Cloning Two Genes for Nicotianamine Aminotransferase, a Critical Enzyme in Iron Acquisition (Strategy II) in Graminaceous Plants

Takahashi, Michiko; Yamaguchi, Haruhisa; Nakanishi, Hiromi; Shioiri, Takayuki; Nishizawa, Naoyuki; Mori, Satoshi

doi:10.1104/pp.121.3.947

Cited by 221 publications

(155 citation statements)

References 46 publications

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“…Transcript levels for TAT1 (designated here as AtTyrAT-1) increased in response to MeJA or methyl 12-oxophytodienoic acid treatment and to wounding. The deduced amino acid sequence of TAT1 showed 35% identity to human and rat TyrATs and shares extensive sequence similarity with nicotianamine aminotransferase, involved in the biosynthesis of mugineic acid family phytosiderphores (Takahashi et al, 1999). However, the TyrAT activity of TAT1 remains controversial.…”

Section: Involvement Of Tyrat In Bia Metabolism In Opium Poppymentioning

confidence: 99%

Tyrosine Aminotransferase Contributes to Benzylisoquinoline Alkaloid Biosynthesis in Opium Poppy

Lee

Facchini

2011

Plant Physiology

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Tyrosine aminotransferase (TyrAT) catalyzes the transamination of L-Tyr and a-ketoglutarate, yielding 4-hydroxyphenylpyruvic acid and L-glutamate. The decarboxylation product of 4-hydroxyphenylpyruvic acid, 4-hydroxyphenylacetaldehyde, is a precursor to a large and diverse group of natural products known collectively as benzylisoquinoline alkaloids (BIAs). We have isolated and characterized a TyrAT cDNA from opium poppy (Papaver somniferum), which remains the only commercial source for several pharmaceutical BIAs, including codeine, morphine, and noscapine. TyrAT belongs to group I pyridoxal 5#-phosphate (PLP)-dependent enzymes wherein Schiff base formation occurs between PLP and a specific Lys residue. The amino acid sequence of TyrAT showed considerable homology to other putative plant TyrATs, although few of these have been functionally characterized. Purified, recombinant TyrAT displayed a molecular mass of approximately 46 kD and a substrate preference for L-Tyr and a-ketoglutarate, with apparent K m values of 1.82 and 0.35 mM, respectively. No specific requirement for PLP was detected in vitro. Liquid chromatography-tandem mass spectrometry confirmed the conversion of L-Tyr to 4-hydroxyphenylpyruvate. TyrAT gene transcripts were most abundant in roots and stems of mature opium poppy plants. Virus-induced gene silencing was used to evaluate the contribution of TyrAT to BIA metabolism in opium poppy. TyrAT transcript levels were reduced by at least 80% in silenced plants compared with controls and showed a moderate reduction in total alkaloid content. The modest correlation between transcript levels and BIA accumulation in opium poppy supports a role for TyrAT in the generation of alkaloid precursors, but it also suggests the occurrence of other sources for 4-hydroxyphenylacetaldehyde.

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Section: Involvement Of Tyrat In Bia Metabolism In Opium Poppymentioning

confidence: 99%

Tyrosine Aminotransferase Contributes to Benzylisoquinoline Alkaloid Biosynthesis in Opium Poppy

Lee

Facchini

2011

Plant Physiology

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“…MAs form Fe(III)-MAs complexes that are absorbed into the root via YS1 transporters [4]. Among the graminaceous plants, barley is highly tolerant to Fe deficiency and possesses a series of MAs biosynthetic genes, including NAS, NAAT, DMAS, IDS2, and IDS3 ( [2,6,11,16,25]; Fig. 1).…”

Section: Introductionmentioning

confidence: 99%

Increase in Iron and Zinc Concentrations in Rice Grains Via the Introduction of Barley Genes Involved in Phytosiderophore Synthesis

Masuda

Suzuki

Morikawa

et al. 2008

Rice

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“…The biosynthetic pathways of MAs (Fig. 1A) have been determined Kawai et al, 1988;Shojima et al, 1990;Ma et al, 1999), and almost all the genes involved have been isolated in our laboratory (Higuchi et al, 1999b;Takahashi et al, 1999;Nakanishi et al, 2000;Kobayashi et al, 2001). NAS is a key enzyme in MA biosynthesis, catalyzing the trimerization of SAM into one molecule of NA (Higuchi et al, 1999b).…”

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Three Nicotianamine Synthase Genes Isolated from Maize Are Differentially Regulated by Iron Nutritional Status

et al. 2003

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Nicotianamine synthase (NAS) is an enzyme that is critical for the biosynthesis of the mugineic acid family of phytosiderophores in graminaceous plants, and for the homeostasis of metal ions in nongraminaceous plants. We isolated one genomic NAS clone, ZmNAS3, and two cDNA NAS clones, ZmNAS1 and ZmNAS2, from maize (Zea mays cv Alice). In agreement with the increased secretion of phytosiderophores with Fe deficiency, ZmNAS1 and ZmNAS2 were positively expressed only in Fe-deficient roots. In contrast, ZmNAS3 was expressed under Fe-sufficient conditions, and was negatively regulated by Fe deficiency. This is the first report describing down-regulation of NAS gene expression in response to Fe deficiency in plants, shedding light on the role of nicotianamine in graminaceous plants, other than as a precursor in phytosiderophore production. ZmNAS1-green fluorescent protein (sGFP) and ZmNAS2-sGFP were localized at spots in the cytoplasm of onion (Allium cepa) epidermal cells, whereas ZmNAS3-sGFP was distributed throughout the cytoplasm of these cells. ZmNAS1 and ZmNAS3 showed NAS activity in vitro, whereas ZmNAS2 showed none. Due to its duplicated structure, ZmNAS2 was much larger (65.8 kD) than ZmNAS1, ZmNAS3, and previously characterized NAS proteins (30-38 kD) from other plant species. We reveal that maize has two types of NAS proteins based on their expression pattern and subcellular localization.To acquire Fe, graminaceous plants secrete Fe chelators, known as mugineic-acid family phytosiderophores (MAs). MAs dissolve Fe in the rhizosphere, followed by reabsorption of the Fe(III)-MA complexes through YS1 transporters in the plasma membrane (Takagi, 1976; Curie et al., 2001). Only graminaceous plants use the MA mechanism of acquiring Fe(III), classified as the Strategy II mechanism (Marschner et al., 1986). Fe deficiency is a problem in crop production worldwide, especially in calcareous soils, where Fe is sparingly soluble due to the high soil pH. The ability of graminaceous plants to tolerate Fe deficiency is thought to depend on the quantity of MAs secreted during Fe deficiency (Takagi, 1976;Mori et al., , 1988Rö mheld, 1987;Kawai et al., 1988;Mihashi and Mori, 1989;Singh et al., 1993). The biosynthetic pathways of MAs (Fig. 1A) have been determined Kawai et al., 1988;Shojima et al., 1990;Ma et al., 1999), and almost all the genes involved have been isolated in our laboratory (Higuchi et al., 1999b;Takahashi et al., 1999;Nakanishi et al., 2000;Kobayashi et al., 2001). NAS is a key enzyme in MA biosynthesis, catalyzing the trimerization of SAM into one molecule of NA (Higuchi et al., 1999b). NAS activity in graminaceous plants is well correlated with tolerance to Fe deficiency. In maize (Zea mays), a plant susceptible to Fe deficiency, NAS activity is very low (Higuchi et al., 1996a), and maize secretes lower amounts of MAs than barley or oat (Avena sativa), cereals that are tolerant of low Fe supply (Rö mheld, 1987;Lytle and Jolley, 1991). NAS is also important for growth in nongraminaceous plants, which do not ...

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Cloning Two Genes for Nicotianamine Aminotransferase, a Critical Enzyme in Iron Acquisition (Strategy II) in Graminaceous Plants

Cited by 221 publications

References 46 publications

Tyrosine Aminotransferase Contributes to Benzylisoquinoline Alkaloid Biosynthesis in Opium Poppy

Tyrosine Aminotransferase Contributes to Benzylisoquinoline Alkaloid Biosynthesis in Opium Poppy

Increase in Iron and Zinc Concentrations in Rice Grains Via the Introduction of Barley Genes Involved in Phytosiderophore Synthesis

Three Nicotianamine Synthase Genes Isolated from Maize Are Differentially Regulated by Iron Nutritional Status

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