Subcellular reprogramming of metabolism during cold acclimation in Arabidopsis thaliana

Metabolite changes in plant leaves during exposure to low temperatures involve re-allocation of a large number of metabolites between sub-cellular compartments. Therefore, metabolite determination at the whole cell level may be insufficient for interpretation of the functional significance of cellular compounds. To investigate the cold-induced metabolite dynamics at the level of individual sub-cellular compartments, an integrative platform was developed that combines quantitative metabolite profiling by gas chromatography coupled to mass spectrometry (GC-MS) with the non-aqueous fractionation technique allowing separation of cytosol, vacuole and the plastidial compartment. Two mutants of Arabidopsis thaliana representing antipodes in the diversion of carbohydrate metabolism between sucrose and starch were compared to Col-0 wildtype before and after cold acclimation to investigate interactions of cold acclimation with subcellular re-programming of metabolism. A multivariate analysis of the data set revealed dominant effects of compartmentation on metabolite concentrations that were modulated by environmental condition and genetic determinants. While for both, the starchless mutant of plastidial phospho-gluco mutase (pgm) and a mutant defective in sucrose-phosphate synthase A1, metabolic constraints, especially at low temperature, could be uncovered based on subcellularly resolved metabolite profiles, only pgm had lowered freezing tolerance. Metabolic profiles of pgm point to redox imbalance as a possible reason for reduced cold acclimation capacity.