High-Resolution Mass Spectrometry Approach for Proteomic and Metabolomic Analyses of High-Protein Soybean Seeds

Soybeans are a valuable source of vegetable protein and edible oil. Fast neutron (FN) radiation was employed to produce large chromosomal deletions in soybean Glycine max (L.) Merrill. We conducted proteomic and metabolomic profiling of a high-protein soybean mutant (G15FN-12) developed through FN mutagenesis to identify the metabolic pathways that underlie the elevated protein content. A deletion of 137 genes located on chromosome-12 had occurred in G15FN-12. Tandem tag-based protein profiling of the mutant and wild type identified 6098 proteins, of which 175 showed increased abundance and 239 showed decreased abundance in the mutant seeds. Using liquid chromatography-mass spectrometry (LC-MS)-based metabolomic profiling, we identified 610 metabolites, of which 294 metabolites showed increased and 157 showed reduced content in mutant seeds as compared to wild type. Proteomic and metabolomic profiling revealed a decrease in ubiquitin-proteasome-associated proteins and an increase in heat shock proteins in the mutant seed. We hypothesize that decreased protein degradation, together with enhanced refolding of misfolded protein by molecular chaperones, contributes to elevated protein content in the mutant seed. The development of value-added seed traits such as increased protein using advanced metabolic engineering techniques can be achieved by further exploring the metabolic pathways identified in this investigation.