[Molecular mechanism of StTCP11-mediated anthraquinone biosynthesis in Senna tora L.]

The seeds of Senna tora L.are the core organs for the biosynthesis of anthraquinones, and their medicinal value is highly dependent on the content of anthraquinones. However, TCP transcription factors play a key regulatory role in the biosynthesis of plant secondary metabolites. Nevertheless, whether TCP transcription factors regulate the accumulation of anthraquinone compounds has not been reported. Therefore, in this study, qRT-PCR analysis was performed to determine the expression pattern of StTCP11 at different growth and development stages of S. tora seeds. An overexpression vector was constructed to obtain two types of S. tora lines: StTCP11-overexpressing lines and empty vector (control) lines, which were used to explore the effect of StTCP11 on the accumulation of anthraquinones in seeds. The interactions betweenStTCP11 and key enzymes in anthraquinone biosynthesis were analyzed by yeast one-hybrid (Y1H) and dual-luciferase (Dual-LUC) reporter gene assays. The results showed that the expression level of StTCP11 was higher at the late stage of seed development. Compared with the control, the StTCP11-overexpressing lines showed significantly increased content of aurantio-obtusin, chrysophanol, emodin, and physcion in the seeds. Y1H and Dual-LUC assays confirmed that StTCP11could directly bind to the promoter of StDXS and activate its transcription, thereby positively regulating the accumulation of anthraquinones. This study revealed the molecular mechanism of StTCP11 in promoting anthraquinone synthesis in S. tora seeds through targeted regulation of StDXS transcription, which provided a key theoretical basis for resolving the quality regulation network of S. tora seeds and breeding new high-quality varieties.