Two Glutathione S-transferases, PaGSTδ1 and PaGSTω1 Are Involved in Pyrethroids Detoxification in the American Cockroach, Periplaneta Americana

The American cockroach, Periplaneta americana (L.), is a notorious pest. Pyrethroids are one of the most applied insecticides in controlling the pest. Although previous work indicated that glutathione S-transferases (GSTs) detoxified pyrethroids, the roles of GSTs in the pyrethroids detoxification in P. americana remained unknown. Herein, two P. americana GSTs, PaGST & delta;1 and PaGST & omega;1, highly expressed in the midgut and fat body were identified. Their expression levels show significant and immediate increase after exposure to four pyrethroids, including bifenthrin, cypermethrin, & lambda;-cyhalothrin and & beta;-cyfluthrin, with PaGST & delta;1 mostly expressed from bifenthrin exposure. RNAi-mediated knockdown of PaGST & delta;1 and PaGST & omega;1 increased the sensitivity of the P. americana to these four pyrethroids, especially to bifenthrin. Both recombinant PaGST & delta;1 and PaGST & omega;1 proteins can bind pyrethroids, with in vitro metabolism confirmed for bifenthrin and & lambda;-cyhalothrin for recombinant PaGST & delta;1. This study identifies the role of PaGST & delta;1 and PaGST & omega;1 in the detoxification of pyrethroids, and suggests the necessity of rotation between bifenthrin and other insecticides to avoid resistance in P. americana control.