Ecdysone Receptor Present in Insects is a Novel Target for Insecticide (original) (raw)
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Pakistan Journal of Agricultural Sciences, 2020
Storage of cereals and their products is a vital part of postharvest operations through which food commodities passes from farmer field (producer) to the ultimate consumer. Annual post-harvest losses of stored cereals due to various biological factors in the storages range from 10-20% of overall production (Phillips and Throne, 2010). There is a continuous need to protect the stored grains and their products against deterioration, especially the loss of weight and quality during storage. Insect pests are the main factor responsible for these losses as they reduce both the quality and quantity of grains (Weaver and Subramanyam, 2000). Sabet and Sabr, 2015). The Khapra Beetle, Trogoderma granarium (Everts) is a serious pest of stored grains and their products (Burges, 2008; Mark et al., 2010). The khapra beetle generally restricts its activity to the top 12 inches of the stored grains. The beetle has a substantial economic impact due to its capability to cause huge losses to grains th...
Phytoparasitica, 1991
Neuropeptides regulate a vast range of critical events associated with embryonic or postembryonic development, and metabolism. Events such as ecdysteroid and juvenile hormone synthesis, behavior, muscular contraction, fat and sugar metabolism, cuticular assembly and coloration, water balance, and so forth, are under the regulation of neuropeptides from early embryogenesis through adult reproduction. By interfering with neuropeptide function, new avenues for controlling insect life processes may be opened. To realize this potential, we must understand neuropeptides at both the functional and molecular levels. Sensitive, reliable bioassays are requisite for the discovery of activities, peptide purification, and the design of peptidomimetics. Determination of primary structure provides leads to structure-function studies, access to molecular genetics, and identification of proneurohormones. Characterization of proneurohormones is crucial to the identification of processing enzymes, the latter being models for the design and synthesis of enzyme
Do european corn borer females detect and avoid laying eggs in the presence of 20-hydroxyecdysone?
Journal of chemical ecology, 2007
European corn borer larvae detect and avoid feeding in the presence of phytoecdysteroids (PEs) such as 20-hydroxyecdysone (20E). Therefore, we hypothesized that females would have taste receptors similar to larvae and avoid laying eggs in the presence of 20E. We found female-specific taste sensilla on the tarsi that respond to 20E at concentrations as low as 10 −6 M, a threshold comparable to that of larvae. However, in choice tests, females laid a similar number of eggs on 20E-treated and on nontreated artificial substrates (filter paper, glass, and nylon), although they spent significantly more time in behavioral sequences related to substrate assessment when 20E was present. In contrast, when given a choice between maize plants (eight leaves) sprayed with 20E or only the solvent, females laid 70% fewer eggs on the treated than on control plants. These observations suggest that other chemical cues of plant origin must be present at the same time as 20E for females to modify their oviposition behavior.
Role of ecdysone in larval metamorphosis
Parasitologists United Journal
Larvae of almost all insects and nematodes have to undergo a cycle of molting for growing and further development, and with the final molt, adults emerge (complete metamorphosis). In insects, it seems that complete metamorphosis takes place through a dormant stage (pupa), in which all larval cells (muscles, salivary glands, gut, etc.) disintegrate by apoptosis. That is why adult forms appear completely different from their pre-pupa larval stages. In contrast, adult nematodes resemble their final larval stages because dormant pupa stages are absent. In insects, molting with or without pupation requires a pro-thoracicotropic hormone (PTTH) secreted by two pairs of cells in the larval brain. This hormone activates prothoracic glands to secrete a steroid hormone, known as the ecdysone. Also by these glands, sufficient production of the juvenile hormone (JH), promotes larva molting. In case of lower JH production, steroid hormones promote pupation, while complete loss of JH leads to direct formation of the adult from the last final larval molt [1]. Steroid hormones have an essential role on the physiological development and behavior of various organisms. Ecdysone is a major steroid hormone that directs major transitions during developmental stages in the life cycle of some helminth and almost all insects by coordinating larval molting and metamorphosis. Ecdysteroid is produced by the prothoracic gland of all insects as 20-hydroxyecdysone. Increase of ecdysteroid induces the expression of genes controlling protein production for larval development. In adult female insects, ecdysone signaling is critical for reproduction as it mediates egg-chamber maturation during oogenesis, whereas in adult males, ecdysteroids have a role in sperm maturation. It is also present in several plants to protect them from agricultural insects. The ecdysone receptor (EcR) is a nuclear receptor found in the cells of reproduction in all insects, and is activated through binding with ecdysteroid. Once activated, it leads to activation of several genes responsible for physiological changes leading to larval ecdysis (molting). EcR is a non-covalent heterodimer of two proteins; EcR protein and ultraspiracle protein (USP), which are homologous to the mammalian farnesoid X receptor (FXR) and retinoid X receptor (RXR) proteins, respectively. The term USP is usually used for the EcR partner from dipteran and lepidopteran insects, while RXR is applied in other insects. This means that EcR consists of EcR protein and USP for dipteran and lepidopteran insects, whereas it consists of EcR protein and RXR for other insects [2-5]. EcR is mainly applied to control gene expression with two uses; for gene therapy in medical and agricultural fields, and for drug development and vector control in Parasitology researches. The present editorial aims to throw light on the second application.
a b s t r a c t 20-Hydroxyecdysone (20E) controls molting, metamorphosis and reproduction of insects. It binds to a heterodimeric complex of ecdysone receptor (EcR) and ultraspiracle (USP), and regulates the transcription of genes containing ecdysone response elements (EcREs). However, the 20E regulation of silk fibroin genes is largely unexplored. In most lepidopteran larvae, the silk fibroin primarily consists of a large protein, heavy chain fibroin (H-fibroin) that is associated with two small proteins, L-chain fibroin and P25. In the present study, we demonstrate that 20E regulates the expression of H-fibroin gene in Corcyra cephalonica, in a dose-dependent manner during the last instar larval development. Semi-quantitative and real-time PCR studies reveal that physiological doses of 20E do not alter the normal expression, whereas higher doses cause a significant decline in the expression. Luciferase activity assays and gel shift experiments further confirm the presence of a functional EcRE in the upstream region of H-fibroin which regulates the ecdysteroid dependent transcriptional activity of fibroin gene through EcR.
Spodoptera mauritia is a sporadic pest of paddy which causes, great economic loss. Insect Growth Regulators (IGRs) belong to a group of compounds which interfere with normal growth, development and reproduction in insects by disrupting hormonally regulated physiological processes. As IGRs are more target-specific, non-persistent, biodegradable and environmentally benign substances with less toxicity to non-target organisms, they are ideal for pest control programs. In this study we demonstrate the effect of methoxyfenozide, an ecdysone mimic, on the haemolymph protein profile of 6 th instar larvae of Spodoptera mauritia. When the sixth instar day 0 larvae of Spodoptera mauritia was treated with different concentrations of methoxyfenozide, there was a statistically significant increase in the haemolymph protein concentration after 24 hours. The haemolymph collected after 24 hours when subjected to SDS-PAGE, there was an increase in the intensity of the major protein band of 83kDa compared to control. Storage proteins are the major proteins in the haemolymph of last instar lepidopteran larvae. Whether the increase in storage protein concentration by methoxyfenozide is related to insecticide detoxification and resistance is worth investigating and studies in this direction are ongoing.
Egyptian Academic Journal of Biological Sciences. A, Entomology
The cotton leafworm, Spodoptera littoralis is destructive pest of cotton and various crops all over the year. The present study was carried out aiming to assess the effects of Precocene I (PI) on the most important parameters of adult performance and reproductive potential of this pest. Five sublethal doses: 150, 120, 90, 30 and 15 µg/larva had been topically applied (once) onto 1-day old larvae of 5 th (penultimate) instar and 6 th (last) instar. The adult emergence was slightly, or drastically, blocked, depending on the dose level and larval instar under treatment. PI exhibited a slightly extended toxic effect on the adult females only with the higher two doses. Some adult deformities were produced after treatment of 6 th instar larvae with PI. With regard to the adult longevity, the major effect of PI was the promotion of adult females to live longer lifetime. Both preoviposition and oviposition periods had been slightly, or considerably, shortened. After topical application of PI onto 5 th instar larvae, the oviposition rate was drastically regressed only at the lower two doses. After treatment of 6 th instar larvae with PI, the oviposition rate was drastically regressed in a dose-dependent course. Both fecundity and fertility were dramatically reduced. Complete sterility was recorded after treatment of 5 th instar larvae with PI but complete sterility had been recorded after treatment of 6 th instar larvae only with 150 and 30 µg/larva. The incubation period was remarkably prolonged.