The goal of this proposal is to examine the molecular basis of the physiological phenomenon termed `competence' which is used here to describe the appearance of responsiveness to a hormone that results in the expression of new genes. The appearance of the competent state is thought to be due to structural changes in regulatory regions of these genes that permit the binding of proteins, such as hormone receptors and other transcriptional factors, to specific nucleotide sequences. This study should help us to understand how hormones regulate gene expression. Two genes expressed during egg development in the mosquito, Aedes aegypti, will be examined; a vitellogenin and a vitelline envelope protein gene, both of which are under the control of 20- hydroxyecdysone. We have shown that the vitellogenin gene of the newly enclosed adult female is not capable of responding to 20- hydroxyecdysone, and that competence to respond appears during the first two days after eclosion in response to juvenile hormone. We propose to use a mobility shift assay to follow changes in the binding of proteins to the regulatory regions of these two genes during the acquisition of competence and after exposure to 20- hydroxyecdysone and juvenile hormone.
