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1

Electronic Resource

Hydrogen peroxide and jasmonic acid mediate oligogalacturonic acid-induced saponin accumulation in suspension-cultured cells of Panax ginseng (2003)

Hu, Xiangyang ; Neill, Steven ; Cai, Weiming ; [et al.]

Oxford, UK : Munksgaard International Publishers

Physiologia plantarum 118 (2003), S. 0

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ISSN: 1399-3054

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: The signalling pathways mediating defence responses induced in suspension cultures of ginseng, Panax ginseng C. A. Meyer, by the plant cell wall-derived elicitor oligogalacturonic acid (OGA), were investigated. OGA induced the rapid generation and release of hydrogen peroxide, H2O2, potentially via an NADPH oxidase-like enzyme. In addition, OGA elicited the accumulation of jasmonic acid (JA) and the defence compound saponin, and expression of genes encoding squalene synthase (SQS; EC 2.5.1.21) and squalene epoxidase (SQE; EC 1.14.99.7), key enzymes of saponin biosynthesis. H2O2 and JA also induced saponin accumulation and transcription of sqs and sqe. The accumulation of JA, but not that of H2O2, was inhibited by an inhibitor of JA biosynthesis, whereas the accumulation of both H2O2 and JA were inhibited by treatments that removed H2O2 or inhibited its production. Moreover, H2O2 stimulated JA accumulation, but JA treatment had no effect on H2O2 generation. These data place H2O2 and JA as early signalling intermediaries in the cellular responses mediating saponin biosynthesis in response to OGA, and position H2O2 upstream of JA. Inhibitors of calcium fluxes and protein phosphorylation inhibited all responses to some extent, indicating the requirements for a protein kinase and calcium in at least one step in the signal cascade leading to saponin accumulation.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1034/j.1399-3054.2003.00124.x

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2

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Shoot growth in willow (Salix viminalis) in relation to abscisic acid, plant water status and photoperiod (1987)

Barros, Raimundo S. ; Neill, Steven J.

Oxford, UK : Blackwell Publishing Ltd

Physiologia plantarum 70 (1987), S. 0

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ISSN: 1399-3054

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: The decline in growth rate of field-grown willow trees in Aberystwyth, U.K., began in mid-summer and was followed by the senescence and abortion of shoot tips. These events were not triggered by a decline in the length of the natural photoperiod but were coincident with low leaf water potentials that developed in summer. Transient increases in the abscisic acid (ABA) content of shoot tips were observed during the period of declining water potential. These increases were roughly coincident with the onset of growth decline and preceded abortion and senescence of shoot tips. Under controlled conditions growth of both rooted cuttings and potted plants was arrested by short days (8 h) without any increase in tip ABA levels. Growth of rooted cuttings under long days (16 h) was inhibited by exogenous ABA; this inhibition could be relieved by addition of gibberellic acid (GA3) to the nutrient solution. Growth of aseptically cultured apices was also inhibited by ABA; this inhibition was relieved by joint application of GA9 and zeatin riboside.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1399-3054.1987.tb04328.x

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3

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Abscisic acid signal transduction in epidermal cells of Pisum sativum L. Argenteum: both dehydrin mRNA accumulation and stomatal responses require protein phosphorylation and dephosphorylation (1997)

Hey, Sandra J. ; Bacon, Andrea ; Burnett, Edward ; [et al.]

Springer

Planta 202 (1997), S. 85-92

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ISSN: 1432-2048

Keywords: Key words: Abscisic acid ; Dehydrin ; Guard cell ; Gene expression ; Pisum (ABA ; stomate) ; Signal transduction

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract. The effects of a number of treatments, both in planta and in vitro, on the accumulation of mRNA encoding dehydrin, an abscisic acid (ABA)-inducible protein, were determined for guard cells and mesophyll cells prepared from leaves of the Argenteum mutant of Pisum sativum L. Guard cells and mesophyll cells treated for 10 d with ABA in planta accumulated dehydrin mRNA. However, after 1 or 3 d treatment, dehydrin mRNA was induced only in guard cells. Wilting induced dehydrin mRNA accumulation in leaves and epidermal cells. Induction of mRNA in epidermal cells was correlated with an increased ABA content after either ABA application or following wilting. Isolated mesophyll and guard cells responded to ABA in vitro by the induction of dehydrin mRNA. However, osmotic stress, imposed by incubation in mannitol, had no effect on ABA and dehydrin mRNA synthesis in mesophyll cells, and only a slight effect on guard cells. Both protein phosphorylation and dephosphorylation were shown to be required for ABA-induced dehydrin gene expression and stomatal movements. Inhibitors of protein kinases (K-252a) and protein phosphatases 1/2A (okadaic acid) and protein phosphatase 2B (cyclosporin A) all inhibited ABA-induced dehydrin mRNA accumulation. They also reduced the inhibitory effects of ABA on stomatal opening, as did the protein kinase activator phorbol myristate acetate (PMA). While K-252a, cyclosporin A and PMA also inhibited ABA-induced stomatal closure, okadaic acid enhanced the ABA effect, indicating the involvement of multiple protein phosphorylation/dephosphorylation steps in ABA signal transduction in guard cells.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s004250050106

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4

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Harpin induces mitogen-activated protein kinase activity during defence responses in Arabidopsis thaliana suspension cultures (1999)

Desikan, Radhika ; Clarke, Andrew ; Atherfold, Paul ; [et al.]

Springer

Planta 210 (1999), S. 97-103

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ISSN: 1432-2048

Keywords: Key words:Arabidopsis ; Defence response ; Harpin ; Inhibitor (PD98059) ; Mitogen-activated protein kinase ; Tyrosine phosphorylation

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract. Elicitation of Arabidopsis thaliana (L.) Heynh. suspension cultures with the bacterial protein harpin (from Pseudomonas syringae pv. syringae) induced the activation of two kinases of 39 and 44 kDa, as demonstrated by in-gel kinase assays using myelin basic protein (MBP) as a substrate. Both these kinases appeared to be tyrosine-phosphorylated upon activation, as demonstrated by treatment with tyrosine phosphatase and immunoprecipitation using an anti-phosphotyrosine monoclonal antibody. An inhibitor of mammalian mitogen-activated protein kinase (MAPK) activation, PD98059, inhibited harpin-induced MBPK activation, but did not inhibit the activity of these kinases. PD98059 also inhibited harpin-induced programmed cell death and defence gene expression, suggesting the involvement of harpin-induced MAPKs in defence responses in Arabidopsis thaliana.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s004250050658

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5

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Characterization of a cDNA from Arabidopsis thaliana encoding a potential thiol protease whose expression is induced independently by wilting and abscisic acid (1994)

Williams, Jacqueline ; Bulman, Michael ; Huttly, Alison ; [et al.]

Springer

Plant molecular biology 25 (1994), S. 259-270

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ISSN: 1573-5028

Keywords: abscisic acid ; Arabidopsis thaliana ; gene expression ; mutants ; signal transduction ; stress ; thiol protease ; wilting

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract The sequence and expression characteristics are described of a wilt-inducible gene in Arabidopsis thaliana. A 1494 encodes a potential thiol protease whose mRNA accumulates rapidly in shoot tissue upon the loss of turgor. A1494 mRNA levels peaked after ca. 4 h and declined thereafter. Dehydration also induced rapid biosynthesis of the phytohormone abscisic acid (ABA), which continued for at least 9 h. Exogenous ABA induced the accumulation of A1494 mRNA, with kinetics similar to those after wilting. Rehydration of wilted shoots led to a rapid decline in the content of both ABA and A1494 mRNA. Wilting and ABA independently induced A1494 expression as evidenced by the effects of ABA and wilting on the ABA-deficient aba-1 and ABA-insensitive abi-1 and abi-3 genotypes. A1494 mRNA was not detectable in aba-1 shoots but accumulated rapidly after either wilting or ABA treatment, whereas the shoot ABA content was increased only by ABA treatment. ABA had no effect on A1494 mRNA levels in the abi-1 and abi-3 mutants but wilting did result in enhanced A1494 expression. Heat shock had only a minor effect on A1494 mRNA levels, whereas exposure to low temperature resulted in substantial accumulation of A1494 mRNA in wild-type shoots. However, this latter response, unlike that to drought, was mediated exclusively via ABA synthesis as demonstrated by the lack of A1494 mRNA accumulation in cold-treated aba-1 shoots.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00023242

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6

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The monoclonal antibody JIM19 modulates abscisic acid action in barley aleurone protoplasts (1995)

Wang, Mei ; Heimovaara-Dijkstra, Sjoukje ; Meulen, Rene M. ; [et al.]

Springer

Planta 196 (1995), S. 271-276

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ISSN: 1432-2048

Keywords: Abscisic acid ; Gene expression ; Hordeum ; Monoclonal antibody ; Signal perception and transduction

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract A panel of hybridoma products generated against pea (Pisum sativum L.) guard-cell protoplasts has been assayed for anti-abscisic acid (ABA) biological activity in barley (Hordeum vulgare L.) aleurone protoplasts. The effects of the antibodies on ABA-induced accumulation of mRNA transcribed from RAB-16, a gene responsive to ABA, were determined. Most of the antibodies, and culture medium, had no effect, but five monoclonal antibodies (MAbs) were found to inhibit ABA-induced RAB-16 gene expression and one MAb enhanced it. The effects of one inhibitory MAb, JIM19, were studied in some detail. These effects were specific to ABA-induced events, as incubation with JIM19 had no effect on the expression of a constitutively-expressed gene, GAPDH, encoding glyceraldehyde-3-phosphate dehydrogenase, and only a slight effect on the production of α-amylase induced by gibberellic acid. Increasing concentrations of ABA in the incubation medium partly overcame the inhibitory effect of JIM19. Immunolabelling and biological activity remained together during immuno-purification of JIM19 from hybridoma culture supernatant. Immunoblotting of JIM19 to membrane preparations from barley aleurone protoplasts revealed that JIM19 recognised a number of proteins.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00201384

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7

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Identification of novel cell surface epitopes using a leaf epidermal-strip assay system (1995)

Paul Knox, J. ; Peart, Janet ; Neill, Steven J.

Springer

Planta 196 (1995), S. 266-270

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ISSN: 1432-2048

Keywords: Cell surface epitope ; Commelina ; Guard cell ; Leaf epidermis assay ; Monoclonal antibody ; Pisum

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Using indirect immunofluorescence with hybridoma supernatants on intact epidermal peels of the argenteum mutant of Pisum sativum L. and Commelina communis L. as a secondary screen, three monoclonal antibodies have been derived and characterized. The distribution of the antibody binding to the epidermal strips indicated restricted occurrence of the corresponding epitopes in the cell wall material exposed on the inner face of the epidermal tissue. The monoclonal antibody JIM18 bound to the lining of the stomatal pore in pea and the exposed surface of the epidermal tissue corresponding to the stomatal complexes, including the subsidiary cells, in C. communis. JIM19 and JIM20 bound to the exposed surface of non-guard-cell epidermal cells in pea and the exposed surface of cells other than the guard cells and subsidiary cells in C. communis. However, the JIM19 epitope was revealed in the wall in the regions of the stomatal complexes subsequent to a short treatment with wall-digesting enzymes. This indicates regulation of epitope occurrence within cell walls in relation to adhered and un-adhered plant cell surfaces and also in relation to wall architecture in the complex epidermal tissues. The JIM18, JIM19 and JIM20 epitopes/antigens have distinct biochemical properties. JIM18 recognized a low-molecular-weight component which was present at the dye-front of a sodium dodecyl sulfate-polyacrylamide gel electrophoresis gel and which was soluble in chloroform, was periodate-sensitive and is likely to be a glycolipid. JIM19 and JIM20 recognized epitopes of hydroxyproline rich glycoproteins known to be regulated in relation to developmental anatomy. JIM19, in addition, as demonstrated in the companion report (Wang et al. 1995, 196, 271–276), has biological activity in relation to abscisic acid (ABA) interaction with ABA-sensitive barley aleurone cells.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00201383

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