From stem cell activity to shoot morphology

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Plant form is dependent on the activity of continuously active stem cell systems, called meristems. While it is well established that dynamic signaling cascades are central for setting up stable patterns that can be translated into functional morphologies, much less is known about the contribution of basic cellular parameters, such as cell size, cell shape or cell mechanics. Building on our results from the first FOR2581 funding phase, we will now address these issues by leveraging the Big Cells in Epidermis (bce) mutant we have isolated and characterized. The causal gene for the bce phenotype is a ribosomal RNA processing factor and we will hence study how defects in ribogenesis give rise to large and unevenly shaped cells under aim 1. In aim 2, we will use the bce mutant as a tool to study the role of cell size, volume and mechanics in morphogenetic processes from the molecular to the tissue level. Finally, we will ask how cellular parameters in defined domains of the meristem contribute to shoot morphogenesis and how physical cell state impinges on cell decision making by autonomous and non-autonomous mechanisms in aim 3. We will work closely with other groups of FOR2581 in areas including image segmentation, recording of mechanical features of cells and mathematical modelling to synthesize our multilevel data into testable hypotheses and predictions. Taken together, this proposal will leverage the bce mutant characterized in the first funding phase to advance our understanding of the interplay of basic cellular parameters, such as cell size, shape or mechanics, with well-studied signaling systems that act in concert to give rise to stable morphogenetic patterns of the shoot.