Dempseycooper8418

Oxathiapiprolin, the first successful oxysterol binding protein (OSBP) inhibitor for oomycete control, is regarded as an important milestone in the history of fungicide discovery. However, its interaction with OSBP remain unclear. Moreover, some plant pathogenic oomycetes have developed medium to high resistance to oxathiapiprolin. In this paper, the three-dimensional (3D) structure of OSBP from Phytophthora capsici (pcOSBP) was built, and its interaction with oxathiapiprolin was systematically investigated by integrating molecular docking, molecular dynamics simulations, and molecular mechanics Poisson-Boltzmann surface area (MM/PBSA) calculations. The computational results showed that oxathiapiprolin bound to pcOSBP forms H-bonds with Leu73, Lys74, Ser69, and water molecules. Then, based on its interaction with pcOSBP, oxathiapiprolin was structurally modified to discover new analogs with high fungicidal activity and a low risk of resistance. Fortunately, compound 1e was successfully designed and synthesized as the most potent candidate, and it showed a much lower resistance risk (RF less then 1) against LP3-M and LP3-H in P. capsici. The present work indicated that the piperidinyl-thiazole-isoxazoline moiety is useful for further optimization. Furthermore, compound 1e could be used as a lead compound for the discovery of new OSBP inhibitors.RNA interference (RNAi) is a revolutionary technique for silencing gene expression, but the success of this technique is dependent upon the stability of double-stranded RNA (dsRNA) molecules. In many insects, especially lepidopteran species, RNAi efficiency is limited by high instability of dsRNA in the gut and/or hemolymph, preventing the development of RNAi-based strategies for many serious pests. Previous attempts to perform RNAi on Ostrinia nubilalis (ECB, Lepidoptera Crambidae) indicate low RNAi efficiency with both dsRNA injection and feeding. To investigate the contribution of dsRNA instability to low RNAi efficiency in ECB, a serious of ex vivo incubation experiments were performed where dsRNA integrity was assessed following incubation in larval gut continents and hemolymph using gel electrophoresis or RT-qPCR. DsRNA was less stable in the gut contents from ECB than in gut contents from Diabrotica virgifera virgifera, a coleopteran exhibiting high RNAi efficiency. #link# Furthermore, characterization of dsRNA stability in ECB gut contents and hemolymph revealed that dsRNA was rapidly degraded under physiologically relevant conditions as a result of enzymatic activity that was neither size- nor sequence-dependent. These findings suggest that instability of dsRNA in ECB tissues is a contributing factor to the poor efficiency of RNAi in this pest. This work advances our understanding of mechanisms impacting RNAi efficiency in ECB and related lepidopteran insects for which novel pest management strategies are needed, and may facilitate the development of strategies for enhancing dsRNA stability in ECB tissues.Hypoxylon species are distributed worldwide and have been isolated from different habitats. The endophyte Hypoxylon anthochroum strain Gseg1 was isolated from healthy leaves of Gliricidia sepium. A chemical study of the culture medium and mycelium organic extracts of the endophytic fungus H. anthochroum Gseg1 led to the isolation of three known isobenzofuranones, 7-hydroxy-4,6-dimethyl-3H-isobenzofuran-1-one, 1, 7-methoxy-4,6-dimethyl-3H-isobenzofuran-1-one, 2, 6-formyl-4-methyl-7-methoxy-3H-isobenzofuran-1-one, 3, and one compound was isolated for the first time as a natural product, 7-methoxy-4-methyl-3H-isobenzofuran-1-one, 4. In addition, the chemical synthesis of 1 and 2, and a derivative, 7-methoxy-6-methyl-3H-isobenzofuran-1-one, 5, was performed. The isobenzofuranones showed antifungal and antioomycete activities. Compounds 1-5 inhibited the growth of Fusarium oxysporum, Alternaria alternata, Pythium aphanidermatum, and Phytophthora capsici, in addition, 1, 2 and 5 interrupted the respiration and caused electrolyte leakage due to cell membrane damage. Compound 2 was the most active, inhibiting the growth of the four microorganisms, affecting the respiration and increasing the relative conductivity due to electrolyte leakage. Compounds 1-4 also induce morphological changes in the plant pathogens' mycelia and hyphae. These compounds could be useful for the control of plant pathogenic fungi and oomycetes of agricultural relevance.Xanthomonas oryzae pv. oryzae (Xoo) is an important pathogen in rice. C15surfactin A, produced by Bacillus velezensis HN-2, displayed antibacterial activity against Xoo and effectively inhibited its infection of rice. The median inhibitory concentration of C15surfactin A was 9.27 μg/mL. Scanning electron and transmission electron microscopy examination showed that C15surfactin A caused significant damage to the cell wall structure of Xoo cells. On the other hand, dramatic increases in the activity of phenylalanine ammonia-lyase (Pal) and H2O2 content were observed in rice leaves inoculated with Xoo from 0 h to 72 h. link2 Quantitative PCR assays indicated that C15surfactin A exposure upregulated the expression of the genes Pr1a, CatA, and Pal. The results showed that C15surfactin A could inhibit the growth of Xoo and effectively induce rice resistance to Xoo by triggering a hypersensitive reaction (HR) via mediation of the activities of antioxidant-related enzymes. Taken together, C15surfactin A has strong antibiotic activity against Xoo and effectively induces rice resistance to Xoo. These results highlight the potential of C15surfactin A as a biocontrol agent against Xoo in rice.Diamondback moth (DBM), Plutella xylostella, is an important pest of crucifers worldwide. The extensive use of flubendiamide has led to the development of resistance in field populations and reports of control failures. In this study, the lab-selected (Rf) and field-collected (Rb) flubendiamide-resistant strains of P. xylostella with LC50 resistance ratios of 1890-fold and 1251-fold, respectively, were used, as well as a lab-reared flubendiamide-susceptible strain (S). The results showed that the fecundity of the Rf and Rb-resistant strains was significantly lower than that of S strain. The contents of vitellin and transcripts of P. xylostella vitellogenin (PxVg) and P. xylostella vitellogenin receptor (PxVgR) genes in the Rf and Rb strains were significantly higher than those of S strains at 0-48 h after adult eclosion. At 96 h after eclosion, the content of vitellin in the Rf and Rb strains did not differ significantly from those of S strains, whereas transcripts of the PxVg and PxVgR genes in the Rf and Rbnism of fecundity reduction concurrent with flubendiamide-resistance in P. xylostella.Pyrethroid resistance has been a major hurdle limiting the effective control of bed bugs (Cimex lectularius L.). Alternative approaches that include the use of plant essential oils (EOs) have been proposed for effective management of bed bugs. However, EO resistance level comparisons between pyrethroid susceptible and resistant bed bug populations have not been previously conducted. The goal of this study was twofold (i) determine deltamethrin resistance levels and associated resistance mechanisms in the field-collected Knoxville strain and (ii) quantify resistance levels of the Knoxville strain to five EOs (thyme, oregano, clove, geranium and coriander), their major insecticidal constituents (thymol, carvacrol, eugenol, geraniol and linalool) and an EO-based product (EcoRaider®). First, we found that the Knoxville strain was 72,893 and 291,626 fold more resistant to topically applied deltamethrin in comparison to the susceptible Harlan strain at the LD25 and LD50 lethal dose levels, respectively. Synergist bioassays and detoxification enzyme assays revealed significantly higher activity of cytochrome P450 and esterase enzymes in the resistant Knoxville strain. Further, Sanger sequencing revealed the presence of the L925I mutation in the voltage-sensitive sodium channel α subunit gene. The Knoxville strain that possesses both enzymatic and target site deltamethrin resistance, however, did not show any resistance to EOs, their major insecticidal constituents and EcoRaider® in topical bioassays (resistance ratio of ~1). In conclusion, this study demonstrated that a deltamethrin-resistant strain of bed bugs is susceptible to EOs and their insecticidal constituents.Tomato spotted wilt orthotospovirus (TSWV) causes devastating losses to agronomic and ornamental crops worldwide. Currently, there is no effective strategy to control this disease. Use of biotic inducers to enhance plant resistance to viruses maybe an effective approach. link3 Our previous study indicated that Tagitinin A (Tag A) has a high curative and protective effect against TSWV. However, the underlying molecular mechanism of Tag A-mediated antiviral activity remains unknown. In this study, Tag A reduced the expression of the NSs, NSm genes was very low in untreated leaves following TSWV infection. In addition, the expression of all TSWV genes in the inoculated and systemic leaves was inhibited in the protective assay, and with an inhibition rate of more than 85% in systemic leaves. Tag A increased phenylalanine ammonia-lyase (PAL) activity in the curative and protective assays. The concentrations of jasmonic acid (JA) and jasmonic acid -isoleucine (JA-Ile) and the expression of its key gene NtCOI1 in Tag A-treated and systemic leaves of treated plants were significantly higher than those of the control plant. Furthermore, Tag A-induced resistance to TSWV could be eliminated by VIGS-mediated silencing of the NtCOI1 gene. These indicated that Tag A acts against TSWV by activating the JA defense signaling pathway.Descurainia sophia L. is one of the most notorious broadleaf weeds in winter wheat fields of China. In this study, 95 out of 163 (58.3%) D. sophia populations which were collected from provinces of Hebei, Shandong, Henan, Shanxi, Shaanxi and Jiangsu, have evolved resistance to tribenuron-methyl. The als1 and als2 were cloned in all test D. sophia populations, while als3 and als4 were identified only in some of the populations. Resistant mutations of Pro-197-Ser/Thr/Leu/His/Ala/Arg, Asp-376-Glu and Trp-574-Leu were identified in tribenuron-methyl-resistant (TR) D. sophia plants, while the Pro-197-Arg was first identified in D. sophia in this study. These resistant mutations displayed no preference between ALS1 and ALS2. However, Pro-197-Ser/Thr and Trp-574-Leu were identified in all ALS isozymes, while the other mutations were not. In addition, some resistant mutations displayed regional differences, the frequency of Pro-197-Ser in Shandong and Trp-574-Leu in Shanxi province is much higher than that in other provinces.Neurophysiological recordings were employed to quantify neuronal sensitivity to neurotoxic insecticides and assessed toxicity across field and laboratory fall armyworm (FAW) populations. Topical toxicity resistance ratios (RR) in field-collected FAW was 767-fold compared to laboratory strains and, importantly, a 1750-fold reduction in potency was observed for λ-cyhalothrin in neurophysiological assays. LMK-235 collected FAW were found to have a RR of 12 to chlorpyrifos when compared to the susceptible strain and was 8-fold less sensitive in neurophysiological assays. Surprisingly, there were no point mutations identified in the voltage-gated sodium channel known to cause pyrethroid resistance. For acetylcholinesterase, FAW had more than 80% of their nucleotide sequences consistent with A201 and F290 of the susceptible strains although 60% of the tested population was heterozygous for the G227A mutation. These data indicate that point mutations did not contribute to the high level of pyrethroid resistance and nerve insensitivity in this population of field collected FAW.