OsBph32 Contributes to Coordinated Cell Wall and Metabolic Responses in Rice Resistance to Brown Planthopper.

The brown planthopper (BPH, Nilaparvata lugens) is a major insect pest of rice (Oryza sativa L.) causing severe yield losses across Asia. Although the resistance gene OsBph32 from the cultivar Ptb33 enhances BPH resistance, its molecular and physiological mechanisms remain unclear. Here, we investigated its function using OsBph32-overexpressing lines combined with physiological, transcriptomic, and metabolomic analyses. Overexpression of OsBph32 in the susceptible cultivar 9311 significantly increased resistance to BPH, as indicated by reduced plant damage and suppressed insect growth. This was associated with increased reactive oxygen species accumulation and callose deposition, suggesting activation of early defense responses. Multi-omics analyses revealed that OsBph32 is associated with transcriptional changes in genes involved in cell wall biosynthesis, phenylpropanoid metabolism, and carbon metabolism. Metabolomic profiling further showed increased accumulation of flavonoids, phenolamides, and lignin-related metabolites under BPH infestation, together with changes in carbon metabolism and starch accumulation. Collectively, these results suggest that OsBph32 is associated with coordinated changes in structural reinforcement, secondary metabolism, and carbon metabolism during insect attack, which may contribute to enhanced rice resistance and provide new insights into non-NLR-mediated insect defense mechanisms in plants.