Odorant-Binding Protein Can Mediate Flavones Perception in Rice Planthopper to Exacerbate the Damage Under Elevated CO2.

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.