TmTCP6 and TmTCP25 transcription factors mediate ABA signaling to increase chicoric acid biosynthesis in Taraxacum mongolicum

Chicoric acid (CA) represents a high-value specialized metabolite with demonstrated potential against HIV integrase, diabetes, and tuberculosis; related drug candidates are currently advancing through Phase II clinical trials, with the global market experiencing substantial expansion driven by escalating demand in pharmaceutical and nutraceutical sectors. However, the transcriptional networks driving its biosynthesis remain elusive. Although TCP transcription factors are known regulators of secondary metabolism, their involvement in CA production remains uncharacterized. Here, 28 non-redundant TmTCP genes were identified and categorized into PCF, CIN, and CYC/TB1 subclades. Integration promoter motif analysis with tissue-specific and ABA-responsive expression profiling, we predicted that TmTCP6, TmTCP17 , and TmTCP25 may be involved in regulating CA biosynthesis. Functional studies confirmed that both transient and transgenic overexpression of TmTCP6 , as well as transient overexpression of TmTCP25, significantly enhanced CA accumulation. TmTCP6 directly activates TmHTT1 via the TBS2 motif and upregulates the positive regulator TmbZIP1 via TBS1, establishing a transcriptional cascade in which TmbZIP1 subsequently activates Tm4CL1 to promote CA accumulation. TmTCP6 coordinates direct and indirect transcriptional control to fine-tune ABA-responsive CA biosynthesis. Meanwhile, TmTCP25 directly up-regulates the expression of TmHTT1 to enhance CA accumulation. Our work reveals a complex transcriptional module governing CA biosynthesis and provides specific genetic strategies for the precision metabolic engineering of high-value phenylpropanoids in medicinal plants.