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Odorant binding proteins (OBPs) play key roles in the insect olfactory system by assisting the neuronal response to hydrophobic odor molecules, understanding their interaction with ligands will facilitate the virtual screening of behaviorally active compounds in insects. Here, we successfully cloned and confirmed CmedOBP13, an antennae-biased OBP from the rice leaffolder Cnaphalocrocis medinalis, as a secreted protein. Recombinant CmedOBP13 was obtained using the Escherichia coli system, and its binding affinities to 35 volatile compounds emitted by rice plants and three sex pheromone components from female moths were assessed by a competitive binding assay. The results revealed that CmedOBP13 exhibited binding affinity to 23 rice volatiles, while no binding affinity for sex pheromone components. Furthermore, the stability of its conformation was found to be dependent on the pH level. Finally, the interaction between CmedOBP13 and odorants was predicted and confirmed by molecular docking and mutation functional assays, respectively. The combination of multiple hydrophobic residues created an adequate hydrophobic setting for ligands, and three residues (Glu13, Arg34, and Tyr115) might form hydrogen bonds with 15 odorants. Single mutations of Glu13, Arg34, Leu72, and Tyr115 diminished the binding affinities of CmedOBP13 to corresponding odorants, respectively. These findings provided valuable insights into the mode of action of CmedOBP13 interacting with the volatiles of rice plants and will guide the screening of behaviorally active compounds against C. medinalis in future., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

Petal blight caused by fungi is among the most destructive diseases of Rhododendron, especially Rhododendron agastum. Nonetheless, the metabolite changes that occur during petal blight are unknown. We used untargeted gas chromatography time-of-flight mass spectrometry (GC-TOF-MS) and ultra-high performance liquid chromatography quadrupole time-of-flight tandem mass spectrometry (UHPLC-QTOF-MS/MS) to compare the metabolite profiles of healthy and petal blight R. agastum flowers. Using GC-TOF-MS, 571 peaks were extracted, of which 189 metabolites were tentatively identified. On the other hand, 364 and 277 metabolites were tentatively identified in the positive and negative ionization modes of the UHPLC-QTOF-MS/MS, respectively. Principal component analysis (PCA) and orthogonal projections to latent structures-discriminant analysis (OPLS-DA) were able to clearly discriminate between healthy and petal blight flowers. Differentially abundant metabolites were primarily enriched in the biosynthesis of specialized metabolites. 17 accumulated specialized metabolites in petal blight flowers have been reported to have antifungal activity, and literature indicates that 9 of them are unique to plants. 3 metabolites (chlorogenic acid, medicarpin, and apigenin) are reportedly involved in resistance to blight caused by pathogens. We therefore speculate that the accumulation of chlorogenic acid, medicarpin, and apigenin may be involved in the resistance to petal blight. Our results suggest that these metabolites may be used as candidate biocontrol agents for the control fungal petal blight in Rhododendron., (Copyright © 2021 Elsevier Ltd. All rights reserved.)