A remarkable variety of plant shapes are observed in nature. Wasp-shaped orchid flowers, gigantic stinking corpse lilies, towering sequoia trees, and massive baobabs are just a few conspicuous examples. While there are a limited number of building blocks that make up a plant (a root, an internode, a leaf, and a flower), the shape and size of these organs vary greatly, giving rise to the prolific variation in plant appearance. Driven by natural selection, the form of an organ is directly related to its function. The shape of a flower promotes effective pollination, and the size and shape of leaves allow for optimal photosynthesis with minimal harm by heat and drought. An important driver of organ shape is establishment of an active growth region and of boundary zones where cells divide very slowly. This project investigates molecular mechanisms controlling the shape of flower organs and formation of boundary zones during various stages of flower development. It examines the initiation and spacing of ovules, which will contribute to understanding how the number of seeds is established within a fruit. To support education, a website will be created with links to high-quality videos aimed at undergraduate level Plant Physiology courses. The proposed research will also promote education through the training of postdoctoral, graduate, undergraduate, and high school students. A special effort will be made to attract minorities to the research program.

The shape of a plant depends on the timing of cell proliferation, the extent of cell elongation, and the establishment of boundaries. These processes rely on coordinated cell behavior and require cell-to-cell communications. One of the key signaling pathways regulating plant morphogenesis is initiated by the ERECTA family (ERf) of receptors and their extracellular ligands, EPFLs. This pathway is important for morphogenesis of all aboveground organs; however, the specific developmental processes that are targeted are not known. This project will study ERf-EPFL signaling during morphogenesis of flowers, a complex developmental program requiring numerous avenues of coordinated differentiation and proliferation of cells. It will explore the function of ERf-EPFLs during formation of a variety of flower structures including ovules, integuments, and anthers with the goal of identifying processes similarly controlled in different tissues. The role of ERf-EPFL signaling will be studied in specification of boundaries between outgrowing structures and in modification of auxin transport during outgrowth of protrusions. The experimental design includes genetic studies, imaging, next-generation sequencing, and biochemical approaches. Taken together, the proposed activities have the potential to uncover novel molecular mechanisms controlling morphogenesis in plants.

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.

National Science Foundation (NSF)
Division of Integrative Organismal Systems (IOS)
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Anne W. Sylvester
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University of Tennessee Knoxville
United States
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