Targeted lipidome analysis reveals nutritionally enhanced foxtail millet genotypes across diverse grain colours

Abstract

Foxtail millet (Setaria italica), a small-grained cereal crop, is a rich source of carbohydrates, proteins, minerals, fibers, and lipids, with lipid content ranging from 1–5% of the total grain composition. Whole grain is an excellent natural source of nutraceutical properties and health-beneficial components that significantly reduce chronic inflammation, cardiovascular disease, metabolic syndrome, and type 2 diabetes. Different grain colours in foxtail millet are associated with distinct metabolome composition. However, the relationship between lipid composition and grain colour remains largely unexplored. In this study, a comprehensive metabolomic analysis of eight differently coloured foxtail millet grains led to the identification of 352 distinct metabolites. Among these, 44 metabolites were chemically classified into categories such as fatty acids, steroids, hydrocarbons, benzenes, monoradylglycerols, quinones, and hydroquinones. Linoleic acid was identified as the predominant fatty acid, while lutein emerged as the most abundant carotenoid across all accessions. Gene expression profiling of carotenoid biosynthesis genes revealed significant genotype-specific variations, with SiPSY1, SiPSY2, SiPSY3, SiZDS, SiLCYB, and SiLCYE exhibiting markedly higher expression in the golden yellow genotype SI 101. Furthermore, several unique compounds, including decane 1-iodo, dodecane 4, 6-dimethyl, hexadecane, heptadecane, eicosane, heneicosane, bis (2-ethylhexyl) phthalate, dotriacontane, 2-methylhexacosane, hexatriacontane, squalene, tetrapentacontane, and tetracosane, were identified in foxtail millet grains. These findings provide valuable insights into the metabolic diversity and the differential accumulation of bioactive compounds in among foxtail millet grains with different colours. The study also assists in selecting foxtail millet genotypes with desirable lipid traits for sustainable crop improvement.