An Autolysis-Derived Trypsin Peptide Disrupts Digestive Homeostasis and Reduces Fitness in Spodoptera Frugiperda Caterpillars

Abstract

The fall armyworm, Spodoptera frugiperda J.E. Smith (Lepidoptera: Noctuidae), is a significant agricultural pest, and its management is increasingly impeded by resistance to conventional insecticides, underscoring the need for alternative control strategies. This research examined the effects of the synthetic peptide GORE3 on digestive protease homeostasis and larval performance using an integrated approach that combined molecular dynamics simulations, enzymatic assays, physiological analyses, and histopathology. Comparative analyses employed benzamidine and soybean Kunitz trypsin inhibitor (SKTI) as reference inhibitors. Molecular dynamics simulations demonstrated that the trypsin-GORE3 complex is highly stable, with lower Root Mean Square Deviation (RMSD) values and sustained intermolecular interactions compared with benzamidine, while maintaining a favorable binding free-energy profile. In vivo analyses demonstrated that GORE3 induces a dynamic regulation of midgut digestive enzymes, initially suppressing activity, followed by a significant compensatory enhancement in trypsin-like and overall protease activities. Despite this enzymatic compensation, caterpillars exposed to GORE3 has low survival rates, reduced larval weight, prolonged developmental periods, and impaired food conversion efficiency. Nutritional indices indicated a breakdown between digestion and biomass conversion, implying metabolic costs linked to compensatory responses. Histopathological investigations identified midgut damage, including epithelial disruption, epithelial cell disorganization, and structural deterioration with all trypsin inhibitors tested. Oxidative stress responses were detected but played a secondary role relative to digestive dysregulation. Overall, GORE3 disrupts digestive homeostasis by triggering a compensatory yet ineffective proteolytic response, thereby reducing caterpillar fitness. These findings underscore the potential of synthetic peptides targeting digestive proteases as potential bioinsecticides and establish a mechanistic framework linking molecular interactions to organismal effects.