CoPIs: Cornelius Barry and A. Daniel Jones (Michigan State University) and Eran Pichersky (University of Michigan)
The long-term goal of this research is to understand the principles that underlie the tremendous diversity of plant specialized metabolites (also known as secondary metabolites or natural products). These chemicals are part of the plant's arsenal for defense against biological and environmental stress and include compounds that contribute to flavors and aromas as well as medically important drugs. Storage/secreting glandular trichomes (SGTs) on the aerial surfaces of the plant are especially active in producing such compounds and thus are excellent for studying their biosynthesis. Cultivated tomato (Solanum lycopersicum) and related species have anatomically diverse types of SGTs on leaves, stems, and reproductive structures and each type produces a distinct set of specialized metabolites including terpenes, methylated or glycosylated flavonoids, and acylsugars, with surprising diversity observed within and between species. It is becoming increasingly clear that Solanum SGTs utilize novel biochemical mechanisms for producing some of these products, and recent results indicate that the combination of comparative and functional genomics, metabolomics, and biochemical methods is a particularly promising approach to elucidate these pathways and the overall pattern of their diversification. Building on the progress made in the previous funding period, this project will provide a detailed analysis of the biosynthesis of terpenes and acylsugars, two classes of compounds with documented biological effects against biotic stress agents, in distinct types of SGTs. The approach is designed to elucidate specific reactions and enzymes but also patterns of pathway evolution and regulation. Acylsugar biosynthesis is currently poorly understood, and the genetics and genomics resources created under this project will provide valuable insight into how these diverse compounds are synthesized. More is known about terpene biosynthesis, but previous results indicated that some of the tenets about substrate utilization and roles of specific classes of terpene synthases are imperfect and instead these proteins display a tremendous potential to evolve new functions, a process that will be examined in this project.
The broader impacts of this project fall into two general categories: advancement of the fields of biology impacted by the project and educational outreach. The results of these studies will reveal the biochemical and genetic mechanisms by which plants produce these important compounds in SGTs and other cell types, and inform breeding and transgenic approaches to modify their synthesis in crop plants to enhance resistance to insects and disease. Discovery of novel mechanisms also offers opportunities to exploit these biochemical pathways in new technologies for the production of bioactive chemicals and chemical feedstocks. In order to maximize the utility and accessibility of the data generated through this project, data will be submitted to long-term community databases that include the NCBI (www.ncbi.nlm.nih.gov/), Trichome (www.trichome.msu.edu/), TrichOME (www.planttrichome.org/trichomedb/) and the Sol Genomics Network (http://solgenomics.net/). Because the project includes laboratories expert in analytical chemistry, biochemistry, genetics and genomics, it provides a natural platform for interdisciplinary training. In addition to cross-training of undergraduate and graduate students and postdoctoral researchers throughout the year, this project will integrate research and education in complementary ways: first, through summer research experiences for three undergraduate students each year as part of the Plant Genomics @ Michigan State University program which places an emphasis on the recruitment of women and underrepresented minority group members; and second, through training opportunities for faculty from primarily undergraduate schools.
