Poaceae practically dominate staple crops for humans. In addition to the issue of sustenance, there is a growing interest in the secondary metabolites of these staple crops and their functions on health. In this study, metabolomic variations were investigated among six important species of Poaceae with a total of 17 cultivars, including wheat, maize, rice, sorghum, foxtail millet, and broomcorn millet. A total of 201 flavonoid metabolites and 29 carotenoid metabolites were identified based on the UPLC-ESI-MS/MS system. Among them, 114, 128, 101, 179, 113, and 92 flavonoids and 12, 22, 17, 15, 21, and 18 carotenoids were found in wheat, maize, rice, sorghum, foxtail millet, and broomcorn millet, respectively. Only 46 flavonoids and 8 carotenoids were shared by the six crops. Crop-specific flavonoids and carotenoids were identified. Flavone, anthocyanins, flavanone and polyphenol were the major metabolite differences, which showed species specificity. The flavonoid content of the grains from 17J1344 (sorghum), QZH and NMB (foxtail millet) and carotenoids from Mo17 (maize) were higher than the other samples. This study provides a better knowledge of the differences in flavonoid and carotenoid metabolites among Poaceae crops, as well as provides a theoretical basis for the identification of functional metabolites in these grains.

Foxtail millet (Setaria italica), a cereal crop in China, is renowned for its resilience to abiotic stresses, including saline-alkali conditions. This study examined the transcriptomic and metabolomic responses of two contrasting foxtail millet varieties, B103 (tolerant) and B323 (sensitive), under saline-alkali stress. Physiological analysis showed that B103 exhibited higher growth parameters and chlorophyll content than B323, highlighting its enhanced tolerance. Transcriptomic analysis identified differentially expressed genes (DEGs) enriched in stress-response pathways such as phenylpropanoid biosynthesis, flavonoid metabolism and calcium signaling. Metabolomic profiling revealed differentially accumulated metabolites (DMs) involved in energy and secondary metabolism, including citrate, fumarate and flavonoids. Integration of DEGs and DMs revealed key gene-metabolite interactions, particularly those involving the nicotinamide compound and three candidate genes Si9g20070, Si7g22360 and Si5g39810, for future functional validation, which may contribute to stress adaptation. Dynamic clustering of gene expression trends highlighted the importance of rapid stress responses. These findings establish a molecular framework for understanding saline-alkali stress tolerance and provide genetic resources for developing stress-resilient foxtail millet varieties.

The γ-aminobutyric acid (GABA), a ubiquitous non-protein amino acid in plants and animals, exhibits diverse biological activities and holds promise in human disease prevention and treatment. Prior studies have shown that germination could substantially elevate GABA levels in rice, but these investigations typically focused on limited germplasms, hindering the generalization of their findings. This study aims to identify optimal conditions for enriching GABA in a diverse set of 225 rice germplasms by examining the effects of various germination times, temperatures, and soaking solution pH levels, while elucidating the key factors influencing GABA enrichment in germinated brown rice. The optimal GABA enrichment in germinated brown rice was achieved under the following conditions: a germination temperature of 37 °C, a germination duration of 48 h, and a soaking solution pH of 5.5. Under these conditions, we found significant differences in GABA content among different germplasms. Subsequent correlation analyses demonstrated that GABA content showed significant positive correlations with embryo weight in brown rice, relative embryo weight, relative embryo weight in germinated brown rice, as well as glutamate (Glu) and proline (Pro) concentrations. Therefore, larger brown rice embryos, higher Glu and Pro content in germinated brown rice, and external Glu application contribute to increased GABA content. Our findings provide essential materials and theoretical insights for screening and developing GABA-rich functional rice germplasms, facilitating variety selection and breeding programs.