Silica deposition by a strongly cationic proline-rich protein from systemically resistant cucumber plants.

Infection of one leaf of cucumber (Cucumis sativa) plants can render other leaves resistant to various pathogens. This so-called systemic acquired resistance (SAR) can be functionally mimicked by certain chemicals. All these treatments enhanced expression of a gene encoding a novel proline-rich protein (PRP1) which has C-terminal repetitive sequences containing an unusually high amount of lysine and arginine residues.

Induction of competence for elicitation of defense responses in cucumber hypocotyls requires proteasome activity.

The epidermal cells of hypocotyls from etiolated cucumber seedlings are not constitutively competent for elicitation of the rapid H2O2 defense response. However, elicitor competence developed while conditioning the surface-abraded seedlings by rotating them in buffer for 4 h. Competence development was greatly potentiated by inducers of systemic acquired resistance and suppressed by specific inhibitors of proteasome activity, clastolactacystin beta-lactone (LAC) and carboxybenzoyl-L-leucyl-L-leucyl-L-leucinal (LLL).

Cucumber hypocotyls respond to cutin monomers via both an inducible and a constitutive H(2)O(2)-generating system.

Hypocotyls from etiolated cucumber (Cucumis sativa L.) seedlings were gently abraded at their surface to allow permeation of elicitors. Segments from freshly abraded hypocotyls were only barely competent for H(2)O(2) elicitation with fungal elicitor or hydroxy fatty acids (classical cutin monomers).

Cutin monomers and surface wax constituents elicit H2O2 in conditioned cucumber hypocotyl segments and enhance the activity of other H2O2 elicitors.

Hypocotyls from etiolated cucumber (Cucumis sativus L.) seedlings were gently abraded at their epidermal surface and cut segments were conditioned to develop competence for H2O2 elicitation. Alkaline hydrolysates of cutin from cucumber, tomato, and apple elicited H2O2 in such conditioned segments.

Low-molecular-weight precursors for defense-related cell wall hydroxycinnamoyl esters in elicited parsley suspension cultures.

Cell walls from suspension cultures of parsley (Petroselinum crispum L.) induced with a fungal elicitor contained hydroxycinnamoyl ester groups presumably not bound to pectic polysaccharides. Extracts from these cells were separated into a range of low-molecular-weight compounds containing esterified ferulic and p-coumaric acid as well as glucose and some arabinose.

Influence of Salicylic Acid on the Induction of Competence for H2O2 Elicitation (Comparison of Ergosterol with Other Elicitors).

Hypocotyls from etiolated cucumber (Cucumis sativus L.) seedlings were gently abraded at their epidermal surface, and cut segments were used to study the rapid and transient elicitation of H2O2 by ergosterol, chitosan, mastoparan, and a polymeric fungal elicitor. Freshly abraded segments were only barely competent for any H2O2 production, but they developed this competence subsequent to abrasion.

Competence for Elicitation of H2O2 in Hypocotyls of Cucumber Is Induced by Breaching the Cuticle and Is Enhanced by Salicylic Acid.

To study H2O2 production, the epidermal surfaces of hypocotyl segments from etiolated seedlings of cucumber (Cucumis sativus L.) were gently abraded. Freshly abraded segments were not constitutively competent for rapid H2O2 elicitation.

Pretreatment of Parsley Suspension Cultures with Salicylic Acid Enhances Spontaneous and Elicited Production of H2O2.

Suspension-cultured cells of parsley (Petroselinum crispum L.) were used to study the regulation of extracellular H2O2. After resuspension, the washed cells regulated the H2O2 concentration spontaneously to a constant level that was greatly increased when the cultures were pretreated for 1 d with salicylic acid (SA).

Defense Responses in Infected and Elicited Cucumber (Cucumis sativus L.) Hypocotyl Segments Exhibiting Acquired Resistance.

Segments from dark-grown cucumber (Cucumis sativus L.) hypocotyls were used to study defense reactions occurring upon fungal infection and induced by elicitors in the same tissue. The segments were rendered resistant to infection by Colletotrichum lagenarium either by growing the seedlings in the presence of dichloroisonicotinic acid (DCIA) or by preincubation of the cut segments with DCIA, salicylic acid (SA), or 5-chlorosalicylic acid (5CSA).

Pretreatment of Parsley (Petroselinum crispum L.) Suspension Cultures with Methyl Jasmonate Enhances Elicitation of Activated Oxygen Species.

Suspension-cultured cells of parsley (Petroselinum crispum L.) were used to demonstrate an influence of jasmonic acid methyl ester (JAME) on the elicitation of activated oxygen species. Preincubation of the cell cultures for 1 d with JAME greatly enhanced the subsequent induction by an elicitor preparation from cell walls of Phytophtora megasperma f.

Conditioning of Parsley (Petroselinum crispum L.) Suspension Cells Increases Elicitor-Induced Incorporation of Cell Wall Phenolics.

The elicitor-induced incorporation of phenylpropanoid derivatives into the cell wall and the secretion of soluble coumarin derivatives (phytoalexins) by parsley (Petroselinum crispum L.) suspension cultures can be potentiated by pretreatment of the cultures with 2,6-dichloroisonicotinic acid or derivatives of salicylic acid. To investigate this phenomenon further, the cell walls and an extracellular soluble polymer were isolated from control cells or cells treated with an elicitor from Phytophthora megasperma f.

Methyl jasmonate conditions parsley suspension cells for increased elicitation of phenylpropanoid defense responses.

Pre-incubation of suspension-cultured parsley cells with methyl jasmonate greatly enhances their ability to respond to fungal elicitors by secretion of coumarin derivatives. The effect is most pronounced at relatively low elicitor concentration and also observed for the incorporation of esterified hydroxycinnamic acids and of "lignin-like" polymers into the cell wall. These three responses correspond to defense reactions induced locally when a fungal pathogen attacks plant cells.

Biosynthesis of ferulic acid esters of plant cell wall polysaccharides in endomembranes from parsley cells.

A microsomal preparation from suspension-cultured parsley cells is able to transfer ferulic acid from the respective CoA thioester to endogenous acceptors. The reaction is not enhanced by digitonin but stimulated by Mg2+, Ca2+ and Co2+. Spermine can partly replace divalent ions.

The protein kinase inhibitor, K-252a, decreases elicitor-induced Ca2+ uptake and K+ release, and increases coumarin synthesis in parsley cells.

An elicitor preparation from fungal cell walls known to induce coumarin synthesis in suspension-cultured parsley cells also elicits a rapid and transient Ca2+ uptake, K+ release and external alkalinization, and increases uptake of 45Ca2+ into the cells. The latter three responses were inhibited by the protein kinase inhibitor K-252a at 0.2 microM.

Partial purification and immunological characterization of 1,3-β-glucan synthase from suspension cells of Glycine max.

The plasma-membrane-localized 1,3-β-glucan synthase (EC 2.4.1.

The degrees of polymerization and N-acetylation of chitosan determine its ability to elicit callose formation in suspension cells and protoplasts of Catharanthus roseus.

Partially and fully deacetylated chitosan fragments and oligomers were compared for their potency to elicit formation of the 1.3-β-glucan callose in suspension-cultured cells and protoplasts of Catharanthus roseus (line 385). Chitosan oligomers induced little callose formation, while callose synthesis increased with the degree of polymerization of chitosan up to several thousand corresponding to a molecular mass near 10(6) Da.

Chitosan-elicited synthesis of callose and of coumarin derivatives in parsley cell suspension cultures.

In suspension cultured cells of parsley (Petroselinum crispum), chitosan elicited a rapid deposition of the 1,3-ß-glucan callose on the cell wall and a slower formation of coumarins. With cells remaining in conditioned growth medium, fully N-deacetylated chitosans and partially N-acetylated chitosans were about equally active, the potency increased with the degree of polymerization up to several thousand and addition of reduced glutathione increased the sensitivity of the cells. These results indicate common initial events in the induction of callose and coumarin synthesis although two fully independent metabolic pathways are involved.

Binding of the phytotoxin zinniol stimulates the entry of calcium into plant protoplasts.

Zinniol [1,2-bis(hydroxymethyl)-3-methoxy-4-methyl-5-(3-methyl-2-butenyloxy)benzene], a toxin produced by fungi of the Alternaria group, causes symptoms in plants that resemble those induced by the fungi. The phytotoxin binds to carrot protoplasts and isolated membranes in a saturable and reversible manner. Receptor occupancy stimulates entry of calcium into protoplasts.

Induced net Ca(2+) uptake and callose biosynthesis in suspension-cultured plant cells.

In suspension-cultured cells of Glycine max and Catharanthus roseus, marked callose synthesis can be induced by digitonin and chitosan. Leakage of a limited pool of electrolytes precedes callose formation, K(+) representing the major cation lost. Poly-L-ornithine, as well as the ionophores A 23187 and ionomycin, also induces some callose synthesis but to a lesser extent.

Calcium ions and polyamines activate the plasma membrane-located 1,3-β-glucan synthase.

Sucrose-density-gradient centrifugation and partitioning in a polyethylene glycol/dextran two-phase system were used to isolate plasmamembrane vesicles from microsomal preparations of soybean cell suspension cultures. Both methods resulted in the enrichment of the activity of a 1,3-β-glucan synthase which forms a polymer consisting of more than 99% of 1,3-linked glucose (callose). Digitonin increases the 1,3-β-glucan synthase activity in the various membrane fractions to a different degree, supporting the suggestion that this enzyme is vectorially arranged in the plasma membrane.

Influence of Free Fatty Acids, Lysophosphatidylcholine, Platelet-Activating Factor, Acylcarnitine, and Echinocandin B on 1,3-beta-d-Glucan Synthase and Callose Synthesis.

The activity of 1,3-beta-d-glucan synthase assayed in the presence of digitonin in a microsomal preparation from suspension-cultured cells of Glycine max can be fully inhibited by unsaturated fatty acids, trienoic acids being most effective. Lysophosphatidylcholine, platelet-activating factor, acylcarnitine, and Echinocandin B can also fully inhibit the enzyme. Inhibition is observed both when the enzyme is activated by Ca(2+) or by trypsinization.

Chitosan-elicited callose synthesis in soybean cells as a ca-dependent process.

A new method for the rapid and quantitative fluorometric determination of callose is described. In suspension-cultured cells of Glycine max, synthesis of callose starts within 20 minutes of treatment with chitosan and parallels over hours the accumulation of 1,3-linked glucose in the wall. Poly-l-lysine also elicits callose synthesis.

Callose biosynthesis as a Ca2+-regulated process and possible relations to the induction of other metabolic changes.

Chitosan and poly-L-lysine induce electrolyte leakage in suspension-cultured soy bean cells due to their polycationic nature. Similar effects are caused by Polymyxin B at certain concentrations. After any of these treatments electrolyte leakage is followed by a rapid onset of callose synthesis, as studied quantitatively by its fluorescence with Aniline Blue.

Adhesion of Colletotrichum lindemuthianum Spores to Phaseolus vulgaris Hypocotyls and to Polystyrene.

Adhesion of Colletotrichum lindemuthianum spores to Phaseolus vulgaris hypocotyls and to polystyrene was inhibited by the respiratory inhibitors sodium azide and antimycin A, indicating a requirement for metabolic activity in adhesion. Various commercial proteins and Tween 80 also reduced adhesion to both surfaces. Binding was enhanced by the presence of salts: sodium, potassium, calcium, and magnesium chlorides were equally effective.