OsJAC1 Positively Regulates Brown Planthopper Resistance in Rice Through Priming of Diterpenoid Biosynthesis and Amplification of Jasmonic Acid Signaling

Brown planthopper (BPH) is a devastating rice pest worldwide, and enhancing intrinsic plant resistance represents a sustainable strategy for its control. Here, we report that OsJAC1, a gene encoding a protein harboring dirigent and jacalin-related lectin domains, positively regulates BPH resistance in rice by priming diterpenoid biosynthesis and amplifying jasmonic acid (JA) signaling. Overexpression of OsJAC1 (OE) in japonica cv. Zhonghua 11 significantly enhanced resistance, whereas CRISPR/Cas9 knockout (KO) increased susceptibility. Transcriptomic profiling revealed that OE plants constitutively upregulated diterpenoid biosynthetic genes, including OsCPS4, OsKSL4 and CYP99A3, with further induction upon BPH infestation, accompanied by enrichment of MYB and bHLH transcription factors. Targeted metabolomics showed elevated momilactone A and B levels in OE plants. Hormonal assays demonstrated that JA accumulation was amplified in OE after BPH attack. Collectively, OsJAC1 confers resistance via a dual mechanism: constitutive priming of diterpenoid metabolism and attack-triggered amplification through JA signaling, but the precise biochemical function remains to be determined. Our findings uncover a regulatory cascade from transcriptional activation to phytoalexin accumulation and identify OsJAC1 as a promising target for breeding BPH-resistant rice.