Liquiritigenin (LG),isoliquiritigenin (Iso-LG),together with their respective glycoside derivatives liquiritin (LN) and isoliquiritin (Iso-LN),are the main active flavonoids of Glycyrrhiza uralensis,which is arguably the most widely used medicinal plant with enormous demand on the market,including Chinese medicine prescriptions,preparations,health care products and even food.Pharmacological studies have shown that these ingredients have broad medicinal value,including anti-cancer and antiinflammatory effects.Although the biosynthetic pathway of glycyrrhizin,a triterpenoid component from G.uralensis,has been fully analyzed,little attention has been paid to the biosynthesis of the flavonoids of this plant.To obtain the enzyme-coding genes responsible for the biosynthesis of LN,analysis and screening were carried out by combining genome and comparative transcriptome database searches of G.uralensis and homologous genes of known flavonoid biosynthesis pathways.The catalytic functions of candidate genes were determined by in vitro or in vivo characterization.This work characterized the complete biosynthetic pathway of LN and achieved the de novo biosynthesis of liquiritin in Saccharomyces cerevisiae using endogenous yeast metabolites as precursors and cofactors for the first time,which provides a possibility for the economical and sustainable production and application of G.uralensis flavonoids through synthetic biology.