Inositol and Plant Cell Wall Polysaccharide Biogenesis

Loewus, Frank A.

doi:10.1007/0-387-27600-9_2

Cited by 34 publications

(31 citation statements)

References 152 publications

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“…1). Frank Loewus pioneered studies in the myoinositol oxidation pathway, which contributes to D-GlcUA synthesis via myoinositol oxidation to ascorbate synthesis pathways in animals (for review, see Loewus, 2006). However, studies on strawberry (Fragaria species) and parsley (Petroselinum crispum) indicated that radiolabeled myoinositol did not undergo conversion into ascorbate (Loewus et al, 1962;Loewus, 1963).…”

Section: The Impact Of Imp On Ascorbate Synthesismentioning

confidence: 99%

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VTC4 Is a Bifunctional Enzyme That Affects Myoinositol and Ascorbate Biosynthesis in Plants

et al. 2009

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Myoinositol synthesis and catabolism are crucial in many multiceullar eukaryotes for the production of phosphatidylinositol signaling molecules, glycerophosphoinositide membrane anchors, cell wall pectic noncellulosic polysaccharides, and several other molecules including ascorbate. Myoinositol monophosphatase (IMP) is a major enzyme required for the synthesis of myoinositol and the breakdown of myoinositol (1,4,5)trisphosphate, a potent second messenger involved in many biological activities. It has been shown that the VTC4 enzyme from kiwifruit (Actinidia deliciosa) has similarity to IMP and can hydrolyze L-galactose 1-phosphate (L-Gal 1-P), suggesting that this enzyme may be bifunctional and linked with two potential pathways of plant ascorbate synthesis. We describe here the kinetic comparison of the Arabidopsis (Arabidopsis thaliana) recombinant VTC4 with D-myoinositol 3-phosphate (D-Ins 3-P) and L-Gal 1-P. Purified VTC4 has only a small difference in the V max /K m for L-Gal 1-P as compared with D-Ins 3-P and can utilize other related substrates. Inhibition by either Ca 2+ or Li + , known to disrupt cell signaling, was the same with both L-Gal 1-P and D-Ins 3-P. To determine whether the VTC4 gene impacts myoinositol synthesis in Arabidopsis, we isolated T-DNA knockout lines of VTC4 that exhibit small perturbations in abscisic acid, salt, and cold responses. Analysis of metabolite levels in vtc4 mutants showed that less myoinositol and ascorbate accumulate in these mutants. Therefore, VTC4 is a bifunctional enzyme that impacts both myoinositol and ascorbate synthesis pathways.

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Section: The Impact Of Imp On Ascorbate Synthesismentioning

confidence: 99%

“…1). Its primary breakdown product, D-GlcUA, is utilized for the synthesis of cell wall pectic noncellulosic compounds (for review, see Loewus, 2006) and, in some organisms, ascorbate (for review, see Linster and Van Schaftingen, 2007). Thus, myoinositol synthesis and catabolism affect metabolites involved in many different and critical biochemical pathways.…”

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confidence: 99%

VTC4 Is a Bifunctional Enzyme That Affects Myoinositol and Ascorbate Biosynthesis in Plants

et al. 2009

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“…The oxidation product of myo-inositol (D-glucuronic acid) is used for cell wall pectic noncellulosic compounds (Loewus et al, 1962;Loewus, 1965Loewus, , 2006 and, in some organisms, for synthesis of ascorbic acid (Baig et al, 1970;Allison and Stewart, 1973;Banhegyi et al, 1997). Thus, myo-inositol synthesis and catabolism impact metabolites involved in many different and critical plant biochemical pathways.…”

Section: Introductionmentioning

confidence: 99%

TheArabidopsis thaliana Myo-Inositol 1-Phosphate Synthase1 Gene Is Required forMyo-inositol Synthesis and Suppression of Cell Death

et al. 2010

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L-myo-inositol 1-phosphate synthase (MIPS; EC 5.5.1.4) catalyzes the rate-limiting step in the synthesis of myo-inositol, a critical compound in the cell. Plants contain multiple MIPS genes, which encode highly similar enzymes. We characterized the expression patterns of the three MIPS genes in Arabidopsis thaliana and found that MIPS1 is expressed in most cell types and developmental stages, while MIPS2 and MIPS3 are mainly restricted to vascular or related tissues. MIPS1, but not MIPS2 or MIPS3, is required for seed development, for physiological responses to salt and abscisic acid, and to suppress cell death. Specifically, a loss in MIPS1 resulted in smaller plants with curly leaves and spontaneous production of lesions. The mips1 mutants have lower myo-inositol, ascorbic acid, and phosphatidylinositol levels, while basal levels of inositol (1,4,5)P 3 are not altered in mips1 mutants. Furthermore, mips1 mutants exhibited elevated levels of ceramides, sphingolipid precursors associated with cell death, and were complemented by a MIPS1-green fluorescent protein (GFP) fusion construct. MIPS1-, MIPS2-, and MIPS3-GFP each localized to the cytoplasm. Thus, MIPS1 has a significant impact on myo-inositol levels that is critical for maintaining levels of ascorbic acid, phosphatidylinositol, and ceramides that regulate growth, development, and cell death.

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“…myo-inositol emerged early during evolution and evolved into diverse derivatives, such as phosphoinositides (PIs), inositol phosphates, glycosylphosphatidylinositol, and various inositol conjugates (Michell, 2008). Inositol and its derivatives are involved in various biochemical and physiological processes, including intracellular signal transduction (Irvine and Schell, 2001), membrane construction and trafficking (Cullen et al, 2001), membrane-related protein anchoring (Tiede et al, 1999;Peskan et al, 2000;Borner et al, 2005), and cell wall construction (Loewus 1973). They also act as protein cofactors (Macbeth et al, 2005;Tan et al, 2007) and play roles in auxin storage and trafficking in plant seeds (Hall and Bandurski, 1986).…”

Section: Introductionmentioning

confidence: 99%

d-myo-Inositol-3-Phosphate Affects Phosphatidylinositol-Mediated Endomembrane Function inArabidopsisand Is Essential for Auxin-Regulated Embryogenesis

et al. 2011

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In animal cells, myo-inositol is an important regulatory molecule in several physiological and biochemical processes, including signal transduction and membrane biogenesis. However, the fundamental biological functions of myo-inositol are still far from clear in plants. Here, we report the genetic characterization of three Arabidopsis thaliana genes encoding D-myo-inositol-3-phosphate synthase (MIPS), which catalyzes the rate-limiting step in de novo synthesis of myo-inositol. Each of the three MIPS genes rescued the yeast ino1 mutant, which is defective in yeast MIPS gene INO1, and they had different dynamic expression patterns during Arabidopsis embryo development. Although single mips mutants showed no obvious phenotypes, the mips1 mips2 double mutant and the mips1 mips2 mips3 triple mutant were embryo lethal, whereas the mips1 mips3 and mips1 mips2 +/2 double mutants had abnormal embryos. The mips phenotypes resembled those of auxin mutants. Indeed, the double and triple mips mutants displayed abnormal expression patterns of DR5:green fluorescent protein, an auxin-responsive fusion protein, and they had altered PIN1 subcellular localization. Also, membrane trafficking was affected in mips1 mips3. Interestingly, overexpression of PHOSPHATIDYLINOSITOL SYNTHASE2, which converts myoinositol to membrane phosphatidylinositol (PtdIns), largely rescued the cotyledon and endomembrane defects in mips1 mips3. We conclude that myo-inositol serves as the main substrate for synthesizing PtdIns and phosphatidylinositides, which are essential for endomembrane structure and trafficking and thus for auxin-regulated embryogenesis.

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Inositol and Plant Cell Wall Polysaccharide Biogenesis

Cited by 34 publications

References 152 publications

VTC4 Is a Bifunctional Enzyme That Affects Myoinositol and Ascorbate Biosynthesis in Plants

VTC4 Is a Bifunctional Enzyme That Affects Myoinositol and Ascorbate Biosynthesis in Plants

TheArabidopsis thaliana Myo-Inositol 1-Phosphate Synthase1 Gene Is Required forMyo-inositol Synthesis and Suppression of Cell Death

d-myo-Inositol-3-Phosphate Affects Phosphatidylinositol-Mediated Endomembrane Function inArabidopsisand Is Essential for Auxin-Regulated Embryogenesis

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