Developmental biology seeks not only to learn more about the fundamental processes of growth and pattern per se, but to understand how they synergize to enable the morphogenesis of multicellular organisms. Our goal is to perform real-time analyses of these developmental processes in an intact developing organ. By applying a vital imaging approach, we can circumvent the normal limitations of inferring cellular dynamics from static images or molecular data, and obtain the real dynamic view of growth and patterning. The wing imaginal disc of Drosophila, which starts out as a simple epithelial structure and gives rise to a precisely structured adult limb, will serve as an ideal model system. This system has the combined advantages of relative simplicity and genetic tractability. We will create several innovations that expand the current toolkit and thus facilitate the detailed dissection of growth and patterning. A key early step will be to develop novel reporters to dynamically and faithfully monitor signaling cascades involved in growth and patterning, such as the Dpp and Hippo pathways. We will also implement quantification techniques that are currently being set up in collaboration with an experimental physicist, to deduce, and alter, the mechanical forces that develop in the cells of a growing tissue. The large amount of quantitative data that will be generated allow us derive computational models of the individual pathways and their interaction. The focus of the study will be to answer the following questions: 1) Is the Hippo pathway regulated spatially and temporally, and by what signaling pathways? 2) Do mechanical forces play a pivotal controlling role in organ morphogenesis? 3) What are the global effects on growth, when pathways controlling patterning, cell competition or compensatory proliferation are perturbed? The proposed project will bring the approaches taken to define the mechanisms underlying and controlling growth and patterning to the next level.