Integrated Metabolomics and Transcriptomics Provide Key Molecular Insights into Floral Stage-Driven Flavonoid Pathway in Safflower

Safflower (<i>Carthamus tinctorius</i> L.) is a traditional Chinese medicinal herb renowned for its high flavonoid content and significant medicinal value. However, the dynamic changes in safflower petal flavonoid profiles across different flowering phases present a challenge in optimizing harvest timing and medicinal use. To enhance the utilization of safflower, this study conducted an integrated transcriptomic and metabolomic analysis of safflower petals at different flowering stages. Our findings revealed that certain flavonoids were more abundant during the fading stage, while others peaked during full bloom. Specifically, seven metabolites, including p-coumaric acid, naringenin chalcone, naringenin, dihydrokaempferol, apigenin, kaempferol, and quercetin, accumulated significantly during the fading stage. In contrast, dihydromyricetin and delphinidin levels were notably reduced. Furthermore, key genes in the flavonoid biosynthesis pathway, such as <i>4CL</i>, <i>DFR</i>, and <i>ANR</i>, exhibited up-regulated expression with safflower's flowering progression, whereas <i>CHI</i>, <i>F3H</i>, and <i>FLS</i> were down-regulated. Additionally, exposure to UV-B stress at full bloom led to an up-regulation of flavonoid content and altered the expression of key flavonoid biosynthetic genes over time. This study not only elucidates the regulatory mechanisms underlying flavonoid metabolism in safflower but also provides insights for maximizing its medicinal and industrial applications.