Collaborative Research: The Role of Tryptophan Metabolism in Auxin Homeostasis

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Plants and microbes are unique in their ability to synthesize compounds from the amino acid tryptophan. One of these compounds is indole-3-acetic acid, an important member of the class of plant growth regulators called auxins. Indole-3-acetic acid is synthesized by virtually all plant species. In the cruciferous plant, Arabidopsis thaliana, tryptophan is also used to produce the plant defense compounds indole glucosinolates (IGs) and camalexin. There is evidence in Arabidopsis for intricate cross-talk between the biosynthetic pathways used to produce these different tryptophan-derived compounds. The secondary metabolite profile in the non-crucifer tobacco does not include IGs or camalexin. Thus, tobacco provides a tractable alternative model system in which Trp metabolism can be compared to that of Arabidopsis.The goal of this research is to understand how the interactions among tryptophan metabolism pathways are the same or different between Arabidopsis and other plant species that do not produce the same spectrum of tryptophan-derived compounds as Arabidopsis. The research scope of this project is twofold:1) Use previously identified mutant plants perturbed in tryptophan metabolism to define the role of compounds predicted to serve as intermediate steps for the biosynthesis of indole-3-acetic acid. In addition, new mutants disrupted in these metabolic pathways will be identified.2) Determine which known indole-3-acetic acid biosynthetic pathways contribute to the formation of a chemically distinct naturally occurring auxin called indole-3-butyric acid. The broader impacts of this research include the training of graduate students in biochemical and genetic methodologies. This training will prepare them for more advanced positions in the fields of plant biochemistry and metabolomics. In addition, this research will be carried out as collaboration among three institutions (University of Massachusetts Amherst, Boston University and Lincoln University) that are partner institutions in an NSF-supported alliance designed to increase the number of minorities in the professoriate of science technology, engineering and mathematics (STEM) disciplines. Interactions between the three labs will be facilitated by having students from Lincoln University participate in ongoing summer minority research programs in the laboratories of the PIs from University of Massachusetts and Boston University. Co-mentorship of Lincoln University students among the three PIs will facilitate the identification, recruiting and mentoring of minority students with an interest in plant biology graduate programs.