<i>Myo</i>-Inositol-Dependent Sodium Uptake in Ice Plant1

Nelson, Donald E.; Koukoumanos, Michelle; Bohnert, Hans J.

doi:10.1104/pp.119.1.165

Cited by 103 publications

(66 citation statements)

References 58 publications

(19 reference statements)

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“…8). Increased synthesis of inositol and its transport has been shown previously to play a major role in sequestration of sodium ions and maintenance of photosynthetic competence during salt stress (42,46). A protective role for inositol in maintaining the photosynthetic efficiency of the plants, as demonstrated previously for other osmolytes like glycine-betaine or proline (43,(47)(48), may also be inferred from such results.…”

Section: Discussionsupporting

confidence: 51%

A Novel Salt-tolerant l-myo-Inositol-1-phosphate Synthase from Porteresia coarctata (Roxb.) Tateoka, a Halophytic Wild Rice

Majee

Maitra

Dastidar

et al. 2004

Journal of Biological Chemistry

168

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L-myo-Inositol-1-phosphate synthase (EC 5.5.1.4, MIPS), an evolutionarily conserved enzyme protein, catalyzes the synthesis of inositol, which is implicated in a number of metabolic reactions in the biological kingdom. Here we report on the isolation of the gene (PINO1) for a novel salt-tolerant MIPS from the wild halophytic rice, Porteresia coarctata (Roxb.) Tateoka. Identity of the PINO1 gene was confirmed by functional complementation in a yeast inositol auxotrophic strain. Comparison of the nucleotide and deduced amino acid sequences of PINO1 with that of the homologous gene from Oryza sativa L. (RINO1) revealed distinct differences in a stretch of 37 amino acids, between amino acids 174 and 210. Purified bacterially expressed PINO1 protein demonstrated a salt-tolerant character in vitro compared with the salt-sensitive RINO1 protein as with those purified from the native source or an expressed salt-sensitive mutant PINO1 protein wherein amino acids 174 -210 have been deleted. Analysis of the salt effect on oligomerization and tryptophan fluorescence of the RINO1 and PINO1 proteins revealed that the structure of PINO1 protein is stable toward salt environment. Furthermore, introgression of PINO1 rendered transgenic tobacco plants capable of growth in 200 -300 mM NaCl with retention of ϳ40 -80% of the photosynthetic competence with concomitant increased inositol production compared with unstressed control. MIPS protein isolated from PINO1 transgenics showed salt-tolerant property in vitro confirming functional expression in planta of the PINO1 gene. To our knowledge, this is the first report of a salt-tolerant MIPS from any source.Inositols are six-carbon cyclohexane hexitols found ubiquitously in the biological kingdom, and its metabolism plays a vital role in growth regulation, membrane biogenesis, osmotolerance, and in many other processes. As phosphorylated derivatives, its role as a phosphorus store and as a "second messenger" in signal transduction pathways has long been recognized. myo-Inositol, physiologically the most favored stereoisomer among the eight possible geometric isomers of inositol, also enters into an array of biochemical reactions having diverse functions in cellular metabolism both as free and conjugated and phosphorylated or methylated forms (1-3).The primary enzyme for the synthesis of L-myo-inositol 1-phosphate from glucose 6-phosphate is L-myo-inositol-1-phosphate synthase (EC 5.5.1.4; referred to as MIPS), 1 which synthesizes L-myo-inositol 1-phosphate through an internal oxidoreduction reaction involving NAD ϩ . Free inositol is generated by dephosphorylation of the MIPS product by a specific Mg 2ϩ -dependent inositol-1-phosphate phosphatase (EC 3.1.3.25). This mechanism is followed by all myo-inositolproducing organisms throughout the phylogenetic lines, and MIPS has been identified as an evolutionarily conserved protein (4). The structural gene coding for cytosolic MIPS, termed INO1, was first identified in yeast, Saccharomyces cerevisiae (5, 6) and cloned by Klig and Henry (7)....

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Section: Discussionsupporting

confidence: 51%

A Novel Salt-tolerant l-myo-Inositol-1-phosphate Synthase from Porteresia coarctata (Roxb.) Tateoka, a Halophytic Wild Rice

Majee

Maitra

Dastidar

et al. 2004

Journal of Biological Chemistry

168

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“…Despite these essential functions of myoinositol in plant biology, little is known about the partitioning of this molecule between different cells, tissues, or subcellular compartments. The first plant myoinositol transporters, MITR1 and MITR2 (Mesembryanthemum INOSITOL TRANSPORTER), were described as tonoplast proteins catalyzing the inositoldependent efflux of Na 1 ions from vacuoles (Nelson et al, 1999;Chauhan et al, 2000), where phytate is largely accumulated. Free myoinositol is regarded as a ubiquitous constituent of plant tissues and is a more widespread compound in a variety of life forms than generally realized (Loewus and Murthy, 2000).…”

Section: Discussionmentioning

confidence: 99%

An Arabidopsis Purple Acid Phosphatase with Phytase Activity Increases Foliar Ascorbate

et al. 2007

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Ascorbate (AsA) is the most abundant antioxidant in plant cells and a cofactor for a large number of key enzymes. However, the mechanism of how AsA levels are regulated in plant cells remains unknown. The Arabidopsis (Arabidopsis thaliana) activationtagged mutant AT23040 showed a pleiotropic phenotype, including ozone resistance, rapid growth, and leaves containing higher AsA than wild-type plants. The phenotype was caused by activation of a purple acid phosphatase (PAP) gene, AtPAP15, which contains a dinuclear metal center in the active site. AtPAP15 was universally expressed in all tested organs in wild-type plants. Overexpression of AtPAP15 with the 35S cauliflower mosaic virus promoter produced mutants with up to 2-fold increased foliar AsA, 20% to 30% decrease in foliar phytate, enhanced salt tolerance, and decreased abscisic acid sensitivity. Two independent SALK T-DNA insertion mutants in AtPAP15 had 30% less foliar AsA and 15% to 20% more phytate than wild-type plants and decreased tolerance to abiotic stresses. Enzyme activity of partially purified AtPAP15 from plant crude extract and recombinant AtPAP15 expressed in bacteria and yeast was highest when phytate was used as substrate, indicating that AtPAP15 is a phytase. Recombinant AtPAP15 also showed enzyme activity on the substrate myoinositol-1-phosphate, indicating that the AtPAP15 is a phytase that hydrolyzes myoinositol hexakisphosphate to yield myoinositol and free phosphate. Myoinositol is a known precursor for AsA biosynthesis in plants. Thus, AtPAP15 may modulate AsA levels by controlling the input of myoinositol into this branch of AsA biosynthesis in Arabidopsis.

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“…Independent analyses with exogenously supplied myoinositol showed a similar increase of Na 1 flux from the roots to the leaves and, based on this correlation, the authors speculated that the uptake of Na 1 ions into the xylem might be coupled to the uptake of myoinositol. Furthermore, they suggested that this capacity to couple Na 1 and myoinositol fluxes might be a specific property of salt-tolerant plants that is missing in glycophytes (Nelson et al, 1999).…”

mentioning

confidence: 99%

Arabidopsis INOSITOL TRANSPORTER4 Mediates High-Affinity H+ Symport of Myoinositol across the Plasma Membrane

Schneider

Schneidereit²,

Konrad³

et al. 2006

Plant Physiology

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Four genes of the Arabidopsis (Arabidopsis thaliana) monosaccharide transporter-like superfamily share significant homology with transporter genes previously identified in the common ice plant (Mesembryanthemum crystallinum), a model system for studies on salt tolerance of higher plants. These ice plant transporters had been discussed as tonoplast proteins catalyzing the inositol-dependent efflux of Na 1 ions from vacuoles. The subcellular localization and the physiological role of the homologous proteins in the glycophyte Arabidopsis were unclear. Here we describe Arabidopsis INOSITOL TRANSPORTER4 (AtINT4), the first member of this subgroup of Arabidopsis monosaccharide transporter-like transporters. Functional analyses of the protein in yeast (Saccharomyces cerevisiae) and Xenopus laevis oocytes characterize this protein as a highly specific H 1 symporter for myoinositol. These activities and analyses of the subcellular localization of an AtINT4 fusion protein in Arabidopsis and tobacco (Nicotiana tabacum) reveal that AtINT4 is located in the plasma membrane. AtINT4 promoter-reporter gene plants demonstrate that AtINT4 is strongly expressed in Arabidopsis pollen and phloem companion cells. The potential physiological role of AtINT4 is discussed.

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Myo-Inositol-Dependent Sodium Uptake in Ice Plant1

Cited by 103 publications

References 58 publications

A Novel Salt-tolerant l-myo-Inositol-1-phosphate Synthase from Porteresia coarctata (Roxb.) Tateoka, a Halophytic Wild Rice

A Novel Salt-tolerant l-myo-Inositol-1-phosphate Synthase from Porteresia coarctata (Roxb.) Tateoka, a Halophytic Wild Rice

An Arabidopsis Purple Acid Phosphatase with Phytase Activity Increases Foliar Ascorbate

Arabidopsis INOSITOL TRANSPORTER4 Mediates High-Affinity H+ Symport of Myoinositol across the Plasma Membrane

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