Journal of Pesticide Science
Online ISSN : 1349-0923
Print ISSN : 1348-589X
ISSN-L : 0385-1559
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Showing 1-17 articles out of 17 articles from the selected issue
Editorial
Preface
Commentary
  • Marek Jindra
    2021 Volume 46 Issue 1 Pages 3-6
    Published: February 20, 2021
    Released: February 26, 2021
    [Advance publication] Released: January 29, 2021
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    Insect Growth Regulators (IGRs) represent advanced, bio-rational insecticides. This Special Issue reflects progress in IGR development that has been enabled by insight into the molecular principles of biosynthetic or hormone signaling pathways. The unifying principle is aiming at processes and molecular targets that are unique to arthropods and ideally to narrower insect taxa representing pests or disease vectors. While some strategies of obtaining the desired compounds for chemical intervention rely on rational, structure-based design or computational power, others exploit technologies allowing automated, high-throughput screening of large chemical libraries. All avenues leading to selective and environmentally safe pest control are valid as we face the imminent threat of the declining world insect population.

Reviews
  • Marie-Ève Picard, Michel Cusson, Stephanie E. Sen, Rong Shi
    2021 Volume 46 Issue 1 Pages 7-15
    Published: February 20, 2021
    Released: February 26, 2021
    [Advance publication] Released: January 28, 2021
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    Reducing the use of broad-spectrum insecticides is one of the many challenges currently faced by insect pest management practitioners. For this reason, efforts are being made to develop environmentally benign pest-control products through bio-rational approaches that aim at disrupting physiological processes unique to specific groups of pests. Perturbation of hormonal regulation of insect development and reproduction is one such strategy. It has long been hypothesized that some enzymes in the juvenile hormone biosynthetic pathway of moths, butterflies and caterpillars (order Lepidoptera) display unique structural features that could be targeted for the development of Lepidoptera-specific insecticides, a promising avenue given the numerous agricultural and forest pests belonging to this order. Farnesyl diphosphate synthase, FPPS, is one such enzyme, with recent work suggesting that it has structural characteristics that may enable its selective inhibition. This review synthesizes current knowledge on FPPS and summarizes recent advances in its use as a target for insecticide development.

  • Ramaseshadri Parthasarathy, Subba Reddy Palli
    2021 Volume 46 Issue 1 Pages 16-22
    Published: February 20, 2021
    Released: February 26, 2021
    [Advance publication] Released: February 04, 2021
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    The discovery of juvenile hormones (JH) and their synthetic analogs (JHA) generated excitement and hope that these compounds will replace first- and second-generation insecticides that have not so desirable environmental and human safety profiles. However, JHAs used commercially during the past four decades did not meet these expectations. The recent availability of advanced molecular and histological methods and the discovery of key players involved in JH action provided some insights into the functioning of JHA in a stage and species-specific manner. In this review, we will summarize recent findings and stage-specific action of JHA, focusing on three commercially used JHA, methoprene, hydroprene and pyriproxyfen and economically important pests, the red flour beetle, Tribolium castaneum, and the tobacco budworm, Heliothis virescens, and disease vector, the yellow fever mosquito, Aedes aegypti.

  • Naoki Okamoto, Naoki Yamanaka
    2021 Volume 46 Issue 1 Pages 23-28
    Published: February 20, 2021
    Released: February 26, 2021
    [Advance publication] Released: January 15, 2021
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    Ecdysteroids are a class of steroid hormones in arthropods that control molting and metamorphosis through interaction with intracellular nuclear receptors. In contrast to the extensive literature describing their biosynthetic pathways and signaling components, little has been known about how these hormones are traveling into and out of the cells through lipid bilayers of the cell membranes. Recently, a series of studies conducted in the fruit fly Drosophila melanogaster revealed that membrane transporters have critical functions in trafficking ecdysteroids across cell membranes, challenging the classical simple diffusion model of steroid hormone transport. Here we summarize recent advances in our understanding of membrane transporters involved in ecdysteroid signaling in Drosophila, with particular focus on Ecdysone Importer (EcI) that is involved in ecdysteroid uptake in peripheral tissues. We then discuss the potential advantage of EcI blockers as a novel pest management tool as compared to classical insect growth regulators.

  • Sayoko Ito-Harashima, Takashi Yagi
    2021 Volume 46 Issue 1 Pages 29-42
    Published: February 20, 2021
    Released: February 26, 2021
    [Advance publication] Released: January 28, 2021
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    A reporter gene assay (RGA) is used to investigate the activity of synthetic chemicals mimicking the molting hormones (MHs) and juvenile hormones (JHs) of insects, so-called insect growth regulators (IGRs). The MH receptor, a heterodimer of the ecdysone receptor (EcR) and ultraspiracle (USP), and the JH receptor Methoprene-tolerant (Met) are ligand-dependent transcription factors. Ligand-bound EcR-USP and Met bind to specific cis-acting DNA elements, referred to as the ecdysone-responsive element (EcRE) and the JH-responsive element (JHRE), respectively, in order to transactivate target genes. Insect hormone-induced transactivation systems have been reconstituted by the introduction of reporter genes under the control of EcRE and JHRE, or two-hybrid reporter genes, into insect, mammalian, and yeast cells expressing receptor proteins. RGA is easy to use and convenient for examining the MH- and JH-like activities of synthetic chemicals and is suitable for the high-throughput screening of novel structural classes of chemicals targeting EcR-USP and Met.

  • Yingchen Li, Lin Liu, Jun Yang, Qing Yang
    2021 Volume 46 Issue 1 Pages 43-52
    Published: February 20, 2021
    Released: February 26, 2021
    [Advance publication] Released: February 04, 2021
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    Chitin deacetylase (CDA) is a key enzyme involved in the modification of chitin and plays critical roles in molting and pupation, which catalyzes the removal of acetyl groups from N-acetyl-D-glucosamine residues in chitin to form chitosan and release acetic acid. Defects in the CDA genes or their expression may lead to stunted insect development and even death. Therefore, CDA can be used as a potential pest control target. However, there are no effective pesticides known to target CDA. Although there has been some exciting research progress on bacterial or fungal CDAs, insect CDA characteristics are less understood. This review summarizes the current understanding of insect CDAs, especially very recent advances in our understanding of crystal structures and the catalytic mechanism. Progress in developing small-molecule CDA inhibitors is also summarized. We hope the information included in this review will help facilitate new pesticide development through a novel action mode, such as targeting CDA.

Regular Articles
  • Takumi Kayukawa, Kenjiro Furuta, Kiyoaki Yonesu, Takayoshi Okabe
    2021 Volume 46 Issue 1 Pages 53-59
    Published: February 20, 2021
    Released: February 26, 2021
    [Advance publication] Released: January 29, 2021
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    Supplementary material

    Juvenile hormone (JH) is an insect-specific hormone that regulates molting and metamorphosis. Hence, JH signaling inhibitors (JHSIs) and activators (JHSAs) can be used as effective insect growth regulators (IGRs) for pest management. In our previous study, we established a high-throughput screening (HTS) system for exploration of novel JHSIs and JHSAs using a Bombyx mori cell line (BmN_JF&AR cells) and succeeded in identifying novel JHSIs from a chemical library. Here, we searched for novel JHSAs using this system. The four-step HTS yielded 10 compounds as candidate JHSAs; some of these compounds showed novel basic structures, whereas the others were composed of a 4-phenoxyphenoxymethyl skeleton, the basic structure of several existing JH analogs (pyriproxyfen and fenoxycarb). Topical application of seven compounds to B. mori larvae significantly prolonged the larval period, suggesting that the identified JHSAs may be promising IGRs targeting the JH signaling pathway.

  • Shouya Naruse, Mayuko Ogino, Takao Nakagawa, Yoko Yasuno, Akiya Jourak ...
    2021 Volume 46 Issue 1 Pages 60-67
    Published: February 20, 2021
    Released: February 26, 2021
    [Advance publication] Released: January 20, 2021
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    Supplementary material

    Insect juvenile hormone (JH) mimics (JHMs) are known to have ovicidal effects if applied to adult females or eggs. Here, we examined the effects of exogenous JHMs on embryonic development of the bean bug, Riptortus pedestris. The expression profiles of JH early response genes and JH biosynthetic enzymes indicated that JH titer was low for the first 3 days of the egg stage and increased thereafter. Application of JH III skipped bisepoxide (JHSB3) or JHM on Day 0 eggs when JH titer was low caused reduced hatchability, and the embryos mainly arrested in mid- or late embryonic stage. Application of JHMs on Day 5 eggs also resulted in an arrest, but this was less effective compared with Day 0 treatment. Interestingly, ovicidal activity of synthetic JHMs was much lower than that of JHSB3. This study will contribute to developing novel insecticides that are selective among insect species.

  • Taiyo Yokoi, Taku Nabe, Shinri Horoiwa, Ken’ichiro Hayashi, Sayoko Ito ...
    2021 Volume 46 Issue 1 Pages 68-74
    Published: February 20, 2021
    Released: February 26, 2021
    [Advance publication] Released: January 29, 2021
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    Supplementary material

    Juvenile hormone (JH) agonists constitute a subclass of insect growth regulators and play important roles in insect pest management. In this work, a multi-step virtual screening program was executed to find novel JH agonists. A database of 5 million purchasable compounds was sequentially processed with three computational filters: (i) shape and chemical similarity as compared to known JH-active compounds; (ii) molecular docking simulations against a Drosophila JH receptor, methoprene-tolerant; and (iii) free energy calculation of ligand–receptor binding using a modified MM/PBSA (molecular mechanics/Poisson–Boltzmann surface area) protocol. The 11 candidates that passed the three filters were evaluated in a luciferase reporter assay, leading to the identification of a hit compound that contains a piperazine ring system (EC50=870 nM). This compound is structurally dissimilar to known JH agonists and synthetically easy to access; therefore, it is a promising starting point for further structure optimization.

  • Kotaro Koiwai, Kana Morohashi, Kazue Inaba, Kana Ebihara, Hirotatsu Ko ...
    2021 Volume 46 Issue 1 Pages 75-87
    Published: February 20, 2021
    Released: February 26, 2021
    [Advance publication] Released: February 04, 2021
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    Supplementary material

    Insect growth regulators (IGRs) can be developed by elucidating the molecular mechanisms of insect-specific biological events. Because insect molting, and metamorphosis are controlled by ecdysteroids, their biosynthetic pathways can serve as targets for IGR development. The glutathione S-transferase Noppera-bo (Nobo), which is conserved in dipteran and lepidopteran species, plays an essential role in ecdysteroid biosynthesis. Our previous study using 17β-estradiol as a molecular probe revealed that Asp113 of Drosophila melanogaster Nobo (DmNobo) is essential for its biological function. However, to develop IGRs with a greater Nobo inhibitory activity than 17β-estradiol, further structural information is warranted. Here, we report five novel non-steroidal DmNobo inhibitors. Analysis of crystal structures of complexes revealed that DmNobo binds these inhibitors in an Asp113-independent manner. Among amino acid residues at the substrate-recognition site, conformation of conserved Phe39 was dynamically altered upon inhibitor binding. Therefore, these inhibitors can serve as seed compounds for IGR development.

  • Christopher Browning, Alastair G. McEwen, Kotaro Mori, Taiyo Yokoi, Di ...
    2021 Volume 46 Issue 1 Pages 88-100
    Published: February 20, 2021
    Released: February 26, 2021
    [Advance publication] Released: February 04, 2021
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    Supplementary material

    The ecdysone receptor (EcR) possesses the remarkable capacity to adapt structurally to different types of ligands. EcR binds ecdysteroids, including 20-hydroxyecdysone (20E), as well as nonsteroidal synthetic agonists such as insecticidal dibenzoylhydrazines (DBHs). Here, we report the crystal structures of the ligand-binding domains of Heliothis virescens EcR/USP bound to the DBH agonist BYI09181 and to the imidazole-type compound BYI08346. The region delineated by helices H7 and H10 opens up to tightly fit a phenyl ring of the ligands to an extent that depends on the bulkiness of ring substituent. In the structure of 20E-bound EcR, this part of the ligand-binding pocket (LBP) contains a channel filled by water molecules that form an intricate hydrogen bond network between 20E and LBP. The water channel present in the nuclear receptor bound to its natural hormone acts as a critical molecular adaptation spring used to accommodate synthetic agonists inside its binding cavity.

  • Minori Ueno, Taiyo Yokoi, Yoshiaki Nakagawa, Hisashi Miyagawa
    2021 Volume 46 Issue 1 Pages 101-108
    Published: February 20, 2021
    Released: February 26, 2021
    [Advance publication] Released: February 04, 2021
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    Supplementary material

    Tetrahydroquinolines (THQs), a class of nonsteroidal ecdysone agonists, are good candidates for novel mosquito control agents because they specifically bind to mosquito ecdysone receptors (EcRs). We have recently performed quantitative structure–activity relationship (QSAR) analyses of THQs to elucidate the physicochemical properties important for the ligand–receptor interaction. Based on previous QSAR results, here, we newly synthesized 15 THQ analogs with a heteroaryl group at the acyl moiety and evaluated their binding affinity against Aedes albopictus EcRs. We also measured the larvicidal activity of the combined set of previously and newly synthesized compounds against A. albopictus to examine the contribution of receptor-binding to larvicidal activity. Multiple regression analyses showed that the binding affinity and the molecular hydrophobicity of THQs are the key determinants of their larvicidal activity.

  • Eikoh Satoh, Ryota Kasahara, Kosuke Fukatsu, Takao Aoki, Hiroto Haraya ...
    2021 Volume 46 Issue 1 Pages 109-114
    Published: February 20, 2021
    Released: February 26, 2021
    [Advance publication] Released: January 27, 2021
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    Benzpyrimoxan (5-(1,3-dioxan-2-yl)-4-{[4-(trifluoromethyl)phenyl]methoxy}pyrimidine, NNI-1501) was discovered as a novel insecticide structurally characterized by a pyrimidine derivative substituted with 1,3-dioxanyl and 4-trifluoromethylbenzyloxy groups. The compound showed remarkable activity against nymphs of rice planthoppers, including strains resistant to existing insecticides. Furthermore, benzpyrimoxan had low adverse effects on pollinators and beneficial arthropods. Because of these features, benzpyrimoxan is expected to be a suitable part of an integrated pest management strategy. In this report, the history of the discovery to reach benzpyrimoxan and details of the structure–activity relationships are described.

  • Yuhichi Mushiake, Aya Tsuchida, Asami Yamada, Hiroshi Kanzaki, Toru Ok ...
    2021 Volume 46 Issue 1 Pages 115-119
    Published: February 20, 2021
    Released: February 26, 2021
    [Advance publication] Released: February 04, 2021
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    Supplementary material

    Three novel analogs of pochonicine (1) were isolated from a solid fermentation culture of the fungal strain Pochonia suchlasporia var. suchlasporia TAMA 87, and their structures were elucidated as 7-deoxypochonicine (2), 6-deoxypochonicine (3), and 6,7-dideoxypochonicine (4). These analogs were found to possess the same stereochemistry as pochonicine. Comparison of β-N-acetylglucosaminidase (GlcNAcase) inhibitory activity between these analogs and pochonicine suggested that the C-6 hydroxy group of pochonicine was essential to its potent GlcNAcase inhibitory activity and that the C-7 hydroxy group also contributed to the activity, but to a lesser extent than the C-6 hydroxy group.

Brief Report
  • Kotaro Mori, Hideya Tokuoka, Hisashi Miyagawa, Yoshiaki Nakagawa
    2021 Volume 46 Issue 1 Pages 120-123
    Published: February 20, 2021
    Released: February 26, 2021
    [Advance publication] Released: January 16, 2021
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    Supplementary material

    Benzoylphenylureas (BPUs) were discovered as novel type insecticides about a half century ago; many analogs have been launched as insecticides and acaricides. BPUs are known to inhibit chitin synthesis in insects and other arthropods, but they have no effect against microorganisms such as fungi. We designed new chitin synthesis inhibitors based on the hypothesis that biomolecules that play important roles in cellulose and chitin biosynthesis are similar. In the full automatic modeling system (FAMS), the cellulose synthase was selected as a template three-dimensional structure. Thus, we focused on the structure of cellulose synthase inhibitor, isoxaben, to develop new chemistry. The 1,1-diethylethyl [-C(CH3)(CH2CH3)2] group of isoxaben was changed to a 4-substituted phenyl group bearing Cl, Et, or Ph. These compounds significantly inhibited chitin synthesis in the cultured integument of the rice stem borer Chilo suppressalis. The activity of the 4-ethylphenyl analog was enhanced 30-fold by adding piperonyl butoxide to the culture medium.

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