Preface

To accommodate growth, insects must undergo repeated molts. The change in form in holo- and hemi-metabolous insects is accomplished by metamorphosis. Both molting and metamorphosis are regulated by two major hormones: sesquiterpenoid juvenile hormones (JHs) and steroids (ecdysteriods, 20-hydroxyecdysone, 20E is the most active form). During molting and metamorphosis, insects shed their old exoskeleton and synthesize new exoskeleton. Complexes of protein and chitin, a polymer of N-acetyl-D-glucosamine, are the exoskeleton’s major constituents. Since JH, 20E and chitin are present in a few groups of animals, including arthropods, the biosynthesis, metabolism, transport, and action of these hormones and chitin could serve as excellent targets for insecticide discovery and development. Several chitin synthesis inhibitors, ecdysone, and JH analogs are currently used as insecticides to control pests and disease vectors. These insecticides are classified as insect growth regulators (IGRs). We present a collection of review articles and original research papers on IGRs in this special issue.

Five review articles covering the latest research on IGRs are included in this issue. 1) Enzymes involved in JH biosynthesis are potential targets of insecticide development. A review by Marie-Ève Picard et al. (Cusson’s group) summarized recent advances in the use of lepidopteran specific farnesyl diphosphate synthase as the target for insecticide development. 2) Parthasarathy and Palli reviewed the stage-specific action of three commercially used JH analogs, methoprene, hydroprene and pyriproxyfen in economically important pests, the red flour beetle, Tribolium castaneum and the tobacco budworm, Heliothis virescens, and disease vector, the yellow fever mosquito, Aedes aegypti. 3) Okamoto and Yamanaka wrote about ecdysone importer (EcI) that is involved in ecdysteroid uptake in peripheral tissues and their potential use in identification EcI blockers for the development of insecticides with a novel mode of action. 4) Simple and user-friendly bioassay are necessary for discovering IGR. Ito-Harashima and Yagi reviewed yeast reporter assays developed for JH and ecdysteroid agonists screening. 5) Crystal structures and the catalytic mechanism of chitin deacetylases that could help in developing small-molecule inhibitors of this enzyme for pest control were covered by Li et al. (Yang’s group).

Nine original research articles present the latest research on ecdysone receptors’ crystal structures, modeling, virtual and high throughput screening to identify novel and potent insect growth regulators. Identification of novel JH analogs by high-throughput screening of a chemical library and bioassays of seven identified compounds in Bombyx mori were reported by Kayukawa et al. Naruse et al. (Minakuchi’s group) studied the mode of action of JH mimics, especially for their ovicidal activity in the bean bug, Riptortus pedestris. Identification of novel piperazine-based insect juvenile hormone agonist by virtual screening and reporter bioassays is reported in the paper by Yokoi et al. (Nakagawa’s group). Nonsteroidal inhibitors of Drosophila steroidogenic glutathione S-transferase Noppera-bo are included in the paper by Koiwai et al. (Niwa’s group). Browning et al. (Billas’s group) solved the structure ecdysone receptor complex occupied by nonsteroidal ecdysone receptor agonists and show that these agonists use a water channel for binding to the receptor complex. Receptor-binding affinity and larvicidal activity of tetrahydroquinoline-type ecdysone agonists against Aedes albopictus are reported by Ueno et al. (Nakagawa’s group). Design, synthesis, and biological activity of a novel insecticide, benzpyrimoxan is included in Satoh et al. paper. Mushiake et al. (Nitoda’s group) report on new analogs of pochonicine, a potent β-N-acetylglucosaminidase inhibitor from fungus Pochonia suchlasporia var. suchlasporia TAMA 87. Mori et al. (Nakagawa’s group) showed that the isoxaben analogs inhibit chitin synthesis in the cultured integument of Chilo suppressalis. Dr. Marek Jindra, an expert on insect hormones and development, wrote a commentary for this special issue. We trust you will enjoy reading these articles reporting exciting results on insect growth regulators.