Evolution and Structural Basis of Curcuminoid and Gingerol Formation in Turmeric and Ginger

Washington State University, Pullman WA

Investigators

Abstract

Two large and important questions in plant metabolism are: what are the mechanisms that lead to the large array of compounds produced by plants and how do these mechanisms evolve? Ginger and turmeric contain a large array of compounds that are similar in structure and that appear to be produced by the same biochemical pathway. These compounds, including curcumin, other diarylheptanoids, gingerols and gingerol-like compounds, are produced by polyketide synthase-like enzymes (PKSs). Because these two species produce such a large array of related compounds, they are an ideal system to use to study the molecular and structural basis for differences in production of such compounds in plants. These compounds were chosen as the focus of this project because of their importance to plant defense, to plants' adaptation to the environment, and to human health, and because a large set of genes (41 in total so far) have been identified in ginger and turmeric related to but distinct from known PKSs (such as chalcone synthase) that are expressed differentially between tissues and developmental stages of the two species. This project will focus on identifying which specific members of this gene family are responsible for production of specific curcuminoids, gingerols, other diarylheptanoids or gingerol-related compounds. It will also determine the biochemical function of individual PKSs in ginger or turmeric. This project will then determine the structural basis for differential activity among the different PKSs. This information will address the important questions of how changes in enzyme structure lead to differences in enzyme function and how these changes evolve in the context of plant metabolism. Broader Impacts This project will impact understanding of the evolution of enzyme function, especially with regard to how enzymes develop new functions. This in turn will impact understanding of factors that lead to compound diversification in the plant kingdom and ultimately to plant diversity in the biosphere. This project will also produce information that could be used to better tailor the production of specific compounds in target plants, increasing the ability to produce "designer plants". Undergraduate students and high school teachers will work with post-doctoral fellows in this research. The high school teachers (supported by summer internships) will take purified PKS proteins to their classrooms and then will work with their students to crystallize these proteins. These proteins will include altered forms of the enzymes, which will be produced to probe the questions of structure and function in this enzyme class, as well as control proteins that easily crystallize, so that the students will have a successful experience. Thus, the high school teachers and their students will work directly on a research project that will have potentially important findings regarding enzyme function, and they will learn about structural biology in the process.