Transcriptomic and Metabolomic Analyses Reveal Color Variation and Taste Formation of Different Radish Sprouts

Radish sprouts, which are nutritious microgreen vegetables, exhibit diverse colors and flavors. To elucidate the molecular mechanisms underlying these quality traits, we performed integrated transcriptomic and metabolomic analyses. Comparative studies across green, red, and purple radish sprouts identified 31 key genes regulating flavonoid accumulation, with RsPAL, Rs4CL, and others significantly upregulated in purple sprouts, followed by red sprouts. Specifically, the peak expression of RsFLS genes in red radish sprouts may lead to an elevated accumulation of kaempferol derivatives and a bitter taste. Additionally, 12 genes, including RsCYSD1 and RsOASC, were linked to glucosinolate accumulation with higher expression in red varieties. Consistently, higher aliphatic GSLs (5-oxoheptyl glucosinolate) and indole GSLs (indolylmethyl desulfoglucosinolate) were identified in red radish sprouts. The high myrosinase activity may lead to sulforane accumulation and pungent and sulfurous flavor in purple radish sprouts. These findings provide comprehensive insights into the genetic and metabolic bases of radish sprout coloration and taste formation.