Midgut juice of Plutella xylostella highly resistant to Bacillus thuringiensis Cry1Ac contains a three times larger amount of glucosinolate sulfatase which binds to Cry1Ac compared to that of susceptible strain

Abstract

Midgut juice of Plutella xylostella strain PXR which is resistant to Cry1Ac was biochemically characterized relative to the susceptible PXS strain. The midgut juice of PXR (PXR-Juice) was shown to process Cry1Ac protoxin to 60kDa active toxin with the same processing pattern as that of juice from PXS (PXS-Juice) in SDS-PAGE. PXS larvae which were given the Cry1Ac toxin pre-processed with PXR-Juice were killed with the same rate as that with Cry1Ac pre-activated by trypsin. PXR-Juice was found to contain three times larger amount of 66kDa protein (P66) than PXS-Juice and the N-terminal amino acid sequence of P66 was matched to that of glucosinolate sulfatase in data base search. The protein band of P66 was coincided with the band of p-nitro phenyl sulfatase activity in zymogram. P66 purified to homogeneity in SDS-PAGE bound to Cry1Ac and soybean agglutinin, and K D for Cry1Ac was estimated to be 718 nM with surface plasmon resonance analysis. Using purified sulfatase, K m and V max were estimated and involvement of the enzyme in the PXR resistance was discussed. © 2011 Elsevier Inc.