GalNAc pretreatment inhibits trapping of Bacillus thuringiensis Cry1Ac on the peritrophic membrane of Bombyx mori

Abstract
Bombyx mori (Shunrei × Shogetsu) is sensitive to Cry1Aa and resistant to Cry1Ac, both insecticidal proteins of Bacillus thuringiensis. Cry1Aa passed through the peritrophic membrane (PM) much faster (0.37 μg/mm2 PM/h) than Cry1Ac (0.05 μg/mm2 PM/h) during the initial observation period. Both Cry1Aa and Cry1Ac bound to the PM but only the binding of Cry1Ac was specifically inhibited by N‐acetylgalactosamine (GalNAc). When Cry1Ac was pretreated with GalNAc, Cry1Ac permeated the PM much faster. These results suggested that Cry1Ac bound a PM protein via GalNAc on a sugar side chain. The role of the PM on Cry1Ac resistance of B. mori was briefly discussed.