OCCURRENCE OF 3 DIFFERENT BINDING-SITES FOR BACILLUS-THURINGIENSIS DELTA-ENDOTOXINS IN THE MIDGUT BRUSH-BORDER MEMBRANE OF THE POTATO-TUBER MOTH, PHTHORIMAEA-OPERCULELLA (ZELLER)

The potato tuber moth is susceptible to at least three insecticidal crystal proteins (ICPs) from Bacillus thuringiensis: CrylA(b), CrylB, and CrylC. To design useful combinations of toxin genes either in transgenic plants or in new genetically modified B. thuringiensis strains, it is necessary to determine the binding characteristics of the different ICPs so as not to combine a pair sharing the same binding site. This has been accomplished using two different techniques: I-125-labeling of the ICPs with further measurement of the radioactivity bound to brush border membrane vesicles, and microscopic visualization of the bound ICPs by enzyme-linked reagents such as antibodies or streptavidin using biotinylated ICPs. Our results st-cow that CrylA(b), CrylB, and CrylC bind to different sites in the brush border membrane of midgut epithelial cells. Also, the affinity of the binding sites for the ICPs and their concentration in brush border membrane vesicles has been determined in a laboratory strain and a storage collected population. No significant differences were found between these two strains. (C) 1994 Wiley-iiss, Inc.