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Pical C, Westergren T, Dove SK, Larsson C, Sommarin M. Salinity and hyperosmotic stress induce rapid increases in phosphatidylinositol 4,5-bisphosphate, diacylglycerol pyrophosphate, and phosphatidylcholine in Arabidopsis thaliana cells. J Biol Chem 1999; 274:38232-40. [PMID: 10608898 DOI: 10.1074/jbc.274.53.38232] [Citation(s) in RCA: 155] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In animal cells, phosphoinositides are key components of the inositol 1,4,5-trisphosphate/diacylglycerol-based signaling pathway, but also have many other cellular functions. These lipids are also believed to fulfill similar functions in plant cells, although many details concerning the components of a plant phosphoinositide system, and their regulation are still missing. Only recently have the different phosphoinositide isomers been unambiguously identified in plant cells. Another problem that hinders the study of the function of phosphoinositides and their derivatives, as well as the regulation of their metabolism, in plant cells is the need for a homogenous, easily obtainable material, from which the extraction and purification of phospholipids is relatively easy and quantitatively reproducible. We present here a thorough characterization of the phospholipids purified from [(32)P]orthophosphate- and myo-[2-(3)H]inositol-radiolabeled Arabidopsis thaliana suspension-cultured cells. We then show that NaCl treatment induces dramatic increases in the levels of phosphatidylinositol 4,5-bisphosphate and diacylglycerol pyrophosphate and also affects the turnover of phosphatidylcholine. The increase in phosphatidylinositol 4,5-bisphosphate was also observed with a non-ionic hyperosmotic shock. In contrast, the increase in diacylglycerol pyrophosphate and the turnover of phosphatidylcholine were relatively specific to salt treatments as only minor changes in the metabolism of these two phospholipids were detected when the cells were treated with sorbitol instead of NaCl.
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Affiliation(s)
- C Pical
- Department of Plant Biochemistry, Lund University, SE-22100 Lund, Sweden
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Munnik T, Irvine RF, Musgrave A. Phospholipid signalling in plants. BIOCHIMICA ET BIOPHYSICA ACTA 1998; 1389:222-72. [PMID: 9512651 DOI: 10.1016/s0005-2760(97)00158-6] [Citation(s) in RCA: 257] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- T Munnik
- Institute for Molecular Cell Biology, BioCentrum Amsterdam, University of Amsterdam, The Netherlands.
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Lee Y, Choi YB, Suh S, Lee J, Assmann SM, Joe CO, Kelleher JF, Crain RC. Abscisic Acid-Induced Phosphoinositide Turnover in Guard Cell Protoplasts of Vicia faba. PLANT PHYSIOLOGY 1996; 110:987-996. [PMID: 12226236 PMCID: PMC157799 DOI: 10.1104/pp.110.3.987] [Citation(s) in RCA: 80] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Guard cell protoplasts of Vicia faba treated with 10 [mu]M (+)abscisic acid (ABA) in the light exhibited a 20% decrease in diameter within 1.5 h, from 24.1 to 19.6 [mu]m. Within 10 s of administration of ABA, a 90% increase in levels of inositol 1,4,5-trisphosphate was observed, provided that cells were treated with Li+, an inhibitor of inositol phosphatase activity, prior to incubation. Concomitantly, levels of 32P-labeled phosphatidylinositol 4,5-bisphosphate and phosphatidylinositol 4-phosphate decreased 20% compared to levels in control cells; levels of label in the membrane lipids phosphatidylcholine, phosphatidylethanolamine, and phosphatidylglycerol did not change significantly in response to ABA treatment. These results show that phosphoinositide turnover is activated in response to ABA in guard cells. We conclude that phosphoinositide signaling is likely to be a step in the biochemical cascade that couples ABA to guard cell shrinking and stomatal closure.
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Affiliation(s)
- Y. Lee
- Department of Life Science, Pohang University of Science and Technology, Pohang 790-600, Korea (Y.L., Y.B.C., S.S., J.L.)
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Lakin-Thomas PL. Effects of inositol starvation on the levels of inositol phosphates and inositol lipids in Neurospora crassa. Biochem J 1993; 292 ( Pt 3):805-11. [PMID: 8391257 PMCID: PMC1134185 DOI: 10.1042/bj2920805] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
An inositol-requiring strain of Neurospora crassa was labelled during growth in liquid medium with [3H]inositol, and the levels of inositol phosphates and phosphoinositides were determined under inositol-sufficient and inositol-starved conditions. Because the mutant has an absolute requirement for inositol, the total mass of inositol-containing compounds could be determined. Inositol-containing lipids were identified by deacylation and co-migration with standards on h.p.l.c.; PtdIns3P, PtdIns4P, and PtdIns(4,5)P2 were found in approximately equal amounts, in addition to large amounts of PtdIns. Inositol starvation decreased the level of PtdIns to 10% of the sufficient level, and decreased the levels of the other phosphoinositides to about 25%. A number of inositol phosphates were found, including several InsP3s, InsP4s and InsP5s and phytic acid. Ins(1,4,5)P3 was identified by co-migration with standards on h.p.l.c. and by digestion with inositol phosphomonoesterase. High concentrations of all inositol phosphates were found in the extracellular medium in inositol-starved cultures. Inositol starvation on both liquid and solid agar media decreased the intracellular levels of some inositol phosphates, but increased the levels of phytic acid and several other inositol phosphates which may be its precursors and/or breakdown products. These results may indicate that inositol starvation induces phytic acid synthesis as a protection against the free-radical production and lipid peroxidation characteristic of inositol-less death.
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Brearley CA, Hanke DE. Pathway of synthesis of 3,4- and 4,5-phosphorylated phosphatidylinositols in the duckweed Spirodela polyrhiza L. Biochem J 1993; 290 ( Pt 1):145-50. [PMID: 8382475 PMCID: PMC1132394 DOI: 10.1042/bj2900145] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
[3H]Inositol and [32P]Pi labelling of the aquatic plant Spirodela polyrhiza L. revealed the presence of PtdIns(3,4)P2, in addition to PtdIns3P, PtdIns4P and PtdIns(4,5)P2 previously identified [Brearley and Hanke (1992) Biochem. J. 283, 255-260]. PtdIns(3,4,5)P3 was not detected. Throughout a 40 min [32P]Pi-labelling period the specific radioactivity of the gamma-phosphate of ATP and of the ATP pool as a whole increased. Chemical and enzymic dissection of phosphoinositides obtained from plants labelled for 35 min with [32P]Pi showed that over 99.7% of the label in PtdIns3P and PtdIns4P was accounted for by the monoester phosphates. The 3- and 4-monoester phosphates of PtdIns(3,4)P2 accounted for 23.1% and 76.6% respectively of the label, whereas the 4- and 5-monoester phosphates of PtdIns(4,5)P2 accounted for 21.1% and 78.6% respectively. These results are consistent with the synthesis of PtdIns(4,5)P2 via PtdIns4P. The labelling of the individual phosphates of PtdIns(3,4)P2 is, however, inconsistent with synthesis from PtdIns(4,5)P2 via PtdIns(3,4,5)P3, but instead suggests that PtdIns(3,4)P2 is synthesized by 4-phosphorylation of PtdIns3P. These results afford the first evidence that in plants in vivo, synthesis of PtdIns(4,5)P2 follows the pathway described in animal cells and also that plants possess PtdIns3P 4-kinase activity similar to that reported from animal cells.
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Affiliation(s)
- C A Brearley
- Department of Plant Sciences, University of Cambridge, U.K
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Coté GG, Crain RC. Artifactual Elevation of the Apparent Levels of Phosphatidic Acid and Phosphatidylinositol 4,5-Bisphosphate during Short-Term Labeling of Plant Tissue with Radioactive Precursor. PLANT PHYSIOLOGY 1992; 100:1042-3. [PMID: 16653014 PMCID: PMC1075663 DOI: 10.1104/pp.100.2.1042] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Some pulvini of Samanea saman Mehr. labeled with radioactive phosphate show apparent remarkable elevations of the levels of phosphatidic acid and phosphatidylinositol 4,5-bisphosphate. The elevated levels, however, appear to be illusory and to result from rapid initial incorporation of label into these phospholipids relative to others. These results demonstrate the need for caution in interpreting apparent changes in the levels of phosphatidic acid or inositol phospholipids in cultures or plants labeled with radioactive precursors.
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Affiliation(s)
- G G Coté
- Department of Molecular and Cell Biology, U-125, University of Connecticut, Storrs, Connecticut 06269-3125
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Murthy PP, Pliska-Matyshak G, Keranen LM, Lam P, Mueller HH, Bhuvarahamurthy N. Evidence of two isomers of phosphatidylinositol in plant tissue. PLANT PHYSIOLOGY 1992; 98:1498-501. [PMID: 16668820 PMCID: PMC1080377 DOI: 10.1104/pp.98.4.1498] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
The structure of phosphatidylinositol in barley (Hordeum vulgare) aleurone layers was investigated by chemical degradation. In vivo myo-[2-(3)H]inositol-labeled phosphatidylinositol was first converted to glycerophosphoinositol and, subsequently, after removal of the glycerol moiety, to inositol monophosphate. Here, we present data that show that, in addition to the commonly occurring 1,2-diacylglycero-3-(d-myo-inositol-1-phosphate), barley aleurone cells contain a novel second isomer of phosphatidylinositol that differs in structure of the head group.
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Affiliation(s)
- P P Murthy
- Department of Chemistry and Phytotechnology Research Center, Michigan Technological University, Houghton, Michigan 49931-1295
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Brearley CA, Hanke DE. 3- and 4-phosphorylated phosphatidylinositols in the aquatic plant Spirodela polyrhiza L. Biochem J 1992; 283 ( Pt 1):255-60. [PMID: 1567374 PMCID: PMC1131022 DOI: 10.1042/bj2830255] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Labelling of Spirodela polyrhiza L. plants with [3H]inositol and [32P]Pi yielded a series of phosphoinositides which were identified as PtdIns, PtdIns4P and PtdIns(4,5)P2. In addition, systematic degradation of a phospholipid extract identified PtdIns3P. Analysis of the distribution of 32P label between the monoester and diester phosphate groups of PtdIns3P and PtdIns4P revealed differences in the labelling of the monoester phosphate, suggesting that the two PtdInsP species are not synthesized or metabolized in a co-ordinate manner.
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Musgrave A, Kuin H, Jongen M, de Wildt P, Schuring F, Klerk H, van den Ende H. Ethanol stimulates phospholipid turnover and inositol 1,4,5-trisphosphate production in Chlamydomonas eugametos gametes. PLANTA 1992; 186:442-9. [PMID: 24186742 DOI: 10.1007/bf00195326] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 10/08/1991] [Indexed: 05/10/2023]
Abstract
Alcohols induce mating-structure activation in Chlamydomonas eugametos gametes. From the effect of ethanol on the (32)P-labelling of polyphosphoinositides, we conclude that the synthesis of these lipids is stimulated. Biologically inactive concentrations of ethanol (<6%) had no effect on synthesis, but 6-8% ethanol stimulated synthesis for upto 60 min. The (32)P incorporated into polyphosphoinositides and phosphatidic acid during ethanol treatment was readily chased out when 1 mM unlabelled Na3PO4 was added. Using a binding assay for inositol 1,4,5-trisphosphate, we show that the production of this phospholipid constituent is dramatically increased after ethanol treatment. This effect, coupled to a rise in intracellular calcium concentration, could explain gamete activation. The significance of these results in explaining other ethanol-induced phenomena in algae is discussed.
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Affiliation(s)
- A Musgrave
- Department of Molecular Cell Biology, University of Amsterdam, Kruislaan 318, NL-1098, SM Amsterdam, The Netherlands
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Quarmby LM, Yueh YG, Cheshire JL, Keller LR, Snell WJ, Crain RC. Inositol phospholipid metabolism may trigger flagellar excision in Chlamydomonas reinhardtii. J Cell Biol 1992; 116:737-44. [PMID: 1309818 PMCID: PMC2289324 DOI: 10.1083/jcb.116.3.737] [Citation(s) in RCA: 89] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Chlamydomonas reinhardtii cells shed their flagella in response to environmental stress. Under favorable conditions, flagella are quickly regrown. To learn more about the signals that trigger flagellar excision and regrowth we have investigated inositol phospholipid metabolites, molecules implicated in signal transduction in several other systems. After deflagellation by low pH or mastoparan, a potent activator of G proteins, there was a rapid increase in levels of inositol 1,4,5-trisphosphate measured by use of receptor-binding assays and HPLC. This increase was concomitant with a decrease in levels of phosphatidylinositol 4,5-bisphosphate and was followed by an increase in phosphatidic acid, results consistent with activation of phospholipase C and diacylglycerol kinase. Additional experiments suggest that this activated phospholipase C is not important for flagellar regrowth but plays a role in informing the excision apparatus of the environmental stress. Addition of neomycin (an inhibitor of phospholipase C) before exposure of cells to low pH or mastoparan prevented the increase in inositol 1,4,5-trisphosphate and also prevented deflagellation. Addition of neomycin after deflagellation blocked increases in inositol 1,4,5-trisphosphate that normally followed deflagellation, but did not block flagellar assembly. Furthermore, a flagellar excision-defective mutant, fa-1, did not shed its flagella in response to low pH or mastoparan, yet both of these agents activated phospholipase C in these cells. The results suggest that activation of phospholipase C, possibly via a G protein, is a proximal step in the signal transduction pathway inducing deflagellation in Chlamydomonas.
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Affiliation(s)
- L M Quarmby
- Department of Molecular and Cell Biology, University of Connecticut, Storrs 06269-3125
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Irvine RF, Letcher AJ, Stephens LR, Musgrave A. Inositol polyphosphate metabolism and inositol lipids in a green alga, Chlamydomonas eugametos. Biochem J 1992; 281 ( Pt 1):261-6. [PMID: 1310008 PMCID: PMC1130671 DOI: 10.1042/bj2810261] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Swimming suspensions of Chlamydomonas eugametos were pelleted and homogenized, and the metabolism of inositol polyphosphates by cellular homogenates or supernatants was investigated. Ins(1,4,5)P3 was dephosphorylated under physiological conditions to yield a single InsP2, Ins(1,4]2. In the presence of ATP it was phosphorylated to give Ins(1,3,4,5)P3 as the only InsP4. The Ins(1,4,5)P3 3-kinase activity was predominantly soluble, was not detectably affected by calmodulin or Ca2+, and had a Km for Ins(1,4,5)P3 of 50 microM (two orders of magnitude higher than its mammalian counterpart). Ins(1,3,4,5)P4 was dephosphorylated by the cellular supernatants to Ins(1,3,4)P3 and Ins(1,4,5)P3, and could be phosphorylated to Ins(1,3,4,5,6)P4. No Ins(1,3,4)P3 6-kinase activity could be detected, and experiments with [3H]Ins(1,4,[32P]5)P3 revealed that Ins(1,3,4,5,6)P5 is formed from Ins(1,4,5)P3 with little loss of the 5-phosphate, i.e. the predominant route of synthesis is probably by a direct 6-phosphorylation of Ins(1,3,4,5)P4. Similar experiments with an (NH4)2SO4 fraction of turkey erythrocyte cytosol gave essentially the same result, i.e. direct phosphorylation of Ins(1,3,4,5)P4 in the 6 position is the predominant route of synthesis of InsP5 from that InsP4 in vitro. No InsP6 formation was detected in any of these experiments, but labelling of intact C. eugametos with [3H]inositol revealed that the cells do synthesize InsP6. The lipids of C. eugametos cells contain PtdIns, PtdIns(4)P and PtdIns(4,5)P2 [Irvine, Letcher, Lander, Drøbak, Dawson & Musgrave (1989) Plant Physiol. 64, 888-892]. Further examination of 32P-labelled lipids revealed that about 20% of the PtdInsP was the PtdIns(3)P isomer, and about 1% or less of the PtdInsP2 was the PtdIns(3,4)P2 isomer. The overall inositide metabolism of C. eugametos resembles that of a mammalian cell more closely than it does that of a plant cell or slime mould, and this suggests firstly that the known metabolism of inositol polyphosphates arose at an early time in eukaryotic evolution, and secondly that Chlamydomonas might prove a useful organism for genetic and comparative studies of inositide enzymology.
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Affiliation(s)
- R F Irvine
- Department of Biochemistry, AFRC Institute of Animal Physiology and Genetics Research, Babraham, Cambridge, U.K
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Kamada Y, Muto S. Ca2+ regulation of phosphatidylinositol turnover in the plasma membrane of tobacco suspension culture cells. BIOCHIMICA ET BIOPHYSICA ACTA 1991; 1093:72-9. [PMID: 1646649 DOI: 10.1016/0167-4889(91)90140-s] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The biochemical properties of the enzymes involved in phosphatidylinositol (PI) turnover in higher plants were investigated using the plasma membrane isolated from tobacco suspension culture cells by aqueous two-phase partitioning. Submicromolar concentrations of Ca2+ inhibited PI kinase and phosphatidylinositol 4-phosphate (PIP) kinase and stimulated phospholipase C. Diacylglycerol (DG) kinase was inhibited by Ca2+, but required a higher concentration than the physiological level. From the above results we postulate the following scheme: signal coupled activation of phospholipase C produces IP3 which induces Ca2+ release from the intracellular Ca2+ compartment, the increased cytoplasmic Ca2+ in turn activates phospholipase C and causes a further increase of the cytoplasmic Ca2+ level. This inhibits PI kinase and PIP kinase and brings about a limited supply of PIP2, the substrate of phospholipase C. Consequently, IP3 production decreases and Ca2+ mobilization ceases. Then cytosolic Ca2+ returns to the stationary level by the Ca2+ pump at the plasma membrane and at the endoplasmic reticulum and Ca2+/H+ antiporter at the plasma membrane and at the tonoplast.
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Affiliation(s)
- Y Kamada
- Institute of Applied Microbiology, University of Tokyo, Japan
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Brederoo J, de Wildt P, Popp-Snijders C, Irvine RF, Musgrave A, van den Ende H. Polyphosphoinositol lipids in Chlamydomonas eugametos gametes. PLANTA 1991; 184:175-181. [PMID: 24194067 DOI: 10.1007/bf00197945] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 10/26/1990] [Indexed: 06/02/2023]
Abstract
In Chlamydomonas eugametos gametes, phosphatidylinositol 4-phosphate (PtdInsP) and phosphatidylinositol 4,5-bisphosphate (PtdInsP2) comprised 0.4 and 0.3% of the whole-cell phospholipids. They were concentrated in the plasma membrane around the cell body and were present in low concentrations in the flagellar membrane. When gametes were fed (32)PO 4 (-) , the label was rapidly incorporated into PtdInsP and PtdInsP2 and only slowly incorporated into structural lipids such as phosphatidylethanolamine and phosphatidylglycerol. Similarly, when a pulse of (32)PO 4 (-) was chased with PO 4 (-) , the label was rapidly lost from the polyphosphoinositol lipids but not from the structural lipids. The major fatty acids in the polyphosphoinositides were C-22 carbon polyenoic acids (70%). The significance of these results in relationship to intracellular signalling via inositol phosphates and Ca(2+) is discussed.
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Affiliation(s)
- J Brederoo
- Department of Molecular Cell Biology, University of Amsterdam, Kruislaan 318, NL-1098, SM Amsterdam, The Netherlands
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Zocchi G. Comparison of the effect of indoleacetic Acid and fusicoccin on the breakdown of phosphatidylinositol in maize coleoptiles. PLANT PHYSIOLOGY 1990; 94:1009-11. [PMID: 16667789 PMCID: PMC1077334 DOI: 10.1104/pp.94.3.1009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
The effect of indoleacetic acid (IAA) and fusicoccin (FC) on the breakdown of phosphatidylinositol in maize (Zea mays L.) coleoptiles has been studied. Coleoptiles were able to incorporate [(3)H] myo-inositol into the phospholipid fraction almost linearly for 8 hours. Thin layer chromatography analysis of total phospholipids showed that [(3)H]myo-inositol was incorporated only into phosphatidylinositol. Prelabeled coleoptiles treated with IAA showed a loss of the radioactivity incorporated in the phospholipid fraction, whose level decreased by 34% after 1 hour. Treatment with FC, on the contrary, did not modify the content of labelled phosphatidylinositol with respect to the control. The different effects of IAA and FC and a possible mechanism of IAA action on growth are discussed.
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Affiliation(s)
- G Zocchi
- Istituto Chimica Agraria, Università di Milano, Via Celoria 2, 20133 Milano, Italy
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Einspahr KJ, Thompson GA. Transmembrane Signaling via Phosphatidylinositol 4,5-Bisphosphate Hydrolysis in Plants. PLANT PHYSIOLOGY 1990; 93:361-6. [PMID: 16667474 PMCID: PMC1062519 DOI: 10.1104/pp.93.2.361] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Recent investigations have confirmed the presence of the polyphosphoinositides, phosphatidylinositol 4-phosphate and phosphatidylinositol 4,5-bisphosphate (PIP(2)), as well as inositol phospholipid-specific phospholipase C in higher plant and microalgal cells. In addition, it has been shown that stimulation of some photosynthetic cell types by environmental or hormonal challenge is accompanied by degradation of the polyphosphoinositides. The products of phospholipase C-catalyzed PIP(2) hydrolysis, inositol 1,4,5-trisphosphate and diacylglycerol, appear to be capable of releasing organelle-bound Ca(2+) and stimulating protein kinase C-like activity in vitro. However, a direct cause and effect relationship between stimulated PIP(2) breakdown and changes in intracellular calcium, protein phosphorylation, or cell function has not yet been unequivocally established. Despite a number of technical difficulties slowing progress in this field, it is likely that photosynthetic organisms will soon be shown to transmit physiologically significant extracellular signals across their plasma membranes by a PIP(2)-mediated transduction mechanism.
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Affiliation(s)
- K J Einspahr
- Department of Immunology, Mayo Clinic and Foundation, Rochester, Minnesota 55905
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Signal Transduction at the Membrane Level of Plant Cells. ACTA ACUST UNITED AC 1990. [DOI: 10.1007/978-94-009-2103-0_72] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Tate BF, Schaller GE, Sussman MR, Crain RC. Characterization of a Polyphosphoinositide Phospholipase C from the Plasma Membrane of Avena sativa. PLANT PHYSIOLOGY 1989; 91:1275-9. [PMID: 16667176 PMCID: PMC1062179 DOI: 10.1104/pp.91.4.1275] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
A phosphoinositide-specific phospholipase C activity was identified in oat root (Avena sativa, cv Victory) plasma membranes purified by separation in an aqueous two-phase polymer system. The enzyme is highly active toward inositol phospholipids but only minimally active toward phosphatidylethanolamine and phosphatidylcholine. Activity approaches maximal levels at 200 micromolar phosphatidylinositol 4-phosphate (PIP) and is highly dependent on calcium; it is inhibited by 1 millimolar EGTA and is activated by calcium with an apparent activation constant of 2 micromolar. At 10 micromolar calcium and 200 micromolar inositol phospholipid, the enzyme is specific for phosphatidylinositol 4,5-bisphosphate (PIP(2)) and PIP, which are hydrolyzed at 10 and 4 times, respectively, the rate of phosphatidylinositol (PI) hydrolysis. The principle water soluble products of hydrolysis, as determined by high performance liquid chromatography, are inositol 1,4,5-trisphosphate from PIP(2), inositol 1,4-bisphosphate from PIP, and inositol phosphate from PI.
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Affiliation(s)
- B F Tate
- Department of Molecular and Cell Biology U-125 University of Connecticut, Storrs, Connecticut 06269-3125
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