White-backed planthopper, Sogatella furcifera (Horváth) (Hemiptera: Delphacidae), one of the main agricultural insect pests in China, is resistant to a wide variety of insecticides. We used transcriptome analysis to compare the expression patterns of resistance- and stress-response genes in S. furcifera subjected to imidacloprid, deltamethrin, and triazophos stress, to determine the molecular mechanisms of resistance to these insecticides. A comparative analysis of gene expression under imidacloprid, deltamethrin, and triazophos stress revealed 1,123, 841, and 316 upregulated unigenes, respectively, compared to the control. These upregulated genes included seven P450s (two CYP2 clade, three CYP3 clade, and two CYP4 clade), one GST, one ABC transporter (ABCF), and seven Hsps (one 90 and six Hsp70s) under imidacloprid stress; one P450 (CYP3 clade), two ABC transporters (one ABCF and one ABCD), and one Hsp (Hsp90) under deltamethrin stress; one P450 (CYP3 clade) and one ABC transporter (ABCF) under triazophos stress. In addition, 80 genes were commonly upregulated in response to the three insecticide treatments, including laminin, larval cuticle protein, and fasciclin, which are associated with epidermal formation. These results provide a valuable resource for the molecular characterisation of insecticide action in S. furcifera, especially the molecular characteristics of insecticide cross resistance.

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.

The brown planthopper (BPH), Nilaparvata lugens, is an important pest of rice that severely affects production. Insecticides are an important means of controlling BPH, but their long-term use has led to resistance. To provide insight into BPH responses to insecticide stress, we determined the expression levels of BPH ABCG transporter genes under treatment with thiamethoxam, abamectin, and cyantraniliprole at LC₁₀, LC₂₅, LC₅₀, and LC₉₀. We cloned 13 BPH ABCG transporters, named NlABCG1 to NlABCG13. Conservative domain analysis showed that all 13 transporters have one nucleotide binding domain and one transmembrane domain, typical of semi-molecular transporters. Real-time quantitative PCR showed that thiamethoxam, abamectin, and cyantraniliprole stress increased the expression of some NlABCG transporters gene in BPH. However, after treatment with thiamethoxam at LC₂₅ and abamectin at LC₁₀, there was no significant upregulation of NlABCG. These results indicate that the expression of NlABCG varies in response to stress from different insecticides. These findings provide baseline information for further understanding of the molecular mechanisms of insecticide resistance in BPH.

Trehalase (Tre) is a crucial enzyme involved in trehalose metabolism, and it plays pivotal roles in insect development and metamorphosis. However, the biological function of Tre genes in Sogatella furcifera remains unclear. In the present study, two Tre genes—SfTre1 and SfTre2—were cloned and identified based on the S. furcifera transcriptome data. Bioinformatic analysis revealed that the full-length complementary DNA of SfTre1 and SfTre2 genes were 3700 and 2757 bp long, with 1728- and 1902-bp open reading frame encoding 575 and 633 amino acid residues, respectively. Expression analysis indicated that SfTre1 and SfTre2 were expressed at all developmental stages, with the highest expression in day two adults. Furthermore, the highest expression levels of SfTre1 and SfTre2 were observed in the ovary; enriched expression was also noted in head tissues. The knockdown of SfTre1 and SfTre2 via injecting double-stranded RNAs decreased the transcription levels of the corresponding mRNAs and led to various malformed phenotypes and high lethality rates. The results of our present study indicate that SfTre1 and SfTre2 play crucial roles in S. furcifera growth and development, which can provide referable information for Tre genes as a potential target for planthopper control.