Lipids of brush border membrane vesicles (BBMV) from Plutella xylostella resistant and susceptible to Cry1Ac δ-endotoxin of Bacillus thuringiensis

Abstract

Plutella xylostella (PX) that were 130 000-fold more resistant to Cry1Ac were selected from the susceptible strain and maintained in the laboratory. The LC 50 of the susceptible strain (PXS) was 0.38 μg toxin/g diet, whereas that of the resistant strain (PXR) was 4800 μg toxin/g diet. Brush border membrane vesicles (BBMV) were prepared from both PXS and PXR. In ligand blot analysis, Cry1Ac bound to a 120-kDa protein of BBMV; however, the intensity of the band was almost equal in both strains of insect. Hence, we analyzed the lipid components of BBMV from PXS and PXR. BBMV lipids were fractionated into non-polar lipid, phospholipid, neutral glycolipid and acidic glycolipid. Neutral glycolipid content was substantially lower in the BBMV of PXR than of PXS. The same trend was observed when lipids were extracted from whole midgut instead of BBMV. Thin layer chromatography of midgut neutral glycolipids revealed the presence of more than seven components. Among the midgut neutral glycolipids, a possible hexasaccharylceramide and a possible trisaccharylceramide of PXR were less than half the level found in PXS. The other lipid fractions in PXR and PXS were similar to each other.