Analysis of the Arabidopsis Cytosolic Proteome Highlights Subcellular Partitioning of Central Plant Metabolism

The plant cell cytosol is a dynamic and complex intracellular matrix that, by definition, contains no compartmentalization. Nonetheless, it maintains a wide variety of biochemical networks and often links metabolic pathways across multiple organelles. There have been numerous detailed proteomic studies of organelles in the model plant Arabidopsis thaliana, although no such analysis has been undertaken on the cytosol. The cytosolic protein fraction from cell suspensions of Arabidopsis thaliana was isolated and analyzed using offline strong cation exchange liquid chromatography and LC−MS/MS. This generated a robust set of 1071 cytosolic proteins. Functional annotation of this set revealed major activities in protein synthesis and degradation, RNA metabolism and basic sugar metabolism. This included an array of important cytosol-related functions, specifically the ribosome, the set of tRNA catabolic enzymes, the ubiquitin-proteasome pathway, glycolysis and associated sugar metabolism pathways, phenylpropanoi...