Completion of the cytosolic post-chorismate phenylalanine biosynthetic pathway in plants

• Published in: Nature communications Vol. 10; no. 1; p. 15
• Main Authors: Qian, Yichun, Lynch, Joseph H., Guo, Longyun, Rhodes, David, Morgan, John A., Dudareva, Natalia
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 03-01-2019; Nature Publishing Group; Nature Portfolio
• Subjects: 38; 38/39; 38/77; 38/88; 38/89; 631/449; 631/45; 82/1; 82/58; 82/80; 82/83; Amino Acids, Dicarboxylic - metabolism; Biosynthesis; Biosynthetic Pathways; Chorismate mutase; Chorismate Mutase - metabolism; Cyclohexanecarboxylic Acids - metabolism; Cyclohexenes - metabolism; Cytosol; Cytosol - metabolism; Dehydration; Genetic analysis; Humanities and Social Sciences; Localization; Metabolic flux; Metabolites; Microorganisms; Molecular structure; multidisciplinary; Phenylalanine; Phenylalanine - metabolism; Phenylpyruvic Acids - metabolism; Plants (botany); Plants - genetics; Plants - metabolism; Plastids; Plastids - genetics; Plastids - metabolism; Prephenate dehydratase; Prephenate Dehydratase - genetics; Prephenate Dehydratase - metabolism; Proteins; Science; Science (multidisciplinary); Secondary metabolites; Transaminases - metabolism; Transcription; Transcription Initiation Site; Tyrosine - analogs & derivatives; Tyrosine - metabolism
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-018-07969-2

In addition to being a vital component of proteins, phenylalanine is also a precursor of numerous aromatic primary and secondary metabolites with broad physiological functions. In plants phenylalanine is synthesized predominantly via the arogenate pathway in plastids. Here, we describe the structure, molecular players and subcellular localization of a microbial-like phenylpyruvate pathway for phenylalanine biosynthesis in plants. Using a reverse genetic approach and metabolic flux analysis, we provide evidence that the cytosolic chorismate mutase is responsible for directing carbon flux towards cytosolic phenylalanine production via the phenylpyruvate pathway. We also show that an alternative transcription start site of a known plastidial enzyme produces a functional cytosolic prephenate dehydratase that catalyzes the conversion of prephenate to phenylpyruvate, the intermediate step between chorismate mutase and phenylpyruvate aminotransferase. Thus, our results complete elucidation of phenylalanine biosynthesis via phenylpyruvate in plants, showing that this pathway splits from the known plastidial arogenate pathway at chorismate, instead of prephenate as previously thought, and the complete pathway is localized in the cytosol.
Phenylalanine is mostly synthesized in plant plastids, but cytosolic transamination of phenylpyruvate also contributes. Here the authors show that a cytosolic chorismate mutase and a prephenate dehydratase encoded by an isoform of the plastidial ADT3 enzyme, produce phenylpyruvate in the cytosol.