The ancestry of deuterostome photoreceptors - molecular and structural investigations in echinoids and enteropneusts

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The integration of molecular and structural data put forth new intriguing insights into evolution and function of animal photoreceptor cells and overrode several traditional evolutionary hypotheses. It became clear that opsins diverged early during animal evolution giving rise to several distinct opsin and photoreceptor cell types with own functional specifity. This scenario is corroborated by the existence of photoreceptor cell type specific sets of cell fate determining transcription factors in distinctly related organisms. Even in vertebrates and the allied tunicates and cephalochordates numerous new opsins and photoreceptor cell types were recently found and an exciting research field arose covering biochemical, physiological and developmental aspects of light sensation. In the applied collaborative project we aim to uncover the evolutionary roots of this observed diversity by combining gene expression studies of opsins and other molecular photoreceptor cell markers with immunohistochemical and electron microscopic investigations in basal deuterostomes. Analysis of the recently sequenced genomes of the echinoid S. purpuratus and the enteropneust S. kowalevskii uncovered the existence of several different opsin types in these animals. With our integrate approach we will identify and characterize the respective photoreceptor cells and get deep insights into the evolutionary origin and ancestral function of various types of deuterostome photoreceptors.