Proteomic analysis of japonica sorghum following microwave intermittent drying based on label-free technology

The aim of this study was to investigate the influence of microwave drying on the protein quality of japonica sorghum following an intermittent drying test. Using label-free technology and liquid chromatography-tandem mass spectrometry for proteomic analysis, the effects of microwave drying on sorghum differential protein expression, functional classification, and metabolic pathways were analyzed at the molecular level. After sorghum was dried using a microwave, 85 differential proteins were identified. Among them, 51 showed up-regulated expression while 34 had down-regulated expression. The up-regulation and down-regulation of differential protein expressions significantly changed them, and proteins with larger up-regulated and down regulated expressions were postulated to affect biological and metabolic processes of sorghum during subsequent processing. Differential proteins were significantly (P < 0.01) involved in metabolic pathways, such as carbon metabolism, glycolysis/ gluconeogenesis, carbon fixation in photosynthetic organisms, biosynthesis of amino acids, amino sugar and nucleotide sugar metabolism, and the TCA cycle. For the protein interaction network, glyceraldehyde-3-phosphate dehydrogenase of the down regulated proteins was postulated to be the key factor affecting the entire metabolic system or signal transduction pathway. Up-regulated proteins, including phosphoglycerate mutase and phosphopyruvate hydratase, as well as down-regulated proteins such as glyceraldehyde-3-phosphate dehydrogenase and fructose-bisphosphate aldolase, not only directly or indirectly affected a variety of metabolic processes, but were specifically closely related to glycolysis and glycometabolism. Overall, this study showed that among the related metabolic pathways, differential protein changes in glycometabolism pathways may have the greatest impact on metabolic processes. The research results discussed herein can provide theoretical support for the industrial application of microwave drying and deep processing of sorghum.