Phenylpropanoid metabolism products have important biological functions in plants. Lignin is one of the important phenylpropanoid metabolites, which strengthens the biotic and abiotic stress resistance and defense of plants. However, the presence of lignin is a major source of pollution in papermaking. Meanwhile, lignin in forage is not conducive to the animal's digestion and nutrient absorption. In recent years, the genes of main enzyme in lignin biosynthesis have been cloned, and the regulation of plant l...