(332f) Towards Genome-Scale Metabolic Reconstruction of Plant Metabolism

The scope and breadth of genome-scale metabolic reconstructions has continued to evolve over the last decade. However, only a limited number of efforts to reconstruct plant metabolism are currently available and all of them are focused on a single model plant system (i.e., Arabidopsis thaliana). In this talk, we present progress in the development of a genome-scale model for a plant with direct applications to foodstuff and bioenergy production (i.e., maize). Maize is a monocot grass species used as a model plant to study and understand plant biology and genetics. Unlike A. thaliana, annotation of maize is still underway which introduces significant challenges in the association of metabolic functions to genes. The developed model is designed to meet rigorous standards on gene-protein-reaction (GPR) associations, elementally and charged balanced reactions and a biomass reaction showing how different biomass precursors are involved into the existence of a plant cell. The metabolic network contains over 1,800 metabolites involved in over 1,600 reactions from primary and secondary metabolism of maize. As many as 350 reactions and 200 metabolites are unique to maize compared to A. thaliana. All reactions are elementally and charged balanced and localized into five different intracellular compartments (i.e., cytoplasm, mitochondrion, plastid, peroxisome and vacuole). GPR associations are also established based on the functional annotation information and homology prediction and categorized into five major classes of monofunctional proteins, multifunctional proteins, isozymes, multimeric proteins and protein complexes. We describe results from performing flux balance analysis under different physiological conditions, (i.e., photosynthesis, photorespiration and respiration) and explore their impact on biomass formation, lignin formation, and carbohydrate yield. The developed model corresponds to the largest and more complete to-date effort at cataloguing metabolism for a plant species.