Transcriptomic analysis of rice treated with ZnO nanoparticles after brown planthopper (Nilaparvata lugens (Stål), BPH) infestation

The brown planthopper ( Nilaparvata lugens (Stål), BPH) is a major rice pest that causes significant yield losses. In this study, zinc oxide nanoparticles (ZnO-NPs) were employed to induce the activation of rice defense genes against BPH infestation. Rice seedlings were grown in ZnO-NPs supplemented medium under aseptic conditions for 8 weeks, after which they were transferred to pots prior to BPH infestation. Transcriptional profiles of rice plants treated with ZnO-NPs (Azn) and untreated (Ac) were examined following BPH infestation and compared with rice plants without BPH infestation (Bc). ZnO-NPs specifically induced the up-regulation of genes associated with zinc transport ( AP3d1 ), helicase enzyme ( DNA 2_4 ), grain quality and development ( LGG , MADS-box ), lignin biosynthesis ( DIR48 , CCR24 ) and the NINJA transcription factor involved in jasmonic acid (JA) signaling. This study also revealed that both Ac and Azn samples exhibited basal gene expression following BPH infestation, with activation of defense-related genes such as PR1a , phytoalexin ( KS4 ), NBS-LRR ( YR48 ), β-glucosidase ( G4 ), pectin lyase ( GAE1 ), lipase ( GELP45,67 ). Moreover, the Ac sample without ZnO-NPs treatment exhibited down-regulation of basal metabolic pathways, including protein metabolism ( CL24, L40, L34 ), carbohydrate metabolism and chlorophyll-binding proteins. This metabolic suppression was consistent with the yellowing and wilting symptoms observed in Ac plants following BPH infestation. Gene ontology (GO) analysis supported the DEG findings, revealing that zinc transporter and stress-responsive genes, including those involved in JA signaling, wound response and oxidative stress were uniquely enriched in Azn-treated plants. The qRT-PCR validation showed results consistent with the RNA-seq expression profiles, confirming the reliability of the transcriptome data. Notably, genes such as Os03g0245800 , Os09g0530200 and Os11g0590700 were markedly overexpressed under Azn treatment. ZnO-NPs may function as a biofertilizer and contribute to reducing insecticide dependence during BPH outbreaks. • Rice tissues uptake ZnO-NPs, as indicated by GO enrichment and DEG analyses showing significant enrichment of zinc transport and oxidative stress -responsive genes. • ZnO-NP treatment significantly improved rice seedling survival under BPH infestation, indicating a strong protective effect compared with untreated plants. • ZnO-NPs induced key defense-related genes, including NBS-LRR, β-glucanase, lignin biosynthesis enzymes, helicases, and JA-responsive pathways mediated by NINJA, suggesting a synergistic molecular defense mechanism against BPH. • ZnO-NPs stimulated genes associated with growth promotion and yield-related gene such as large-grain traits, β-expansin, cell wall remodeling and MADS-box transcription factors, linking enhanced stress tolerance with improved growth and grain quality.