Blue light as an eco-elicitor effectively enhances flavonoid biosynthesis and antioxidant capacity in dandelion revealed by integrated metabolomic and transcriptomic analyses

BACKGROUND: Dandelion (Taraxacum mongolicum) is a globally important medicinal herb rich in antioxidant flavonoids. Blue light (BL) serves as a key environmental signal known to regulate the biosynthesis of plant secondary metabolites. However, the molecular mechanisms in regulating flavonoid biosynthesis in non-model medicinal plants like dandelion remain poorly understood, particularly the roles of WRKY transcription factors (TFs) in this process. RESULTS: BL irradiation not only inhibited vegetative expansion but also enhanced photosynthetic pigment accumulation in dandelion. This treatment further boosted the plant’s antioxidant capacity and elevated its total flavonoid content. Notably, the levels of key antioxidant flavonoids such as rutin, apigenin, and quercetin derivatives were significantly increased. Transcriptomic profiling indicated a coordinated upregulation of structural genes (including CHS, CHI, ANR, DFR, UGT) in the flavonoid biosynthesis pathway. Genome-wide analysis identified 69 WRKY TFs (TmWRKYs) in dandelion. Among them, TmWRKY2, TmWRKY 21, TmWRKY 47, and TmWRKY 55 were significantly induced by BL. Correlation analyses indicated that TmWRKY2 and TmWRKY55 expression was strongly positively correlated with both the expression of key flavonoid biosynthetic genes and the accumulation of antioxidant flavonoids. Furthermore, promoter analysis of these correlated structural genes revealed abundant W-box cis-elements, suggesting potential direct regulation by these WRKY TFs. CONCLUSIONS: Our study suggests that BL enhances flavonoid accumulation in dandelion, likely through a transcriptional activation model​ involving specific WRKY TFs, including TmWRKY2 and TmWRKY55. The identification of W-box elements in the promoters of key structural genes further supports this proposed regulatory network. These findings provide novel insights into light-transcription factor-metabolite interactions in medicinal plants and highlight potential targets for molecular breeding and cultivation strategies to improve dandelion’s nutraceutical value.