Inhibitory efficacy of tripeptides on trypsin-like activity in soybean caterpillars Anticarsia gemmatalis (Lepidoptera: Erebidae) with dysbiosis

Anticarsia gemmatalis (Hübner, 1818) (Lepidoptera: Erebidae) larvae inflict damage on host plants by consuming their leaves. Controlling them represents a key strategy for mitigating economic losses in Brazilian soybean cultivation. In this study, we elucidate the impact of dysbiosis, induced via exposure to the antibiotic tetracycline (TCN), on A. gemmatalis in the presence or absence of the protease inhibitors GORE1 and GORE2. These peptides, each comprising three amino acids (VAL-LEU-LYS and VAL-LEU-ARG, respectively), were investigated. In vitro analyses revealed that the affinity of trypsin-like enzymes for the substrate diminished in caterpillars with dysbiosis that were concurrently exposed to the peptides. Noteworthy differences emerged across treatments in survival analyses, nutritional parameters, and pupal weight. Among these, caterpillars exposed to the GORE2 peptide exhibited the highest mortality and lowest pupal weight. Histological alterations were observed in A. gemmatalis exposed to TCN and peptides. Digestive cells exhibited cytoplasmic vacuolation and heightened apocrine secretion within the intestinal lumen compared to the control group. The present study has successfully demonstrated notable shifts in protein degradation, particularly evident in the altered affinity of A. gemmatalis trypsin-like enzymes when subjected to TCN and the inhibitory effects of GORE1 and GORE2 peptides. Encouragingly, the antibiotic exposure exhibited no detrimental impacts on the survival, nutritional parameters, or overall fitness of A. gemmatalis. Moreover, our findings collectively underscore the potential efficacy of integrating GORE1 and GORE2 peptides for A. gemmatalis management. These peptides have demonstrated significant inhibitory capabilities, coupled with morphological alterations observed in midgut cells, possibly arising from the delayed expression of proteases. This morphological shift appears to impede the pest's nutrition and survival, positioning these tripeptides as a promising tool in addressing the challenges posed by this soybean pest.