Characterization and application of a novel pest‐inducible promoter, OsCYP92C21 , in conferring resistance to striped stem borer and brown planthopper in rice

BACKGROUND: Inducible promoters enable precise spatiotemporal control of resistance gene expression in transgenic crops, which minimizes the metabolic burden and fitness costs caused by constitutive promoters. This study aimed to characterize the OsCYP92C21 promoter from rice and evaluate its utility in driving pest-inducible resistance against striped stem borer (SSB) and brown planthopper (BPH). RESULTS: The native OsCYP92C21 promoter drove strong inducible expression of Cry1C* and LecRK1* upon SSB and BPH infestation, respectively, conferring significant resistance in transgenic rice. Larval mortality reached 75.56% in P-Cry1C* lines, and seedling mortality was reduced by up to 89.9% in P-LecRK1* lines. Promoter dissection identified a pest-inducible region (PIR, -711 to -446 bp) essential for SSB-specific induction. A synthetic 3×PIR-mini35S promoter conferred SSB-inducible Cry1C* expression and enhanced resistance but did not respond to BPH. Transgenic lines using native or synthetic promoters showed agronomic performance comparable with wild-type plants, in contrast to constitutive expression lines. CONCLUSION: The OsCYP92C21 promoter is a dual-pest inducible promoter with distinct regulatory modules for different pests. By contrast, the synthetic 3×PIR-mini35S promoter confers SSB-inducible expression but does not respond to BPH. The PIR element enables SSB-specific resistance without detectable agronomic penalties, providing a valuable tool for precision breeding.