Ecdysteroid ingestion suppresses carbohydrate hydrolysis in larvae of the silkworm Bombyx mori
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ORIGINAL PAPER
Ecdysteroid ingestion suppresses carbohydrate hydrolysis in larvae of the silkworm Bombyx mori Takumi Suzuki 1,2
&
Masafumi Iwami 1
Received: 2 February 2020 / Revised: 2 June 2020 / Accepted: 11 June 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Ecdysteroids are widely found in terrestrial organisms, including insects, crustaceans, fungi, and plants. The function of ecdysteroids has been extensively studied in insects for decades because ecdysteroids regulate metamorphosis. In plants, in contrast, ecdysteroids (called phytoecdysteroids) do not show apparent hormonal activity and their function remains unclear. However, it has been proposed that phytoecdysteroids have an antifeedant function. Ecdysteroid ingestion disrupts insect development and alters behavior to deter insect feeding, resulting in reduced plant damage by the insect. These points of view are generally accepted, but the function of phytoecdysteroids in specific contexts has not been unveiled. In the present study, we used larvae of the silkworm, Bombyx mori, to investigate the biological significance of phytoecdysteroids. To mimic the situation where larvae consume plant leaves that contain phytoecdysteroids, 26 or 30 larvae were fed the diet containing ecdysteroid or the control diet. We show that ecdysteroid ingestion dramatically suppressed carbohydrate processing in the larval midgut to reduce the nutritional value of the ingested diet. Based on the present results, we propose a new explanation of phytoecdysteroid function: ingested ecdysteroids may lead to the erroneous perception that the plant is poor in nutrients and consequently result in cessation of feeding. Keywords Nutrient . Insect-plant interaction . Glucosidase . Ecdysteroid . Digestion
Introduction Ecdysteroids are important and irreplaceable hormones required for the successful development of arthropods, including insects. They have a wide variety of functions including regulation of growth, behavior, reproduction, and nutrient metabolism as well as metamorphosis. This steroid hormone is, however, not limited to arthropods and has also been isolated Communicated by: Peter Schausberger Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00114-020-01684-z) contains supplementary material, which is available to authorized users. * Takumi Suzuki [email protected] 1
Laboratory of Developmental Biology, Division of Life Sciences, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan
2
Department of Science, Laboratory of Developmental Biology and Physiology, College of Science, Ibaraki University, 1-1-2 Bunkyo, Mito 310-8512, Japan
from plants (Galbraith and Horn 1966; Nakanishi et al. 1966; Takemoto et al. 1967). Many plants are thought to contain and endogenously synthesize ecdysteroids. These plant ecdysteroids, called phytoecdysteroids, slightly impact the morphology and physiology of Arabidopsis thaliana (Golovats
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