In order to investigate how brown planthopper (BPH, Nilaparvata lugens) responds to the stimulation of tricin, an insect-resistant compound in rice, and reveal the transcriptional regulation mechanism behind it, this study systematically analyzed the transcriptional changes in salivary gland tissue of BPH under the stimulation of tricin using RNA-seq. The results showed that, compared with the blank control, 49 and 232 differentially expressed genes (DEGs) were found in the salivary glands of BPH after treatment with tricin for 6 h and 24 h, respectively, and 23 shared DEGs were found between both time points. The number of DEGs caused by long-term treatment of tricin was significantly higher than that caused by short-term treatment, and the expression levels of these genes also exhibited a temporal induction pattern. Further analysis by Gene Ontology (GO) functional annotation indicated that these shared DEGs were mainly involved in biological processes such as response to stimuli and response to stress. At the same time, Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis further demonstrated that these genes were mainly concentrated in protein digestion and absorption and endocrine regulation and other related pathways. RT-qPCR analysis of shared DEGs confirmed that tricin stimulation could indeed induce the expression of trypsin, maltase and transporter-related genes in the salivary glands of BPH. These results will help to reveal the molecular mechanism of BPH response to tricin stimulation, and also indicate that trypsin and organic anion transporter LOC111045154 may serve as potential targets for future control of BPH.

NlMyc is an extremely important transcription factor in living organisms, playing a crucial role in a various of cellular activities, including cell cycle, growth, proliferation, and apoptosis among others. However, how transcription factors regulate the virulence of brown planthopper (Nilaparvata lugens (Stål)) on rice remains unreported. This study cloned and identified the transcription factor NlMyc gene of brown planthopper, revealing a full-length sequence of 1 830 bp encoding 609 amino acids. Using RT-qPCR technology to detect the resistance expression level of NlMyc gene and its spatio-temporal expression pattern in brown planthopper, the study found that the expression level of NlMyc gene was significantly higher after brown planthopper fed on resistant rice than that of brown planthopper fed on susceptible rice, and the expression level of NlMyc gene was the highest in 1-day-old female adults and salivary gland tissues. After RNAi silencing of NlMyc gene, the number of feeding holes of brown planthopper on tricin-enhanced resistant rice significantly increased to (28.9 ± 8.5), compared to the control groups (Control, dsGFP), which were (13.5 ± 4.3) and (16.2 ± 8.4) feeding holes, respectively. Additionally, the average honeydew secretion of brown planthopper treated with dsNlMyc, Control and dsGFP for 48 hours was 2.44 mg, 5.30 mg and 4.60 mg, respectively; the weight gain was 0.23 mg, 0.49 mg, and 0.47 mg, indicating a significant decrease in honeydew secretion and weight gain in the dsNlMyc group compared to the control groups. This indicated that silencing the NlMyc gene impaired the fitness and feeding ability of brown planthopper, thereby regulated the virulence of brown planthopper on resistane rice. This study demonstrates that NlMyc is a key transcription factor regulating the virulence of brown planthopper on tricin-enhanced resistant rice, which not only provides new insights into the exploration of the virulence variation of brown planthopper, but also offers a novel molecular target for pest control.