The photoreceptors of the vertebrate retina express a large number of proteins that are involved in the process of light transduction. The molecular mechanisms that regulated gene expression in these cells is unknown. The work described in this proposal focuses on the molecular mechanisms of transcriptional control of phototransduction genes. The approach undertaken will be to investigate the cis-acting elements that control the three most abundantly expressed genes win the rod cell and to identify the transcription factors which bind to these sequences. The studies will be carried out in Xenopus laevis in order to take advantage of the versatile features of this organism provides for developmental studies. The specific aims of the proposal are to line cDNAs and genomic DNA encoding opsin, transducing alpha subunit and arresting from the abundant rod in Xenopus and to analyze the cis-acting element in these genes using a transient transfections assays in Xenopus embryos. The proteins which bind to the cis-acting elements will be characterized by biochemical techniques and cDNA clones will be isolated using a recognition site screening strategy. The information gained from this study will advanced our understanding of regulation of gene expression in the retina and provide a framework for future studies on signal transduction pathways that act during cellular differentiation.