanism by which this expanded potency is conferred. The role of protein stability, processing, and in vivo effects of Vip3Ab1 and Vip3Ab1-740 in both of these species was investigated. Biochemical characterization of the midgut fluids of these two species indicated no obvious differences in the composition and activity of digestive enzymes, which protease inhibitor studies indicated were likely serine proteases. Histological examination demonstrated that both proteins cause midgut disruption in , while only Vip3Ab1-740 affects . Immunolocalization indicated that both proteins were present in the midgut of , but only Vip3Ab1-740 was detected in the midgut of . We conclude that the gain of toxicity of Vip3Ab1-740 to is due to an increase in protein stability in the midgut, which was conferred by C-terminal modification.