Characterization of Metabolic States of Arabidopsis thaliana Under Diverse Carbon and Nitrogen Nutrient Conditions via Targeted Metabolomic Analysis

Plant growth and metabolism are regulated in response to various environmental factors. To investigate modulations in plant metabolism by the combined action of elevated atmospheric CO(2) concentration and other nutritional factors, we performed targeted metabolomic analysis using Arabidopsis thaliana plants grown under 24 different conditions where the CO(2) concentration, amounts and species of nitrogen source, and light intensity were modified. Our results indicate that both the biosynthesis of diverse metabolites and growth are promoted in proportion to the CO(2) concentration at a wide range of CO(2) levels, from ambient concentrations to an extremely high concentration (3,600 p.p.m.) of CO(2). This suggests that A. thaliana has the potential to utilize effectively very high concentrations of CO(2). On the other hand, ammonium (but not nitrate) supplied as an additional nitrogen source induced drastic alterations in metabolite composition, including increases in the contents of glucose, starch and several amino acids, and reductions in the tricarboxylic acid (TCA) cycle-related organic acid content under any CO(2) conditions. Hierarchical clustering analysis using the metabolite profiles revealed that ammonium is a prominent factor determining metabolic status, while the CO(2) concentration is not. However, ammonium-induced metabolic alterations were differently modified by high concentrations of CO(2). Hence, our results imply that increases in CO(2) concentration may differently influence plant metabolism depending on the nitrogen nutrient conditions.