Odorant-Binding Protein Can Mediate Flavones Perception in Rice Planthopper to Exacerbate the Damage Under Elevated...

Studies indicate that elevated CO₂ (eCO₂) can exacerbate the damage caused by brown planthopper Nilaparvata lugens to rice plants compared to ambient CO₂ (aCO₂), though the underlying mechanism remains unclear. In this study, targeted metabonomics analysis showed that the differential secondary metabolites of rice plants under aCO₂ and eCO₂ were mainly enriched in the "flavone and flavonol biosynthesis" pathway, and the contents of six flavones (i.e., apigenin, apigetrin, cynaroside, luteolin, orientin and rhoifolin) that could stimulate N. lugens feeding were significantly increased in rice plants under eCO₂. Meanwhile, knockdown of OBP7 of N. lugens markedly reduced this feeding stimulation. In vitro fluorescence competitive binding assays verified the specific binding between OBP7 and feeding-stimulating flavones. Molecular docking and site-directed mutagenesis further identified Gly132, Gly135, His136 and Glu137 as essential residues mediating OBP7-flavone interactions. Additionally, virtual screening and functional validation identified benzoylpaeoniflorin as a competitive inhibitor of OBP7-flavones, suppressing feeding and inducing oxidative stress in N. lugens. Exogenous application of benzoylpaeoniflorin effectively mitigated the aggravating damage of N. lugens to rice plants under eCO₂. These findings elucidate how OBP7 in N. lugens senses eCO₂-induced flavones to aggravate herbivory, offering novel pest control strategies under climate change scenarios.