Metabolic profiling reveals altered nitrogen nutrient regimes have diverse effects on the metabolism of hydroponically-grown tomato (Solanum lycopersicum) plants

The role of inorganic nitrogen assimilation in the production of amino acids is one of the most important biochemical processes in plants. For this reason, a detailed broad-range characterization of the metabolic response of tomato (Solanum lycopersicum) leaves to the alteration of nitrate level was performed. Tomato plants were grown hydroponically in liquid culture under three different nitrate regimes: saturated (8 mM NO3-), replete (4 mM NO3-) and deficient (0.4 mM NO3-). All treatments were performed under varied light intensity, with leaf samples being collected after 7, 14, and 21 d. In addition, the short-term response (after 1, 24, 48, and 94 h) to varying nutrient status was evaluated at the higher light intensity. GC-MS analysis of the levels of amino acids, tricarboxylic acid cycle intermediates, sugars, sugar alcohols, and representative compounds of secondary metabolism revealed substantial changes under the various growth regimes applied. The data presented here suggest that nitrate nutrition has wide-ranging effects on plant leaf metabolism with nitrate deficiency resulting in decreases in many amino and organic acids and increases in the level of several carbohydrates and phosphoesters, as well as a handful of secondary metabolites. These results are compared with previously reported transcript profiles of altered nitrogen regimes and discussed within the context of current models of carbon nitrogen interaction.