Deciphering the Complex Metabolic Network in Snapdragon Flowers: An Integrative Approach

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Recent progress in the field of secondary metabolism has uncovered the importance of secondary metabolites, not only for plant life, but also for humans. The involvement of secondary metabolites in plant survival in the surrounding ecosystem and their impact on food quality, attractiveness of ornamentals, and human health reveal the importance of genetic improvements leading to their formation. Genetic engineering of secondary metabolites has enormous potential. However, its success largely depends on our understanding of the entire cellular metabolic network. The long-term goal of this project is to provide a comprehensive understanding of in vivo metabolism and to characterize the carbon flow through the metabolic network in photosynthetic and non-photosynthetic floral tissues over the lifespan of the flower. A unique integrative approach, including transient stable isotope labeling and metabolic flux analysis over flower development, combined with corresponding transcriptome analysis, will be used to obtain a novel picture of the dynamic relationships between in vivo flux and gene expression profiles in central carbon, nitrogen, and secondary metabolism of flowers. This research will lead to the generation of a temporal flux map in which each biochemical step will contain a developmental profile for the corresponding flux and gene expression. The developmental aspect of flux analysis incorporated into the temporal flux map will add a new dimension to our vision of primary and secondary metabolism. The integration of global flux analysis and enzyme activity with gene expression will uncover the potential regulatory steps within pathways or branchways. An integrative map developed in this research will help to conceptualize the temporal and spatial aspects of the network regulation and guide diverse efforts in metabolic engineering of plant secondary metabolism. Moreover, this project will fill important gaps in the understanding of floral metabolism and provide powerful modeling tools for general use in the metabolic engineering of plant metabolic pathways. Broader impacts: This project has a strong multidisciplinary training component for the next generation of plant scientists. Undergraduate and graduate students, as well as post-doctoral scientists (including women and minorities) participating in this research will get 'the big picture' of cellular metabolism and gain an appreciation of whole plant physiology, in vivo isotopic labeling, analytical biochemistry, molecular biology, genetics and integrative modeling. The overall instructional goal is to provide students with a more comprehensive understanding of plant metabolism. In addition to training students, new course modules on secondary metabolism, metabolic engineering, and integrative modeling will be developed and incorporated via the web using WebCT into existing courses at Purdue University. Plant metabolic modeling software developed as part of this project as well as the teaching modules will be released as freeware on the Purdue Horticulture web server.