Key Contributions of the OverexpressedPlutella xylostellaSigma GlutathioneS-Transferase 1 Gene (PxGSTs1) in the Resistance Evolution to Multiple Insecticides

Abstract

The overexpression of insect detoxification enzymes is a typical adaptive evolutionary strategy for insects to cope with insecticide pressure. In this study, we identified a glutathione S-transferase (GST) gene, PxGSTs1, that exhibited pronounced expression in the field-resistant population of Plutella xylostella. By using RNAi (RNA interference), the transgenic fly models, and quantitative real-time polymerase chain reaction (RT-qPCR) methods, we confirmed that the augmented expression of PxGSTs1 mediates the resistance of P. xylostella to various types of insecticides, including chlorantraniliprole, novaluron, λ-cyhalothrin, and abamectin. PxGSTs1 was found to bolster insecticide resistance in two ways: direct detoxification and enhancing antioxidative defenses. In addition, our findings demonstrated that pxy-miR-8528a exerts a pivotal influence on forming insecticide resistance in P. xylostella by downregulating PxGSTs1 expression. In summary, we elucidated the multifaceted molecular and biochemical underpinnings of PxGSTs1-driven insecticide resistance in P. xylostella. Our results provide a new perspective for understanding the insecticide resistance mechanism of P. xylostella.

Functional Analysis of Insecticide Inhibition and Metabolism of Six Glutathione S-Transferases in the Rice Stem Borer, Chilo suppressalis

“…citri, PcGSTm5 was overexpressed in abamectin-resistant strain and could be further induced by abamectin, and RNAi also confirmed the involvement of PcGSTm5 in detoxification of abamectin, however, no metabolite was found in the metabolism assay of recombinant PcGSTm5 to abamectin . Similar results were found in the metabolisms of BdGSTd2 to cyhalothrin, chlorpyrifos, and clothianidin as well as the metabolisms of PxGSTs1 to novaluron, where no metabolite was found in the metabolisms. , The present in vitro metabolism assay showed that no specific metabolite was generated after the incubation of abamectin with six CsGSTs, respectively, and suggested that the six CsGSTs were unable to metabolize abamectin directly. These GSTs might participate in the detoxification by catalyzing the conjugation of GSH to insecticides or via the noncatalytic passive binding instead of the direct metabolism of insecticides …”

“…Although the IC 50 values of abamectin and chlorpyrifos on six CsGSTs were unable to be calculated under the assay conditions, however, low concentration of the insecticide, especially for the abamectin (0.005 mM), could effectively inhibit the activities of CsGSTs including CsGSTd1, CsGSTe4, CsGSTo2, CsGSTs3, and CsGSTu1. Studies about recombinant GSTs of insects and mites revealed that 0.05 mM of abamectin could effectively inhibit the activities of TuGSTd01 and TuGSTd14 while there was no significant inhibitory effect on the activities of TuGSTd10, TuGSTm09, and PcGSTm5, respectively, ,, and the 0.5–1 mM of abamectin was unable to inhibit the activity of PxGSTs1 from Plutella xylostella; while studies also found that 0.1 mM of abamectin significantly inhibited GST activities by 40.17 and 69.37% in Micromelalopha troglodyta and Clostera anachoreta, respectively . These studies indicating the diverse inhibitions of abamectin on the activities of GSTs from different species and the high binding affinities of abamectin with CsGSTd1, CsGSTe4, CsGSTo2, CsGSTs3, and CsGSTu1 might suggest the involvement of these CsGSTs in the metabolism of abamectin.…”

“…In insects, there are several general approaches to evaluate the contribution of GSTs in detoxification of insecticides, including the measurement of total GST activity, synergism bioassay using GST inhibitors, determination of the expression change of GST gene/protein, suppression of the mRNA level of GST gene employing RNA interference (RNAi), and functional expression of recombinant GSTs in vitro ; , among which the functional expression of recombinant GSTs is widely used to study the specific enzymatic property of GSTs, which can not only provide the direct interaction of GSTs with insecticides but also help to identify the potential metabolite derived from the metabolism of GSTs to insecticides. ,, In order to further explore the possible metabolism of CsGSTs to insecticides, six recombinant CsGSTs were expressed and purified in the present study. Determination of enzymatic properties showed that all of the six CsGSTs could catalyze the conjugation of substrate CDNB with GSH and were inhibited by the typical GST inhibitor GTX.…”

Insights into the Early Steps of the Symbiotic Interaction between Soybean (Glycine max) and Sinorhizobium fredii Symbiosis Using Transcriptome, Small RNA, and Degradome Sequencing

“…The expression levels of the miRNA and mRNA genes were normalized with gma-MIR1515a and GmActin , respectively, as internal controls. − The experiment involved three replicates. Statistical data were calculated based on 2 –ΔΔCt …”