ABSTRACT
This chapter shows that the ecdysterone-inducible genes identified using cell lines are a linked cluster that can be independently activated by heat shock or other stress conditions. Morphological transformations are a characteristic ecdysterone response of nearly every unselected cell line examined. The elongation response suggested that ecdysterone might produce some qualitative or quantitative change in tubulin composition, leading to a reorganization of the cytoskeleton. A pupal molt occurring in the presence of ecdysterone alone leads to the development of adult structures. The aggregation of motile cells has been correlated with the appearance of over 30 new cell-surface glycoproteins, some of which are thought to be involved in the aggregation process. Exposure of Drosophila melanogaster cells to ecdysterone leads to the rapid synthesis and accumulation of low molecular weight proteins. Ecdysterone also leads to the induction of several enzyme activities in responsive cells. Small hsp gene expression was shown to be developmentally regulated in vivo.
