Collaborative Research: Elucidating the Molecular Architecture and Dynamics of Phenylalanine Biosynthesis in Plants

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The amino acid phenylalanine is the precursor for the synthesis of 8000 phenolic compounds in plants, which have profound impacts on plant growth, development, reproduction and defense. Phenylalanine serves as a precursor for numerous plant natural products that are widely used in medicine and as food supplements. This project will characterize a new pathway for phenylalanie synthesis in the plant cytostol determine the contribution of this pathway to the total phenylalanine production. The results will significantly contribute to the fundamental knowledge of a major plant metabolic network and provide a better understanding of aromatic amino acid biosynthesis. Such information will allow rational metabolic engineering of phenylalanine levels for production of important phenylalanine-derived compounds to improve agronomic traits, biofuel production, palatability of produce, and commercial value of ornamentals. The plannned research will provide multidisciplinary training to undergraduate and graduate students. The educational program will also introduce students from a local middle school to STEM-based research through direct classroom interactions and facilitating laboratory exercises where students generate and test hypotheses. It has long been accepted that aromatic amino acid biosynthesis occurs exclusively in plastids where it is subject to complex feedback regulation both at the entry point into the network and at the committed steps towards individual amino acids. The recent finding that phenylalanine is also formed in the cytosol raises new questions about how plants regulate carbon flux distribution between the parallel pathways. This project will employ an integrative strategy comprised of genetics, molecular biology, metabolic profiling, protein and membrane biochemistry, stable-isotope labeling, and metabolic flux analysis to determine if (i) plants contain a complete cytosolic pathway, (ii) this route is subject to less stringent feedback regulation, and (iii) the flux through this pathway increases when the demand for phenylalanine production and consumption increases. Petunia flowers, which are amenable to genetic alterations without deleterious effects to plant vitality, and are rich in phenylalanine and phenylalanine-derived volatiles, will be used as a model system. Specifically, this project will uncover the pathway structure and the molecular players of the cytosolic phenylalanine biosynthesis. Moreover, the project will reveal the capacity and relative contribution of the cytosolic route to overall production of phenylalanine.