PMID:18487352

Citation	Yamada, T, Matsuda, F, Kasai, K, Fukuoka, S, Kitamura, K, Tozawa, Y, Miyagawa, H and Wakasa, K (2008) Mutation of a rice gene encoding a phenylalanine biosynthetic enzyme results in accumulation of phenylalanine and tryptophan. Plant Cell 20:1316-29
Abstract	Two distinct biosynthetic pathways for Phe in plants have been proposed: conversion of prephenate to Phe via phenylpyruvate or arogenate. The reactions catalyzed by prephenate dehydratase (PDT) and arogenate dehydratase (ADT) contribute to these respective pathways. The Mtr1 mutant of rice (Oryza sativa) manifests accumulation of Phe, Trp, and several phenylpropanoids, suggesting a link between the synthesis of Phe and Trp. Here, we show that the Mtr1 mutant gene (mtr1-D) encodes a form of rice PDT with a point mutation in the putative allosteric regulatory region of the protein. Transformed callus lines expressing mtr1-D exhibited all the characteristics of Mtr1 callus tissue. Biochemical analysis revealed that rice PDT possesses both PDT and ADT activities, with a preference for arogenate as substrate, suggesting that it functions primarily as an ADT. The wild-type enzyme is feedback regulated by Phe, whereas the mutant enzyme showed a reduced feedback sensitivity, resulting in Phe accumulation. In addition, these observations indicate that rice PDT is critical for regulating the size of the Phe pool in plant cells. Feeding external Phe to wild-type callus tissue and seedlings resulted in Trp accumulation, demonstrating a connection between Phe accumulation and Trp pool size.
Links	PubMed PMC2438470 Online version:10.1105/tpc.107.057455
Keywords	Amino Acid Sequence; Chromatography, Liquid; Hydro-Lyases/genetics; Hydro-Lyases/metabolism; Models, Biological; Molecular Sequence Data; Molecular Structure; Mutation; Phenylalanine/biosynthesis; Phenylalanine/chemistry; Phenylalanine/metabolism; Plant Proteins/genetics; Plant Proteins/metabolism; Point Mutation; Prephenate Dehydratase/genetics; Prephenate Dehydratase/metabolism; Sequence Analysis, DNA; Sequence Homology, Amino Acid; Tandem Mass Spectrometry; Tryptophan/chemistry; Tryptophan/metabolism
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
ORYSJ:Q6Z3Y3		GO:0009507: chloroplast	ECO:0000314:		C		Figure 8 shows an in vitro assay of recombinant PDT being imported into chloroplasts and processed, and protected from thermolysin degradation.	complete CACAO 5558
ORYSJ:Q6Z3Y3		GO:0009094: L-phenylalanine biosynthetic process	ECO:0000315:		P		Figure 6 and 7 show increase Phe content in a PDT mutant (M47) that has a mutation in the regulatory site. Table 1 shows that this mutant is less sensitive to feedback inhibition by Phe.	complete CACAO 5561
ORYSJ:Q6Z3Y3		GO:0004664: prephenate dehydratase activity	ECO:0000314:		F		Table 1 shows kinetic properties of the PDT activity of the synthesized wild type PDT	complete CACAO 5559
ORYSJ:Q6Z3Y3		GO:0047769: arogenate dehydratase activity	ECO:0000314:		F		Table 1 shows the kinetic properties of the ADT activity of synthesized PDT.	complete CACAO 5560
ORYSJ:Q6Z3Y3	part_of	GO:0009507: chloroplast	ECO:0000314: direct assay evidence used in manual assertion		C		Seeded From UniProt	complete
ORYSJ:Q6Z3Y3	enables	GO:0004664: prephenate dehydratase activity	ECO:0000314: direct assay evidence used in manual assertion		F		Seeded From UniProt	complete
ORYSJ:Q6Z3Y3	enables	GO:0047769: arogenate dehydratase activity	ECO:0000314: direct assay evidence used in manual assertion		F		Seeded From UniProt	complete
ORYSJ:Q6Z3Y3	involved_in	GO:0009094: L-phenylalanine biosynthetic process	ECO:0000315: mutant phenotype evidence used in manual assertion		P		Seeded From UniProt	complete

References

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