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Hypersensitive Reaction (hypersensitive + reaction)

Distribution by Scientific Domains

Life Sciences	68%
Medical Sciences	25%

Selected Abstracts

Cloning, Expression and Characterization of Protein Elicitors from the Soyabean Pathogenic Fungus Phytophthora sojae

JOURNAL OF PHYTOPATHOLOGY, Issue 3 2000
J. Becker
The oomycete Phytophthora sojae is a severe pathogen of soybean. Several resistance genes against races of P. sojae exist in soybean but the nature of corresponding avirulence genes is unknown. Clones encoding four different isoforms of a protein elicitor from P. sojae (sojein 1,4) belonging to the class of acidic ,-elicitins have been isolated. These 98 amino acid proteins show high homology to elicitins from other Phytophthora species. The different sojein isoforms were expressed in Escherichia coli as His-tagged fusion proteins. Purified sojein as well as recombinant sojein isoforms induce hypersensitive reaction (HR)-like lesions in tobacco but are not active as race-specific elicitors in soybean. However all sojein isoforms induce defence-related genes like those encoding phenylalanine ammonia lyase, glutathione-S-transferase and chalcone synthase in tobacco and soybean plants and cell cultures. It is concluded that sojeins contribute to the induction of defence responses but that they are not involved in race specific recognition of the P. sojae races by soybean plants. Zusammenfassung Klonierung, Expression und Charactier von Proteinelictoren aus dem Soyabohnenpathogen Phytophthora sojae Der Oomycet Phytophthora sojae ist ein ernstes Pathogen der Sojabohne. In der Sojabohne gibt es mehrere Resistenzgene gegen verschiedene Rassen von P. sojae, jedoch ist die Natur der korrespondierenden Avirulenzgene unbekannt. Wir haben 4 verschiedene Isoformen eines Protein-Elicitors aus P. sojae (Sojein 1,4) kloniert, die zur Klasse der sauren ,-Elicitine gehören. Sie kodieren für Proteine mit 98 Aminosäuren und zeigen hohe Homologie zu Elicitinen aus anderen Phytophthora Spezies. Aus genomischer DNA und aus revers-transkribierter mRNA wurden die gleichen 4 Isoformen erhalten. Die verschiedenen Sojeine wurden in Escherichia coli als His-markierte Fusionproteine exprimiert. Sowohl gereinigtes als auch rekombinantes Sojein induziert HR-ähnliche Läsionen in Tabak. In der Sojabohne sind sie allerdings nicht als rassenspezifische Elicitoren aktiv. Dagegen induzieren alle Sojein-Isoformen Abwehrgene wie die Phenylalanin Ammonium-Lyase, Glutathion-S-Transferase und Chalkonsynthase in Tabak-und Sojabohnenpflanzen und Zellkulturen. Die Sojeine tragen also zur Induktion von Abwehrreaktionen bei, sind aber nicht in die rassenspezifische Erkennung von P. sojae durch Sojabohnenpflanzen involviert. [source]

Resolution of orofacial granulomatosis with amalgam removal

JOURNAL OF THE EUROPEAN ACADEMY OF DERMATOLOGY & VENEREOLOGY, Issue 3 2003
E Guttman-Yassky
ABSTRACT A 61-year-old woman presented with a 2-year history of an abnormal erythematous swelling on the upper lip and cheek. Upon examination there were no other physical findings. Histological examination found discreet sarcoidal granulomas in the lower dermis. Routine laboratory studies, chest radiographs and pulmonary functions were all normal. Clinical presentation and histological findings were, therefore, compatible with the diagnosis of orofacial granulomatosis (OFG). The patient was patch tested with an extended standard series that included metal,salt, dental prosthesis, bakery and corticosteroids series. The patch test was positive (score ++) after 48 and 72 h for mercury in the metal,salt and dental prosthesis series. During the past decade the patient had received amalgam fillings of several dental cavities, including one adjacent to the swollen cheek. The unilateral localization of the soft tissue swelling adjacent to the amalgam tooth fillings, along with the positive patch test for mercury, raised the possibility that the OFG was part of a delayed hypersensitive reaction to the fillings. The patient therefore underwent a total amalgam replacement procedure; complete disappearance of the swelling overlying the right cheek was observed within 7 weeks and the swelling of the upper lip subsided completely within 6 months. We propose that mercury in amalgam tooth fillings is another cause of OFG and suggest appropriate patch testing in patients who do not have an apparent cause of OFG. [source]

Type III-dependent translocation of the Xanthomonas AvrBs3 protein into the plant cell

MOLECULAR MICROBIOLOGY, Issue 1 2002
Boris Szurek
Summary Many plant pathogenic bacteria utilize a conserved type III secretion system (TTSS) to deliver effector proteins into the host tissue. Indirect evidence has suggested that at least some effector proteins are translocated from the bacterial cytoplasm into the plant cell. Using an immunocytochemical approach, we demonstrate that the type III effector AvrBs3 from Xanthomonas campestris pv. vesicatoria localizes to nuclei of infected pepper leaves. Importantly, AvrBs3 translocation was observed in situ in native tissues of susceptible and resistant plants. AvrBs3 was detected in the nucleus as soon as 4 h post infection, which was dependent on a functional TTSS and the putative translocator HrpF. N-terminal AvrBs3 deletion derivatives are no longer secreted by the TTSS in vitro and could not be detected inside the host cells, suggesting that the N-terminus of AvrBs3 is important for secretion. Deletion of the nuclear localization signals in the AvrBs3 C-terminus, which are required for the AvrBs3-mediated induction of the hypersensitive reaction in resistant pepper plants, abolished AvrBs3 localization to the nucleus. This is the first report on direct evidence for translocation of a native type III effector protein from a plant pathogenic bacterium into the host cell. [source]

From bacterial avirulence genes to effector functions via the hrp delivery system: an overview of 25 years of progress in our understanding of plant innate immunity

MOLECULAR PLANT PATHOLOGY, Issue 6 2009
JOHN W. MANSFIELD
SUMMARY Cloning the first avirulence (avr) gene has led not only to a deeper understanding of gene-for-gene interactions in plant disease, but also to fundamental insights into the suppression of basal defences against microbial attack. This article (focusing on Pseudomonas syringae) charts the development of ideas and research progress over the 25 years following the breakthrough achieved by Staskawicz and coworkers. Advances in gene cloning technology underpinned the identification of both avr and hrp genes, the latter being required for the activation of the defensive hypersensitive reaction (HR) and pathogenicity. The delivery of Avr proteins through the type III secretion machinery encoded by hrp gene clusters was demonstrated, and the activity of the proteins inside plant cells as elicitors of the HR was confirmed. Key roles for avr genes in pathogenic fitness have now been established. The rebranding of Avr proteins as effectors, proteins that suppress the HR and cell wall-based defences, has led to the ongoing search for their targets, and is generating new insights into the co-ordination of plant resistance against diverse microbes. Bioinformatics-led analysis of effector gene distribution in genomes has provided a remarkable view of the interchange of effectors and also their functional domains, as the arms race of attack and defence drives the evolution of microbial pathogenicity. The application of our accrued knowledge for the development of disease control strategies is considered. [source]

Histopathology and PR-protein markers provide insight into adult plant resistance to stripe rust of wheat

MOLECULAR PLANT PATHOLOGY, Issue 2 2008
JENNIFER MOLDENHAUER
SUMMARY Stripe rust, caused by Puccinia striiformis f. sp. tritici, is a serious disease of wheat. The spring wheat cultivar Kariega expresses complete adult plant resistance to stripe rust, whereas Avocet S is susceptible. In former studies, quantitative trait loci (QTL) analysis of doubled haploid lines derived from a Kariega × Avocet S cross revealed two major QTL (QYr.sgi-7D and QYr.sgi-2B.1) and two minor QTL (QYr.sgi-1A and QYr.sgi-4A.1) responsible for the adult resistance of Kariega in the field. Avocet S contains none of these QTL. In the present study, stripe rust development was compared, by means of fluorescence and confocal laser scanning microscopy, in flag leaves of Kariega, Avocet S and six doubled haploid (DH) lines, containing all four, none or one QTL. Depending on the QTL present, the infection types of the DH lines ranged from resistant to fully susceptible. No differences in fungal growth were observed during the first 5 days post inoculation (dpi), whereas the mean length of the fungal colonies started to differ at 6 dpi. Interestingly, MP 51 carrying QYr.sgi-7D responded with lignification to the fungal growth without restricting it, whereas MP 35 containing QYr.sgi-2B.1 did not show lignified host tissue, but fungal growth was restricted. RT PCR experiments with sequences of pathogenesis-related (PR) proteins resulted in a slightly stronger induction of PR 1, 2 and 5, known markers for the hypersensitive reaction, and peroxidases in MP 51, whereas a second band for chitinases was detected in MP 35 only. [source]

cDNA-AFLP reveals genes differentially expressed during the hypersensitive response of cassava

MOLECULAR PLANT PATHOLOGY, Issue 2 2005
BENJAMIN P. KEMP
SUMMARY The tropical staple cassava is subject to several major diseases, such as cassava bacterial blight, caused by Xanthomonas axonopodis pv. manihotis. Disease-resistant genotypes afford the only practical solution, yet despite the global importance of this crop, little is known about its defence mechanisms. cDNA-AFLP was used to isolate cassava genes differentially expressed during the hypersensitive reaction (HR) of leaves in response to an incompatible Pseudomonas syringae pathovar. Seventy-eight transcript-derived fragments (TDFs) showing differential expression (c. 75% up-regulated, 25% down-regulated) were identified. Many encoded putative homologues of known defence-related genes involved in signalling (e.g. calcium transport and binding, ACC oxidases and a WRKY transcription factor), cell wall strengthening (e.g. cinnamoyl coenzyme A reductase and peroxidase), programmed cell death (e.g. proteases, 26S proteosome), antimicrobial activity (e.g. proteases and ,-1,3-glucanases) and the production of antimicrobial compounds (e.g. DAHP synthase and cytochrome P450s). Full-length cDNAs including a probable matrix metalloprotease and a WRKY transcription factor were isolated from six TDFs. RT-PCR or Northern blot analysis showed HR-induced TDFs were maximally expressed at 24 h, although some were produced by 6 h; some were induced, albeit more slowly, in response to wounding. This work begins to reveal potential defence-related genes of this understudied, major crop. [source]

The role of lipopolysaccharides in induction of plant defence responses

MOLECULAR PLANT PATHOLOGY, Issue 5 2003
Gitte Erbs
SUMMARY Lipopolysaccharides (LPS) are ubiquitous, indispensable components of the cell surface of Gram-negative bacteria that apparently have diverse roles in bacterial pathogenesis of plants. As an outer membrane component, LPS may contribute to the exclusion of plant-derived antimicrobial compounds promoting the ability of a bacterial plant pathogen to infect plants. In contrast, LPS can be recognized by plants to directly trigger some plant defence-related responses. LPS also sensitize plant tissue to respond more rapidly or to a greater extent to subsequently inoculated phytopathogenic bacteria. Sensitization is manifested by an accelerated synthesis of antimicrobial hydroxycinnamoyl-tyramine conjugates, in the expression patterns of genes coding for some pathogenesis-related (PR) proteins, and prevention of the hypersensitive reaction caused by avirulent bacteria. The description at the molecular level of the various effects of LPS on plants is a necessary step towards an understanding of the signal transduction mechanisms through which LPS triggers these responses. A definition of these signal transduction pathways should allow an assessment of the contribution that LPS signalling makes to plant disease resistance in both natural infections and biocontrol. [source]

Non-host resistance of barley is associated with a hydrogen peroxide burst at sites of attempted penetration by wheat powdery mildew fungus

MOLECULAR PLANT PATHOLOGY, Issue 4 2001
Ralph Hückelhoven
Summary In barley, non-host resistance against the wheat powdery mildew fungus (Blumeria graminis f.sp. tritici, Bgt) is associated with the formation of cell wall appositions and a hypersensitive reaction in which epidermal cells die rapidly in response to fungal attack. In the interaction of barley with the pathogenic barley powdery mildew fungus (Blumeria graminis f.sp. hordei, Bgh), these defence reactions are also associated with accumulation of H2O2. To elucidate the mechanism of non-host resistance, the accumulation of H2O2 in response to Bgt was studied in situ by histochemical staining with diaminobenzidine. H2O2 accumulation was found in cell wall appositions under appressoria from Bgt and in cells undergoing a hypersensitive reaction. A mutation (mlo5) at the barley Mlo locus, that confers broad spectrum resistance to Bgh, did not influence the barley defence phenotype to Bgt. Significantly, Bgt triggered cell death on mlo5 -barley while Bgh did not. [source]

Isolate specificity of quantitative trait loci for partial resistance of barley to Puccinia hordei confirmed in mapping populations and near-isogenic lines

NEW PHYTOLOGIST, Issue 3 2008
Thierry C. Marcel
Summary ,,Partial resistance is considered race-nonspecific and durable, consistent with the concept of ,horizontal' resistance. However, detailed observations of partial resistance to leaf rust (Puccinia hordei) in barley (Hordeum vulgare) revealed small cultivar × isolate interactions, suggesting a minor-gene-for-minor-gene interaction model, similar to so-called ,vertical' resistance. ,,Three consistent quantitative trait loci (QTLs), labelled Rphq2, Rphq3 and Rphq4, that were detected in the cross susceptible L94 × partially resistant Vada have been incorporated into the L94 background to obtain near-isogenic lines (NILs). Three isolates were used to map QTLs on seedlings of the L94 × Vada population and to evaluate the effect of each QTL on adult plants of the respective NILs under field conditions. ,,Rphq2 had a strong effect in seedlings but almost no effect in adult plants, while Rphq3 was effective in seedlings and in adult plants against all three isolates. However, Rphq4 was effective in seedlings and in adult plants against two isolates but ineffective in both development stages against the third, demonstrating a clear and reproducible isolate-specific effect. The resistance governed by the three QTLs was not associated with a hypersensitive reaction. ,,Those results confirm the minor-gene-for-minor-gene model suggesting specific interactions between QTLs for partial resistance and P. hordei isolates. [source]

Local early induced resistance of plants as the first line of defence against bacteria,

PEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 4 2003
Zoltán Klement
Abstract This paper is an overview of a non-specific local early induced resistance (EIR) mechanism, distinct from the incompatible-specific hypersensitive reaction (HR). We have shown that the local induced resistance (LIR) described earlier is not a single and uniform response to pathogen infection, because an early (EIR) and a late form can be distinguished. EIR operates from 3,6,h post-inoculation (hpi) until about 20,hpi, and is inhibited by a short heat-shock or the eukaryotic protein synthesis inhibitor, cycloheximide. In contrast, LIR, which corresponds to the induced resistance forms discovered earlier, requires more time (about 24,h) and intensive illumination to develop, and is effective for a longer period. EIR develops parallel with HR and is sometimes able to prevent it when the induction time of HR is longer than the time required for the development of EIR. It seems that EIR inhibits the metabolism of bacteria and the activity of hrp genes which otherwise are required for the induction of HR. In a compatible host,pathogen relationship the effect of EIR fails to take place. The rapid development of EIR is greatly influenced by temperature and the physiological state of the plant. EIR activates the accumulation of hydrogen peroxide at the bacterial attachment, expressing new peroxidase isoenzymes in the initiated plant tissue. It seems that this is a native general local defence mechanism which can localise foreign organisms even at the penetration site. © 2003 Society of Chemical Industry [source]

The relationship between changes in the cell wall, lipid peroxidation, proliferation, senescence and cell death

PHYSIOLOGIA PLANTARUM, Issue 1 2003
Gerhard Spiteller
Plants and mammals contain polyunsaturated fatty acids (PUFAs) in their membranes. PUFAs belong to the most oxygen sensitive molecules encountered in nature. It would seem that nature has selected this property of PUFAs for signalling purposes: PUFAs are stored in the surface of cells and organelles not in free form but conjugated to phospho- and galactolipids. Any change in membrane structure apparently activates membrane-bound phospholipases, which cleave the conjugates. The obtained free PUFAs are substrates for lipoxygenases (LOX). These transform PUFAs to lipidhydroperoxides (LOOHs). LOOHs are converted to a great variety of secondary products. These lipid-peroxidation (LPO) products and the resulting generated products thereof represent biological signals, which do not require a preceding activation of genes. They are produced as a non-specific response to a large variety of external or internal impacts, which therefore do not need interaction with specific receptors. When, due to an external impact, e.g. attack of a microorganism, or to a change in temperature, the amount of liberated free PUFAs exceeds a certain threshold, LOX commit suicide. Thus iron ions, located in the active centre of LOX, are liberated. Iron ions react with LOOHs in the close surroundings by generating alkoxy radicals (LO.). These induce a non-enzymatic LPO. A fraction of the LO. radicals generated from linoleic acid (LPO products derived from linoleic acid play a dominant role in signalling which was previously overlooked) is converted to 2,4-dienals which induce the programmed cell death (PCD) and the hypersensitive reaction (HR). While peroxyl radicals (LOO.) generated as intermediates in the course of an enzymatic LPO are transformed within the enzyme complex to corresponding anions (LOO,), and thus lose their reactivity, peroxyl radicals generated in non-enzymatic reactions are not deactivated. They not only react by abstraction of hydrogen atoms from activated X-H bonds of molecules in their close vicinity, but also by epoxidation of double bonds and oxidation of a variety of biological molecules, causing a dramatic change in molecular structure which finally leads to cell death. As long as reducing agents, like glutathione, or compounds with free phenolic groups are available, the amount of LOOHs is kept low. Cell death is induced in a defined way by apoptosis. But when the reducing agents have been consumed, PCD seems to switch to necrotic processes. Thus proliferation is induced by minor changes at the cell membrane, while slow changes at cell membranes are linked with apoptosis (e.g. response to attack of microorganisms or drought) and necrosis (severe wounding), depending only on the amount, but not on the type, of applied stimulus. [source]

Distribution and diversity of type III secretion system-like genes in saprophytic and phytopathogenic fluorescent pseudomonads

FEMS MICROBIOLOGY ECOLOGY, Issue 3 2004
Sylvie Mazurier
Abstract Type three secretion systems (TTSSs) are protein translocation mechanisms associated with bacterial pathogenicity in host plants, and hypersensitive reactions in non-host plants. Distribution and diversity of TTSS-like genes within a collection of saprophytic and phytopathogenic fluorescent pseudomonads were characterized. This collection included 16 strains belonging to 13 pathogenic species, and 87 strains belonging to five saprophytic species isolated from plant rhizosphere and soil. Presence of conserved hypersensitive reaction/pathogenicity (hrp) genes (hrc RST) was assessed both by PCR using primers designed to amplify the corresponding sequence and by dot-blot hybridization using a PCR-amplified hrc RST fragment as a probe. PCR allowed the detection of TTSS-like genes in 75% and 32% of the phytopathogenic and saprophytic strains, respectively, and dot-blot hybridization in 100% and 49% of the phytopathogenic and saprophytic strains, respectively. The restriction fragment length polymorphism (RFLP) of 26 amplified hrc RST fragments revealed a considerable diversity. Twenty-one distinct RFLP types were identified and one hrc RST fragment was sequenced per RFLP type. The obtained hrc RST sequences clustered into three groups. Two of these groups included both phytopathogenic and saprophytic strains. The diversity of 16S rRNA genes, commonly used as an evolution marker, was characterized using PCR-RFLP. Polymorphism of the 16S rRNA genes corresponded to that of hrc RST genes, suggesting that these genes have followed a similar evolution. However, the occurrence of few mismatches suggests that sometimes TTSS-like genes might have undergone horizontal genetic transfer. [source]

Zinc and copper plasma levels in Icelandic horses with Culicoides hypersensitivity

EQUINE VETERINARY JOURNAL, Issue 5 2001
G. STARK
Summary Zinc concentration has been shown to have a potent immunomodulatory capacity, particularly influencing T helper cell organisation and cytokine secretion. Culicoides hypersensitivity (CHS) in horses resembles the early and late phase of type I hypersensitive reactions in man, characterised by a shift from T helper cell subtype 1 to T helper cell subtype 2 cytokine profile. In this pilot study, zinc and copper levels were measured in the plasma of 48 CHS-affected and 56 healthy Icelandic horses age 4,25 years (mean , 11 years) kept on 7 farms. Affected horses were divided into 3 groups according to the severity of disease. Time of blood collection and feeding management was constant. No differences in zinc or copper plasma levels and plasma copper/zinc ratio were determined among CHS horses and controls by univariate analysis of variance. Therefore, the most significant influences on zinc and copper plasma levels were affected by the location of housing. However, Spearman correlation showed a negative coefficient between the plasma zinc concentration and the severity of CHS (r =,0.31). Due to a probability value of P = 0.002 the null hypothesis r = 0 is rejected, although only 9% of the total variation of plasma zinc is presently explained by its relationship to CHS. In contrast, the Spearman correlation coefficient between plasma copper levels and severity of CHS was not significant (r =,0.14; P = 0.16). The minor deviations in plasma zinc concentrations in association with the severity of CHS may be real or due to neurohumoral or cytokine-mediated mechanisms, but appear too minimal to be relevant. [source]

Distribution and diversity of type III secretion system-like genes in saprophytic and phytopathogenic fluorescent pseudomonads

Occupational exposure of Brazilian neonatal intensive care workers to latex antigens

ALLERGY, Issue 1 2004
R. A. M. Lopes
Background:, Frequent exposure to latex causes various reactions such as respiratory symptoms and anaphylactic shock. In these cases, proteins found in natural latex are responsible for the serious systemic antilatex-mediated immediate hypersensitive reactions. Methods:, Cross-sectional descriptive survey focusing on 96 Brazilian health care workers (HCW) in the neonatal intensive care unit at CAISM, State University of Campinas UNICAMP, Brazil. All subjects were interviewed, donated blood samples for the latex-specific immunoglobulin E measurement and underwent the skin prick test (SPT) with an antigen extracted from latex gloves. Results:, The prevalence of latex positive SPT was 8%. There were eight SPT positive and only one serologic test was in agreement with the SPT. Overall, there was evidence of an association between the latex SPT and reported eczema (P = 0.01); food allergy (P = 0.009) with pineapple (P = 0.01). Conclusions:, These results suggest that the identification of reactions of immediate hypersensitivity mediated by antilatex antibodies in HCW should be encouraged to prevent occupational exposure to latex products. [source]

Effects of a pseudoallergen-free diet on chronic spontaneous urticaria: a prospective trial

ALLERGY, Issue 1 2010
M. Magerl
Abstract Background:, Chronic spontaneous urticaria is a skin disorder that is difficult to manage and can last for years. ,Pseudoallergens' are substances that induce hypersensitive/intolerance reactions that are similar to true allergic reactions. They include food additives, vasoactive substances such as histamine, and some natural substances in fruits, vegetables and spices. Eliminating pseudoallergens from the diet can reduce symptom severity and improve patient quality of life. Aim:, To assess the effects of a pseudoallergen-free diet on disease activity and quality of life in patient's chronic spontaneous urticaria. Methods:, Study subjects had moderate or severe chronic spontaneous urticaria that had not responded adequately to treatment in primary care. For 3 weeks, subjects followed a pseudoallergen-free diet. They kept a clinical diary, which recorded their wheal and pruritus severity each day, to yield a clinical rating of chronic spontaneous urticaria severity (the UAS4 score). The subjects also completed the DLQI, a validated quality-of-life instrument. Use of antihistamines and glucocorticoids was minimized, recorded, and analysed. Subjects were classified into nine response categories, according to the changes in symptom severity (UAS4), quality of life (DLQI) and medication usage. Results:, From the 140 subjects, there were 20 (14%) strong responders and 19 (14%) partial responders. Additionally, there were nine (6%) subjects who made a substantial reduction in their medication without experiencing worse symptoms or quality of life. Conclusions:, Altogether the pseudoallergen-free diet is beneficial for one in three patients. The pseudoallergen-free diet is a safe, healthy and cost-free measure to identify patients with chronic spontaneous urticaria that will benefit from avoiding pseudoallergens. [source]