Ultrasound-Assisted Enhancement of Germinated Sorghum: Multi-Omics Insights into Amino Acid and Carbohydrate Metabolic Regulation

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Germination represents a recognized strategy for improving the nutritional profile and promoting the enrichment of bioactive constituents in cereal crops. However, the regulatory mechanisms through which physical treatments such as ultrasound influence metabolic processes during germination remain insufficiently understood. This study investigates the effects of ultrasound-assisted germination (50 kHz, 240 W, 30 min) on amino acid and carbohydrate metabolism in sorghum while employing integrated metabolomic and transcriptomic approaches. Total protein and starch contents decreased during germination, with starch content in fully germinated ultrasound-treated grains (FG + U) declining to 344.27 mg/g. Protease and α-amylase activities increased during germination and were further improved by ultrasound treatment, suggesting increased mobilization of storage reserves during germination. Metabolomic analysis identified 110 amino acids and 49 carbohydrates as differentially accumulated metabolites under ultrasound treatment at the fully germinated stage, including six essential amino acids and increased D-glucose levels. Transcriptomic analysis revealed 7,791 genes shared between germination-related and ultrasound-responsive differentially expressed genes (DEGs). These genes were significantly enriched in metabolic pathways, including alanine, aspartate, and glutamate metabolism; glycolysis/gluconeogenesis; and the pentose phosphate pathway. Based on the Weighted gene co-expression network analysis (WGCNA)-derived gene modules, transcription factor-target gene network analysis further identified three highly connected transcription factors, including bHLH137 (LOC8060932), R-S (LOC8056590) and EIL1 (LOC110434014), as candidate hub transcription factors associated with amino acid and carbohydrate metabolism. These results provide systems-level insights into the transcriptional and metabolic responses associated with ultrasound-assisted germination and identify candidate regulatory components for future functional investigation.