Plant Inositol Monophosphatase Is a Lithium-Sensitive Enzyme Encoded by a Multigene Family

Gillaspy, Glenda E.; Keddie, James S.; Oda, Kazuhiro; Gruissem, Wilhelm

doi:10.2307/3870160

Cited by 34 publications

(54 citation statements)

References 2 publications

(2 reference statements)

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“…LiCl was found to be as e¡ective as NaCl in inducing Ins(1,4,5)P 3 elevations. This is a little surprising as Li is known to inhibit plant inositol monophosphatase [12] and a¡ect salt-induced Ca 2 transients in Arabidopsis [3]. However, we ¢nd it unlikely that the short-term exposure to LiCl in our experiments could dramatically a¡ect cellular levels of inositol and subsequently the size of the phosphoinositide pool.…”

Section: Resultsmentioning

confidence: 82%

Inositol(1,4,5)trisphosphate production in plant cells: an early response to salinity and hyperosmotic stress

Drøbak

Watkins

2000

FEBS Letters

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Salinity and hyperosmotic stress are environmental factors that severely affect the growth and development of plants. Adaptation to these stresses is known to be a complex multistep process, but a rise in cytoplasmic Ca 2+ and increased polyphosphoinositide turnover have now been identified as being amongst the early events leading to the development of tolerance. To determine whether a causal link exists between these two events we have investigated the effects of several salts and osmotic agents on levels of inositol(1,4,5)trisphosphate (Ins(1,4,5)P 3 ) in plant cells. Our data show that salts as well as osmotic agents induce a rapid and up to 15-fold increase in cellular Ins(1,4,5)P 3 levels. The increase in Ins(1,4,5)P 3 occurs in a dose-dependent manner and levels remain elevated for at least 10 min. These data indicate that increased Ins(1,4,5)P 3 production is a common response to salt and hyperosmotic stresses in plants and that it may play an important role in the processes leading to stress tolerance. ß

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Section: Resultsmentioning

confidence: 82%

Inositol(1,4,5)trisphosphate production in plant cells: an early response to salinity and hyperosmotic stress

Drøbak

Watkins

2000

FEBS Letters

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“…Gillaspy et al (1995) demonstrated that IMP, the enzyme catalyzing the dephosphorylation of myoinositol 1-phosphate, is found in the phloem in higher amounts than in other cells. The result also indicates that this cell type is a major site of synthesis.…”

Section: Discussionmentioning

confidence: 99%

Regulation of Cell-Specific Inositol Metabolism and Transport in Plant Salinity Tolerance

1998

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myo-Inositol and its derivatives are commonly studied with respect to cell signaling and membrane biogenesis, but they also participate in responses to salinity in animals and plants. In this study, we focused on L -myo -inositol 1-phosphate synthase (INPS), which commits carbon to de novo synthesis, and myo -inositol O -methyltransferase (IMT), which uses myo -inositol for stress-induced accumulation of a methylinositol, D -ononitol. The Imt and Inps promoters are transcriptionally controlled. We determined that the transcription rates, transcript levels, and protein abundance are correlated. During normal growth, INPS is present in all cells, but IMT is repressed. After salinity stress, the amount of INPS was enhanced in leaves but repressed in roots. IMT was induced in all cell types. The absence of myo -inositol synthesis in roots is compensated by inositol/ononitol transport in the phloem. The mobilization of photosynthate through myo -inositol translocation links root metabolism to photosynthesis. Our model integrates the transcriptional control of a specialized metabolic pathway with physiological reactions in different tissues. The tissue-specific differential regulation of INPS, which leads to a gradient of myo -inositol synthesis, supports root growth and sodium uptake. By inducing expression of IMT and increasing myo -inositol synthesis, metabolic end products accumulate, facilitating sodium sequestration and protecting photosynthesis. INTRODUCTIONA central focus of our work is to determine genes that underlie mechanisms providing salinity tolerance in higher plants. In addition, we hope to learn how whole plants adapt metabolically. Many researchers have studied tolerance mechanisms in plants. Their findings show the importance of metabolite accumulation, which generally is attributed to osmotic adjustment leading to water retention and/or protection of biochemical pathways. When single enzymes were tested in transgenic plants, the accumulation of mannitol, proline, fructans, trehalose, glycine betaine, or ononitol (Tarczynski et al., 1993;Kavi Kishor et al., 1995;Pilon-Smits et al., 1995;Holmström et al., 1996;Hayashi et al., 1997;Sheveleva et al., 1997) provided marginally higher salinity and cold or drought tolerance. The manipulation of biochemical pathways by the transfer of multiple genes will be an even more appropriate strategy that is expected to provide broader tolerance because salinity tolerance is a multigenic trait Warne et al., 1995;Bohnert and Jensen, 1996). Salinity tolerance is also a multicellular trait, and the remodeling of complex pathways in transgenic plants will require knowledge of the distribution of such pathways throughout the plant. We have analyzed the myo -inositol biosynthetic pathway-leading to methylated inositols-that feeds into a pathway specific to salinity tolerance in a halophyte, the common ice plant ( Mesembryanthemum crystallinum ) (Loewus and Dickinson, 1982;Vernon and Bohnert, 1992).myo -Inositol is a central component of several biochemical pathways. It i...

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“…27 Moreover, the tomato plant Lycopersicon esculentum has been reported to possess three different IMPA-like genes. 28 In humans an additional transcript almost identical to the IMPA1 mRNA originates from chromosome 8q, but this transcript contains an early stop codon and seems to represent a pseudogene of IMPA1. 15 It is plausible that the ancestral IMPA gene duplicated early in evolution and Molecular Psychiatry as a result, species from different phyla have more than one IMPA gene encoding homologous enzymes with IMPase like functions.…”

Section: The Evolutionary Relationship Between Impa1 and Impa2mentioning

confidence: 99%

A human myo-inositol monophosphatase gene (IMPA2) localized in a putative susceptibility region for bipolar disorder on chromosome 18p11.2: genomic structure and polymorphism screening in manic-depressive patients

Sjøholt¹,

Gulbrandsen²,

Løvlie³

et al. 2000

Mol Psychiatry

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For several decades, lithium has been the drug of choice in the long-term treatment of manicdepressive illness, but the molecular mechanism(s) mediating its therapeutic effects remain to be determined. The enzyme myo-inositol monophosphatase (IMPase) in the phospholipase C signaling system is inhibited by lithium at therapeutically relevant concentrations, and is a candidate target of lithium's mood-stabilizing action. Two genes encoding human IMPases have so far been isolated, namely IMPA1 on chromosome 8q21.13-21.3 and IMPA2 on chromosome 18p11.2. Interestingly, several studies have indicated the presence of a susceptibility locus for bipolar disorder on chromosome 18p11.2. IMPA2 is therefore a candidate for genetic studies on both etiology and lithium treatment of manic-depressive illness. Here we report that the genomic structure of IMPA2 is composed of eight exons, ranging in size from 46 bp to 535 bp. The promoter region contains several Sp1 elements and lacks a TATA-box, features typical for housekeeping genes. By a preliminary polymorphism screening of exons 2-8 in a sample of 23 Norwegian bipolar patients, we have identified nine single nucleotide polymorphisms (SNPs). Seven of the polymorphisms were located in the introns, one was a silent transition in exon 2 (159TϾC) and one was a transition in exon 5 (443GϾA) resulting in a predicted amino acid substitution (R148Q). Our data show that even in a small sample of bipolar patients, several variants of the IMPA2 gene can be identified. IMPA2 is therefore an intriguing candidate gene for future association studies of manic-depressive illness. Molecular Psychiatry (2000) 5, 172-180.

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Plant Inositol Monophosphatase Is a Lithium-Sensitive Enzyme Encoded by a Multigene Family

Cited by 34 publications

References 2 publications

Inositol(1,4,5)trisphosphate production in plant cells: an early response to salinity and hyperosmotic stress

Inositol(1,4,5)trisphosphate production in plant cells: an early response to salinity and hyperosmotic stress

Regulation of Cell-Specific Inositol Metabolism and Transport in Plant Salinity Tolerance

A human myo-inositol monophosphatase gene (IMPA2) localized in a putative susceptibility region for bipolar disorder on chromosome 18p11.2: genomic structure and polymorphism screening in manic-depressive patients

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