Identification of a plastidial phenylalanine exporter that influences flux distribution through the phenylalanine biosynthetic network

• Published in: Nature communications 2015-09, Vol.6 (1), p.8142-8142, Article 8142
• Main Authors: Widhalm, Joshua R., Gutensohn, Michael, Yoo, Heejin, Adebesin, Funmilayo, Qian, Yichun, Guo, Longyun, Jaini, Rohit, Lynch, Joseph H., McCoy, Rachel M., Shreve, Jacob T., Thimmapuram, Jyothi, Rhodes, David, Morgan, John A., Dudareva, Natalia
• Format: Article
• Language: English
• Subjects: 13/89; 14/19; 38/91; 631/449/1659; 631/449/2675; 631/449/448/2651; 82/80; Amino Acid Transport Systems, Basic - metabolism; BASIC BIOLOGICAL SCIENCES; Biosynthetic Pathways; Escherichia coli; Humanities and Social Sciences; Metabolic Flux Analysis; multidisciplinary; Petunia; Phenylalanine - metabolism; Plant Proteins - metabolism; Plants, Genetically Modified; Plastids - metabolism; Real-Time Polymerase Chain Reaction; Reverse Transcriptase Polymerase Chain Reaction; RNA Interference; Science; Science (multidisciplinary); Sequence Analysis, RNA; Tyrosine - metabolism; Volatile Organic Compounds - metabolism
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms9142

In addition to proteins, L -phenylalanine is a versatile precursor for thousands of plant metabolites. Production of phenylalanine-derived compounds is a complex multi-compartmental process using phenylalanine synthesized predominantly in plastids as precursor. The transporter(s) exporting phenylalanine from plastids, however, remains unknown. Here, a gene encoding a Petunia hybrida plastidial cationic amino-acid transporter (PhpCAT) functioning in plastidial phenylalanine export is identified based on homology to an Escherichia coli phenylalanine transporter and co-expression with phenylalanine metabolic genes. Radiolabel transport assays show that PhpCAT exports all three aromatic amino acids. PhpCAT downregulation and overexpression result in decreased and increased levels, respectively, of phenylalanine-derived volatiles, as well as phenylalanine, tyrosine and their biosynthetic intermediates. Metabolic flux analysis reveals that flux through the plastidial phenylalanine biosynthetic pathway is reduced in PhpCAT RNAi lines, suggesting that the rate of phenylalanine export from plastids contributes to regulating flux through the aromatic amino-acid network. Phenylalanine is synthesized in plant chloroplasts and is then exported to the cytosol, where it is a precursor for various secondary metabolites. Here, the authors identify PhpCAT as a plastid phenylalanine transporter required to maintain metabolic flux in petunia.