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Odorant-binding protein (OBP) is a potential target for developing insect behavior control agents due to its properties in transporting semiochemicals. In this study, 12 novel jasmonic acid (JA) derivatives were rationally designed and synthesized based on the binding features between

Strigolactones (SLs) are a class of plant hormones and rhizosphere communication signals of great interest. They perform diverse biological functions including the stimulation of parasitic seed germination and phytohormonal activity. However, their practical use is limited by their low abundance and complex structure, which requires simpler SL analogues and mimics with maintained biological function. Here, new, hybrid-type SL mimics were designed, derived from Cinnamic amide, a new potential plant growth regulator with good germination and rooting-promoting activities. Bioassay results indicated that compound 6 not only displayed good germination activity against the parasitic weed O. aegyptiaca with an EC50 value of 2.36 × 10−8 M, but also exhibited significant inhibitory activity against Arabidopsis root growth and lateral root formation, as well as promoting root hair elongation, similar to the action of GR24. Further morphological experiments on Arabidopsis max2-1 mutants revealed that 6 possessed SL-like physiological functions. Furthermore, molecular docking studies indicated that the binding mode of 6 was similar to that of GR24 in the active site of OsD14. This work provides valuable clues for the discovery of novel SL mimics.

Background: Downy mildew is one of the major fungi causing significant economic losses to crops. The resistance of this fungus to current fungicides is increasing and new fungicides with a unique mode of action are needed. Objective: To find a novel pyrazole amide derivative as a potential fungicide. Methods: A series of pyrazole-5-carboxamide derivatives containing a diaryl ether were designed and synthesized by the Intermediate derivatization method (IDM). Their fungicidal activities against Pseudoperonospora cubensis (P. cubensis, cucumber downy mildew) were evaluated in the greenhouse. Results: Bioassays indicated that several compounds exhibited excellent fungicidal activity against P. cubensis in vivo. In particular, T24 (EC50 = 0.88 mg L-1) had the highest activity compared with Dimethomorph and Fluazinam and other analogues. The relationship between the activity and the structure of these derivatives was analyzed, and an accurate and reliable three-dimensional quantitative structure-activity relationship (3D-QSAR) model was established to determine that electrostatic and steric fields had important effects on the improvement of fungicidal activity. Conclusion: The novel pyrazole-5-carboxamide derivative T24 can be considered a potential fungicide for P. cubensis control.

Background Succinate dehydrogenase inhibitors (SDHIs) play an increasingly important role in controlling plant diseases. However, the similar structures of SDHIs result in rapid development of cross-resistance development and a clear bottleneck of poor activity against oomycetes. Therefore, the need to seek new SDHI fungicides with novel structure is urgent. Results Innovative pyrazolyl oxime ethers were designed by replacing amide with oxime ether based on the SDH structure, and 19 pairs of Z- and E-isomers were efficiently prepared for the discovery of SDHI compounds with novel bridge. Their biological activities against four fungi and two oomycetes were evaluated, and substantial differences were observed between Z- and E- isomer of the title compounds. Furthermore, most of these compounds exhibited remarkable activities against Rhizoctonia solani with EC50 values of less than 10 mg/L in vitro, and bioassay in vivo further confirmed that E-I-6 exhibited good protective efficacy (76.12%) at 200 mg/L. In addition, Z-I-9 provided better activity against the oomycetes Pythium aphanidermatum and Phytophthora capsici (EC50 = 1.56 mg/L and 0.93 mg/L) than those of boscalid. Moreover, E-I-9 exhibited excellent SDH inhibition (IC50 = 0.21 mg/L) thanks to its good binding ability to the SDH by hydrogen-bonding interactions, π-cation interaction and hydrophobic interactions. Conclusion Novel pyrazolyl oxime ethers have the potential as SDHI compounds for future development, and the strategy of replacing amide bond with oxime ether may offer an alternative option in SDHI fungicide discovery. This article is protected by copyright. All rights reserved.

BACKGROUND: The aphid alarm pheromone, (E)‐β‐farnesene (EβF), is a natural product secreted from the aphid cornicle as a signal to warn companions of danger. Odorant binding proteins (OBPs) are the vital targets in insect signal transduction pathways. To improve bioactivity of EβF as more economic and stable aphid control agents, EβF derivatives containing an active substructure, salicylic acid moiety, were designed, synthesized, and evaluated for their bioactivities in a structure–function study under laboratory conditions. RESULTS: EβF derivatives, (E)‐3,7‐dimethylocta‐2,6‐dien‐1‐yl‐2‐hydroxy‐3‐methylbenzoate and (E)‐3,7‐dimethylocta‐2,6‐dien‐1‐yl‐2‐hydroxy‐3‐methoxybenzoate showed outstanding aphid‐repellent activity at a dose of 5 μg against Acyrthosiphon pisum (repellency proportions of 67.3% and 71.2%, respectively) and Myzus persicae (repellency proportions of 80.0% and 74.4%, respectively) in laboratory. EβF and most of its derivatives bound strongly to ApisOBP9 with a higher affinity than those of the reported potential targets AphisOBP3 and ApisOBP7. The binding affinities to these three ApisOBPs were generally consistent with the in vivo aphid‐repellent activity. A molecular docking study suggested that the hydrophobic effect was crucial for the interactions between the derivatives and the OBPs. CONCLUSION: New EβF derivatives containing salicylic acid moiety and their repellent activity, binding mechanism with three potential OBPs are presented. A new OBP, ApisOBP9, was characterized as a potential EβF and EβF derivatives binding protein for the first time. The hydrophobic nature of these analogues is responsible for their activity. Two analogues 3b and 3e with outstanding aphid‐repellent activity could be new leads for aphid control agents.

The compound N-(5-(4-chlorobenzyl)-1,3,5-triazinan-2-ylidene)nitramide (C10H12ClN5O2, M = 269.70) was synthesized and structurally confirmed by 1H NMR, 13C NMR, HRMS and single-crystal x-ray diffraction. The crystal belongs to the monoclinic system with space group P21/c. The title compound consisted of a benzene ring and a 1,3,5-triazine ring. All carbon atoms in the benzene ring were nearly coplanar with a dihedral (C6&ndash, C5&ndash, C10 and C7&ndash, C8&ndash, C9) angle of 1.71&deg, and all non-hydrogen atoms of the 1,3,5-triazine ring were not planar, but exhibited a half-chair conformation. The crystal structure was stabilized by a strong intramolecular hydrogen bonding interaction N(3)&ndash, H(3)&middot, &middot, O(2) and three intermolecular hydrogen bonding interactions, N(2)&ndash, H(2)&middot, O(1), N(2)&ndash, N(4) and N(3)&ndash, Cl(1). The preliminary bioassay showed that the title compound showed not only aphicidal activity against Sitobion miscanthi (inhibition rate: 74.1%) and Schizaphis graminum (77.5%), but also antifungal activities against Pythium aphanidermatum (62.0%). These results provide valuable guidelines for the design and synthesis of novel aphid control agents and fungicides.

Odorant-binding proteins (OBPs) play an important role as ligand-transfer filters in olfactory recognition in insects. (E)-β-farnesene (EBF) is the main component of the aphid alarm pheromone and could keep aphids away from crops to prevent damage. Computational insight into the molecular binding mode of EBF analogs containing a heterocycle based on the structure of Megoura viciae OBP 3 (MvicOBP3) was obtained by molecular docking and molecular dynamics simulations. The results showed that high affinity EBF analogs substituted with an aromatic ring present a unique binding conformation in the surface cavity of MvicOBP3. A long EBF chain was located inside the cavity and was surrounded by many hydrophobic residues, while the substituted aromatic ring was exposed to the outside due to limitations from the formation of multiple hydrogen bonds. However, the low activity EBF analogs displayed an exactly inverted binding pose, with EBF loaded on the external side of the protein cavity. The affinity of the recently synthesized EBF analogs containing a triazine ring was evaluated in silico based on the binding modes described above and in vitro through fluorescence competitive binding assay reported later. Compound N1 not only showed a similar binding conformation to that of the high affinity analogs but was also found to have a much higher docking score and binding affinity than the other analogs. In addition, the docking score results correlated well with the predicted logP values for these EBF analogs, suggesting highly hydrophobic interactions between the protein and ligand. These studies provide an in silico screening model for the binding affinity of EBF analogs in order to guide their rational design based on aphid OBPs.