Developmental expression and stress induction of glutathione S-transferasein the spruce budworm, Choristoneura fumiferana

Developmental and stress-induced expression of Choristoneura fumiferana glu tathione S-transferase (CfGST) mRNA and protein were examined using Norther n blots and Western blots. High levels of CfGST mRNA and protein were detec ted in 1st instar larvae and diapausing 2nd instar larvae. Expression of Cf GST gradually decreased during larval development from 3rd to 5th instar, a fter which the expression increased once again, reaching peak levels in 6th instar larvae. CfGST mRNA and protein were undetectable in the pupal stage . Exposure to low temperature did not induce an increase in CfGST expressio n. Feeding on balsam fir foliage resulted in an increase in the expression of CfFST as compared to larvae that fed on artificial diet. The bacterial i nsecticide, Bacillus thuringiensis delta-endotoxin (Bt), the non-steroidal ecdysone analog, tebufenozide, and the synthetic pyrethroid, permethrin, in duced the expression of CfGST mRNA in 5th instar larvae, whereas the chitin synthesis inhibitor, diflubenzuron, did not have any such effect. These re sults suggest that CfGST plays an important role in detoxifying various all elochemicals and insecticides in the spruce budworm. The developmental expr ession pattern strongly suggests that in addition to detoxification, CfGST might be involved in other functions. Crown Copyright (C) 2000 Published by Elsevier Science Ltd. All rights reserved.