Light microscope immunolocation of Bacillus thuringiensis kurstaki delta-endotoxin in the midgut and Malpighian tubules of the tobacco budworm, Heliothis virescens.

Light microscope immunofluorescence was used to localize the membrane binding of Bacillus thuringiensis kurstaki 63-kDa delta-endotoxin in Heliothis virescens midgut and Malpighian tubules. Staining was observed along all exposed mucosal (apical microvillar) plasma membranes. Interpretation of the serosal (basal) plasma membrane staining was complicated because the basal lamina also stained. The results suggest that the toxin binds to all exposed plasma membranes without apparent specificity for particular membrane domains.