Selective secretion of free glycine, a neutralizer against a plant defense chemical, in the digestive juice of the privet moth larvae

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• 作者：Konno ; Kotaro ; Okada ; Sachiko ; Hirayama ; Chikara
• 关键词：Glycine ; Digestive juice ; Amino acid transport ; Plant&ndash ; herbivore interactions ; Chemical ecology
• 刊名：Journal of Insect Physiology
• 出版年：2001
• 出版时间：December, 2001
• 年：2001
• 卷：47
• 期：1
• 页码：1451-1457
• 全文大小：175 K

文摘

The larva of the privet moth, Brahmaea wallichii (Brahmaeidae) is a specialist feeder of the privet tree, Ligustrum obtusifolium (Oleaceae). A very high concentration (50 mM or 0.4 % ) of free glycine, found in the digestive juice of the larvae, works as a neutralizer against the very strong protein-denaturing activity of privet leaves that is caused by oleuropein, an iridoid that functions in chemical defense. Concentration of free glycine was high in the anterior region of the midgut lumen and low in the posterior region. To examine if some glycine-specific secretion mechanism exists, injection experiments were performed using ¹⁵N-labeled amino acids. When 13 μmol (1 mg) of ¹⁵N-glycine was injected into hemolymph of fifth instar larvae of B. wallichii, a high concentration of ¹⁵N (5 mM or 75 μg/g midgut content) was detected in the anterior parts of the midgut lumen 1 h after injection. ¹⁵N-NMR data indicated at least 60 % of the ¹⁵N found in midgut lumen existed as ¹⁵N-glycine. Approximately, 25 % of the injected ¹⁵N-glycine was estimated to have moved from the hemolymph to the midgut lumen. In contrast, no ¹⁵N was detected in the midgut lumen when 13 μmol of ¹⁵N-labeled alanine, lysine and glutamate were injected into hemolymph. Glycine was the only amino acid whose concentration was higher in the midgut lumen (50 mM) than in the hemolymph (22 mM). These data suggest the existence of some active and glycine-specific secretory mechanism in the midgut of B. wallichii.