Differential expression of flavonoid biosynthesis genes and biochemical composition in different tissues of pigmented and non-pigmented rice

Ever since the flavonoids and other antioxidants in rice were demonstrated with immense health benefits, much interest has been diverted to study the native indigenous rice landraces. In the present investigation, three pigmented rare Indian rice landraces and two non-pigmented rice varieties were analyzed for their phytoconstituents like total phenolic content (TPC), total flavonoid content (TFC), total anthocyanin content and antioxidant potential using 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity. The phytochemical profile was compared between seed, seedling, stem, leaf and root tissues of the different varieties. Pigmented rice cultivars demonstrated higher levels of bioactive compounds as compared to the non-pigmented cultivars exhibiting a strong correlation between the antioxidant activity of the grain and their phenolic and flavonoid content. Among the five different rice studied, black navara was found to be superior in terms of its phytochemical composition. Further, the expression levels of flavonoid genes among pigmented and non-pigmented rice was studied. Higher gene expression profiles were observed in the 8 flavonoid genes studied in pigmented rice varieties as compared to non-pigmented varieties. The colorlessness of non-pigmented rice and its lower levels of phytoconstituents correlated with the low transcript levels of flavonoid genes recorded in them. This study provides a basis for understanding the health-promoting properties of pigmented rice over non-pigmented rice at the biochemical and molecular levels.