Metabolomic Insights into Primary and Secondary Metabolites Variation in Common and Glutinous Rice (Oryza sativa L.)

Abstract

Abstract: Interest in glutinous rice consumption has been expanding in East Asia. However, the extent of metabolite variation between common and glutinous rice has not been fully explored to identify metabolic targets for rice quality improvement. Thus, the objective of this study was to provide insights into the variation of metabolites and nutraceuticals between common and glutinous rice. Two black rice (common rice, BL-N, and glutinous rice, BL-G) and two white rice (common rice, WH-N, and glutinous rice, WH-G) types were analysed via LC-MS-based widely targeted metabolic profiling. We identified 441 and 343 types, including 160 key overlapping differentially accumulated metabolites between BL-N_vs_BL-G and WH-N_vs_WH-G, respectively. Glutinous rice showed a higher relative content of most categories of metabolites, except for quinones (in BL-N) and tannins (in WH-N). Seven vitamins, including B6, B3, B5, B13, isonicotinic acid, N-(beta-D-glucosyl)nicotinate, and 4-pyridoxic acid-O-glucoside, were significantly up-regulated in BL-G compared to BL-N. The biosynthesis of cofactors, zeatin biosynthesis, citrate cycle, amino acid metabolism, alpha-linolenic acid metabolism, and glyoxylate and dicarboxylate metabolism was the most differentially regulated pathway. Key differential metabolites in citrate cycle include citrate, isocitrate, fumarate, malate, succinate, and 2-oxoglutarate; in amino acid metabolism (L-serine, L-cysteine, L-lysine, L-glutamine, L-methionine, and L-tryptophan); and in glycolysis (UDP-glucose, D-glucose-1P, D-glucose-6P, and D-fructose-6P). The data resources in this study may contribute to a better understanding of the function and nutritional value of glutinous rice.