Impact of yolk-cellular blastoderm-egg shell interactions on the evolution of animal gastrulation

ongoing

Early animal development, including the process of gastrulation, exhibits tremendous diversity of morphogenetic mechanisms. How does this morphological divergence evolve under the constraints imposed on early embryos remains unclear. In this proposal, I will ask how interactions between cells of the early embryo, the yolk component of the egg and the attachment to the surrounding egg shell affects gastrulation morphogenesis. I will focus on the comparison of two insect embryos, Drosophila and Tribolium, that exhibit strikingly different flows and foldings of the fundamentally very similar cellular blastoderm epithelium during gastrulation. I will ask how contacts between the cellular blastoderm, the yolk-sac and the surrounding vitelline envelope confine and shape tissue movements. What are the molecular mechanisms mediating the contacts and what functional consequences their disruption has for the embryo’s viability. I will probe the tissue interactions by embryological and biophysical manipulations, in toto electron and live microscopy and through genetic manipulations of the integrin adhesion pathway that I recently showed to impact insect gastrulation by mediating cellular blastoderm-vitelline envelope attachment. Using the comparative approach, I will ask how changes in the regulation of tissue interactions sculpt gastrulation morphogenesis in these insect species. I will then expand the investigation beyond arthropods and probe the tissue-shell interaction in several non-model species in order to understand its evolutionary origin and significance for shaping animal phylogeny. Taken together, the research will bridge two relatively isolated disciplines – evolution of development and tissue morphogenesis. By combining their methodological and conceptual approach, I will shed new light on the mechanisms governing diversification of early development and lay the foundations for understanding the phylogeny of morphogenesis.