Our original drug-hypersensitive fission yeast-based fungicide screening system identified clavatol (1) as a selective active compound against drug-hypersensitive fission yeast (more than 30-fold selectivity over multidrug-sensitive budding yeast). Compound 1, which was originally isolated from Penicillium species, has several biological activities including a very weak antifungal activity against Botrytis cinerea (the 50% effective concentration (EC50) value was 0.058 mg/mL). However, the selectivity of 1 against drug-hypersensitive fission yeast over the budding yeast prompted us to investigate overlooked antifungal activities. After evaluation, we revealed that 1 showed great antifungal activity against quinone outside inhibitors (QoI)-resistant Pyricularia oryzae. Furthermore, we evaluated the anti-P. oryzae activity of 8 compounds having structural features similar to those of 1 in order to elucidate the structure-activity relationship. Our research indicates that the drug-hypersensitive fission yeast-based fungicide screening system is a useful approach for discovering new fungicidal candidates and that 1 has great potential and would be a promising natural product as an agrochemical seed.
Acibenzolar-S-methyl (ASM), a functional analogue of salicylic acid, induces systemic acquired resistance and restricts infection by several RNA viruses, yet its mechanisms against DNA viruses remain unknown. By examining the accumulation of tomato yellow leaf curl virus (TYLCV) DNA in inoculated leaves of Nicotiana benthamiana, we investigated whether ASM suppresses begomovirus infection. TYLCV was inoculated by agroinfiltration, and virion-sense (VS) and complementary-sense (CS) strands of TYLCV DNA were quantified separately using two-step strand-specific qPCR. ASM pretreatment significantly reduced the total TYLCV DNA accumulation at 1, 2, and 3 days post-inoculation. To determine whether this reduction reflected a direct effect on TYLCV rather than impaired Agrobacterium-mediated T-DNA delivery, we used a replication-defective mutant (TYLCVΔC1) as a delivery control and confirmed that ASM did not affect T-DNA delivery. Both VS and CS strands of wild-type TYLCV were substantially reduced by ASM treatment, providing the first direct evidence that ASM suppresses begomovirus infection by targeting viral DNA accumulation at the replication stage.
Microbial secondary metabolites have historically provided numerous agrochemicals with novel chemical scaffolds and distinctive modes of action, contributing substantially to modern pesticide science. However, the long-term accumulation of natural product screening efforts has resulted in the frequent rediscovery of known compounds, and this issue, combined with the global spread of pesticide-resistant pests and pathogens, has become a serious challenge in agrochemical research. This commemorative review summarizes the research achievements of the author focusing on the discovery of pesticide seed compounds from microbial secondary metabolites. Particular emphasis is placed on two original strategies developed by the author: the activation of silent biosynthetic gene clusters in filamentous fungi via introduction of the global transcriptional regulator laeA and the construction of innovative bioassay platforms for antifungal and insecticidal screening using drug-hypersensitive model organisms. These approaches successfully expanded accessible chemical diversity, markedly improved hit rates, and enabled the identification of bioactive compounds with novel molecular targets. Collectively, these studies demonstrate a practical and versatile framework for natural-product-based pesticide discovery that supports sustainable crop protection.
Based on the structure of the natural active molecule piperine, a series of novel piperidine-phenylenediamine derivatives were designed and synthesized using a molecular hybridization strategy. The antifeedant activity of all of the compounds against Spodoptera exigua and their cytotoxicity toward Sf9 insect cells were evaluated. The results showed that most of the derivatives exhibited good antifeedant activity, which correlated with their structures. Among them, compound D5 showed the strongest antifeedant activity (EC50=0.184 mg/mL). In the cytotoxicity study, compounds D15 and J1 showed particularly potent antiproliferative effects, with IC50 values of 4.137 µM and 3.726 µM, respectively. Mechanistic studies revealed that both compounds inhibit proliferation by inducing apoptosis and arresting the cell cycle, as evidenced by cell morphology observation, fluorescence staining, and flow cytometry analysis. In summary, the present study provides potential candidates for the development of new environmentally friendly insecticides based on the combination principle.
Mediterranean fruit fly (Ceratitis capitata) is a top horticultural pest, affecting a variety of fruits and increasingly damaging extra-early citrus cultivars. Lambda-cyhalothrin, a commonly used pyrethroid insecticide, is losing effectiveness due to resistance in C. capitata, driven by repeated and sublethal treatments. In this work, we have developed an eco-friendly nanosystem based on mesoporous silica nanoparticles loaded with lambda-cyhalothrin and capped with hydrolysed corn protein that both attracts protein-feeding insects and seals the insecticide inside. This design protects the active ingredient from premature degradation and photolysis and ensures targeted release-triggered by protease enzymes in the fly's saliva, thereby activating the insecticide only upon ingestion. Field tests on clementine leaves demonstrated sustained insecticidal activity for over four weeks, far longer than conventional pyrethroid sprays, while minimizing offtarget exposure and sublethal dosing.
Derivatives of 1-heterocyclic 2-methylbenzimidazoles (HMBIs), prepared from previously reported 1-benzyl-2-methylbenzimidazoles, were synthesized to assess their larvicidal activity against the silkworm, Bombyx mori. Among the series, 2-methyl-1-(thiophen-2-yl)-methylbenzimidazole (SGH2) produces a distinctive biological phenotype characterized by growth retardation arising from epidermal abnormalities, together with defects in molting and pupation. To explore the basis of these effects, we examined the potential disruption of endocrine signaling as a causal mechanism. Specifically, we evaluated the binding of SGH2 to lepidopteran hemolymph juvenile hormone (JH)-binding protein (JHBP), an important modulator of insect hormone function, using a fluorescence-based ligand-sensor system that couples JHBP to two reporter fluorophores. SGH2 exhibited binding to JHBP with an EC50 of 2.13±0.34 µM, a potency comparable to that of JH. These findings indicate that HMBI derivatives, such as SGH2, can interfere with JH-mediated developmental processes in Lepidoptera and identify a promising scaffold for the design of novel insect growth regulators aimed at controlling lepidopteran pests.
Scorpion venom contains antimicrobial peptides (AMPs). These AMPs are classified into three families based on peptide length: long-chain (>35 residues), intermediate-chain (20-35 residues), and short-chain (13-19 residues) AMPs. Previously, we identified both short- and intermediate-chain AMPs from the venom of the scorpion Isometrus maculatus. A comparative analysis of their antibacterial activities revealed that shortchain AMPs exhibit relatively weaker activity than intermediate-chain AMPs. A structural comparison indicated that intermediate-chain AMPs possess a longer C-terminal region enriched in basic residues, a feature absent in short-chain AMPs. Removal of this C-terminal basic region from intermediate-chain AMPs resulted in a marked loss of antibacterial activity. Conversely, the addition of basic residues at the C-termini of shortchain AMPs significantly enhanced their activity. These results demonstrate that basic residues in the C-terminal region of scorpion intermediate-chain AMPs are crucial for antibacterial activity.
The environmental fate of dimefluthrin (DIM), 2,3,5,6-tetrafluoro-4-(methoxymethyl)benzyl (1R,3R)-2,2-dimethyl-3-(2-methylprop-1-en-1-yl)cyclopropanecarboxylate, was investigated in a water-sediment system in the USA. The study focused on the formation of degradation products and non-extractable residues (NER) using 14C-DIM labelled either at the benzyl or cyclopropyl carbon. The degradation half-life was calculated to be 15.6 days at 20°C, which is well below the regulatory persistence threshold of 120 days. The primary degradation pathway was hydrolysis of the ester linkage. Other reactions, such as oxidation at various positions, produced several minor metabolites that were subsequently mineralised to CO2 and/or incorporated into NER. Specifically, in the cyclopropyl-labelled samples, NER exceeded 10% of the applied radioactivity (% AR) with 78-86% of the total NER consisting of non-hazardous biogenic residues (type-III NER) as verified by 14C-labelled amino acid analysis. Potentially hazardous type-I NER were negligible, accounting for less than 0.5% AR for both labels. These insights into NER formation, particularly regarding the role of microbial activity in the environmental distribution of DIM and its metabolites, indicate minimal environmental risks from such residues.
All eight stereoisomers of aptosimon (9-oxosesamin) were synthesized by employing Evans' anti- and syn-aldol condensations. Among them, the (7S,7'R,8R,8'S)-aptosimon was more active than (+)- and (-)-sesamin at 1×10-5 M in promoting lettuce root growth under illumination conditions (44 µmol·m-2·s-1). The effect of the 9-oxo group on the promotion of lettuce root growth was not observed from the results of activity experiments of stereoisomers carrying the same stereochemistry as those of (+)- and (-)-sesamin (1). However, the importance of 7S-configurations of aptosimon (9-oxosesamin) stereoisomers for the higher promotion of lettuce root growth was suggested. Based on optical rotation data and NMR analysis of the synthesized stereoisomers, the diacylglycerol acyltransferase inhibitory aptosimon was determined to be (7S,7'S,8S,8'R)-aptosimon and its enantiomer.
A practical and regioselective method has been developed for 3-halo-2H-chromene synthesis via decarboxylative halogenation. These chromenes are key intermediates in synthesizing isoflavene derivatives and related bioactive compounds, including molecules of interest in agrochemical research. In this study, 3-carboxy-2Hchromenes, prepared from salicylaldehyde-derived cyanochromenes, were subjected to decarboxylative halogenation under mild conditions. Systematic evaluation of halogen sources, bases, solvents, and other reaction parameters revealed that combining tetrabutylammonium tribromide with sodium-containing bases in acetonitrile promotes decarboxylative bromination with high regioselectivity. This method was designed for chromene substrates bearing oxygencontaining functional groups, which are often difficult to synthesize due to competing electrophilic aromatic substitutions. The optimized protocol, demonstrated on gram scale, afforded the corresponding 3-bromo-2H-chromene as the sole isolable species without requiring column chromatography. The resulting 3-bromo-2H-chromene was converted into an isoflavene derivative via Suzuki-Miyaura coupling, accomplishing its first convergent synthesis as well as formal total synthesis of an isoflavan natural product.
Using the fugacity model InPestCFD, we predicted the indoor behavior of an active substance in an aerosol intended for controlling flies and mosquitoes under various conditions and conducted a comprehensive risk assessment. In predicting behavior, we examined the impact of spraying methods, room air exchange rates, position of an air inlet, and location of a bed, revealing spatiotemporal behaviors not observed previously. For the risk assessment, we predicted the exposure levels for adults and children based on different scenarios from the predicted concentrations and compared them with the acceptable levels of the active substance. Comparison of the obtained results with the results of risk assessment currently conducted in Japan and the United States revealed that current guidelines are considerably conservative in the United States and sufficiently conservative in Japan.
General trends and strategies for the development of new pesticides are summarized. From 2015 to 2025, 156 chemical pesticides were launched or are under development: 47 fungicides, 54 insecticides/acaricides, 9 nematicides, and 46 herbicides. Most are safe to humans and environmentally friendly. The most developed fungicides are succinate dehydrogenase inhibitors, quinone outside inhibitors, quinone inside inhibitors, and demethylation inhibitors. The general trend of insecticide development is in the progress of four major classes of insecticides: nicotinic insecticides, diamide insecticides, GABA-gated chloride channel allosteric modulators, and insect behavior or growth regulators. Due to the development of resistance to fungicides and insecticides with existing modes of action, many compounds possessing various novel modes of action have been developed. Peptide pesticides and RNAi-based insecticides have been put into practical use. Although no herbicides with novel modes of action appeared for approximately 30 years before 2018, since then eight herbicides with five novel modes of action have emerged, including those for existing herbicides. The development of useful acaricides and nematicides is also progressing.
Plants that live a life fixed to the ground cannot escape from various pathogens and must deal with them. To effectively defend against pathogen infection, plants have various resistance mechanisms, which are in a trade-off relationship with growth. In addition to these disease resistance mechanisms, plants have a system called priming that enhances resistance mechanisms but does not affect growth. Analysis of immune priming induced by mycorrhizal symbiosis in tomato revealed that priming is effective against multiple defense signals mediated by salicylic acid (SA) and jasmonic acid signals and against both pathogenic and non-pathogenic bacteria. In Arabidopsis, strigolactone signaling-induced priming was shown to enhance ethylene signaling and camalexin synthesis in addition to SA signaling. These findings are expected to lead to more effective use of priming to protect plants in the future.
For this study, first, the composition of phytoseiid mite species was examined at vineyards in Shimane Prefecture, western Japan, in 2023 and 2024 using quantitative sequencing (QS) and nucleotide sequencing. Amblyseius eharai and Amblyseius andersoni were the most dominant species. Then, the proportion of sodium channel mutations (M918L and L925V/M) involved in pyrethroid resistance was examined using another QS and nucleotide sequencing. Results revealed wide distributions of both mutations in A. eharai and the former mutation in A. andersoni. Results also revealed the presence of M918L in Neoseiulus barkeri and Neoseiulus californicus, but not in Euseius sojaensis. Genotyping for the other mutation sites using the collected phytoseiid mites revealed that all A. eharai and A. andersoni individuals had S1539T, as did some N. californicus individuals. These results suggest that phytoseiid mite species, with the exception of E. sojaensis, have reduced sensitivity to pyrethroids in vineyards in Shimane Prefecture.
The most harmful weed in African agriculture is the root parasitic witchweed Striga hermonthica, of the family Orobanchaceae, which parasitizes staple food crops. Some broomrapes (Orobanche spp.) and branched broomrapes (Phelipanche spp.) also cause significant loss of leguminous crops and vegetables worldwide. Therefore, the control of root parasitic weeds is an agricultural issue worldwide. Because root parasitic weeds are obligate, reaching the host roots following germination through their radicle elongation is required to complete their life cycles. Conversely, inhibiting germination and radicle elongation may be an effective strategy for controlling root parasitic weeds. We identified a characteristic storage carbohydrate, planteose, in root parasitic plants and examined its metabolism, which may serve as a target for controlling root parasitic weeds. Here, our study of the germination process in the root parasitic weeds is reviewed, and the potential of germination metabolic inhibitors as control agents for root parasitic weeds is discussed.
In this study, we report the results of sensitivity tests to succinate dehydrogenase inhibitor (SDHI) fungicides performed on isolates of cucumber Corynespora leaf spot, powdery mildew, and tomato leaf mold pathogens collected in Japan. Isofetamid and fluopyram showed strong activity against boscalid-resistant isolates of Corynespora cassiicola from Tokushima Prefecture in in vitro antifungal assays and in vivo pot experiments. Isofetamid and fluopyram also showed comparable efficacy against boscalid-and penthiopyrad-resistant isolate of Podosphaera xanthii collected in Saga Prefecture using a leaf disc assay. No change was detected in the amino acid sequence of sdhB in the causal pathogen. In addition, during in vitro antifungal tests, isofetamid demonstrated high activity against Fulvia fulva isolates resistant to boscalid, penthiopyrad, and fluopyram obtained in Gifu Prefecture. Collectively, these results indicated that isofetamid maintained similar efficacy against isolates resistant to other SDHIs as against sensitive isolates of these pathogens.
Tests of sensitivity to isofetamid conducted with Botrytis cinerea isolated from Hokkaido (2011-2016) and other districts in Japan (2017-2018) revealed the absence of isolates with reduced sensitivity. Isolates of B. cinerea with mutation H272Y/R in sdhB, collected in Germany and Japan, resulted in high and moderate resistance to boscalid and many other succinate dehydrogenase inhibitors (SDHIs), respectively. However, these isolates were as sensitive as wild-type isolate to isofetamid. In contrast, isolate BC-50 [P225F] and BC-49 [H272L] caused moderate to high resistance to isofetamid. Considerable differences in mycelial growth, conidiation, conidial germination, and pathogenicity were not observed between these resistant isolates and sensitive isolates. A competitive assay between resistant isolate BC-50 [P225F] and BC-49 [H272L] and B05.10 [wild type], however, revealed the disappearance of resistant isolates after several generations of mixed incubation in in vitro and in vivo conditions.
This study investigated the accumulation of cultivar-specific phytoalexins in rice-abietoryzins and oryzalactone-as well as known phytoalexins-momilactone A, phytocassane A, and oryzalexins A and S-in response to sap sucking by the brown planthopper (BPH) and the green rice leafhopper (GRL). The analysis revealed that BPH feeding induced abietoryzin accumulation in a cultivar known to accumulate these phytoalexins following fungal infection. Additionally, oryzalactone and oryzalexin S accumulated after insect attack in specific cultivars, unlike oryzalexin A. Plant hormone profiling revealed distinct associations: momilactone A accumulation was strongly correlated with salicylic acid (SA); phytocassane A with jasmonic acid, jasmonic acid-isoleucine, isopentenyladenine, and abscisic acid (ABA); and oryzalactone/oryzalexin S with both SA and ABA. These findings suggest that distinct signaling pathways regulate the induction of specific phytoalexins. The analysis of phenolic metabolites showed only minor changes in response to insect feeding. The findings highlight the broad inducibility of phytoalexins in rice and reveal the complex hormonal regulation underlying their biosynthesis during herbivore attack.
Genetically modified micro-organisms (GMMs) can be used in agriculture as crop protection agents against plant pests and diseases or as biostimulants intended to enhance plant nutrition. If GMMs are to be utilized in agriculture, they should conform with safety and regulatory requirements. Both academic and non-academic literature were evaluated for developments and commercial status of experimental GMMs intended as crop protection agents and biostimulants. The review also considers regulatory data requirements for GMMs that are relevant for food safety, as recommended by international organizations and authorities in the EU and USA. Experimental GMMs reported in literature and patents are mainly intended for biocontrol of insect pests and phytopathogenic fungi using specialized strains of bacteria (e.g., Bacillus spp.), fungi (e.g., Trichoderma spp.), and baculoviruses. GMMs with biostimulant or biofertilizer activity include microbes with plant nutrition-enhancing and enhanced nitrogen fixation traits. Food safety data requirements for GMMs, as mandated by EU and US regulations, are similar. By replacing high-risk chemical pesticides, GMMs could help achieve policies towards greater sustainability of agriculture.
New asteltoxins U (1) and V (2) were obtained from the solid-state fermentation of Pochonia suchlasporia TAMA 87. The spectroscopic characterization of 1 and 2 revealed that their chemical structures are similar to that of asteltoxin H, except for the modification of the α-pyrone moiety. Specifically, the methyl group on the γ-position of the α-pyrone moiety in asteltoxin H is replaced with a hydroxymethyl group in 1 and 2. In addition, 1 and 2 are a pair of isomers that differ in the geometry of the double bond between C-11 and C-12 in the conjugated triene moiety and that contain an all-trans (9E, 11E, 13E) moiety and a 9E, 11Z, 13E conjugated triene moiety, respectively. Compound 1 showed inhibitory activity toward the first cleavage of sea urchin embryos with a minimum inhibition concentration value of 3.1 µg/mL, whereas compound 2 did not show inhibitory activity up to a concentration of 25 µg/mL.
