Collaborative Research: Actin-mediated mechanical stress sensing and the control of epidermal tissue integrity

About This Grant

The sizes and shapes of leaves determine plant growth and function in both natural and agricultural environments. At present we do not understand how strong mechanical forces in plant tissues (roots, leaves) simultaneously enable tissue growth and maintain physical connection between cells in tissue. These knowledge gaps preclude rational engineering of plant tissues with desired architecture. This project combines expertise from three different labs in the disciplines of plant biology, soft-matter physics, and computational mechanics. The team will analyze the types of forces that are important, and how they are sensed by individual cell wall and cell signaling proteins within the cells. Experiments on plant tissues will measure tissue mechanical properties to be used in computational mechanics simulations to determine how plant cells sense and respond to different types of forces in the cell wall during growth. This project will also train the next generation of biologists and provide new ways to discover fundamental control mechanisms of plant growth and function. This knowledge is needed to enable future strategies to engineer crops with specified architectures and material properties to maximize efficient production. The forces that drive growth in plants also create mechanical interactions between cells that destabilize connectivity. At present, knowledge about the source, type, and sensing of these intercellular forces is lacking. Adhesion between adjacent cells in the plant epidermis exerts strong controls over organ-scale growth dynamics. This project tests the central hypothesis that the Actin-Related Protein (ARP2/3) complex-dependent actin-cytoskeleton control module mediates focal secretion of proteins and/or polysaccharides that maintain cell-cell adhesion in response to destabilizing wall stresses. Three specific aims are pursued: (1) The bioadhesive properties and biomechanical conditions that govern adhesion of cell-cell interfaces in the leaf epidermis will be analyzed quantitatively; (2) The manner by which localized ARP2/3 activation promotes cell-cell contact and maintains tissue integrity in the growing cotyledon epidermis will be determined; (3) The interactions among cytoskeletal, transport, and cell wall biogenesis genes that mediate tissue integrity will be defined. The research team will integrate live-cell imaging, quantitative micro-mechanical manipulations, and state-of-the-art finite element (FE) mechanics analyses to analyze how the growing epidermis manages enormous tensile forces and avoids mechanical failure. This project is jointly funded by the BIO Extended Frontiers program and the Established Program to Stimulate Competitive Research (EPSCoR), and managed by the Cellular Dynamics and Function program. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.