title: Effects of varying nitrogen sources on amino acid synthesis costs in Arabidopsis thaliana under different light and carbon-source conditions.
abstract: Plants as sessile organisms cannot escape their environment and have to adapt to any changes in the availability of sunlight and nutrients. The quantification of synthesis costs of metabolites, in terms of consumed energy, is a prerequisite to understand trade-offs arising from energetic limitations. Here, we examine the energy consumption of amino acid synthesis in Arabidopsis thaliana. To quantify these costs in terms of the energy equivalent ATP, we introduce an improved cost measure based on flux balance analysis and apply it to three state-of-the-art metabolic reconstructions to ensure robust results. We present the first systematic in silico analysis of the effect of nitrogen supply (nitrate/ammonium) on individual amino acid synthesis costs as well as of the effect of photoautotrophic and heterotrophic growth conditions, integrating day/night-specific regulation. Our results identify nitrogen supply as a key determinant of amino acid costs, in agreement with experimental evidence. In addition, the association of the determined costs with experimentally observed growth patterns suggests that metabolite synthesis costs are involved in shaping regulation of plant growth. Finally, we find that simultaneous uptake of both nitrogen sources can lead to efficient utilization of energy source, which may be the result of evolutionary optimization.
authors.affiliation: Computational Systems Biology, School of Engineering and Science, Jacobs University Bremen, Campus Ring 1, 28759 Bremen, Germany; Systems Biology and Mathematical Modeling Group, Max Planck Institute of Molecular Plant Physiology, 14476 Potsdam, Germany.
authors.forename: Anne
authors.initials: A
authors.lastname: Arnold
authors.affiliation: Systems Biology and Mathematical Modeling Group, Max Planck Institute of Molecular Plant Physiology, 14476 Potsdam, Germany.
authors.forename: Max
authors.initials: M
authors.lastname: Sajitz-Hermstein
authors.affiliation: Systems Biology and Mathematical Modeling Group, Max Planck Institute of Molecular Plant Physiology, 14476 Potsdam, Germany.
authors.forename: Zoran
authors.initials: Z
authors.lastname: Nikoloski
mesh_terms: D000596:Amino Acids / Q000096:biosynthesis*; D017360:Arabidopsis / Q000378:metabolism*; D018533:Biomass; D002244:Carbon / Q000378:metabolism*; D004734:Energy Metabolism / Q000502:physiology; D004777:Environment; D052836:Heterotrophic Processes; D008029:Lighting; D009584:Nitrogen / Q000378:metabolism*
chemical_list: D000596:Amino Acids; D002244:Carbon; D009584:Nitrogen