No herbicide with a new molecular site of action (SOA) has been introduced since the 1980s. Since then, the widespread evolution of resistance of weeds to most commercial herbicides has greatly increased the need for herbicides with new SOAs. Two untried strategies for the discovery on new herbicide SOAs are discussed. Some primary metabolism intermediates are phytotoxic (e.g., protoporphyrin IX and sphingoid bases), and, because of this, the in vivo concentrations of these compounds are maintained at very low levels by plants. The determination of all primary metabolite phytotoxicities and pool sizes will identify targets of interest. Targeting SOAs that result in accumulation of phytotoxic compounds is the first novel approach to herbicide discovery. The second approach is to identify potential SOAs with very low in vivo enzyme levels. We know that higher numbers of enzyme molecules for a SOA requires more herbicide to kill a plant. Modern proteomic methods can identify low enzyme level SOAs for biorational herbicide discovery. These approaches might be useful in discovery of herbicides more closely related to natural compounds and that can be used in lower doses.
Microtransplantation of rat brain neurolemma into the plasma membrane of Xenopus laevis oocytes is an ex vivo method used to study channels and receptors in their native state using standard electrophysiological approaches. In this review, we show that oocytes injected with adult rat brain neurolemma elicited tetrodotoxin-sensitive inward ion currents upon membrane depolarization, which were increased in a concentration-dependent manner by treatment with the pyrethroid insecticides permethrin and deltamethrin. Under our initial protocols, oocyte health was reduced over time and neurolemma incorporation varied between batches of oocytes from different frogs, limiting the usefulness of the assay for regulatory issues. A collection of changes to the assay procedure, data acceptance criteria, and analysis method yield substantially improved precision and, hence, assay performance. These changes established this ex vivo approach as a toxicologically relevant assay to study the toxicodynamic action of pyrethroids on ion channels in their native state using neurolemma fragments prepared from juvenile and adult rat brains.
Modern agribusiness plays a vital role in safeguarding and improving the production, quality, and quantity of food, feed, fiber, and fuel. Growing concerns over the impact of chemical pesticides on health and the environment have stimulated the industry to search for alternative and greener solutions. Over the last years, the RNA interference (RNAi) process has been identified as a very promising new approach to complement the arsenal of foliar spray, soil, or seed treatments applied as chemical and biological pest control agents, and of plant-incorporated protectants (PIPs). RNA-based active ingredients (AIs) possess a unique mode of action and can be implemented via both genetic modification (GM) and biocontrol approaches. RNA-based AIs promise to deliver the selectivity and sustainability desired in future crop protection agents. This is due to their utilization of a natural process to exert control and their high level of selectivity, which leads to reduced risk for non-target organisms (NTOs). This review discusses the advantages and limitations of RNA-based solutions in crop protection and recent research progress toward RNA-based biocontrols against the Colorado potato beetle (CPB), corn rootworm (CRW), and soy stink bug (SSB). Many challenges still exist on the road to the implementation of a broad range of RNA-based products and their widespread use and application. Despite these challenges, it can be expected that RNA-based AIs will become valuable new tools complementing the current arsenal of crop-protection solutions.
Remote sensing technology has long been used to detect and map crop diseases. Airborne and satellite imagery acquired during growing seasons can be used not only for early detection and within-season management of some crop diseases, but also for the control of recurring diseases in future seasons. With variable rate technology in precision agriculture, site-specific fungicide application can be made to infested areas if the disease is stable, although traditional uniform application is more appropriate for diseases that can spread rapidly across the field. This article provides a brief overview of remote sensing and precision agriculture technologies that have been used for crop disease detection and management. Specifically, the article illustrates how airborne and satellite imagery and variable rate technology have been used for detecting and mapping cotton root rot, a destructive soilborne fungal disease, in cotton fields and how site-specific fungicide application has been implemented using prescription maps derived from the imagery for effective control of the disease. The overview and methodologies presented in this article should provide researchers, extension personnel, growers, crop consultants, and farm equipment and chemical dealers with practical guidelines for remote sensing detection and effective management of some crop diseases.
In highly urbanized areas, pollution from anthropogenic activities has compromised the integrity of the land, decreasing soil availability for agricultural practices. Dibenzothiophene (DBT) is a heterocyclic aromatic hydrocarbon frequently found in urbanized areas, and is often used as a model chemical to study the microbial transformation of pollutants. The potential for human exposure and its health risk makes DBT a chemical of concern; thus, it needs to be environmentally managed. We utilized glycerol to stimulate Burkholderia sp. C3 in order to degrade DBT in respect to ① DBT biodegradation kinetics, ② bacterial growth, ③ rhamnolipid (RL) biosynthesis, and ④ RL secretion. Under an optimum glycerol-to-DBT molar ratio, the DBT biodegradation rate constants increased up to 18-fold and enhanced DBT biodegradation by 25%–30% at day 1 relative to cultivation with DBT alone. This enhancement was correlated with an increase in bacterial growth and RL biosynthesis. Proteomics studies revealed the enzymes involved in the upper and main steps of RL biosynthesis. The RL congeners Rha-C10-C10, Rha-Rha-C10-C10, Rha-Rha-C10-C12, and Rha-Rha-C12-C12 were identified in the medium supplemented with glycerol and DBT, whereas only Rha-C12-C12 was identified in cultures without glycerol or with RL inhibitors. The studies indicated that glycerol enhances DBT biodegradation via increased RL synthesis and bacterial growth. The results warrant further studies of environmental biostimulation with glycerol to advance bioremediation technologies and increase soil availability for agricultural purposes.
Essential oil has been used as sedatives, anticonvulsants, and local anesthetics in traditional medical remedies; as preservatives for food, fruit, vegetable, and grain storage; and as bio-pesticides for food production. Linalool (LL), along with a few other major components such as methyl eugenol (ME), estragole (EG), and citronellal, are the active chemicals in many essential oils such as basil oil. Basil oil and the aforementioned monoterpenoids are potent against insect pests. However, the molecular mechanism of action of these chemical constituents is not well understood. It is well-known that the γ-aminobutyric acid type A receptors (GABAARs) and nicotinic acetylcholine receptor (nAChR) are primary molecular targets of the synthetic insecticides used in the market today. Furthermore, GABAAR-targeted therapeutics have been used in clinics for many decades, including barbiturates and benzodiazepines, to name just a few. In this research, we studied the electrophysiological effects of LL, ME, EG, and citronellal on GABAAR and nAChR to further understand their versatility as therapeutic agents in traditional remedies and as insecticides. Our results revealed that LL inhibits both GABAAR and nAChR, which may explain its insecticidal activity. LL is a concentration-dependent, non-competitive inhibitor on GABAAR, as the half-maximal effective concentration values of γ-aminobutyric acid (GABA) for the rat α1β3γ2L GABAAR were not affected by LL: (36.2 ± 7.9) µmol·L−1 and (36.1 ± 23.8) µmol·L−1 in the absence and presence of 5 mmol·L−1 LL, respectively. The half-maximal inhibitory concentration (IC50) of LL on GABAAR was approximately 3.2 mmol·L−1. Considering that multiple monoterpenoids are found within the same essential oil, it is likely that LL has a synergistic effect with ME, which has been previously characterized as both a GABAAR agonist and a positive allosteric modulator, and with other monoterpenoids, which offers a possible explanation for the sedative and anticonvulsant effects and the insecticidal activities of LL.
Reliable knowledge on pathogenic agents contributes to effective plant protection. For most plant pathogens, maintaining protein homeostasis (proteostasis) is essential for unfolding the cellular functions to survive and thrive. However, the fungal proteins involved in proteostasis remain poorly characterized in the process of pathogenesis. In this study, we characterized the function of the nascent polypeptide-associated complex (NAC) in Fusarium graminearum (F. graminearum, FgNAC), one of the top 10 fungal pathogens with predominant scientific/economic importance. We found that FgNACα, a subunit of FgNAC, manifests high structural and functional similarity to its homologous counterparts in yeast and other species. The mutants of F. graminearum lacking NACα are viable but suffer significant defects in vegetative growth, conidial production, and pathogenesis. In addition, we show here that FgNACα can interact with another subunit of NAC (FgNACβ) in a yeast-two-hybrid assay. The subcellular localization results show that FgNACα and FgNACβ are predominantly localized in the cytoplasm. Future studies should focus on deciphering the mechanism by which NAC orchestrates protein biogenesis and consequentially modulates development and pathogenesis.
In recent years, the damage caused by soil nematodes has become increasingly serious; however, the varieties and structures of the nematicides available on the market are deficient. Fluopyram, a succinate dehydrogenase inhibitor (SDHI) fungicide developed by Bayer AG in Germany, has been widely used in the prevention and control of soil nematodes due to its high efficiency and novel mechanism of action. In this paper, two series of novel target compounds were designed and synthesized with nematicidal and fungicidal fluopyram as the molecular skeleton in order to introduce sulfide and sulfone substructures. The structures were identified and characterized by 1H nuclear magnetic resonance (NMR), 13C NMR, and high-resolution mass spectrometer (HRMS). The bioassays revealed that most of the compounds showed excellent nematicidal activities at 200 µg･mL−1 in comparison with fluopyram, while the nematode mortality rate dropped sharply at 100µg･mL−1, except for compounds I-11 and II-6. In terms of fungicidal activity, compound I-9 was discovered to have an excellent inhibitory rate, and a molecular docking simulation was performed that can provide important guidance for the design and exploration of efficient fungicidal lead compounds.
5-Substituted benzylidene 3-acylthiotetronic acids are antifungal. A series of 3-acylthiotetronic acid derivatives with varying substitutions at the 5-position were designed, synthesized, and characterized, based on the binding pose of 3-acyl thiolactone with the protein C171Q KasA. Fungicidal activities of these compounds were screened against Valsa Mali, Curvularia lunata, Fusarium graminearum, and Fusarium oxysporum f. sp. lycopersici. Most target compounds exhibited excellent fungicidal activities against target fungi at the concentration of 50 μg·mL−1. Compounds 11c and 11i displayed the highest activity with a broad spectrum. The median effective concentration (EC50) values of 11c and 11i were 1.9–10.7 and 3.1–7.8 μg·mL−1, respectively, against the tested fungi, while the EC50 values of the fungicides azoxystrobin, carbendazim, and fluopyram were respectively 0.30, 4.22, and > 50 μg·mL−1 against V. Mali; 6.7, 41.7, and 0.18 μg·mL−1 against C. lunata; 22.4, 0.42, and 0.43 μg·mL−1 against F. graminearum; and 4.3, 0.12, and > 50 μg·mL−1 against F. oxysporum f. sp. Lycopersici. The structures and activities of the target compounds against C. lunata were analyzed to obtain a statistically significant comparative molecular field analysis (CoMFA) model with high prediction abilities (q2 = 0.9816, r2 = 0.8060), and its reliability was verified. The different substituents on the benzylidene at the 5-position had significant effects on the activity, while the introduction of a halogen atom at the benzene ring of benzylidene was able to improve the activity against the tested fungi.
Achieving efficient adsorption and desorption processes by controllably tuning the properties of adsorbents at different technical stages is extremely attractive. However, it is difficult for traditional adsorbents to reach the target because of their fixed active sites. Herein, we report on the fabrication of a smart adsorbent, which was achieved by introducing photoresponsive azobenzene derivatives with cis/trans isomers to Ce-doped mesoporous silica. These photoresponsive groups serve as ″molecular switches″ by sheltering and exposing active sites, leading to efficient adsorption and desorption. Ce is also doped to provide additional active sites in order to enhance the adsorption performance. The results show that the cis isomers effectively shelter the active sites, leading to the selective adsorption of methylene blue (MB) over brilliant blue (BB), while the trans isomers completely expose the active sites, resulting in the convenient release of the adsorbates. Both selective adsorption and efficient desorption can be realized controllably by these smart adsorbents through photostimulation. Moreover, the performance of the obtained materials is well maintained after five cycles.
Understanding the transport resistance of water molecules in polyamide (PA) reverse osmosis (RO) membranes at the molecular level is of great importance in guiding the design, preparation, and applications of these membranes. In this work, we use molecular simulation to calculate the total transport resistance by dividing it into two contributions: the interior part and the interfacial part. The interior resistance is dependent on the thickness of the PA layer, while the interfacial resistance is not. Simulation based on the 5 nm PA layer reveals that interfacial resistance is the dominating contribution (> 62%) to the total resistance. However, for real-world RO membranes with a 200 nm PA layer, interfacial resistance plays a minor role, with a contribution below 10%. This implies that there is a risk of inaccuracy when using the typical method to estimate the transport resistance of RO membranes, as this method involves simply multiplying the total transport resistance of the simulated value based on a membrane with a 5 nm PA layer. Furthermore, both the interfacial resistance and the interior resistance are dependent on the chemistry of the PA layer. Our simulation reveals that decreasing the number of residual carboxyl groups in the PA layer leads to decreased interior resistance; therefore, the water permeability can be improved at no cost of ion rejection, which is in excellent agreement with the experimental results.