E75A and E75B have opposite effects on the apoptosis/development choice of the Drosophila egg chamber.

The number of Drosophila egg chambers is controlled by the nutritional status of the female. There is a developmental checkpoint at stage 8, which is controlled by BR-C in the follicle cells along with ecdysteroid. During this period, developmental decision is made in each egg chamber to determine if it will develop or die. During nutritional shortage, inducing apoptosis in the nurse cells of stages 8 and 9 egg chambers reduces the number of egg chambers. We show that ecdysone response genes E75A and E75B are involved in inducing or suppressing apoptosis. It is thus possible that the E75 isoforms A and B are involved in the decision to develop or die in oogenesis. We have established part of the pathway by which ecdysone response genes control apoptosis of the nurse cells and hence select between degeneration or development of individual egg chambers at stages 8 and 9.