Mechano-chemical basis of cellular architecture in plants

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One of the central questions in developmental biology is to understand how growth leads to the form of cells, organs and organisms. This process of morphogenesis, in addition to being under genetic and hormonal control, is also known to be influenced by the laws of mechanics, the role of which is only starting to be explored in plants. As plant cells are immobile, they require a robust machinery enabling them to sense dynamic changes in their environment allowing them to generate and maintain complex cell and tissue architectures. Recent work suggests that indeed mechanical signaling is a fundamental factor in this process of morphogenesis. Turgor driven growth of cells, cell shape control and the response of cells to load is dominated by the presence of the cell-wall, a stiff yet malleable composite mainly consisting of highly organized cellulose microfibrils. As cellulose microfibril synthesis is regulated by the microtubule cytoskeleton an understanding of microtubule dynamics, and how it couples to mechanics, is fundamental to plant morphogenesis. Previously we have shown that mechanical stress guides microtubule organization at subcellular and tissue scales in the multipolar epidermal pavement cells of cotyledons. Using interdisciplinary approaches involving cellular, molecular, computational and biomechanical techniques we aim, in this project, to investigate how biochemical and mechanical inputs regulate aspects of cellular morphogenesis in plants. We will assess the behavior of cellulose synthesizing proteins and the dynamics of the microtubule cytoskeleton at subcellular and tissue scales over developmental time periods in leaf epidermal cells. By means of micromechanical manipulation, mutant analysis and computational modeling we will explore how mechanical signals arising from the surrounding environment, couple to microtubule dynamics and cell-wall biosynthesis giving rise to a supra-cellular feedback loop that controls cell shape. Using similar approaches we will identify microtubule master regulators that are necessary for mechano-sensing and response in plants. The experimental results will be compared and tested using computational tools that will be developed to firstly model the dynamics of microtubules confined to complex surfaces, and secondly to predict the local response of tissues (stress-strain) to mechanical perturbations. The proposed project will allow us to develop a comprehensive understanding of the impact of physical forces on cellulose biosynthesis and microtubule regulation in plants and open up opportunities to not only predict but also to direct morphogenesis of plant-tissues in the future.