Search Results (9)

Extensive use of chemical herbicides has raised serious concerns regarding agricultural sustainability and ecological safety, highlighting the need for environment friendly bioherbicides. In this study, activity-guided fractionation led to the identification of xanthoxylin and α-santonin from the ethanol extract of a dominant desert plant, Seriphidium transiliense, with the phytotoxicity of xanthoxylin being reported for the first time. Petri dish bioassay revealed that both compounds significantly suppressed seedling growth of tested plants in a dose-dependent manner; at 1000 μg/mL, α-santonin inhibited root growth of Amaranthus retroflexus, Setaria viridis, Medicago sativa, and Oxybasis glauca by 98.25%, 79.75%, 71.40%, and 62.75%, respectively, whereas the corresponding inhibition rates for xanthoxylin were 59.15%, 89.71%, 38.80%, and 62.90%. Following pot experiments revealed that both compounds significantly increased MDA content and altered the activities of SOD, CAT, and POD of A. retroflexus seedlings, indicating the induction of oxidative stress. Treated plants also displayed chlorosis and leaf whitening, suggesting possible disturbance of photosynthetic pigment-related processes; subsequent molecular docking further implied that both compounds may interact with protoporphyrinogen IX oxidase (PPO), a key enzyme associated with tetrapyrrole metabolism and chlorophyll biosynthesis. Our results suggests that α-santonin and xanthoxylin have the potential to be developed as bio-herbicides. Full article

In continuation of our efforts to identify novel herbicide lead compounds, twenty new 5-(1-amino-4-phenoxybutylidene)barbituric acid derivatives containing an enamino diketone motif were synthesized and evaluated for their herbicidal activities. The greenhouse bioassay results indicated that several of the target compounds, including BA-1, BA-2, BA-5, BA-18, and BA-20, exhibited notable post-emergence herbicidal activity, with sum inhibition rates exceeding 70% at a dosage of 150 g ha⁻¹, which was superior to that of the commercial herbicide flumiclorac-pentyl (FP). The structure–activity relationship analysis demonstrated that the steric and electronic effects of the R group, as well as the lipophilicity of the target compounds, significantly influenced herbicidal activity. Among these, BA-1 was identified as a promising herbicide lead compound due to its high total herbicidal efficacy, broad-spectrum activity, and favorable crop safety profile. Molecular simulation studies indicated that BA-1 binds effectively to Nicotiana tabacum protoporphyrinogen IX oxidase (NtPPO), suggesting its potential as a novel PPO inhibitor. This study highlights BA-1 as a promising lead compound for the development of novel PPO-inhibiting herbicides. Full article

In continuation of our efforts to identify novel herbicide lead compounds with enhanced activity, a series of eighteen 5-acylbarbituric acid derivatives containing a pyrimidinedione moiety were designed and synthesized. Their herbicidal activities were subsequently evaluated in the greenhouse. Bioassay results demonstrated that most of the newly synthesized compounds exhibited significant herbicidal efficacy at a dosage of 150 g ha⁻¹, with compounds BA-I-2, BA-II-2, BA-III-2, and BA-III-5 achieving complete inhibition of the tested weeds. Further investigation into the herbicidal spectrum revealed that compounds BA-II-2 and BA-III-2 displayed excellent herbicidal activity against 14 and 13 out of 16 tested weed species, respectively, with inhibition rates exceeding 80% at dosages as low as 18.8 g ha⁻¹. More promisingly, compound BA-III-2 was found to be safe for Triticum aestivum at a dosage of 37.5 g ha⁻¹. Molecular mode of action studies, including phenotypic observations, membrane permeability evaluations, and molecular docking, suggested that BA-III-2 may function as a protoporphyrinogen IX oxidase (PPO) inhibitor. The present work indicates that BA-III-2 holds potential as a PPO-inhibiting herbicide for effective weed control in wheat fields and is expected to provide important theoretical foundations for the development of novel and highly efficient herbicides. Full article

Resistance to protoporphyrinogen IX oxidase (PPO)-inhibitors in Amaranthus palmeri and Amaranthus tuberculatus is mainly contributed by mutations in the PPO enzyme, which renders herbicide molecules ineffective. The deletion of glycine210 (ΔG210) is the most predominant PPO mutation. ΔG210-ppo2 is overexpressed in rice (Oryza sativa c. ‘Nipponbare’) and Arabidopsis thaliana (Col-0). A foliar assay was conducted on transgenic T₁ rice plants with 2× dose of fomesafen (780 g ha⁻¹), showing less injury than the non-transgenic (WT) plants. A soil-based assay conducted with T₂ rice seeds confirmed tolerance to fomesafen applied pre-emergence. In agar medium, root growth of WT rice seedlings was inhibited >90% at 5 µM fomesafen, while root growth of T2 seedlings was inhibited by 50% at 45 µM fomesafen. The presence and expression of the transgene were confirmed in the T₂ rice survivors of soil-applied fomesafen. A soil-based assay was also conducted with transgenic A. thaliana expressing ΔG210-ppo2 which confirmed tolerance to the pre-emergence application of fomesafen and saflufenacil. The expression of A. palmeri ΔG210-ppo2 successfully conferred tolerance to soil-applied fomesafen in rice and Arabidopsis. This mutant also confers cross-tolerance to saflufenacil in Arabidopsis. This trait could be introduced into high-value crops that lack chemical options for weed management. Full article

Protoporphyrinogen IX (Protogen IX) oxidase (PPO) catalyzes the oxidation of Protogen IX to Proto IX. PPO is also the target site for diphenyl ether-type herbicides. In plants, there are two PPO encoding genes, PPO1 and PPO2. To date, no PPO gene or mutant has been characterized in monocotyledonous plants. In this study, we isolated a spotted and rolled leaf (sprl1) mutant in rice (Oryza sativa). The spotted leaf phenotype was sensitive to high light intensity and low temperature, but the rolled leaf phenotype was insensitive. We confirmed that the sprl1 phenotypes were caused by a single nucleotide substitution in the OsPPO1 (LOC_Os01g18320) gene. This gene is constitutively expressed, and its encoded product is localized to the chloroplast. The sprl1 mutant accumulated excess Proto(gen) IX and reactive oxygen species (ROS), resulting in necrotic lesions. The expressions of 26 genes associated with tetrapyrrole biosynthesis, photosynthesis, ROS accumulation, and rolled leaf were significantly altered in sprl1, demonstrating that these expression changes were coincident with the mutant phenotypes. Importantly, OsPPO1-overexpression transgenic plants were resistant to the herbicides oxyfluorfen and acifluorfen under field conditions, while having no distinct influence on plant growth and grain yield. These finding indicate that the OsPPO1 gene has the potential to engineer herbicide resistance in rice. Full article

In Arkansas, resistance to protoporphyrinogen IX oxidase (PPO)-inhibiting herbicides in Amaranthus palmeri S. Wats. is mainly due to target site mutations. Although A. palmeri PPO-mutations are well investigated, the cross-resistance that each ppo mutant endows to weed populations is not yet well understood. We aimed to evaluate the response of PPO-resistant A. palmeri accessions, harboring the ppo2 mutations ΔG210 and G399A, to multiple PPO-inhibiting herbicides. Six resistant and one susceptible field accessions were subjected to a dose–response assay with fomesafen, and selected survivors from different fomesafen doses were genotyped to characterize the mutation profile. The level of resistance to fomesafen was determined and a cross-resistance assay was conducted with 1 and 2 times the labeled doses of selected PPO herbicides. The accession with higher predicted dose to control 50% of the population (ED50) had a higher frequency of ΔG210-homozygous survivors. Survivors harboring both mutations, and those that were ΔG210-homozygous, incurred less injury at the highest fomesafen rate tested (1120 g ai ha⁻¹). The populations with a high frequency of ΔG210-homozygous survivors, and those with individuals harboring ΔG210 + G399A mutations, exhibited high potential for cross-resistance to other PPO herbicides. The new PPO–herbicide chemistries (saflufenacil, trifludimoxazin) generally controlled the PPO-resistant populations. Full article

Background: The spread of herbicide-resistance Ambrosia artemisiifolia threatens not only the production of agricultural crops, but also the composition of weed communities. The reduction of their spread would positively affect the biodiversity and beneficial weed communities in the arable habitats. Detection of resistant populations would help to reduce herbicide exposure which may contribute to the development of sustainable agroecosystems. Methods: This study focuses on the application of target-site resistance (TSR) diagnostic of A. artemisiifolia caused by different herbicides. We used targeted amplicon sequencing (TAS) on Illumina Miseq platform to detect amino acid changes in herbicide target enzymes of resistant and wild-type plants. Results: 16 mutation points of four enzymes targeted by four herbicide groups, such as Photosystem II (PSII), Acetohydroxyacid synthase (AHAS), 5-enolpyruvylshikimate 3-phosphate synthase (EPSPS) and protoporphyrinogen IX oxidase (PPO) inhibitors have been identified in common ragweed populations, so far. All the 16 mutation points were analyzed and identified. Out of these, two mutations were detected in resistant biotypes. Conclusions: The applied next-generation sequencing-targeted amplicon sequencing (NGS-TAS) method on A. artemisiifolia resistant and wild-type populations enable TSR detection of large sample numbers in a single reaction. The NGS-TAS provides information about the evolved herbicide resistance that supports the integrated weed control through the reduction of herbicide exposure which may preserve ecological properties in agroecosystems. Full article

The study of human protoporphyrinogen oxidase (hPPO) inhibition can contribute significantly to a better understanding of some pathogeneses (e.g., porphyria, herbicide exposure) and the development of anticancer agents. Therefore, we prepared new potential inhibitors with Schiff base structural motifs (2-hydroxybenzaldehyde-based Schiff bases 9–13 and chromanone derivatives 17–19) as structurally relevant to PPO herbicides. The inhibitory activities (represented by the half maximal inhibitory concentration (IC₅₀) values) and enzymatic interactions (represented by the hPPO melting temperatures) of these synthetic compounds and commercial PPO herbicides used against hPPO were studied by a protoporphyrin IX fluorescence assay. In the case of PPO herbicides, significant hPPO inhibition and changes in melting temperature were observed for oxyfluorten, oxadiazon, lactofen, butafenacil, saflufenacil, oxadiargyl, chlornitrofen, and especially fomesafen. Nevertheless, the prepared compounds did not display significant inhibitory activity or changes in the hPPO melting temperature. However, a designed model of hPPO inhibitors based on the determined IC₅₀ values and a docking study (by using AutoDock) found important parts of the herbicide structural motif for hPPO inhibition. This model could be used to better predict PPO herbicidal toxicity and improve the design of synthetic inhibitors. Full article

The herbicide fomesafen has the advantages of low toxicity and high selectivity, and the target of this compound is protoporphyrinogen IX oxidase (PPO, EC 1.3.3.4). However, this herbicide has a long residual period and can have phytotoxic effects on succeeding crops. To protect maize from fomesafen, a series of thiazole phenoxypyridines were designed based on structure–activity relationships, active substructure combinations, and bioisosterism. Bioassays showed that thiazole phenoxypyridines could improve maize tolerance under fomesafen toxicity stress to varying degrees at a dose of 10 mg·kg⁻¹. Compound 4i exhibited the best effects. After being treated by compound 4i, average recovery rates of growth index exceeded 72%, glutathione content markedly increased by 167% and glutathione S-transferase activity was almost 163% of fomesafen-treated group. More importantly, after being treated by compound 4i, the activity of PPO, the main target enzyme of fomesafen, recovered to 93% of the control level. The molecular docking result exhibited that the compound 4i could compete with fomesafen to bind with the herbicide target enzyme, which consequently attained the herbicide detoxification. The present work suggests that compound 4i could be developed as a potential safener to protect maize from fomesafen. Full article