The multilayered regulation of aromatic amino acid biosynthesis in plants

The shikimate and aromatic amino acid (AAA) biosynthetic pathways are crucial for the production of L-phenylalanine (Phe), L-tyrosine (Tyr), and L-tryptophan (Trp), as well as vitamins, hormones, and an array of plant natural products, including lignin, a major reservoir of organic carbon on Earth. In this review, we summarize recent advances in the mechanisms that dynamically regulate the AAA biosynthetic pathways of plants, with a particular focus on Phe biosynthesis due to its central role as a precursor to phenylpropanoids. The integration of AAA biosynthesis with upstream and downstream plant metabolism is also discussed, as well as how this fundamental knowledge can inform the bioengineering of plant-based platforms for sustainable production of AAA-derived natural products.