ABSTRACT

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117- 2).

Plants must constantly deal with adverse environmental changes, which often negatively impacts their growth. For instance, plants with continuously enhanced defense frequently have compromised growth and vice versa. This growth-defense tradeoff is largely due to limited resources, which are used to produce costly defense metabolites. This issue has become more pressing in recent years with ongoing climate change, which accelerates pathogen infection and pest infestation. However, our understanding of how plants simultaneously coordinate defense and growth remains scarce. This proposed research will reveal mechanisms underlying growth regulation governed by a class of stress compounds called aldoximes. Aldoximes are linked to both plant defense - they are precursors of defense compounds and are induced by stresses - and growth - they affect the production of the plant growth hormone auxins as well as phenylpropanoids such as lignin. This project will elucidate how auxins are made from aldoximes and how aldoximes impede phenylpropanoid production in plants. Completion of this project will provide fundamental understanding of plant metabolic networks coordinating hormones, defense compounds, and lignin under stress conditions. The outcome of this project will provide opportunities to enhance levels of phenylpropanoids such as anthocyanins in crops, and will help foster a competitive and successful agriculture workforce. This project also includes a K-12 educational activity called Phyto-Detective, which will develop a series of videos aimed to raise awareness of phytochemicals for a young student audience.

Aldoximes are stress-inducive compounds and are precursors of defense compounds. In addition, they affect plant growth through modulating the production of plant growth hormone auxins and phenylpropanoids. The accumulation of aldoximes represses phenylpropanoid biosynthesis partially through the transcriptional activation of the F-box genes that function in the degradation of phenylalanine ammonia lyase (PAL). Since PAL functions at the entry point of the phenylpropanoid pathway, aldoxime accumulation shuts down the entire phenylpropanoid pathway. Various species produce two major natural auxins, indole-3-acetic acid (IAA) and phenyl acetic acid (PAA), from their respective aldoximes, indicating the significance of aldoxime metabolism in a multitude of different plants. Although the aldoxime-mediated metabolic network plays a crucial role in stress-triggered growth regulation in plants, molecular mechanisms underlying aldoxime-mediated phenylpropanoid repression and aldoxime-derived auxin production remain elusive. This project will elucidate this hidden metabolic network using two model systems, Arabidopsis and tomato. Using omics and genetics approaches, this project will identify the metabolic route of aldoxime-derived auxin production, determine mechanisms of aldoxime-mediated phenylpropanoid repression, and elucidate the roles of aldoxime metabolism in plant stress adaptation. The educational goal is to foster the next generation of the agriculture workforce and increase public awareness of plants and plant-based compounds. The production and dissemination of educational videos for young students through summer undergraduate interns and a K-12 teacher conference, respectively, will provide educational tools to raise awareness of phytochemicals to the public. In addition, graduate students and postdoctoral associates will receive comprehensive research training while participating in this project.

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.

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