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Pathogen, salicylic acid and developmental dependent expression of a beta-1,3-glucanase/GUS gene fusion in transgenic tobacco plants.

The 5' flanking region of a gene encoding an acidic beta-1,3-glucanase from Nicotiana tabacum was isolated and characterized. A chimeric gene composed of 1759 bp of the promoter sequence from the PR-2 gene was fused to the beta-glucuronidase (GUS) coding region and used to transform tobacco. Transcriptional activation of the PR-2 promoter was investigated in response to inoculation with tobacco mosaic virus (TMV), after treatment of leaves with salicylic acid (SA), and in specific tissues during the normal development of healthy plants. In TMV-inoculated transgenic plants, GUS activity was induced locally around necrotic viral lesions and systemically in uninoculated leaves. GUS activity was also induced by treatment of leaves with SA. The chimeric gene was expressed in floral organs of healthy plants and in newly germinated seedlings. Analyses of a series of 5' deletions of the glucanase promoter indicated that the cis-acting elements necessary for induction by all these signals are localized in the region between -321 bp and -607 bp upstream of the transcription start site.

Amino Acid Sequence↗

Induction of pilocarpine formation in jaborandi leaves by salicylic acid and methyljasmonate.

Jaborandi seedlings were subjected to different treatments in order to study the induction of pilocarpine in the leaves. In addition four extraction methods were assessed to extract the alkaloid from dried leaves. The highest yielding extraction and recovery was observed when dried leaves were first treated with base and then extracted with chloroform. Salt stress (NaCl), wounding, hypoxia, and N and K omission of the nutrient soln caused reductions in pilocarpine contents. Whereas complete nutrient soln and P omission maintained normal levels of the alkaloid. Salicylic acid and methyljasmonate induced a 4-fold increase of pilocarpine, but this increase was dependent on the concentration and time after exposure.

Acetates↗

Salicylic acid is not a bacterial siderophore: a theoretical study.

Using a newly available program for calculating the concentrations and speciation of various ions (Pettit, LD & Powell KJ, 'SolEq' Academic Software, 1999), we have calculated that at pH 7 the amount of free Fe(III) present in an aqueous solution is 1.4 x 10(-9) M and not 10(-18) M as is usually quoted. In the presence of salicylic acid, included in the calculations at 10(-4) M, the solubility of Fe(III) is increased to only 9.8 x 10(-9) M suggesting that salicylate is unable to act as a siderophore although it is produced as an extracellular product by several bacterial genera when grown iron deficiently. In the presence of 40 mM phosphate, the soluble Fe(III) concentration is decreased by 10(4) at pH 7 and again this is hardly affected by the presence of salicylate. Thus, for microorganisms grown either in vitro or in vivo, salicylate is unlikely to function as a iron solubilizing agent. The same conclusions may also apply to 2,3-dihydroxybenzoic acid.

Hydrogen-Ion Concentration↗

The rapid induction of glutathione S-transferases AtGSTF2 and AtGSTF6 by avirulent Pseudomonas syringae is the result of combined salicylic acid and ethylene signaling.

The expression of two members of the glutathione S-transferase (GST) multigene family was studied in Arabidopsis plants inoculated with an avirulent strain of Pseudomonas syringae pv. tomato (Pst). Accumulation of AtGSTF2 and AtGSTF6 transcripts started 4 and 2 h after inoculation, respectively, and clearly preceded the induction of the pathogenesis-related PR-1 gene. The aim of this work was to find the reason for the faster induction of the two GSTs compared with classical salicylic acid (SA)-regulated PR-proteins. Expression studies in Pst-inoculated SA-signaling mutants NahG and npr1 revealed that induction of both GSTs was SA-dependent and partially NPR1-independent. The induction of AtGSTF2 by Pst was also strongly repressed in the ethylene insensitive etr1 mutant. Both GSTs were induced by low amounts of SA (0.1 mM) and ethylene (0.1 ppm) while PR-1 gene expression was unaffected by ethylene. Interestingly, ethylene was about 50-fold less effective in NahG compared with wild-type plants thus suggesting a potentiation effect of SA on ethylene-induced accumulation of AtGST transcripts. Increased AtGST expression in plants inoculated with Pst correlated with increased production of SA and ethylene. However, the initial phase of AtGSTF6 induction was independent of SA- and ethylene-signaling. The jasmonate (JA)-insensitive mutant jar1 showed normal induction kinetics for both GSTs. Our data support the hypothesis that full expression of the pathogen-induced AtGSTF2 and, to a lesser extent AtGSTF6, is the result of combined SA- and ethylene-signaling and that early AtGSTF6 expression depends on additional unknown signaling mechanisms.

Arabidopsis↗

Salicylic acid, ethephon, and methyl jasmonate enhance ester regeneration in 1-MCP-treated apple fruit after long-term cold storage.

Volatile esters, primarily synthesized in peel tissues, are major aromatic components of apple fruits [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.]. The use of cold storage combined with 1-methylcyclopropene (1-MCP) treatment prolongs the life of apples but represses the regeneration of esters during poststorage ripening. In this study, the regeneration of total esters was significantly increased in apple fruits treated with salicylic acid (SA) and Ethephon (ETH) that had been treated once or twice with 1-MCP. However, methyl jasmonate (MeJA) treatment resulted in regeneration of total esters after a single 1-MCP treatment. To determine the mechanism by which SA, ETH, and MeJA regulate ester regeneration, the apple alcohol acyltransferase gene (MdAAT2) was investigated at the mRNA, protein, and enzyme activity levels. Genes associated with ethylene perception were also investigated by RT-PCR. The results suggest that MdAAT2 controls ester regeneration and that MdETR1 plays a key role in ethylene perception and regulation of downstream MdAAT2 gene expression during poststorage. Ester compounds and concentrations differed in peels treated with different signal molecules, indicating that regulation of the pathway upstream of straight-chain ester biosynthesis depended on the regulation of lipoxygenase (LOX) and alcohol dehydrogenase (ADH) activity by SA, ETH, and MeJA during poststorage ripening.

Acetates↗

Salicylic acid and a chitin elicitor both control expression of the CAD1 gene involved in the plant immunity of Arabidopsis.

The Arabidopsis mutant cad1 (constitutively activated cell death 1) shows a phenotype that mimics hypersensitive response (HR)-like cell death. The CAD1 gene, which encodes a protein containing a domain with significant homology to the MACPF (membrane attach complex and perforin) domain of complement components and perforin, is likely to control plant immunity negatively and has a W-box cis-element in its promoter region. We found that expression of the CAD1 gene and other W-box containing genes, such as NPR1 and PR2, was promoted by salicylic acid (SA) and benzothiadiazole (BTH) as a SA agonist. The CAD1 gene was also stimulated by a purified chitin oligosaccharide elicitor (degree of polymerization = 8). This latter control was not under SA, because CAD1 expression was not suppressed in 35SnahG transgenic plants, which are unable to accumulate SA. These expression profiles were confirmed by promoter analysis using pCAD1::GUS transgenic plants. The CAD1 expression promoted by BTH and the chitin elicitor was not suppressed in the npr1 mutant, which is insensitive to SA signaling. These results indicate that the CAD1 gene is regulated by two distinct pathways involving SA and a chitin elicitor: viz., SA signaling mediated through an NPR1-independent pathway, and chitin elicitor signaling, through an SA-independent pathway. Three CAD1 homologs that have multiple W-box elements in their promoters were also found to be under the control of SA.

Amino Acid Sequence↗

Pharmacokinetic investigations in adult humans after parenteral administration of the lysine salt of acetyl-salicylic acid.

The lysine salt of acetylsalicylic acid was administered intravenously to four volunteers and intramuscularly to three of them. The drug was tolerated without any observed side effects. Immediately after intravenous application most of the plasma salicylate was acetylsalicylic acid. The highest concentration of acetylsalicylic acid was found after 2 minutes, highest levels of salicylic acid after 60 minutes. Elimination of acetylsalicylic acid was relatively quick within the first period after intravenous administration according to a half-life of 8 minutes. Half-life of salicylic acid was determined to be 3 hours. Intramuscular application results in a constant blood level for a longer period. Bioavailability of acetylsalicylic acid was slightly lower after intramuscular application than after intravenous administration.

Aspirin↗

RCY1, an Arabidopsis thaliana RPP8/HRT family resistance gene, conferring resistance to cucumber mosaic virus requires salicylic acid, ethylene and a novel signal transduction mechanism.

The dominant locus, RCY1, in the Arabidopsis thaliana ecotype C24 confers resistance to the yellow strain of cucumber mosaic virus (CMV-Y). The RCY1 locus was mapped to a 150-kb region on chromosome 5. Sequence comparison of this region from C24 and a CMV-Y-susceptible C24 mutant predicts that the RCY1 gene encodes a 104-kDa CC-NBS-LRR-type protein. The RCY1 gene from C24, when expressed in the susceptible ecotype Wassilewskija (Ws), restricted the systemic spread of virus. RCY1 is allelic to the resistance genes RPP8 from the ecotype Landsberg erecta and HRT from the ecotype Dijon-17, which confer resistance to Peronospora parasitica biotype Emco5 and turnip crinkle virus (TCV), respectively. Examination of RCY1 plants defective in salicylic acid (SA), jasmonic acid (JA) and ethylene signaling revealed a requirement for SA and ethylene signaling in mounting a resistance response to CMV-Y. The RCY1 nahG etr1 double mutants exhibited an intermediate level of susceptibility to CMV-Y, compared to the resistant ecotype C24 and the susceptible ecotypes Columbia and Nossen. This suggests that in addition to SA and ethylene, a novel signaling mechanism is associated with the induction of resistance in CMV-Y-infected C24 plants. Moreover, our results suggest that the signaling pathways downstream of the RPP8, HRT, and RCY1 have evolved independently.

Amino Acid Sequence↗

Expression of a beta-glucosidase gene results in increased accumulation of salicylic acid in transgenic Nicotiana tabacum cv. Xanthi-nc NN genotype.

A beta-glucosidase gene (bglA) from Butyrivibrio fibrisolvens H17c was cloned into the binary vector pGA482 under the control of the 35S Cauliflower Mosaic Virus (CaMV) promoter. A second construct was generated for accumulation of the bglA gene product in the vacuole of transformed tobacco plants. Reverse transcription-polymerase chain reaction analysis demonstrated that the bglA gene was expressed in 71% of cytosol-targeted and 67% of vacuole-targeted transgenic tobacco T(1) plants. T(1) transgenic plants (pGLU100 and pGLU200) exhibited elevated levels of free salicylic acid (SA) with a concomitant significant decrease in the level of glucosylsalicylic acid (GSA) compared to the untransformed tobacco plants and tobacco plants transformed with the empty vector (pGA482). Following inoculation with Tobacco Mosaic Virus (TMV), lesion area was 51% smaller in pGLU100 plants and 60% smaller in pGLU200 plants compared to inoculated untransformed and negative control plants.

Gene Expression↗

The promoter of an antifungal protein gene from Gastrodia elata confers tissue -specific and fungus-inducible expression patterns and responds to both salicylic acid and jasmonic acid.

Gastrodia antifungal proteins (GAFPs) are a group of mannose-binding lectins purified from Gastrodia elata that show strong resistance against a wide spectrum of fungi. The GAFP-2 promoter was analyzed for its ability to control the expression of the reporter gene, beta-glucuronidase (GUS) in transgenic tobacco plants. The GUS assays revealed that the GAFP-2 promoter is expressed in a tissue-specific manner, which mainly expressed in the vascular cells. The highest GUS activity was observed in roots, followed by stems. GAFP-2-GUS expression was strongly induced by the fungus Trichoderma viride and by the plant stress regulators, salicylic acid and jasmonic acid in the stably transformed tobacco plants. The -537 region of the GAFP-2 promoter was sufficient for its tissue-specific and inducible expression of the promoter.

Cyclopentanes↗

Salicylic acid inhibition of the irreversible effect of acetylsalicyclic aicd on prostaglandin synthetase may be due to competition for the enzyme cationic binding site.

Salicylic acid (SA), a weak inhibitor of the prostaglandin endoperoxide synthetase or fatty acid cyclooxygenase enzyme, is known to prevent irreversible enzyme inhibition by acetylsalicylic acid (ASA). The interaction of arachidonic acid with ferrous sulfate was used as a model to study the reaction of the fatty acid with the postulated enzymic cationic binding site on Fe2+-heme. SA was as potent as ASA in inhibiting the cooxygenation of arachidonic acid and ferrous sulfate. The results suggests that SA could complete effectively for the enzyme cationic site with ASA. Thus SA may block ASA acetylation of the cyclooxygenase by preventing ASA from binding to this site.

Arachidonic Acids↗

Harpin induces disease resistance in Arabidopsis through the systemic acquired resistance pathway mediated by salicylic acid and the NIM1 gene.

Harpin, the product of the hrpN gene of Erwinia amylovora, elicits the hypersensitive response and disease resistance in many plants. Harpin and known inducers of systemic acquired resistance (SAR) were tested on five genotypes of Arabidopsis thaliana to assess the role of SAR in harpin-induced resistance. In wild-type plants, harpin elicited systemic resistance to Peronospora parasitica and Pseudomonas syringae pv. tomato, accompanied by induction of the SAR genes PR-1 and PR-2. However, in experiments with transgenic Arabidopsis plants containing the nahG gene which prevents accumulation of salicylic acid (SA), harpin neither elicited resistance nor activated SAR gene expression. Harpin also failed to activate SAR when applied to nim1 (non-inducible immunity) mutants, which are defective in responding to SA and regulation of SAR. In contrast, mutants compromised in responsiveness to methyl jasmonate and ethylene developed the same resistance as did wild-type plants. Thus, harpin elicits disease resistance through the NIM1-mediated SAR signal transduction pathway in an SA-dependent fashion. The site of action of harpin in the SAR regulatory pathway is upstream of SA.

Acetates↗

Binding of tolmetin and salicylic acid to human serum albumin as a function of temperature.

When drug-protein binding data are evaluated thermodynamically standard free energy (delta G0), standard enthalpy (delta H0) and standard entropy (delta S0) are usually estimated from association constants (Ka) derived from binding data obtained at only two temperatures. Estimation of delta H0 involves the assumption of its constancy in the temperature range studied and linearity of a van't Hoff plot of ln Ka versus 1/T. Sometimes the assumption of such linearity is invalid for theoretical reasons and data obtained at only two temperatures contain no information concerning linearity of this plot. We present data for the binding of both tolmetin and salicylic acid to human serum albumin as a function of temperature which make doubtful the validity of using association constants of these drugs to derive thermodynamic constants other than delta G0 values.

Binding Sites↗

Salicylic Acid Is Needed in Hypersensitive Cell Death in Soybean but Does Not Act as a Catalase Inhibitor.

The function of salicylic acid (SA) in hypersensitive cell death was studied in a soybean (Glycine max)-Pseudomonas syringae pv glycinea system. The infection of cell cultures with bacteria leads to a hypersensitive reaction (HR), which is dependent on an appropriate avirulence gene and on low concentrations of SA. The requirement for SA is essential for a process shortly before the onset of the HR-caused cell death 5 to 6 h after infection with bacteria. SA given 10 to 12 h after infection or preincubation cannot rescue the completion of the cell death program. SA does not inhibit catalase or ascorbate peroxidase in soybean. In addition, the in vivo capacity of the cell culture for the rapid metabolism of H2O2 is not altered by SA. This clearly shows that SA is needed for the HR-caused cell death for a reaction downstream of the oxidative burst. Lipid peroxides accumulate during the HR, but the loss of membrane control precedes the generation of lipid peroxides. The accumulation of lipid peroxides in the HR can be prevented by lipid antioxidants. Nevertheless, cell death kinetics remain unaltered in the presence of antioxidants. It is concluded that lipid peroxides are a consequence of cell death, but not the primary cause of it.

Journal Article↗

The biosynthesis of salicylic acid in potato plants

Spraying potato (Solanum tuberosum L.) leaves with arachidonic acid (AA) at 1500 &mgr;g mL-1 led to a rapid local synthesis of salicylic acid (SA) and accumulation of a SA conjugate, which was shown to be 2-O-beta-glucopyranosylsalicylic acid. Radiolabeling studies with untreated leaves showed that SA was synthesized from phenylalanine and that both cinnamic and benzoic acid were intermediates in the biosynthesis pathway. Using radiolabeled phenylalanine as a precursor, the specific activity of SA was found to be lower when leaves were treated with AA than in control leaves. Similar results were obtained when leaves were fed with the labeled putative intermediates cinnamic acid and benzoic acid. Application of 2-aminoindan-2-phosphonic acid at 40 &mgr;M, an inhibitor of phenylalanine ammonia-lyase, prior to treatment with AA inhibited the local accumulation of SA. When the putative intermediates were applied to leaves in the presence of 2-aminoindan-2-phosphonic acid, about 40% of the expected accumulation of free SA was recovered, but the amount of the conjugate remained constant.

Journal Article↗

Effect of polymer coating on faecal recovery of ingested 5-amino salicylic acid in patients with ulcerative colitis.

It has been suggested that polymer coating might retard jejunal absorption of 5-amino salicylic acid (5-ASA) and thus promote delivery to its colonic site of action. Twenty three patients with active (nine), or quiescent (14) ulcerative colitis were given either uncoated or coated 5-ASA (Asacol) 400 mg qds for one to three weeks, after which they ingested five 1.5 ml dialysis membrane sachets which were recovered from the stool in the next 72 hours. After one week of treatment the concentration of 5-ASA in the faecal dialysate, urine, and fasting plasma in those receiving the coated and uncoated preparations were respectively: 25.4 +/- 5.1 compared with 1.2 +/- 0.4 mmol/l (p less than 0.001); 0.34 +/- 0.21 compared with 0.70 +/- 0.29 mmol/24h (NS) and 11.1 +/- 4.2 compared with 0.07 +/- 0.03 mumol/l (p less than 0.02). Faecal excretion of the drug appeared to be greater in patients with active colitis than in those with quiescent disease. Thus coating with pH dependent methacrylic acid copolymer B is a very effective method of promoting delivery of 5-ASA to the colon, stool dialysate concentrations being 20 fold more than those in controls. Increased trough plasma concentrations in the polymer coating group probably reflect delayed intestinal absorption but no evidence of plasma accumulation after 21 days of therapy was found.

Acrylic Resins↗

Modulation of adhesion molecules and monocyte chemoattractant protein by tumor necrosis factor-alpha and salicylic acid in primary human coronary artery endothelial cells.

Kawasaki disease (KD) is an illness characterized by vascular inflammation of coronary arteries leading to coronary aneurysms and thromboses. Infiltration of immune cells into the intima and adventitia are observed in autopsy tissues of patients with KD. Using semi-quantitative RT-PCR and cell-based ELISA, we demonstrated that tumor necrosis factor-a induced the expression of intercellular adhesion molecules-1 and E-selectin, as well as monocyte chemoattractant protein-1, in a time- and dose-dependent manner in primary human coronary artery endothelial cell cultures. This increase was inhibited by salicylic acid (NaSal), and involved the transcription factor NF-kappaB. Based on these data, we suggest a pathogenetic mechanism for KD, whereby immune cells are attracted to sites of inflammation, undergo extravasation, release enzymes that assist in vascular remodeling, thereby weakening the endothelium and hastening the process of aneurysm formation. NaSal, in addition to preventing thrombosis and lowering fever in KD, may also function in down-regulating adhesion molecules during the inflammatory stage of KD.

Cell Adhesion Molecules↗

Activity of nitric oxide is dependent on, but is partially required for function of, salicylic acid in the signaling pathway in tobacco systemic acquired resistance.

When tobacco plants were treated by injection with nitric oxide (NO)-releasing compounds, the sizes of lesions caused by Tobacco mosaic virus (TMV) on the treated leaves and on upper nontreated leaves were significantly reduced. The reduction in TMV lesion size was caused by NO released from the NO-releasing compounds; the byproduct formed after release of NO from the NO-releasing compound NOC-18, diethylenetriamine, did not itself alter lesion size. Treatment of tobacco plants with inhibitors of nitric oxide synthase or an NO scavenger attenuated but did not abolish the systemic acquired resistance (SAR) induced by salicylic acid (SA). In NahG transgenic tobacco plants, NO had no effect on lesion size following TMV infection. These results are consistent with the hypothesis that NO plays an important role in SAR induction in tobacco and that NO is required for the full function of SA as an SAR inducer. The activity of NO is fully dependent on the function of SA in the SAR signaling pathway in tobacco.

Immunity, Innate↗