Proteomic analysis of BBMV in Helicoverpa armigera midgut with and without Cry1Ac toxin treatment

Abstract

The crystal proteins of Bacillus thuringiensis (Bt) are widely used for insect control. Helicoverpa armigera is the model insect for Bt studies. In this study, brush border membrane vesicle (BBMV) proteins from fifth instar larvae of Helicoverpa armigera were prepared, and proteomic approaches based on two-dimensional (2D) gel electrophoresis and mass spectrometry were used to elucidate changes in BBMV proteins with and without Cry1Ac toxin treatment. Sixty-one protein bands separated by 1D electrophoresis were cut out from the gel for tryptic digestion and were detected with molecular mass spectrometry (ESI-Q-TOF) and High Capacity Ion Trap Ultra (HCT Ultra). BBMV proteins of interest separated by 2D electrophoresis were excised and digested with trypsin, and the resulting peptides were analyzed by mass spectrometry. Mass fingerprints were compared with the non-redundant NCBI Metazoa (Animals) database. We found a noticeable increase in the level of aminopeptidase N (APN) that is important for detoxification reactions. Additionally, a significant decrease in the level of trypsin-like protease is important during early responses and adaptation of the insect to Bt and exposure to its toxins. Furthermore, the increase in V-ATPase subunits indicate elevated cellular energy profile which is necessary to combat toxin stress. The increased level of actin in larvae provides immediate protection by strengthening the midgut epithelium and enhancing cellular defenses in the tissue. This study presents the differences in the BBMV proteins of Helicoverpa armigera with and without Cry1Ac toxin treatment, and provides a theoretical basis for research on the mechanism of action of Bt toxin.