Dpp signaling represses VM32E gene expression in centripetal follicle cells

The correct eggshell morphogenesis requires the combined activity of different signaling pathways. Among these the Dpp pathway plays a major role in defining the position and morphology of the anterior eggshell structures. Howeve, it is not known if this signaling pathway is also involved in controlling the expression of eggshell structural genes. We addressed this question by analizing the expression of the VM32E vitelline membrane gene. An interesting issue on VM32E gene expression pattern concerns its repression in the polar domains of follicular epithelium. The VM32E gene is not expressed in the centripetal follicle cells, where the Dpp pathway is active. This spatial restriction is conserved in the D. pseudoobscura orthologous gene, suggestive of an evolutionary conserved function of VM32E protein. By analyzing the VM32E gene expression in genetic backgrounds altering Dpp signaling, we show that the VM32E gene is negatively regulated by this pathway in the centripetal follicle cells. Therefore, it appears that Dpp signaling executes its control on eggshell morphogenesis also by controlling the expression of eggshell structural genes.