SlGSTE9 participates in the stability of chlorpyrifos resistance in Spodoptera litura

Abstract

BACKGROUND: Spodoptera litura is an important agricultural pest and has developed serious resistance to multiple insecticides. The resistance level to several insecticides is reported to be unstable, but the mechanism is less reported.RESULTS: Chlorpyrifos and phoxim resistance level in a field-collected population of S. litura declined continuously from the first to the tenth generation and remained stable at the 11th and 12th generations without insecticide exposure. Synergist experiment showed that diethyl maleate and piperonyl butoxide significantly increased mortality to chlorpyrifos and phoxim in the first and sixth generations, but not in the 12th generation. The expression of 31 identified glutathione S-transferase (GST) genes in the third-instar larvae of S. litura in the first, sixth and 12th generations was determined, and eight genes were seen to decrease significantly in the sixth and 12th generations compared with the first generation. SlGSTe9 was selected for further functional study as it had higher abundance and significantly higher expression in the chlorpyrifos-resistant population than in the susceptible population. The recombinant protein of SlGSTE9 showed metabolism activity to chlorpyrifos in vitro and in Escherichia coli, but not to phoxim. Silencing of SlGSTe9 increased the cumulative mortality to chlorpyrifos significantly. SlGSTE9 also showed antioxidant activity to cumene hydroperoxide. CONCLUSION: Our results suggest that SlGSTe9 is directly involved in chlorpyrifos resistance stability, but not in phoxim. SlGSTE9 may also participate in insecticides resistance by relieving the oxidase stress induced by insecticides.

SlGSTE8 in Spodoptera litura participated in the resistance to phoxim and chlorpyrifos

“…Spodoptera litura populations used in this study were described in Li, He, Xie, Ge, et al (2021). Briefly, GX population of S. litura , kindly provided by Guangxi Tianyuan Biochemistry Corp Ltd, served as a susceptible population.…”

“…The cDNA full length of SlGSTe8 was cloned and expressed in a prokaryotic expression system E. coli BL21 (DE3) (Tiangen). The heterologous expression of SlGSTE8 was conducted as described in Li, He, Xie, Ge, et al (2021). Briefly, restriction enzyme sites Nde I and Xho I were introduced to the cDNA full length of SlGSTe8 .…”

“…Samples were loaded in the gel and run in buffer at 80 V for 15 min and 150 V for 1 h. The gels were then transferred to Coomassie Blue R‐250 (Tiangen) for staining. To detect the enzyme activity, K m and V max values of recombinant protein SlGSTE8 were determined using 2,4‐dinitrochlorobenzene (CDNB) as the model substrate (Li, He, Xie, Ge, et al, 2021).…”

“…SlGSTe1 was significantly overexpressed in four resistant populations to pyrethroids, and RNA interference‐mediated silence increased the mortality of larvae treated by fenvalerate significantly (Xu et al, 2020). SlGSTe9 was significantly upregulated in a resistant population to pyrethroids and organophosphates (Li, He, Xie, Ge, et al, 2021), while SlGSTe12 was significantly upregulated in a chlorpyrifos selected strain, two resistant populations to pyrethroids, and a resistant population to pyrethroids and organophosphates (Li, He, Xie, Kong, et al, 2021; Zhang et al, 2016). The recombinant protein SlGSTE9 and SlGSTE12 both showed significant metabolic activity to these insecticides, and silencing of SlGSTe9 or SlGSTe12 significantly increased larvae mortality treated by these insecticides (Li et al, 2021, b).…”

The dynamic changes of genes revealed that persistently overexpressed genes drive the evolution of cyflumetofen resistance in Tetranychus cinnabarinus

“…SlGSTE9 with high expression abundance has also been shown to be involved in chlorpyrifos resistance in Spodoptera litura (Li et al. , 2021). In this study, CYP392A1 and TcGSTd05 were respectively found to have the highest upregulation fold change (697.7‐fold) and expression abundance (FPKM > 400) among all overexpressed detoxification enzyme genes in the 3 stages, suggesting they may also contribute to cyflumetofen resistance in the YN‐CyR strain.…”