title: An alternative pathway contributes to phenylalanine biosynthesis in plants via a cytosolic tyrosine:phenylpyruvate aminotransferase.
abstract: Phenylalanine is a vital component of proteins in all living organisms, and in plants is a precursor for thousands of additional metabolites. Animals are incapable of synthesizing phenylalanine and must primarily obtain it directly or indirectly from plants. Although plants can synthesize phenylalanine in plastids through arogenate, the contribution of an alternative pathway via phenylpyruvate, as occurs in most microbes, has not been demonstrated. Here we show that plants also utilize a microbial-like phenylpyruvate pathway to produce phenylalanine, and flux through this route is increased when the entry point to the arogenate pathway is limiting. Unexpectedly, we find the plant phenylpyruvate pathway utilizes a cytosolic aminotransferase that links the coordinated catabolism of tyrosine to serve as the amino donor, thus interconnecting the extra-plastidial metabolism of these amino acids. This discovery uncovers another level of complexity in the plant aromatic amino acid regulatory network, unveiling new targets for metabolic engineering.
authors.affiliation: Department of Horticulture and Landscape Architecture, Purdue University, 625 Agriculture Mall Dr, West Lafayette, Indiana 47907, USA.
authors.forename: Heejin
authors.initials: H
authors.lastname: Yoo
authors.forename: Joshua R
authors.initials: JR
authors.lastname: Widhalm
authors.forename: Yichun
authors.initials: Y
authors.lastname: Qian
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Maeda
authors.forename: Bruce R
authors.initials: BR
authors.lastname: Cooper
authors.forename: Amber S
authors.initials: AS
authors.lastname: Jannasch
authors.forename: Itay
authors.initials: I
authors.lastname: Gonda
authors.forename: Efraim
authors.initials: E
authors.lastname: Lewinsohn
authors.forename: David
authors.initials: D
authors.lastname: Rhodes
authors.forename: Natalia
authors.initials: N
authors.lastname: Dudareva
mesh_terms: D017398:Alternative Splicing / Q000235:genetics*; D003600:Cytosol / Q000201:enzymology*; D032306:Petunia; D010649:Phenylalanine / Q000096:biosynthesis* / Q000235:genetics; D010667:Phenylpyruvic Acids / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D000637:Transaminases / Q000235:genetics / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism
chemical_list: D010667:Phenylpyruvic Acids; D010940:Plant Proteins; D014443:Tyrosine; D010649:Phenylalanine; D000637:Transaminases; C022340:phenylalanine aminotransferase; C031606:phenylpyruvic acid