Regulation of Ecdysone on Vitellogenin Gene Expression in Silkworm Bombyx mori

The ecdysone( 20-hydroxy ecdysone,20E) is secreted by prothoracic gland,which regulates the molting in arthropods insecta,crustaceans and other animals. The silkworm is a holometabolous insect known to undergo four developmental stages from egg to adult. The 20 E is indispensable in the development of silkworm. In this work,the amounts of 20 E in the silkworm's hemolymph before and after metamorphosis were found to have no significant differences between male and female. However,the20 E content was similar to the expression pattern of BmVg. When 20 E was injected to the body cavity or added to the mulberry leaves,the BmVg transcription in the fat body was induced. The treatments also increased the BmVn content and the egg weight. The treatment of 20 E induced BmVg expression directly in the fat body in vitro. We conclude that 20 E induced BmVg expression to increase BmVn levels in the silkworm eggs,thus to increase the egg weight.