351
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Sánchez-Nieto S, de Gómez-Puyou MT, Rodríguez-Sotres R, Carballo A, Gavilanes-Ruíz M. Comparison of plasma membrane H+-ATPase activity in vesicles obtained from dry and hydrated maize embryos. BIOCHIMICA ET BIOPHYSICA ACTA 1998; 1414:175-87. [PMID: 9804948 DOI: 10.1016/s0005-2736(98)00164-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
ATP hydrolysis from H+-ATPase of plasma membrane was measured in vesicles from maize embryos imbibed at times between 0 and 5 h. The activity had a maximum at 2 h of imbibition. In order to detect whether the enzyme had the same characteristics through the first 5 h of imbibition, vanadate and lysophophatydilcholine sensitivities, as well as trypsin, pH and temperature effects on the activity of the H+-ATPase from plasma membrane vesicles isolated from embryos imbibed at 0 or 5 h were studied. The results indicate that the activity expressed at 0 h is very different from the activity at 5 h. The activity from embryos imbibed for 5 h was less sensitive to vanadate, trypsin and lysophosphatidylcholine, more sensitive to denaturing temperatures and with a broader pH dependence, as compared to the activity from embryos that were not imbibed. When vanadate-sensitive ATPase activity was purified by anion exchange chromatography, the peaks obtained from the 0 and 5 h imbibed embryos were different and non-overlapping. These data could be interpreted in terms of different enzyme structures from dry and imbibed embryos due to either different primary structures or covalent modifications, or differences in membrane vicinities.
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Affiliation(s)
- S Sánchez-Nieto
- Departamento de Bioquímica, Facultad de Química, Conjunto E. UNAM, Cd. Universitaria, Coyoacán, 04510 Mexico DF, Mexico
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352
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Link BM, Cosgrove DJ. Acid-growth response and alpha-expansins in suspension cultures of bright yellow 2 tobacco. PLANT PHYSIOLOGY 1998; 118:907-16. [PMID: 9808735 PMCID: PMC34801 DOI: 10.1104/pp.118.3.907] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/1998] [Accepted: 08/17/1998] [Indexed: 05/21/2023]
Abstract
The possibility that Bright Yellow 2 (BY2) tobacco (Nicotiana tabacum L.) suspension-cultured cells possess an expansin-mediated acid-growth mechanism was examined by multiple approaches. BY2 cells grew three times faster upon treatment with fusicoccin, which induces an acidification of the cell wall. Exogenous expansins likewise stimulated BY2 cell growth 3-fold. Protein extracted from BY2 cell walls possessed the expansin-like ability to induce extension of isolated walls. In western-blot analysis of BY2 wall protein, one band of 29 kD was recognized by anti-expansin antibody. Six different classes of alpha-expansin mRNA were identified in a BY2 cDNA library. Northern-blot analysis indicated moderate to low abundance of multiple alpha-expansin mRNAs in BY2 cells. From these results we conclude that BY2 suspension-cultured cells have the necessary components for expansin-mediated cell wall enlargement.
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Affiliation(s)
- B M Link
- Department of Biology, 208 Mueller Laboratory, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
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353
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Affiliation(s)
- D J Cosgrove
- Department of Biology, 208 Mueller Laboratory, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
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354
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Bogoslavsky L, Neumann PM. Rapid regulation by acid pH of cell wall adjustment and leaf growth in maize plants responding to reversal of water stress. PLANT PHYSIOLOGY 1998; 118:701-9. [PMID: 9765556 PMCID: PMC34846 DOI: 10.1104/pp.118.2.701] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/1998] [Accepted: 06/15/1998] [Indexed: 05/21/2023]
Abstract
The role of acid secretion in regulating short-term changes in growth rate and wall extensibility was investigated in emerging first leaves of intact, water-stressed maize (Zea mays L.) seedlings. A novel approach was used to measure leaf responses to injection of water or solutions containing potential regulators of growth. Both leaf elongation and wall extensibility, as measured with a whole-plant creep extensiometer, increased dramatically within minutes of injecting water, 0.5 mM phosphate, or strong (50 mM) buffer solutions with pH </= 5.0 into the cell-elongation zone of water-stressed leaves. In contrast, injecting buffer solutions at pH >/= 5.5 inhibited these fast responses. Solutions containing 0.5 mM orthovanadate or erythrosin B to inhibit wall acidification by plasma membrane H+-ATPases were also inhibitory. Thus, cell wall extensibility and leaf growth in water-stressed plants remained inhibited, despite the increased availability of (injected) water when accompanying increases in acid-induced wall loosening were prevented. However, growth was stimulated when pH 4.5 buffers were included with the vanadate injections. These findings suggest that increasing the availability of water to expanding cells in water-stressed leaves signals rapid increases in outward proton pumping by plasma membrane H+-ATPases. Resultant increases in cell wall extensibility participate in the regulation of water uptake, cell expansion, and leaf growth.
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Affiliation(s)
- L Bogoslavsky
- Plant Physiology Laboratory, Lowdermilk Faculty of Agricultural Engineering, Technion Israel Institute of Technology, Haifa 32000, Israel
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355
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Keller, Van Volkenburgh E. Evidence that auxin-induced growth of tobacco leaf tissues does not involve cell wall acidification. PLANT PHYSIOLOGY 1998; 118:557-64. [PMID: 9765541 PMCID: PMC34831 DOI: 10.1104/pp.118.2.557] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/1998] [Accepted: 06/29/1998] [Indexed: 05/22/2023]
Abstract
Interveinal strips (10 x 1.5 mm) excised from growing tobacco (Nicotiana tabacum L. cv Xanthi) leaves have an auxin-specific, epinastic growth response that is developmentally regulated and is not the result of ethylene induction (C.P. Keller, E. Van Volkenburgh [1997] Plant Physiol 113: 603-610). We report here that auxin (10 &mgr;M naphthalene acetic acid) treatment of strips does not result in plasma membrane hyperpolarization or detectable proton efflux. This result is in contrast to the expected responses elicited by 1 &mgr;M fusicoccin (FC) treatment, which in other systems mimics auxin growth promotion through stimulation of the plasma membrane H+-ATPase and resultant acid wall loosening; FC produced both hyperpolarization and proton efflux in leaf strips. FC-induced growth was much more inhibited by a strong neutral buffer than was auxin-induced growth. Measurements of the osmotic concentration of strips suggested that osmotic adjustment plays no role in the auxin-induced growth response. Although cell wall loosening of some form appears to be involved, taken together, our results suggest that auxin-induced growth stimulation of tobacco leaf strips results primarily from a mechanism not involving acid growth.
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Affiliation(s)
- Keller
- Department of Botany, University of Washington, Box 351330, Seattle, Washington 98195, USA
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356
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Smart LB, Vojdani F, Maeshima M, Wilkins TA. Genes involved in osmoregulation during turgor-driven cell expansion of developing cotton fibers are differentially regulated. PLANT PHYSIOLOGY 1998; 116:1539-49. [PMID: 9536073 PMCID: PMC35063 DOI: 10.1104/pp.116.4.1539] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/1997] [Accepted: 12/08/1997] [Indexed: 05/18/2023]
Abstract
Cotton (Gossypium hirsutum L.) fibers are single-celled trichomes that synchronously undergo a phase of rapid cell expansion, then a phase including secondary cell wall deposition, and finally maturation. To determine if there is coordinated regulation of gene expression during fiber expansion, we analyzed the expression of components involved in turgor regulation and a cytoskeletal protein by measuring levels of mRNA and protein accumulation and enzyme activity. Fragments of the genes for the plasma membrane proton-translocating ATPase, vacuole-ATPase, proton-translocating pyrophosphatase (PPase), phosphoenolpyruvate carboxylase, major intrinsic protein, and alpha-tubulin were amplified by polymerase chain reaction and used as probes in ribonuclease protection assays of RNA from a fiber developmental series, revealing two discrete patterns of mRNA accumulation. Transcripts of all but the PPase accumulated to highest levels during the period of peak expansion (+12-15 d postanthesis [dpa]), then declined with the onset of secondary cell wall synthesis. The PPase was constitutively expressed through fiber development. Activity of the two proton-translocating-ATPases peaked at +15 dpa, whereas PPase activity peaked at +20 dpa, suggesting that all are involved in the process of cell expansion but with varying roles. Patterns of protein accumulation and enzyme activity for some of the proteins examined suggest posttranslational regulation through fiber development.
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Affiliation(s)
- L B Smart
- Department of Vegetable Crops, University of California, Davis 95616, USA
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357
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Abstract
Biochemical dissection of the "acid-growth" process of plant cell walls led to the isolation of a new class of wall loosening proteins, called expansins. These proteins affect the rheology of growing walls by permitting the microfibril matrix network to slide, thereby enabling the wall to expand. Molecular sequence analysis suggests that expansins might have a cryptic glycosyl transferase activity, but biochemical results suggest that expansins disrupt noncovalent bonding between microfibrils and the matrix. Recent discoveries of a new expansin family and gene expression in fruit meristems and cotton fibers have enlarged our view of the developmental functions of this group of wall loosening proteins.
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Affiliation(s)
- M W Shieh
- Department of Biology, Pennsylvania State University, University Park 16802, USA
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358
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Abstract
Growing plant cells are shaped by an extensible wall that is a complex amalgam of cellulose microfibrils bonded noncovalently to a matrix of hemicelluloses, pectins, and structural proteins. Cellulose is synthesized by complexes in the plasma membrane and is extruded as a self-assembling microfibril, whereas the matrix polymers are secreted by the Golgi apparatus and become integrated into the wall network by poorly understood mechanisms. The growing wall is under high tensile stress from cell turgor and is able to enlarge by a combination of stress relaxation and polymer creep. A pH-dependent mechanism of wall loosening, known as acid growth, is characteristic of growing walls and is mediated by a group of unusual wall proteins called expansins. Expansins appear to disrupt the noncovalent bonding of matrix hemicelluloses to the microfibril, thereby allowing the wall to yield to the mechanical forces generated by cell turgor. Other wall enzymes, such as (1-->4) beta-glucanases and pectinases, may make the wall more responsive to expansin-mediated wall creep whereas pectin methylesterases and peroxidases may alter the wall so as to make it resistant to expansin-mediated creep.
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Affiliation(s)
- D J Cosgrove
- Department of Biology, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
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359
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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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360
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Harling H, Czaja I, Schell J, Walden R. A plant cation-chloride co-transporter promoting auxin-independent tobacco protoplast division. EMBO J 1997; 16:5855-66. [PMID: 9312044 PMCID: PMC1170217 DOI: 10.1093/emboj/16.19.5855] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Although auxin plays a central role in plant development, little is known about the signal transduction pathways triggered by auxin regulating cell elongation, division and differentiation. We describe the molecular analysis of the mutant tobacco line axi 4/1, which was regenerated from an auxin-independent callus created by activation T-DNA tagging. Transcriptional enhancer-mediated deregulated expression of the tagged plant gene axi 4 uncouples division of axi 4/1 protoplasts from external auxin stimuli, whereas in untransformed protoplasts expression of axi 4 and cell division are auxin dependent. axi 4 encodes a 109 kDa protein with significant homology to a family of electroneutral cation-chloride co-transporters (CCCs). We show that overexpression of AXI 4 or another member of the CCC family, the Na+/K+/2Cl--co-transporter from shark, triggers auxin-independent growth of tobacco protoplasts. We suggest that Na+/K+/2Cl--co-transporters may play a role in signalling cell division and that this function is highly conserved between AXI 4 and the shark Na+/K+/2Cl--co-transporter. We also demonstrate that a C-terminal fragment of AXI 4 is sufficient to promote auxin-independent cell division, showing that the C-termini of CCCs are functional subunits triggering cell division. This may allow a molecular dissection of this process not only in plants but also in animal cells.
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Affiliation(s)
- H Harling
- Max Planck Institut für Züchtungsforschung, Abteilung Genetische Grundlagen der Pflanzenzüchtung, Carl von Linné Weg 10, 50829 Köln, Germany
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361
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Cosgrove DJ. Creeping walls, softening fruit, and penetrating pollen tubes: the growing roles of expansins. Proc Natl Acad Sci U S A 1997; 94:5504-5. [PMID: 9159099 PMCID: PMC34097 DOI: 10.1073/pnas.94.11.5504] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
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362
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363
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Gomès E, Venema K, Simon-Plas F, Milat ML, Palmgren MG, Blein JP. Activation of the plant plasma membrane H+-ATPase. Is there a direct interaction between lysophosphatidylcholine and the C-terminal part of the enzyme? FEBS Lett 1996; 398:48-52. [PMID: 8946951 DOI: 10.1016/s0014-5793(96)01218-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The antagonistic effects of the fungal toxin beticolin-1 and of L-alpha-lysophosphatidylcholine (lysoPC) were investigated on the plasma membrane H+-ATPase of the plant Arabidopsis thaliana (isoform 2) expressed in yeast, using both wild-type enzyme (AHA2) and C-terminal truncated enzyme (aha2delta92). Phosphohydrolytic activities of both enzymes were inhibited by beticolin-1, with very similar 50% inhibitory concentrations, indicating that the toxin action does not involve the C-terminal located autoinhibitory domain of the proton pump. Egg lysoPC, a compound that activates the H+-ATPase by a mechanism involving the C-terminal part of the protein, was found to be able to reverse the inhibition of AHA2 by beticolin-1. The lack of effect of other detergents and the comparison of different carbon chain length lysoPCs show that the capacity to reverse the enzyme inhibition is clearly related to their ability to activate the pump. Long chain length lysoPC was also shown to reverse the inhibition of aha2delta92 by beticolin-1, which strongly suggests that lysoPC binds to the H+-ATPase on site(s) not located on its autoinhibitory domain.
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Affiliation(s)
- E Gomès
- Laboratoire de Phytopharmacie et Biochimie des Interactions Cellulaires, UA 692 INRA/Université de Bourgogne, Dijon, France
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364
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Gianinazzi-Pearson V. Plant Cell Responses to Arbuscular Mycorrhizal Fungi: Getting to the Roots of the Symbiosis. THE PLANT CELL 1996; 8:1871-1883. [PMID: 12239368 PMCID: PMC161321 DOI: 10.1105/tpc.8.10.1871] [Citation(s) in RCA: 95] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Affiliation(s)
- V. Gianinazzi-Pearson
- Laboratoire de Phytoparasitologie INRA/CNRS, Station de Genetique et d'Amelioration des Plantes, Institut National de la Recherche Agronomique, BV 1540, 21034 Dijon cedex, France
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365
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O'Neill MA, Warrenfeltz D, Kates K, Pellerin P, Doco T, Darvill AG, Albersheim P. Rhamnogalacturonan-II, a pectic polysaccharide in the walls of growing plant cell, forms a dimer that is covalently cross-linked by a borate ester. In vitro conditions for the formation and hydrolysis of the dimer. J Biol Chem 1996; 271:22923-30. [PMID: 8798473 DOI: 10.1074/jbc.271.37.22923] [Citation(s) in RCA: 293] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Rhamnogalacturonan II (RG-II) is a structurally complex pectic polysaccharide present in the walls of growing plant cells. We now report that RG-II, released by endopolygalacturonase treatment of the walls of suspension-cultured sycamore cells and etiolated pea stems, exists mainly as a dimer that is cross-linked by a borate ester. The borate ester is completely hydrolyzed at room temperature within 30 min at pH 1, partially hydrolyzed between pH 2 and 4, and stable above pH 4. The dimer is formed in vitro between pH 2.4 and 6. 2 by treating monomeric RG-II (0.5 mM) with boric acid (1.2 mM); the dimer formed after 24 h at pH 3.4 and 5.0 accounts for approximately 30 and approximately 5%, respectively, of the RG-II. In contrast, the dimer accounts for approximately 80 and approximately 54% of the RG-II when the monomer is treated for 24 h at pH 3.4 and 5.0, respectively, with boric acid and 0.5 m Sr2+, Pb2+, or Ba2+. The amount of dimer formed at pH 3.4 or 5.0 is not increased by addition of 0.5 mM Ca2+, Cd2+, Cu2+, Mg2+, Ni2+, and Zn2+. Steric considerations appear to regulate dimer formation since those divalent cations that enhance dimer formation have an ionic radius >1.1 A. Our data suggest that the borate ester is located on C-2 and C-3 of two of the four 3'-linked apiosyl residues of dimeric RG-II. Our results, taken together with the results of two previous studies (Kobayashi, M., Matoh, T., and Azuma, J.-I. (1996) Plant Physiol. 110, 1017-1020; Ishii, T., and Matsunaga, T. (1996) Carbohydr. Res. 284, 1-9) provide substantial evidence that this plant cell wall pectic polysaccharide is covalently cross-linked.
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Affiliation(s)
- M A O'Neill
- Complex Carbohydrate Research Center and Department of Biochemistry and Molecular Biology, The University of Georgia, Athens, Georgia 30602-4712, USA
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366
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Frías I, Caldeira MT, Pérez-Castiñeira JR, Navarro-Aviñó JP, Culiañez-Maciá FA, Kuppinger O, Stransky H, Pagés M, Hager A, Serrano R. A major isoform of the maize plasma membrane H(+)-ATPase: characterization and induction by auxin in coleoptiles. THE PLANT CELL 1996; 8:1533-44. [PMID: 8837507 PMCID: PMC161296 DOI: 10.1105/tpc.8.9.1533] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
The plasma membrane (PM) H(+)-ATPase has been proposed to play important transport and regulatory roles in plant physiology, including its participation in auxin-induced acidification in coleoptile segments. This enzyme is encoded by a family of genes differing in tissue distribution, regulation, and expression level. A major expressed isoform of the maize PM H(+)-ATPase (MHA2) has been characterized. RNA gel blot analysis indicated that MHA2 is expressed in all maize organs, with highest levels being in the roots. In situ hybridization of sections from maize seedlings indicated enriched expression of MHA2 in stomatal guard cells, phloem cells, and root epidermal cells. MHA2 mRNA was induced threefold when nonvascular parts of the coleoptile segments were treated with auxin. This induction correlates with auxin-triggered proton extrusion by the same part of the segments. The PM H(+)-ATPase in the vascular bundies does not contribute significantly to auxin-induced acidification, is not regulated by auxin, and masks the auxin effect in extracts of whole coleoptile segments. We conclude that auxin-induced acidification in coleoptile segments most often occurs in the nonvascular tissue and is mediated, at least in part, by increased levels of MHA2.
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Affiliation(s)
- I Frías
- Instituto de Biologia Molecular y Celular de Plantas, Universidad Politécnica de Valencia-Consejo Superior de Investigaciones Cientificas, Spain
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367
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Bennett MJ, Marchant A, Green HG, May ST, Ward SP, Millner PA, Walker AR, Schulz B, Feldmann KA. Arabidopsis AUX1 gene: a permease-like regulator of root gravitropism. Science 1996; 273:948-50. [PMID: 8688077 DOI: 10.1126/science.273.5277.948] [Citation(s) in RCA: 588] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The plant hormone auxin regulates various developmental processes including root formation, vascular development, and gravitropism. Mutations within the AUX1 gene confer an auxin-resistant root growth phenotype and abolish root gravitropic curvature. Polypeptide sequence similarity to amino acid permeases suggests that AUX1 mediates the transport of an amino acid-like signaling molecule. Indole-3-acetic acid, the major form of auxin in higher plants, is structurally similar to tryptophan and is a likely substrate for the AUX1 gene product. The cloned AUX1 gene can restore the auxin-responsiveness of transgenic aux1 roots. Spatially, AUX1 is expressed in root apical tissues that regulate root gravitropic curvature.
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Affiliation(s)
- M J Bennett
- Department of Biological Sciences, University of Warwick, Coventry, CV4 7AL, UK
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368
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Abstract
Plant cells are caged within a distended polymeric network (the cell wall), which enlarges by a process of stress relaxation and slippage (creep) of the polysaccharides that make up the load-bearing network of the wall. Protein mediators of wall creep have recently been isolated and characterized. These proteins, called expansins, appear to disrupt the noncovalent adhesion of matrix polysaccharides to cellulose microfibrils, thereby permitting turgor-driven wall enlargement. Expansin activity is specifically expressed in the growing tissues of dicotyledons and monocotyledons. Sequence analysis of cDNAs indicates that expansins are novel proteins, without previously known functional motifs. Comparison of expansin cDNAs from cucumber, pea, Arabidopsis and rice shows that the proteins are highly conserved in size and amino acid sequence. Phylogenetic analysis of expansin sequences suggests that this multigene family diverged before the evolution of angiosperms. Speculation is presented about the role of this gene family in plant development and evolution.
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Affiliation(s)
- D J Cosgrove
- Department of Biology, 208 Mueller Laboratory, Penn State University, University Park, PA 16802, USA.
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369
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Taylor DP, Slattery J, Leopold AC. Apoplastic pH in corn root gravitropism: a laser scanning confocal microscopy measurement. PHYSIOLOGIA PLANTARUM 1996. [PMID: 11539373 DOI: 10.1111/j.1399-3054.1996.tb00475.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
The ability to measure the pH of the apoplast in situ is of special interest as a test of the cell wall acidification theory. Optical sectioning of living seedlings of corn roots using the laser scanning confocal microscope (LSCM) permits us to make pH measurements in living tissue. The pH of the apoplast of corn roots was measured by this method after infiltration with Cl-NERF, a pH-sensitive dye, along with Texas Red Dextran 3000, a pH-insensitive dye, as an internal standard. In the elongation zone of corn roots, the mean apoplastic pH was 4.9. Upon gravitropic stimulation, the pH on the convex side of actively bending roots was 4.5. The lowering of the apoplastic pH by 0.4 units appears to be sufficient to account for the increased growth on that side. This technique provides site-specific evidence for the acid growth theory of cell elongation. The LSCM permits measurements of the pH of living tissues, and has a sensitivity of approximately 0.2 pH units.
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Affiliation(s)
- D P Taylor
- Boyce Thompson Institute for Plant Research, Cornell Univ., Ithaca, NY 14853, USA
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370
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Grabski S, Schindler M. Auxins and Cytokinins as Antipodal Modulators of Elasticity within the Actin Network of Plant Cells. PLANT PHYSIOLOGY 1996; 110:965-970. [PMID: 12226233 PMCID: PMC157796 DOI: 10.1104/pp.110.3.965] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The cytoskeleton of plant and animal cells serves as a transmitter, transducer, and effector of cell signaling mechanisms. In plants, pathways for proliferation, differentiation, intracellular vesicular transport, cell-wall biosynthesis, symbiosis, secretion, and membrane recycling depend on the organization and dynamic properties of actin- and tubulin-based structures that are either associated with the plasma membrane or traverse the cytoplasm. Recently, a new in vivo cytoskeletal assay (cell optical displacement assay) was introduced to measure the tension within subdomains (cortical, transvacuolar, and perinuclear) of the actin network in living plant cells. Cell optical displacement assay measurements within soybean (Glycine max [L.]) root cells previously demonstrated that lipophilic signals, e.g. linoleic acid and arachidonic acid or changes in cytoplasmic pH gradients, could induce significant reductions in the tension within the actin network of transvacuolar strands. In contrast, enhancement of cytoplasmic free Ca2+ resulted in an increase in tension. In the present communication we have used these measurements to show that a similar antipodal pattern of activity exists for auxins and cytokinins (in their ability to modify the tension within the actin network of plant cells). It is suggested that these growth substances exert their effect on the cytoskeleton through the activation of signaling cascades, which result in the production of lipophilic and ionic second messengers, both of which have been demonstrated to directly effect the tension within the actin network of soybean root cells.
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Affiliation(s)
- S. Grabski
- Department of Biochemistry, Michigan State University, East Lansing, Michigan 48824
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371
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Keller CP, Van Volkenburgh E. Osmoregulation by Oat Coleoptile Protoplasts (Effect of Auxin). PLANT PHYSIOLOGY 1996; 110:1007-1016. [PMID: 12226237 PMCID: PMC157801 DOI: 10.1104/pp.110.3.1007] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The effect of auxin on the physiology of protoplasts from growing oat (Avena sativa L.) coleoptiles was investigated. Protoplasts, isolated iso-osmotically from peeled oat coleoptile segments, were found to swell steadily over many hours. Incubated in 1 mM CaCl2, 10 mM KCl, 10 mM 2-(morpholino)ethanesulfonic acid/1,3-bis-[tris(hydroxymethyl)methylamino]propane, pH 6.5, and mannitol to 300 milliosmolal, protoplasts swelled 28.9% [plus or minus] 2.0 (standard error) after 6 h. Addition of 10 [mu]M indoleacetic acid (IAA) increased swelling to 41.1% [plus or minus] 2.1 (standard error) after 6 h. Swelling (in the absence of IAA) was partially dependent on K+ in the bath medium, whereas auxin-induced swelling was entirely dependent on K+. Replacement of mannitol in the bath by Glc increased swelling (in the absence of IAA) and eliminated auxin-induced swelling. Swelling with or without IAA was inhibited by osmotic shock and was completely reversed by 0.1 mM NaN3. Sodium orthovanadate, applied at 0.5 mM, only gradually inhibited swelling under various conditions but was most effective with protoplasts prepared from tissue preincubated in vanadate. Our data are interpreted to suggest that IAA increases the conductance of the plasma membrane to K+.
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Affiliation(s)
- C. P. Keller
- Department of Botany, Box 351330, University of Washington, Seattle, Washington 98195
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372
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Gómez-Gómez L, Carrasco P. Hormonal regulation of S-adenosylmethionine synthase transcripts in pea ovaries. PLANT MOLECULAR BIOLOGY 1996; 30:821-32. [PMID: 8624412 DOI: 10.1007/bf00019014] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Two cDNA clones coding for S-adenosyl-L-methionine synthase (SAMs, EC 2.5.1.6) have been isolated from a cDNA library of gibberellic acid-treated unpollinated pea ovaries. Both cDNAs were sequenced showing a high degree of identity but coding for different SAMs polypeptides. The presence of two SAMs genes in pea was further confirmed by Southern analysis. Expression of the SAMs genes in the pea plant was found at different levels in vegetative and reproductive tissues. We characterized the expression levels of SAMs genes during the development or senescence of pea ovaries. Northern analysis showed that transcription of SAMs genes in parthenocarpic fruits was upregulated by auxins in the same manner as in fruits from pollinated ovaries. In both pollinated and 2,4-dichlorophenoxyacetic acid-treated ovaries, and benzyladenine, although able to induce parthenocarpic development, did not affect SAMs mRNA levels. These data are consistent with an active participation of auxins in the upregulation of SAMs during fruit setting in pea and suggest that, at the molecular level, parthenocarpic development of pea ovaries is different for gibberellin- and cytokinin-treated ovaries than for auxin-induced parthenocarpic biosynthesis since treatment of the ovaries with aminoethoxyvinylglycine resulted in a delay of senescence and prevention of SAMs mRNA accumulation. A possible mechanism for hormonal regulation of SAMs during ovary development is discussed.
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Affiliation(s)
- L Gómez-Gómez
- Departament de Bioquímica i Biologia Molecular, Universitat de València, Spain
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373
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Shcherban TY, Shi J, Durachko DM, Guiltinan MJ, McQueen-Mason SJ, Shieh M, Cosgrove DJ. Molecular cloning and sequence analysis of expansins--a highly conserved, multigene family of proteins that mediate cell wall extension in plants. Proc Natl Acad Sci U S A 1995; 92:9245-9. [PMID: 7568110 PMCID: PMC40961 DOI: 10.1073/pnas.92.20.9245] [Citation(s) in RCA: 135] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Expansins are unusual proteins discovered by virtue of their ability to mediate cell wall extension in plants. We identified cDNA clones for two cucumber expansins on the basis of peptide sequences of proteins purified from cucumber hypocotyls. The expansin cDNAs encode related proteins with signal peptides predicted to direct protein secretion to the cell wall. Northern blot analysis showed moderate transcript abundance in the growing region of the hypocotyl and no detectable transcripts in the nongrowing region. Rice and Arabidopsis expansin cDNAs were identified from collections of anonymous cDNAs (expressed sequence tags). Sequence comparisons indicate at least four distinct expansin cDNAs in rice and at least six in Arabidopsis. Expansins are highly conserved in size and sequence (60-87% amino acid sequence identity and 75-95% similarity between any pairwise comparison), and phylogenetic trees indicate that this multigene family formed before the evolutionary divergence of monocotyledons and dicotyledons. Sequence and motif analyses show no similarities to known functional domains that might account for expansin action on wall extension. A series of highly conserved tryptophans may function in expansin binding to cellulose or other glycans. The high conservation of this multigene family indicates that the mechanism by which expansins promote wall extensin tolerates little variation in protein structure.
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Affiliation(s)
- T Y Shcherban
- Department of Biology, Pennsylvania State University, University Park 16802, USA
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374
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Abstract
The plant growth regulator auxin mediates an enormous range of developmental and growth responses, some of which are manifest rapidly and others manifest only after considerable lag periods. The protein that perceives auxin, the auxin receptor, has been sought by many laboratories and the search has identified a good number of candidates. However, a receptor must not only bind auxin, but also transduce the auxin stimulus into the responses we recognize. Finding evidence for this second condition has always proved very demanding. A key requisite is a convenient assay for auxin activity and preferably one involving a rapid response because this is likely to be linked directly to the perception event. For one auxin-binding protein (ABP1) there is growing evidence that it is a functional auxin receptor. The assays used in this work have been rapid auxin-induced changes in protoplast electrophysiology. There are many other responses induced rapidly by auxin for which a link to ABP1 has yet to be established. We have reviewed the whole range of rapid auxin-mediated responses and by doing so we hope to have provided a comprehensive picture of the many events to which a receptor (or receptors) must connect. Against this framework we match the known properties of all putative receptors, including ABP1. Not only have we tried to identify auxin-binding proteins unlikely to be receptors, but we also highlight the remaining gaps in our understanding of the more likely receptor candidates. Contents Summary 167 I. Introduction 168 II. Gene activation 168 III. Mutants 179 IV. Auxin-induced elongation growth 179 V. Other auxin-binding proteins 191 VI. Auxins and signal transduction 192 VII. Overview 194 Acknowledgements 195 References 195.
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Affiliation(s)
- Richard M Napier
- Horticulture Research International, East Mailing, West Mailing, Kent ME 19 6BJ, UK
| | - Michael A Venis
- Horticulture Research International, East Mailing, West Mailing, Kent ME 19 6BJ, UK
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375
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Abstract
When a plant root is reoriented within the gravity field, it responds by initiating a curvature which eventually results in vertical growth. Gravity sensing occurs primarily in the root tip. It may involve amyloplast sedimentation in the columella cells of the root cap, or the detection of forces exerted by the mass of the protoplast on opposite sides of its cell wall. Gravisensing activates a signal transduction cascade which results in the asymmetric redistribution of auxin and apoplastic Ca2+ across the root tip, with accumulation at the bottom side. The resulting lateral asymmetry in Ca2+ and auxin concentration is probably transmitted to the elongation zone where differential cellular elongation occurs until the tip resumes vertical growth. The Cholodny-Went theory proposes that gravity-induced auxin redistribution across a gravistimulated plant organ is responsible for the gravitropic response. However, recent data indicate that the gravity-induced reorientation is more complex, involving both auxin gradient-dependent and auxin gradient-independent events.
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Affiliation(s)
- P H Masson
- Laboratory of Genetics, University of Wisconsin-Madison 53706
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376
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Hobbie L, Timpte C, Estelle M. Molecular genetics of auxin and cytokinin. PLANT MOLECULAR BIOLOGY 1994; 26:1499-1519. [PMID: 7532026 DOI: 10.1007/bf00016487] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Affiliation(s)
- L Hobbie
- Department of Biology, Indiana University, Bloomington 47405
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377
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Abstract
Plant cell expansion requires the integration of local wall loosening and the controlled deposition of new wall materials. Although we still know little of the latter process, two new classes of proteins have been discovered that may function in the former. Evidence is increasing that the plant extracellular matrix can exert a regulatory effect over cell behaviour. New approaches, in particular a molecular genetic analysis of cell wall mutants, are likely to speed up our understanding of wall biosynthesis, structure and function.
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Affiliation(s)
- K Roberts
- Department of Cell Biology, John Innes Centre, Colney, Norwich, UK
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378
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Taiz L. Expansins: proteins that promote cell wall loosening in plants. Proc Natl Acad Sci U S A 1994; 91:7387-9. [PMID: 11607490 PMCID: PMC44406 DOI: 10.1073/pnas.91.16.7387] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- L Taiz
- Biology Department, University of Santa Cruz, CA 95064, USA
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379
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Grabski S, Xie XG, Holland JF, Schindler M. Lipids trigger changes in the elasticity of the cytoskeleton in plant cells: a cell optical displacement assay for live cell measurements. J Cell Biol 1994; 126:713-26. [PMID: 8045935 PMCID: PMC2120140 DOI: 10.1083/jcb.126.3.713] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
An assay has been developed to quantitatively measure the tension and elasticity of the cytoskeleton in living plant cells. The cell optical displacement assay (CODA) uses a focused laser beam to optically trap and displace transvacuolar and cortical strands through a defined distance within the cell. Results from these experiments provide evidence for the classification of at least two rheologically distinct cytoskeletal assemblies, cortical and transvacuolar, that differ in their tension and response to both signaling molecules and reagents that perturb the cytoskeleton. It is further demonstrated that the tension of the transvacuolar strands can be significantly decreased by the addition of either linoleic acid, 1,2 dioctanoyl-sn-glycerol, or 1,3 dioctanoylglycerol. These decreases in tension could also be induced by lowering the cytoplasmic pH. In contrast, addition of Ca2+, Mg2+, or the ionophore A23187 to the cells caused a considerable increase in the tension of the transvacuolar strands. The data provides evidence that: (a) linoleic acid may be a signaling molecule in plant cells; (b) diacylglycerol functions as a signaling molecule through a protein kinase C-independent pathway mediated by PLA2; and (c) Ca2+ and pH have regulatory roles for controlling cytoskeleton tension and organization.
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Affiliation(s)
- S Grabski
- Department of Biochemistry, Michigan State University, East Lansing 48824
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380
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McQueen-Mason S, Cosgrove DJ. Disruption of hydrogen bonding between plant cell wall polymers by proteins that induce wall extension. Proc Natl Acad Sci U S A 1994; 91:6574-8. [PMID: 11607483 PMCID: PMC44245 DOI: 10.1073/pnas.91.14.6574] [Citation(s) in RCA: 350] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Plant cell enlargement is controlled by the ability of the constraining cell wall to expand. This ability has been postulated to be under the control of polysaccharide hydrolases or transferases that weaken or rearrange the loadbearing polymeric networks in the wall. We recently identified a family of wall proteins, called expansins, that catalyze the extension of isolated plant cell walls. Here we report that these proteins mechanically weaken pure cellulose paper in extension assays and stress relaxation assays, without detectable cellulase activity (exo- or endo- type). Because paper derives its mechanical strength from hydrogen bonding between cellulose microfibrils, we conclude that expansins can disrupt hydrogen bonding between cellulose fibers. This conclusion is further supported by experiments in which expansin-mediated wall extension (i) was increased by 2 M urea (which should weaken hydrogen bonding between wall polymers) and (ii) was decreased by replacement of water with deuterated water, which has a stronger hydrogen bond. The temperature sensitivity of expansin-mediated wall extension suggests that units of 3 or 4 hydrogen bonds are broken by the action of expansins. In the growing cell wall, expansin action is likely to catalyze slippage between cellulose microfibrils and the polysaccharide matrix, and thereby catalyze wall stress relaxation, followed by wall surface expansion and plant cell enlargement.
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Affiliation(s)
- S McQueen-Mason
- Department of Biology, Pennsylvania State University, University Park, PA 16802, USA
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381
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Abstract
The expansion of roots is considered at the level of the single cell. The water relations of cell expansion are discussed. Water entry, solute import and cell wall properties are considered as possible regulatory points. It is argued that root cell expansion can be understood in terms of cell turgor pressure and the physical properties of the cell wall, provided solute supply is not limiting. Various measurements of cell wall properties in roots are presented and the assumptions underlying their measurements are presented. It is concluded that cell wall properties must be measured over short time periods to prevent alterations in wall properties during the experiment. The radial location of the load-bearing layers is discussed and it is concluded that, unlike aerial tissue, growth is limited by the properties of the inner layer of the root cortex. Evidence is presented to show that cell wall properties can change both during development and following turgor perturbation. In general, however, turgor itself is tightly regulated, particularly towards the root tip. A number of environmental situations are presented in which root growth is altered. The mechanism of the alteration is discussed at the single cell level. These 'stresses'include osmotic stress, low temperature and soil compaction. In many cases the alteration of root growth is consistent with changes in the ceil wall properties of the growing ceils. Severe stress, resulting in near cessation of root cell extension, can result in a change (usually an increase) in turgor pressure. The change in turgor pressure of the cells in the growing zone is smaller than that which would be expected from a continuation of an unstressed solute import rate. This exemplifies both the change in cell wall properties and the tight turgor homeostasis of root tips. The biochemical processes which underlie the modulation of cell wall properties are presented as they are currently understood in roots. Measurements of the chemical composition of the wall have not revealed any useful differences which can explain the developmental or stress-induced changes in cell wall properties. Recent work on cell wall enzymes and proteins may provide information about control of cross-linkages within the wall. In the last section the relative importance of apoplastic and symplastic solute transport to the expanding cells is considered. At present the consensus appears to favour the symplastic route, but the apoplastic pathway may also operate, possibly as a scavenging mechanism for leaked ions. The regulation of turgor pressure by linking solute import with wall loosening is discussed. Contents Summary 3 I. Introduction 4 II. Factors controlling cell expansion 4 III. Wall extensibility and yield threshold in roots 6 IV. Environmental effects on root cell expansion 10 V. Modification of cell wall biochemistry 15 VI. Linkage of growth with solute import 18 VII. Future prospects 21 VIII. Acknowledgements 22 IX. References 22.
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Affiliation(s)
- Jeremy Pritchard
- Ysgol Gwyddorau Bioleg, Coleg Prifysgol Gogledd Cymru, Bangor, Gwynedd LL57 2SY, Wales
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382
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Gillaspy G, Ben-David H, Gruissem W. Fruits: A Developmental Perspective. THE PLANT CELL 1993. [PMID: 12271039 DOI: 10.2307/3869794] [Citation(s) in RCA: 176] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Affiliation(s)
- G. Gillaspy
- Department of Plant Biology, University of California, Berkeley, California 94720
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383
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Gillaspy G, Ben-David H, Gruissem W. Fruits: A Developmental Perspective. THE PLANT CELL 1993; 5:1439-1451. [PMID: 12271039 PMCID: PMC160374 DOI: 10.1105/tpc.5.10.1439] [Citation(s) in RCA: 472] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Affiliation(s)
- G. Gillaspy
- Department of Plant Biology, University of California, Berkeley, California 94720
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384
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Yang T, Law DM, Davies PJ. Magnitude and Kinetics of Stem Elongation Induced by Exogenous Indole-3-Acetic Acid in Intact Light-Grown Pea Seedlings. PLANT PHYSIOLOGY 1993; 102:717-724. [PMID: 12231860 PMCID: PMC158841 DOI: 10.1104/pp.102.3.717] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Exogenously applied indole-3-acetic acid (IAA) strongly promoted stem elongation over the long term in intact light-grown seedlings of both dwarf (cv Progress No. 9) and tall (cv Alaska) peas (Pisum sativum L.), with the relative promotion being far greater in dwarf plants. In dwarf seedlings, solutions of IAA (between 10-4 and 10-3 M), when continuously applied to the uppermost two internodes via a cotton wick, increased whole-stem growth by at least 6-fold over the first 24 h. The magnitude of growth promotion correlated with the applied IAA concentration from 10-6 to 10-3 M, particularly over the first 6 h of application. IAA applied only to the apical bud or the uppermost internode of the seedling stimulated a biphasic growth response in the uppermost internode and the immediately lower internode, with the response in the latter being greatly delayed. This demonstrates that exogenous IAA effectively promotes growth as it is transported through intact stems. IAA withdrawal and reapplication at various times enabled the separation of the initial growth response (IGR) and prolonged growth response (PGR) induced by auxin. The IGR was inducible by at least 1 order of magnitude lower IAA concentrations than the PGR, suggesting that the process underlying the IGR is more sensitive to auxin induction. In contrast to the magnitude of the IAA effect in dwarf seedlings, applied IAA only doubled the growth in tall seedlings. These results suggest that endogenous IAA is more growth limiting in dwarf plants than in tall plants, and that auxin promotes stem elongation in the intact plant probably by the same mechanism of action as in isolated stem segments. However, since dwarf plants to which IAA was applied failed to reach the growth rate of tall plants, auxin cannot be the only limiting factor for stem growth in peas.
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Affiliation(s)
- T. Yang
- Section of Plant Biology, Plant Science Building, Cornell University, Ithaca, New York 14853
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385
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Abstract
Most antigenic determinants of yeast ATPase are located within its N-terminal part. Amino acids 24-56, required for insertion at the plasma membrane, are highly accessible. The C-terminus behaves as a modulable auto-inhibitory domain in both yeast and plant ATPases. The expression of functional plant enzyme in yeast allows its mutational analysis. Plant tissues involved in active transport, such as the stomata guard cells, phloem, root epidermis and endodermis, are enriched in ATPase. One isoform is phloem-specific. The fact that auxin induces the synthesis of ATPase in corn coleoptiles provides molecular support to the 'Acid growth' theory.
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Affiliation(s)
- R Serrano
- Departamento de Biotecnologia, Universidad Politécnica, Valencia, Spain
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386
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Cosgrove DJ. Wall extensibility: its nature, measurement and relationship to plant cell growth. THE NEW PHYTOLOGIST 1993; 124:1-23. [PMID: 11537718 DOI: 10.1111/j.1469-8137.1993.tb03795.x] [Citation(s) in RCA: 105] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Expansive growth of plant cells is controlled principally by processes that loosen the wall and enable it to expand irreversibly. The central role of wall relaxation for cell expansion is reviewed. The most common methods for assessing the extension properties of plant cell walls ( wall extensibility') are described, categorized and assessed critically. What emerges are three fundamentally different approaches which test growing cells for their ability (a) to enlarge at different values of turgor, (b) to induce wall relaxation, and (c) to deform elastically or plastically in response to an applied tensile force. Analogous methods with isolated walls are similarly reviewed. The results of these different assays are related to the nature of plant cell growth and pertinent biophysical theory. I argue that the extensibilities' measured by these assays are fundamentally different from one another and that some are more pertinent to growth than others.
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Affiliation(s)
- D J Cosgrove
- Department of Biology, Pennsylvania State University, University Park 16802
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387
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Johansson F, Sommarin M, Larsson C. Fusicoccin Activates the Plasma Membrane H+-ATPase by a Mechanism Involving the C-Terminal Inhibitory Domain. THE PLANT CELL 1993; 5:321-327. [PMID: 12271065 DOI: 10.2307/3869599] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Plasma membrane vesicles isolated from spinach leaves incubated with the fungal toxin fusicoccin showed a twofold increase in ATP hydrolytic activity and a threefold increase in H+ pumping compared to controls. This increase in H+-ATPase activity was largely completed within 4 min of incubation and was not due to de novo synthesis of H+-ATPase as demonstrated by immunoblotting. Incubation with fusicoccin also resulted in a decrease in the apparent Km for ATP of the H+-ATPase from 0.22 to 0.10 mM. The fusicoccin-mediated activation of H+-ATPase activity and the accompanying decrease in the Km for ATP are changes very similar to those observed upon trypsin activation of the H+-ATPase, where an autoinhibitory domain in the C-terminal region of the H+-ATPase is removed. Thus, trypsin treatment of plasma membrane vesicles from control leaves gave a twofold increase in ATP hydrolytic activity and a threefold increase in H+ pumping, as well as a decrease in the apparent Km for ATP of the H+-ATPase from 0.22 to 0.10 mM. Trypsin treatment of plasma membranes from fusicoccin-incubated leaves did not further enhance the H+-ATPase activity, however, and neither was the Km for ATP further decreased. That trypsin really removed a small segment from the fusicoccin-activated H+-ATPase was confirmed by immunoblotting, which showed the appearance of a 90-kD band in addition to the native 100-kD H+-ATPase band upon trypsin treatment. Taken together, our data suggest that in vivo activation of the H+-ATPase by fusicoccin proceeds by a mechanism involving a displacement of the C-terminal inhibitory domain.
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Affiliation(s)
- F. Johansson
- Department of Plant Biochemistry, University of Lund, P.O. Box 7007, S-220 07 Lund, Sweden
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388
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Johansson F, Sommarin M, Larsson C. Fusicoccin Activates the Plasma Membrane H+-ATPase by a Mechanism Involving the C-Terminal Inhibitory Domain. THE PLANT CELL 1993; 5:321-327. [PMID: 12271065 PMCID: PMC160273 DOI: 10.1105/tpc.5.3.321] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Plasma membrane vesicles isolated from spinach leaves incubated with the fungal toxin fusicoccin showed a twofold increase in ATP hydrolytic activity and a threefold increase in H+ pumping compared to controls. This increase in H+-ATPase activity was largely completed within 4 min of incubation and was not due to de novo synthesis of H+-ATPase as demonstrated by immunoblotting. Incubation with fusicoccin also resulted in a decrease in the apparent Km for ATP of the H+-ATPase from 0.22 to 0.10 mM. The fusicoccin-mediated activation of H+-ATPase activity and the accompanying decrease in the Km for ATP are changes very similar to those observed upon trypsin activation of the H+-ATPase, where an autoinhibitory domain in the C-terminal region of the H+-ATPase is removed. Thus, trypsin treatment of plasma membrane vesicles from control leaves gave a twofold increase in ATP hydrolytic activity and a threefold increase in H+ pumping, as well as a decrease in the apparent Km for ATP of the H+-ATPase from 0.22 to 0.10 mM. Trypsin treatment of plasma membranes from fusicoccin-incubated leaves did not further enhance the H+-ATPase activity, however, and neither was the Km for ATP further decreased. That trypsin really removed a small segment from the fusicoccin-activated H+-ATPase was confirmed by immunoblotting, which showed the appearance of a 90-kD band in addition to the native 100-kD H+-ATPase band upon trypsin treatment. Taken together, our data suggest that in vivo activation of the H+-ATPase by fusicoccin proceeds by a mechanism involving a displacement of the C-terminal inhibitory domain.
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Affiliation(s)
- F. Johansson
- Department of Plant Biochemistry, University of Lund, P.O. Box 7007, S-220 07 Lund, Sweden
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389
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McQueen-Mason S, Durachko DM, Cosgrove DJ. Two endogenous proteins that induce cell wall extension in plants. THE PLANT CELL 1992; 4:1425-33. [PMID: 11538167 PMCID: PMC160229 DOI: 10.1105/tpc.4.11.1425] [Citation(s) in RCA: 461] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Plant cell enlargement is regulated by wall relaxation and yielding, which is thought to be catalyzed by elusive "wall-loosening" enzymes. By employing a reconstitution approach, we found that a crude protein extract from the cell walls of growing cucumber seedlings possessed the ability to induce the extension of isolated cell walls. This activity was restricted to the growing region of the stem and could induce the extension of isolated cell walls from various dicot stems and the leaves of amaryllidaceous monocots, but was less effective on grass coleoptile walls. Endogenous and reconstituted wall extension activities showed similar sensitivities to pH, metal ions, thiol reducing agents, proteases, and boiling in methanol or water. Sequential HPLC fractionation of the active wall extract revealed two proteins with molecular masses of 29 and 30 kD associated with the activity. Each protein, by itself, could induce wall extension without detectable hydrolytic breakdown of the wall. These proteins appear to mediate "acid growth" responses of isolated walls and may catalyze plant cell wall extension by a novel biochemical mechanism.
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Affiliation(s)
- S McQueen-Mason
- Department of Biology, Pennsylvania State University, University Park 16802, USA
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