Effect of the diapause hormone on Trehalase activity in pupal ovaries of the silkworm, Bombyx mori L

Abstract

Effect of the diapause hormone on trehalase activity was investigated in the silkworm, Bombyx mori L. Trehalase was located at different activities in various tissues of the pupae, and among the tissues tested ovary trehalase activity alone decreased after extirpation of the subesophageal ganglion (SG), the source of the diapause hormone. Removal of the SG affected neither kinetic properties of ovary trehalase nor the subcellular distribution in ovaries. Among the enzymes concerning with glycogen synthesis in pupal ovaries, trehalase activity was strongly reduced by SG removal, while the other enzyme activities, i.e., hexokinase, phosphoglucomutase, UDPG-pyrophosphorylase and UDPG-glycogen glucosyltransferase were not significantly affected. The pattern of decrease in trehalase activity after SG removal was similar to that of the change in daily glycogen accumulation in SG-removed ovaries, the former anticipating the latter about 1 day. Diapause hormone extracts injected into pupae with the SG removed elevated ovary trehalase activity significantly in about 3 hr, and the activity became maximal in 24 hr. Ovary trehalase activity was elevated roughly in proportion to the dosage of extract injected. It is likely that ovary trehalase in silkworm pupae plays an important role in glycogen accumulation in the ovaries, especially those of the diapause type, and it is suggested that the diapause hormone may elevate its activity through de novo synthesis of the enzyme protein.