Abstract
Precise organization of growing structures is a fundamental problem in developmental biology. In plants, radial growth is mediated by the cambium, a stem cell niche continuously producing wood (xylem) and bast (phloem) in a strictly bidirectional manner. While this process contributes large parts to terrestrial biomass, cambium dynamics eludes direct experimental access due to obstacles in live cell imaging. Here, we present a cell-based computational model visualizing cambium activity and integrating the function of central cambium regulators. Performing iterative comparisons of plant and model anatomies, we conclude that an intercellular signaling module consisting of the receptor-like kinase PXY and its ligand CLE41 constitutes a minimal framework sufficient for instructing tissue organization. Employing genetically encoded markers for different cambium domains in backgrounds with altered PXY/CLE41 activity, we furthermore propose that the module is part of a larger regulatory circuit using the phloem as a morphogenetic center. Our model highlights the importance of intercellular communication along the radial sequence of tissues within the cambium area and shows that a limited number of factors is sufficient to create a stable bidirectional tissue production.
