Transcriptomics Integrated With Widely Targeted Metabolomics Reveals the Mechanism Underlying Grain Color Formation in Wheat at the Grain-Filling Stage

Colored wheat grains have a unique nutritional value. To elucidate the color formation mechanism in wheat seeds, comprehensive metabolomic and transcriptomic analyses were conducted on purple (Dianmai 20-1), blue (Dianmai 20-8), and white (Dianmai 16) wheat at the grain-filling stage. The results showed that the flavonoid biosynthesis pathway was closely related to grain color formation. Among the 603 metabolites identified in all varieties, there were 98 flavonoids. Forty-six flavonoids were detected in purple and blue wheat, and there were fewer flavonoids in white wheat than in colored wheat. Integrated transcriptomic and metabolomic analyses showed that gene expression modulated the flavonoid composition and content, resulting in different metabolite levels of pelargonidin, cyanidin, and delphinidin, thus affecting the color formation of wheat grains. The present study clarifies the mechanism by which pigmentation develops in wheat grains and provides an empirical reference for colored wheat breeding.

Bioactive compounds, nutritional benefits and food applications of colored wheat: a comprehensive review

The consumers' demands have changed from energy providing diet to a diet with a balanced nutrient profile along with metabolic, physiological and functional health benefits. They are seeking colorants derived from natural sources to enhance the nutritional and antioxidant value of foods. Colored wheat (Triticum aestivum) contains many phytochemicals, responsible for numerous health benefits. Colored wheat (blue, black, purple and red) contains a good amount of anthocyanins and carotenoids that are primarily located in the outer aleurone layer. Food regulatory and safety authorities and food processing industries are trying to minimize the usage of synthetic food colorants and dyes. Colored wheat is imperative for food processing industries as high-value pigments present in the bran layer (milling industry co-product) can easily be extracted and utilized as functional foods and natural colorants. The extracted pigments such as anthocyanin can replace synthetic dyes currently used in food, drug and cosmetics. Additionally, natural additives improve the nutritional value, appearance, texture, flavor, and storage properties of food products. This review presents a brief knowledge of the nutritional composition of colored wheat including phytochemicals and bioactive compounds like flavonoids, phenolic compounds, their health benefits, methods and technologies used for processing and extraction as well as the effects of processing on these compounds.