Regulation of Tryptophan Metabolism in Arabidopsis

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Plants produce a wide array of metabolites critical for development and defense. Glucosinolates, the compounds that give vegetables in the mustard/cabbage/broccoli family their characteristic pungent flavor, are metabolites derived from amino acids. Glucosinolates defend plants against insect and herbivore feeding and also have anti-pathogen properties. In addition, glucosinolates are anti-cancer compounds in the human diet. The laboratory mustard Arabidopsis provides a powerful experimental system in which to understand the regulation of glucosinolate synthesis. The Arabidopsis ATR1 protein is a key positive regulator of genes needed to synthesize indolic glucosinolates (IG's) derived from the amino acid tryptophan. High expression of ATR1 increases IG levels, and inactivation of ATR1 causes a partial IG deficiency. The goal of this project is to understand more about the regulation of IG synthesis in Arabidopsis with a particular focus on the role of ATR1. Proteins that are highly related to ATR1 will be tested for whether they also act in IG regulation, or in regulation of other glucosinolate synthesis pathways. The structural features that distinguish proteins like ATR1 that specifically control IG synthesis will be dissected. In parallel, the DNA sequences that are targeted by ATR1 to mediate its activating effects will be identified using biochemical and genetic approaches. The complete annotation of the Arabidopsis genome together with facile assays for IG upregulation offer an unprecedented opportunity to fully understand the regulatory network for this important plant metabolic pathway. Broader Impacts: The project will elucidate how glucosinolate genes are regulated, and provide unique tools for modulating glucosinolates in agricultural plants as a means to improve their insect and pathogen resistance. The project will also provide training in plant genetics and molecular biology for graduate and undergraduate students.