Plant cells differentiate in a position dependent and not a lineage dependent manner. They must, therefore, receive signals that inform them of their position within the multicellular organism and differentiate accordingly. The nature of the signals, their origin, and how they are transmitted is largely unknown. This research project will address these questions by examining how cells in the three layers of the shoot apical meristem maintain functional coordination over the course of meristem ontogeny. To achieve this objective Dr. Sussex proposes to generate graft chimeras between wild type tomato, Lycopersicon esculentum and tomato carrying mutations that affect specific stages of vegetative or reproductive meristem function. The graft partners will also differ in cell layer autonomous markers by which each of the three meristem layers in the chimeras can be identified. The specific aims are: 1) To determine for each of the chimeras whether function and organization of the meristem at a specific stage of its ontogeny is cell layer autonomous or depends on interactions between the cell layers, 2) Where such interactions are fund to occur to determine whether the signal originates in one specific layer and if so whether the position of the layer in the meristem is important. %%% The results of this investigation will provide specific instances in which interactions between cell layers of the growing tip of a plant are required for normal development and how those interactions contribute to development of the plant.
