Protective and Detoxifying Enzyme Activity and ABCG Subfamily Gene Expression in Sogatella furcifera Under Insecticide Stress

Abstract

Sogatella furcifera, an important migratory pest of rice, has substantial detrimental effects on rice production. To clarify the mechanism whereby S. furcifera responds to insecticide stress, we measured the activity of its protective [superoxide dismutase (SOD); peroxidase (POD); catalase (CAT)] and detoxifying [carboxylesterase (CarE); glutathione S-transferase (GST); mixed-function oxidase (MFO)] enzymes and the expression levels of its ATP-binding cassette subfamily G (ABCG) transporter genes in response to sublethal concentrations (LC₁₀ and LC₂₅) of the insecticides thiamethoxam, buprofezin, and abamectin. On the bases of the transcriptome data and the ABCG genes of Laodelphax striatellus, we obtained 14 full-length ABCG sequences for S. furcifera. RT-qPCR results showed that 13, 12, and 9 sfABCG genes were upregulated in the presence of thiamethoxam, buprofezin, and abamectin, respectively, at LC₁₀. Moreover, 13 and 7 sfABCG genes were upregulated following treatment with thiamethoxam and abamectin, respectively, at LC₂₅. Enzyme activity assays showed that although thiamethoxam, buprofezin, and abamectin induced GST, CarE, CAT, POD, and SOD activity, they did so at different concentrations and exposure times. The activity of MFO was generally inhibited with prolonged exposure to the three insecticides, with the inhibitory effect being most significant at 72 h. These results indicate that S. furcifera differs in its response to different types or concentrations of insecticides. Taken together, our results lay the foundations for gaining a deeper understanding of the mechanisms underlying the adaptation of S. furcifera to different types of insecticides, which would be of considerable significance for the development of effective pest management strategies.

Keywords: ATP-binding cassette transporter; detoxifying enzyme; insecticide stress; protective enzyme; response mechanism; white-backed planthopper.

FIGURE 1

Relative expression levels of 14 putative ABC subfamily G (ABCG) transporter genes in Sogatella furcifera under treatment with sublethal concentrations (LC₁₀ and LC₂₅) of thiamethoxam, buprofezin, and abamectin. The mean value ± SE was used to analyze the relative expression levels under different insecticide concentrations using the ΔΔCt method, with non-insecticide treatment (CK) as a reference. Different letters indicate significant differences among treatments at the same time. (A) Thiamethoxam; (B) buprofezin; and (C) abamectin.

FIGURE 2

Summary of the significantly upregulated genes in Sogatella furcifera under treatment with the insecticides thiamethoxam, buprofezin, and abamectin. The Venn diagram shows the putative ABC subfamily G (ABCG) transporter genes found to be significantly upregulated in the insecticide-treated insects compared with the untreated controls.

FIGURE 3

Effects of sublethal concentrations of insecticides on the carboxylesterase (CarE) activity of Sogatella furcifera. Enzyme activities are shown as the mean ± SE. Different letters indicate significant differences among treatments at the same time. (A) Thiamethoxam; (B) buprofezin; and (C) abamectin.

FIGURE 4

Effects of sublethal concentrations of insecticides on the glutathione S-transferase (GST) activity of Sogatella furcifera. Enzyme activities are shown as the mean ± SE. Different letters indicate significant differences among treatments at the same time. (A) Thiamethoxam; (B) buprofezin; and (C) abamectin.

FIGURE 5

Effects of sublethal concentrations of insecticides on the mixed-function oxidase (MFO) activity of Sogatella furcifera. Enzyme activities are shown as the mean ± SE. Different letters indicate significant differences among treatments at the same time. (A) Thiamethoxam; (B) buprofezin; and (C) abamectin.

FIGURE 6

Effects of sublethal concentrations of insecticides on the catalase (CAT) activity of Sogatella furcifera. Enzyme activities are shown as the mean ± SE. Different letters indicate significant differences among treatments at the same time. (A) Thiamethoxam; (B) buprofezin; and (C) abamectin.

FIGURE 7

Effects of sublethal concentrations of insecticides on the peroxidase (POD) activity of Sogatella furcifera. Enzyme activities are shown as the mean ± SE. Different letters indicate significant differences among treatments at the same time. (A) Thiamethoxam; (B) buprofezin; and (C) abamectin.

FIGURE 8

Effects of sublethal concentrations of insecticides on the superoxide dismutase (SOD) activity of Sogatella furcifera. Enzyme activities are shown as the mean ± SE. Different letters indicate significant differences among treatments at the same time. (A) Thiamethoxam; (B) buprofezin; and (C) abamectin.