(391c) Flux Balance Analysis of Plant Suspension Cell Culture

We report the use of flux balance analysis (FBA) for reconstructing flux maps in plant and tree suspension cells. The utility of plants as renewable sources for producing energy and other chemicals merits extensive study of their complex metabolism. FBA uses optimization of constraint-based models of biochemical networks to determine fluxes through metabolic pathways. It has been successfully applied in many cases for estimating fluxes in prokaryotic organisms. Its use in estimating fluxes in eukaryotic systems, especially plants and trees, has been less widespread.

Plant metabolism is much more complex than that of prokaryotes with cellular compartmentation and replication of pathways across compartments. In plants, a couple of pioneering studies have applied FBA for estimating fluxes using plant cell culture (Williams et al., Plant Physiol. 154: 311-323, 2010; Belau et al, Plant Physiol. 149: 585-598, 2009). We have applied FBA for estimating fluxes in cell cultures of Arabidopsis thaliana and poplar (Populus trichocarpa). As part of the work, we will present investigation of the effect of different objective functions for estimating fluxes using FBA. The growth maximization objective function commonly used for prokaryotic organisms is not suitable for eukaryotic organisms due to their complex growth requirements and pathways. By comparing fluxes obtained from FBA with those from isotopic MFA, we will determine the best objective functions that are critical for accurate flux estimation by FBA. Using the optimized objective function, we will present metabolic landscapes obtained for the networks in both systems, and specifically present changes in carbon-nitrogen interactions/metabolism in poplar. Our studies will represent the first application of FBA to a model tree system, and additionally provide insight on the metabolic network in model plant and tree organisms.