Reduction of glycogen in eggs of the silkworm, Bombyx mori, by use of a trehalase inhibitor, trehazolin, and diapause induction in glycogen-reduced eggs

A new trehalase inhibitor, trehazolin, caused a potent inhibition of ovary trehalase in the silkworm, Bombyx mori. A single injection of trehazolin in to pupae (40 mu g/animal) did not interfere with the accumulation of protei ns and lipids, but markedly reduced glycogen content in eggs accompanied by a remarkable increase in hemolymph trehalose levels. The most potent effec t of trehazolin was expressed in eggs that developed at the mid-stage of pu pal-adult development. In these eggs glycogen content was reduced to a trac e level, less than 3% of that of the control. The reduced glycogen content was almost restored to the control level by injection of glucose but not by trehalose. Trehazolin treatment influenced oviposition and larval hatching , whereas embryogenesis went on normally in glycogen-reduced eggs. Injectio n of synthetic diapause hormone into non-diapause type hosts induced an inc idence of 45% diapause in the eggs and increased their glycogen content. Su rprisingly, injection of trehazolin never affected diapause induction by th e hormone, despite considerably reduced glycogen content in these eggs. Thu s, our findings provide a new method for production of eggs containing vari ous amounts of glycogen, and a novel system for analyzing diapause-associat ed metabolism besides the well-known glycogen-sorbitol metabolism. (C) 1998 Elsevier Science Ltd. All rights reserved.