Cluster of Excellence –
University of Freiburg

Mathematical modeling of the self organizing Arabidopsis shoot meristem

Prof. Thomas Laux (Institute of Biology III)

The spatial organization of stem cell niches is stably maintained in plants and animals despite a changing cellular context, but the underlying mechanisms for this are largely unknown. In this proposal, we investigate how the spatial organization of the Arabidopsis shoot meristem is maintained, which harbors pluripotent stem cells that fuel the lifelong formation of new shoot organs. The shoot meristem stem cell niche works in a population mode: stem cell divisions are random and the fate of stem cell daughter cells entirely depends on positional signaling rather than asymmetric inheritance (Aichinger et al, 2012). Because all cells divide, including the niche cells, cell fate regulation in the shoot meristem provides a paradigm to study cell-cell communication of a self-organizing stem cell system. A signaling feedback loop between the stem cells and the subtending organizing center, mediated by WUSCHEL (WUS) and CLAVATA3 (CLV3) activities, regulates the balance between stem cell maintenance and differentiation (Figure 1). We have recently shown that two opposing signal pathways determine the region of stem cell competence by regulating responsiveness of cells to the WUS/CLV3 signals (Knauer et al. unpubl.; Tucker et al, 2008). In collaboration with Dr. C. Fleck (Wageningen), we developed a mathematical framework for stem cell niche patterning based on a reaction-diffusion mechanism.

Aichinger, E., Kornet, N., Friedrich, T., and Laux, T. (2012). Plant Stem Cell Niches. Annu Rev Plant Biol. 63, 615-636.

Tucker, M. R., Hinze, A., Tucker, E. J., Takada, S., Jurgens, G., and Laux, T. (2008). Vascular signalling mediated by ZWILLE potentiates WUSCHEL function during shoot meristem stem cell development in the Arabidopsis embryo. Development. 135, 2839-2843.

Figure 1: Longitudinal section through the Arabidopsis shoot meristem. The feedback communication between stem cells (CLV3) and the Organizing Center (WUS), and the vascular signaling pathway (ZLL) are indicated. Blue, stem cells, green outlines, differentiation zones; yellow, vasculature; red, Organizing Center.