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Enhanced Resistance (enhanced + resistance)
Selected AbstractsEnhanced resistance against systemic Candida albicans infection in mice treated with C. albicans DNAFEMS IMMUNOLOGY & MEDICAL MICROBIOLOGY, Issue 2 2008Petya Dimitrova Abstract In this study, double-stranded Candida albicans DNA was administered in systemic C. albicans infection in at dose of 20 ,g per mouse at 4, 5 and 6 weeks of age. The level of IL-12 in serum was elevated as a result of yeast DNA treatment and correlated with lower mortality and decreased kidney and liver injury. Macrophage activation was demonstrated by an increase of nitric oxide (NO) and IL-12 production. These effects were Janus activation kinases (JAK)/signal transducer and activator of transcription (STAT) dependent as they were inhibited by selective JAK inhibitor tyrphostin AG-490. DNA influenced adaptive immune response through elevation of anti- Candida IgG antibody production in systemic C. albicans infection. Thus, C. albicans DNA augmented innate and adaptive immune responses against the pathogen. [source] Light-Enhanced Resistance to Magnaporthe grisea Infection in the Rice Sekiguchi Lesion MutantsJOURNAL OF PHYTOPATHOLOGY, Issue 4 2000S. Arase The rice sl mutant showed two types of responses to Magnaporthe grisea infection by light treatments. One was an sl -mutant-type response characterized by Sekiguchi lesion expression under light waves of 400,700 nm, and the other was a wild-type response characterized by blast and/or necrotic spot lesion expression in the dark or at wavelength between 290 and 330 nm. There was a large difference in the resistance to M. grisea infection between the mutant- and wild-type responses in the rice sl mutant. When the mutant-type response was induced in the rice sl mutant, the disease resistance was enhanced relative to that in the wild-type response. Enhanced resistance was demonstrated by two components: (a) the number of Sekiguchi lesions was reduced relative to that of blast or necrotic lesions; (b) sporulation of M. grisea was not induced in Sekiguchi lesions. The enhanced resistance was dependent on light of 400,700 nm. Zusammenfassung In Abhängigkeit von einer Bestrahlung mit Licht zeigte die sl -Mutante von Reis zwei Typen von Reaktionen auf Magnaporthe-grisea -Infektionen. Zum einen trat eine Reaktion vom sl-Mutantentyp auf, charakterisiert durch Expression von Sekiguchi-Läsionen bei Wellenlängen von 400 bi 700 nm. Zum anderen war eine Wildtypreak-tion festzustellen, bei der es zu Bräune und/oder Expression nekrotischer Flecken bei Dunkelheit oder bei Wellenlängen zwischen 290 und 330 nm kam. Hinsichtlich der Resistenz gegen die M.-grisea -Infektion bestand ein großer Unterschied zwischen den Mutanten- und den Wildtypreaktionen der sl -Mutante des Reis. Wurde die Reaktion vom Mutantentyp in der sl -Mutante induziert, so war die Krankheitsresistenz im Vergleich zur Wildtypreaktion erhöht. Die höhere Resistenz zeigte sich an zwei Komponenten: (a) die Zahl der Sekiguchi-Läsionen war kleiner als die der braunen bzw. nekrotischen Läsionen (b) in Sekiguchi-Läsionen wurde keine Sporulation von M. grisea induziert. Die erhöhte Resistenz war abhängig von Licht im Wellenlängenbereich 400 bis 700 nm. [source] Enhanced resistance to foliar fungal pathogens in carrot by application of elicitorsANNALS OF APPLIED BIOLOGY, Issue 1 2009J. Jayaraj Abstract Treatment of greenhouse-grown carrot plants with salicylic acid (SA) (100 ,m), chitosan (0.02%) and the nutrient-chelate product Alexin (1%) followed 10 h later by inoculation with the necrotrophic fungal pathogens Alternaria radicina and Botrytis cinerea significantly reduced disease development 10 days after inoculation (d.a.i.) compared with control plants sprayed with water. The most effective treatment was chitosan, followed by Alexin and SA. Additional sprays of elicitors resulted in significantly lower disease development 25 d.a.i. Treated plants had elevated transcript levels of pathogenesis-related protein 1 (PR1), chitinase, lipid transfer protein (LTP), chalcone synthase, nonexpressor of PR1 and pathogenesis-related protein 5 (PR5) genes compared with control plants when assayed 10,70 h after treatment. The activity of peroxidase, polyphenoloxidase, phenylalanine ammonia-lyase, chitinase, ,-1,3-glucanase and lipoxygenase was significantly increased in elicitor-treated plants compared with control plants 12,72 h after treatment. Microscopic examination of treated leaves revealed reduced fungal growth and colonisation, 48 h after treatment, accompanied by fewer lesions at 120 h, compared with the control. Protein extracts from elicitor-treated plants reduced spore germination and germ tube elongation of the pathogens in vitro by 30,45%. Elicitor-treated plants accumulated higher amounts of total phenolics, 6-methoxymellin and H2O2 compared with the control. Both chitosan and Alexin induced responses similar to that of SA, suggesting that these elicitors may activate the salicylate pathway, leading to induction of defence genes, enzymes, phytoalexin and phenolics, which collectively reduced fungal colonisation. [source] Treatment of neonatal mice with Flt3 ligand leads to changes in dendritic cell subpopulations associated with enhanced IL-12 and IFN-, productionEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 7 2004Sabine Vollstedt Abstract Treatment with the hematopoietic growth factor Flt3 ligand (FL) increases DC numbers in neonatal mice and enhances their resistance against intracellular pathogens. Flow cytometric analysis showed the presence of conventional DC (cDC) and plasmacytoid pre-DC (pDC) in neonatal spleens from untreated and FL-treated mice. CD8, and MHC class,II expression on cDC and pDC was higher on DC from FL-treated mice than on DC from control littermates. After FL treatment, two additional subpopulations of DC-lineage cells were found that were able to produce IL-12 and IFN-,. The IL-12 production of cDC from FL-treated animals was more than 50-fold increased and their ability to stimulate T,cell proliferation was also increased. We conclude that the enhanced resistance against intracellular pathogens was due to increased numbers of DC-lineage cells and their increased ability to produce the essential cytokines. [source] Induced resistance of Norway spruce, variation of phenolic compounds and their effects on fungal pathogensFOREST PATHOLOGY, Issue 2 2000P. C. Evensen Summary Three clones of Norway spruce (Picea abies) were studied for their response to mass-inoculation with the blue-stain fungus Ceratocystis polonica. The effect of different pretreatments (fungal inoculation and wounding) before mass-inoculation was investigated for their possible role in an acquired resistance reaction. Pretreated trees showed enhanced resistance to the subsequent mass-inoculation relative to control trees that received no pretreatment. Furthermore, the fungal colonization of inoculated trees was less than that of wounded trees. The phenolic content of the bark, analysed by RP-HPLC, was compared in trees receiving different treatments. Trees inoculated with C. polonica had higher average concentration of (+)-catechin, taxifolin and trans-resveratrol than wounded trees. Both inoculated and wounded trees had higher average concentrations of these compounds than control trees. The effect of the phenolic extract of Norway spruce bark on the growth of the root rot fungus Heterobasidion annosum and the blue-stain fungi C. polonica and Ophiostoma penicillatum were investigated in vitro. Heterobasidion annosum was not negatively affected, and the extracts had fungistatic effects on the blue-stain fungi. The growth of O. penicillatum was more inhibited than the growth of the more aggressive C. polonica. [source] The role and impact of affect in the process of resistance to persuasionHUMAN COMMUNICATION RESEARCH, Issue 2 2001M Pfau This investigation dealt with the role and impact of affect in the process of resistance. A total of 597 participants took part in the study in 4 phases spanning 6 weeks. Initial results indicated that the cognitive, affective-anger, and affective-happiness inoculation treatments all conferred resistance to persuasive attacks. Structural equation analyses were conducted on the cognitive, affective-anger, and affective-happiness experimental inoculation conditions in order to examine the process of resistance. The results across all 3 conditions revealed a direct path in which inoculation treatments directly induced resistance to persuasive attacks. However, indirect paths to resistance varied across the 3 experimental conditions. Cognitive inoculation treatments contributed to receiver threat and counterarguing output, which, in turn, enhanced resistance. Thus, the cognitive inoculation treatments triggered a process that is consistent with McGuire's theoretical explanation for resistance. By contrast, both affective-anger and affective-happiness inoculation treatments relied more heavily on elicited emotional responses. Finally, the results indicated that greater receiver involvement was positively associated with experienced anger and, therefore, indirectly contributed to resistance, whereas greater receiver self-efficacy tended to dampen resistance. [source] The response of Aeromonas hydrophila to oxidative stress induced by exposure to hydrogen peroxideJOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2000J.P.B. Landre Aeromonas hydrophila, an opportunist human pathogen of low virulence, was shown to display a high degree of sensitivity upon exposure to hydrogen peroxide. As with other species, Aer. hydrophila is able to develop the capacity to resist loss of viability induced by such oxidative stress. Development of stress resistance follows the archetypal profile where pre-exposure of a population to sub-lethal levels of H2O2 stimulates onset of tolerance to further exposure. Acquisition of tolerance critically requires nascent protein synthesis. Further analysis demonstrated population growth phase influences the degree of sensitivity of the organism. Late stationary phase cultures demonstrate a decreased sensitivity compared with younger populations. Significantly, it was also determined that stock culture age influenced the level of sensitivity of the derived experimental culture, where an increased stock culture age corresponded with enhanced resistance to H2O2. These data show that Aer. hydrophila population phenotype is influenced by the phenotype of the donor stock culture. [source] Functional genomic approach to identify novel genes involved in the regulation of oxidative stress resistance and animal lifespanAGING CELL, Issue 4 2007Yongsoon Kim Summary Genetic studies in many organisms suggest that an increased animal lifespan phenotype is often accompanied by enhanced resistance toward reactive oxygen species (ROS). In Caenorhabditis elegans, mutations in daf-2, which encode an insulin/insulin-like growth factor 1 receptor-like molecule, lead to an extended animal lifespan and increased resistance to ROS. We have optimized an assay to monitor ROS resistance in worms using the ROS-generating chemical paraquat. We have employed this assay to screen the RNAi library along chromosomes III and IV for genes that, when silenced, confer paraquat resistance. The positive RNAi clones were subsequently screened for a lifespan extension phenotype. Using this approach, we have identified 84 genes that, when inactivated by RNAi, lead to significant increases in animal lifespan. Among the 84 genes, 29 were found to act in a manner dependent on daf-16. DAF-16, a forkhead transcription factor, is known to integrate signals from multiple pathways, including the daf-2 pathway, to regulate animal lifespan. Most of the 84 genes have not been previously linked to aging, and potentially participate in important cellular processes such as signal transduction, cell,cell interaction, gene expression, protein degradation, and energy metabolism. Our screen has also identified a group of genes that potentially function in a nutrient-sensing pathway to regulate lifespan in C. elegans. Our study provides a novel approach to identify genes involved in the regulation of aging. [source] A role for glutamate in growth and invasion of primary brain tumorsJOURNAL OF NEUROCHEMISTRY, Issue 2 2008Harald Sontheimer Abstract The vast majority of primary brain tumors derive from glial cells and are collectively called gliomas. While, they share some genetic mutations with other cancers, they do present with a unique biology and have developed adaptations to meet specific biological needs. Notably, glioma growth is physically restricted by the skull, and, unless normal brain cells are destroyed, tumors cannot expand. To overcome this challenge, glioma cells release glutamate which causes excitotoxic death to surrounding neurons, thereby vacating room for tumor expansion. The released glutamate also explains peritumoral seizures which are a common symptom early in the disease. Glutamate release occurs via system Xc, a cystine,glutamate exchanger that releases glutamate in exchange for cystine being imported for the synthesis of the cellular antioxidant GSH. It protects tumor cells from endogenously produced reactive oxygen and nitrogen species but also endows tumors with an enhanced resistance to radiation- and chemotherapy. Pre-clinical data demonstrates that pharmacological inhibition of system Xc causes GSH depletion which slows tumor growth and curtails tumor invasion in vivo. An Food and Drug Administration approved drug candidate is currently being introduced into clinical trials for the treatment of malignant glioma. [source] Effect of a Photo-synthetic Inhibitor on Tryptamine Pathway-mediated Sekiguchi Lesion Formation in Lesion Mimic Mutant of Rice Infected with Magnaporthe griseaJOURNAL OF PHYTOPATHOLOGY, Issue 9 2008A. Imaoka Abstract A lesion-mimic mutant of rice (cv. Sekiguchi-asahi) showed enhanced resistance to Magnaporthe grisea infection, thereby inducing Sekiguchi lesion (sl) formation and tryptamine accumulation under light. Both Sekiguchi lesion formation and tryptamine accumulation in leaves infected with M. grisea were inhibited by pretreatment with the photosynthetic inhibitor, 3-(3, 4-Dichlorophenyl)-1,1-dimethylurea (DCMU), which suppressed the gene expression of tryptophan decarboxylase (TDC), monoamine oxidase activity, H2O2 generation and DNA fragmentation. Catalase activity was inhibited by M. grisea infection under light, but magnitude of the inhibition was reduced in leaves pretreated with DCMU. Furthermore, tryptophan accumulated in M. grisea- infected leaves under light but not in DCMU-pretreated ones. Interestingly, such DCMU inhibition was reduced in the presence of tryptophan. Our studies suggest that chloroplasts function as the inhibitor of anti-oxidant system such as catalase activity and the supplier of a precursor of tryptamine and tryptophan in the sl mutant infected with M. grisea. [source] Adaptive evolution of baker's yeast in a dough-like environment enhances freeze and salinity toleranceMICROBIAL BIOTECHNOLOGY, Issue 2 2010Jaime Aguilera Summary We used adaptive evolution to improve freeze tolerance of industrial baker's yeast. Our hypothesis was that adaptation to low temperature is accompanied by enhanced resistance of yeast to freezing. Based on this hypothesis, yeast was propagated in a flour-free liquid dough model system, which contained sorbitol and NaCl, by successive batch refreshments maintained constantly at 12°C over at least 200 generations. Relative to the parental population, the maximal growth rate (µmax) under the restrictive conditions, increased gradually over the time course of the experiment. This increase was accompanied by enhanced freeze tolerance. However, these changes were not the consequence of genetic adaptation to low temperature, a fact that was confirmed by prolonged selection of yeast cells in YPD at 12°C. Instead, the experimental populations showed a progressive increase in NaCl tolerance. This phenotype was likely achieved at the expense of others traits, since evolved cells showed a ploidy reduction, a defect in the glucose derepression mechanism and a loss in their ability to utilize gluconeogenic carbon sources. We discuss the genetic flexibility of S. cerevisiae in terms of adaptation to the multiple constraints of the experimental design applied to drive adaptive evolution and the technologically advantageous phenotype of the evolved population. [source] Characterization of four rice mutants with alterations in the defence response pathwayMOLECULAR PLANT PATHOLOGY, Issue 1 2005M. A. CAMPBELL SUMMARY A fast-neutron mutagenized population of rice seedlings was screened with Magnaporthe grisea, the causal agent of rice blast disease, to identify mutants with alterations in the defence response. Three mutant lines, ebr1, ebr2 and ebr3 (enhanced blast resistance) were identified that display enhanced resistance to M. grisea. ebr1 and ebr3 also confer enhanced resistance to the bacterial pathogen Xanthomonas oryzae pv. oryzae (Xoo). ebr3 develops a lesion mimic (LM) phenotype upon inoculation with M. grisea, and the phenotype is also induced by a shift in environmental conditions. The fourth mutant line, ncr1 (necrosis in rice), has an LM phenotype under all conditions tested and lacks enhanced resistance to either M. grisea or Xoo. Complementation testing using the mutant lines ebr3 and ncr1 indicates that the ebr3 and ncr1 loci are nonallelic and recessive. ebr1 and ebr2 display no alterations in expression of the rice pathogenesis-related (PR) genes PBZ1 and PR1, compared to wild-type CO39. ebr3 has an elevated expression of PBZ1 and PR1 only in tissue displaying the LM phenotype. ncr1 strongly expresses PBZ1 in tissue displaying the LM phenotype, whereas PR1 expression in this tissue is similar to wild-type CO39. [source] Contribution of Jules Froment to the study of Parkinsonian rigidityMOVEMENT DISORDERS, Issue 7 2007Emmanuel Broussolle MD Abstract Rigidity is commonly defined as a resistance to passive movement. In Parkinson's disease (PD), two types of rigidity are classically recognized which may coexist, "leadpipe " and "cogwheel". Charcot was the first to investigate parkinsonian rigidity during the second half of the nineteenth century, whereas Negro and Moyer described cogwheel rigidity at the beginning of the twentieth century. Jules Froment, a French neurologist from Lyon, contributed to the study of parkinsonian rigidity during the 1920s. He investigated rigidity of the wrist at rest in a sitting position as well as in stable and unstable standing postures, both clinically and with physiological recordings using a myograph. With Gardère, Froment described enhanced resistance to passive movements of a limb about a joint that can be detected specifically when there is a voluntary action of another contralateral body part. This has been designated in the literature as the "Froment's maneuver " and the activation or facilitation test. In addition, Froment showed that parkinsonian rigidity diminishes, vanishes, or enhances depending on the static posture of the body. He proposed that in PD "maintenance stabilization " of the body is impaired and that "reactive stabilization " becomes the operative mode of muscular tone control. He considered "rigidification " as compensatory against the forces of gravity. Froment also demonstrated that parkinsonian rigidity increases during the Romberg test, gaze deviation, and oriented attention. In their number, breadth, and originality, Froment's contributions to the study of parkinsonian rigidity remain currently relevant to clinical and neurophysiological issues of PD. © 2007 Movement Disorder Society [source] Arbuscular mycorrhizal fungi confer enhanced arsenate resistance on Holcus lanatusNEW PHYTOLOGIST, Issue 1 2002C. Gonzalez-Chavez Summary ,,The role of arbuscular mycorrhizal fungi (AMF) in arsenate resistance in arbuscular mycorrhizal associations is investigated here for two Glomus spp. isolated from the arsenate-resistant grass Holcus lanatus. ,,Glomus mosseae and Glomus caledonium were isolated from H. lanatus growing on an arsenic-contaminated mine-spoil soil. The arsenate resistance of spores was compared with nonmine isolates using a germination assay. Short-term arsenate influx into roots and long-term plant accumulation of arsenic by plants were also investigated in uninfected arsenate resistant and nonresistant plants and in plants infected with mine and nonmine AMF. ,,Mine AMF isolates were arsenate resistant compared with nonmine isolates. Resistant and nonresistant G. mosseae both suppressed high-affinity arsenate/phosphate transport into the roots of both resistant and nonresistant H. lanatus. Resistant AMF colonization of resistant H. lanatus growing in contaminated mine spoil reduced arsenate uptake by the host. ,,We conclude that AMF have evolved arsenate resistance, and conferred enhanced resistance on H. lanatus. [source] Constitutive expression of Arabidopsis NPR1 confers enhanced resistance to the early instars of Spodoptera litura in transgenic tobaccoPHYSIOLOGIA PLANTARUM, Issue 4 2008Gargi Meur In Arabidopsis, NPR1 (AtNPR1) regulates salicylic acid (SA)-mediated activation of PR genes at the onset of systemic acquired resistance. AtNPR1 also modulates SA-induced suppression of jasmonic acid-responsive gene expression, and npr1 mutants manifest enhanced herbivore resistance. We have raised stable transgenic tobacco lines, expressing AtNPR1 constitutively, which showed elevated expression of PR1 and PR2 genes upon SA treatment. Herbivore bioassays with a generalist polyphagous pest, Spodoptera litura, revealed that the transgenic lines exhibited enhanced resistance compared to the wild-type plants, particularly with respect to younger larval populations. Insect-mediated injury induced several protease inhibitors (PIs), more significantly a 40-kDa serine PI in all the tobacco lines, but the induction was higher in the transgenic plants. We show in this communication that heterologous expression of AtNPR1 provides enhanced resistance to early larval populations of the herbivore, Spodoptera in transgenic tobacco plants. [source] SRFR1, a suppressor of effector-triggered immunity, encodes a conserved tetratricopeptide repeat protein with similarity to transcriptional repressorsTHE PLANT JOURNAL, Issue 1 2009Soon Il Kwon Summary Effector-triggered immunity provides plants with strong protection from pathogens. However, this response has the potential to be highly deleterious to the host and needs to be tightly controlled. The molecular mechanisms in the plant that regulate the balance between activation and suppression of resistance are not fully understood. Previously, we identified Arabidopsis suppressor of rps4-RLD 1 (srfr1) mutants with enhanced resistance to the bacterial effector AvrRps4. These mutants were recessive and retained full susceptibility to virulent bacteria, suggesting that SRFR1 functions as a negative regulator and that AvrRps4-triggered immunity was specifically enhanced in the mutants. Consistent with this, we show here that the response to flagellin, an elicitor of basal resistance, is unaltered in srfr1-1. In contrast, resistance to AvrRps4 in srfr1-1 requires EDS1, a central regulator of effector-triggered immunity via multiple resistance genes. SRFR1 is a single-copy gene encoding a pioneer tetratricopeptide repeat protein conserved between plants and animals. The SRFR1 tetratricopeptide repeat domain shows sequence similarity to those of transcriptional repressors in Saccharomyces cerevisiae and Caenorhabditis elegans. Indeed, a sub-pool of SRFR1 transiently expressed in Nicotiana benthamiana leaf cells localizes to the nucleus. Identification of SRFR1 may therefore provide insight into the regulation of the transcriptional reprogramming that is activated by effector-triggered immunity. [source] Overexpression of CRK13, an Arabidopsis cysteine-rich receptor-like kinase, results in enhanced resistance to Pseudomonas syringaeTHE PLANT JOURNAL, Issue 3 2007Biswa R. Acharya Summary Protein kinases play important roles in relaying information from perception of a signal to the effector genes in all organisms. Cysteine-rich receptor-like kinases (CRKs) constitute a sub-family of plant receptor-like kinases (RLKs) with more than 40 members that contain the novel C-X8-C-X2-C motif (DUF26) in the extracellular domains. Here we report molecular characterization of one member of this gene family, CRK13. Expression of this gene is induced more quickly and strongly in response to the avirulent compared with the virulent strains of Pseudomonas syringae, and peaks within 4 h after pathogen infection. In response to dexamethasone (DEX) treatment, plants expressing the CRK13 gene from a DEX-inducible promoter exhibited all tested features of pathogen defense activation, including rapid tissue collapse, accumulation of high levels of several defense-related gene transcripts including PR1, PR5 and ICS1, and accumulation of salicylic acid (SA). In addition, these plants suppressed growth of virulent pathogens by about 20-fold compared with the wild-type Col-0. CRK13 -conferred pathogen resistance is salicylic acid-dependent. Gene expression analysis using custom cDNA microarrays revealed a remarkable overlap between the expression profiles of the plants overexpressing CRK13 and the plants treated with Pst DC3000 (avrRpm1). Our studies suggest that upregulation of CRK13 leads to hypersensitive response-associated cell death, and induces defense against pathogens by causing increased accumulation of salicylic acid. [source] Negative regulation of defense responses in Arabidopsis by two NPR1 paralogsTHE PLANT JOURNAL, Issue 5 2006Yuelin Zhang Summary NPR1 is required for systemic acquired resistance, and there are five NPR1 paralogs in Arabidopsis. Here we report knockout analysis of two of these, NPR3 and NPR4. npr3 single mutants have elevated basal PR-1 expression and the npr3 npr4 double mutant shows even higher expression. The double mutant plants also display enhanced resistance against virulent bacterial and oomycete pathogens. This enhanced disease resistance is partially dependent on NPR1, can be in part complemented by either wild-type NPR3 or NPR4, and is not associated with an elevated level of salicylic acid. NPR3 and NPR4 interact with TGA2, TGA3, TGA5 and TGA6 in yeast two-hybrid assays. Using bimolecular fluorescence complementation analysis, we show that NPR3 interacts with TGA2 in the nucleus of onion epidermal cells and Arabidopsis mesophyll protoplasts. Combined with our previous finding that basal PR-1 levels are also elevated in the tga2 tga5 tga6 triple mutant, we propose that NPR3 and NPR4 negatively regulate PR gene expression and pathogen resistance through their association with TGA2 and its paralogs. [source] WRKY70 modulates the selection of signaling pathways in plant defenseTHE PLANT JOURNAL, Issue 3 2006Jing Li Summary Cross-talk between signal transduction pathways is a central feature of the tightly regulated plant defense signaling network. The potential synergism or antagonism between defense pathways is determined by recognition of the type of pathogen or pathogen-derived elicitor. Our studies have identified WRKY70 as a node of convergence for integrating salicylic acid (SA)- and jasmonic acid (JA)-mediated signaling events during plant response to bacterial pathogens. Here, we challenged transgenic plants altered in WRKY70 expression as well as WRKY70 knockout mutants of Arabidopsis with the fungal pathogens Alternaria brassicicola and Erysiphe cichoracearum to elucidate the role of WRKY70 in modulating the balance between distinct defense responses. Gain or loss of WRKY70 function causes opposite effects on JA-mediated resistance to A. brassicicola and the SA-mediated resistance to E. cichoracearum. While the up-regulation of WRKY70 caused enhanced resistance to E. cichoracearum, it compromised plant resistance to A. brassicicola. Conversely, down-regulation or insertional inactivation of WRKY70 impaired plant resistance to E. cichoracearum. Over-expression of WRKY70 resulted in the suppression of several JA responses including expression of a subset of JA- and A. brassicicola -responsive genes. We show that this WRKY70 -controlled suppression of JA-signaling is partly executed by NPR1. The results indicate that WRKY70 has a pivotal role in determining the balance between SA-dependent and JA-dependent defense pathways. [source] Mechanism of cell death and disease resistance induction by transgenic expression of bacterio-opsinTHE PLANT JOURNAL, Issue 5 2002Dominique Pontier Summary One of the earliest signal transduction events that trigger the hypersensitive response (HR) of plants against pathogen attack is thought to be an alteration of proton flux across the plasma membrane (PM). However, no direct genetic evidence for the involvement of PM-localised proton channels or pumps in the induction of this response has been reported. We previously showed that expression of the bacterial proton pump bacterio-opsin (bO) in transgenic plants resulted in the spontaneous activation of the HR. Here we show that the bO protein is likely localised to the PM in transgenic tobacco plants. Furthermore, mutational analysis shows that induction of the HR by bO expression is dependent upon the capability of bO to translocate protons. Although bO functions as a light-driven proton pump in Halobacteria when assembled with retinal, we also show by mutational analysis that this chromophore binding is unnecessary for its in planta activity. Taken together, our results suggest that expression of bO in plants leads to the insertion of a passive proton channel into the PM. The activity of this channel in the PM results in spontaneous activation of cell death and HR-associated phenotypes including enhanced resistance to a broad spectrum of plant pathogens. Our work provides direct molecular evidence to support a working model in which alterations in ionic homeostasis at the level of the PM may work as one of the critical steps in the signalling pathway for the activation of the HR. [source] Yield and cooking qualities of somaclonal variants of cv. Russet Burbank selected for resistance to common scab disease of potatoANNALS OF APPLIED BIOLOGY, Issue 2 2010C.R. Wilson We previously obtained somaclonal variants of the important French fry processing cultivar Russet Burbank with significantly enhanced resistance to common scab disease. In this study we have shown the commercial merit of a proportion of these variants through comparison of relative yield and tuber quality with the parent cultivar Russet Burbank. Whilst we showed a weak negative correlation between tuber yield (as assessed by weight of tubers per plant) and relative disease resistance within selected variants, we identified several with equivalent yields to the parent cultivar. Furthermore, two disease-resistant variants (TC-RB8 and NZ-24B) consistently yielded more tuber mass than the parent. The majority of our Russet Burbank variants showed equivalent tuber quality characteristics (occurrence of defects, tuber specific gravity and dry matter content, and flesh colour) and cooking qualities (fry colour and presence of dark end defects) to the parent cultivar. Independent testing by a commercial French fry processor confirmed these quality characteristics. We present data demonstrating that highly common scab disease-resistant somaclonal variants of Russet Burbank have commercially acceptable tuber yield and quality characteristics, comparable to the industry standard and parent Russet Burbank cultivar. We also demonstrate the value of in vitro cell selection techniques for potato cultivar improvement. [source] Silicon-augmented resistance of plants to herbivorous insects: a reviewANNALS OF APPLIED BIOLOGY, Issue 2 2009O.L. Reynolds Abstract Silicon (Si) is one of the most abundant elements in the earth's crust, although its essentiality in plant growth is not clearly established. However, the importance of Si as an element that is particularly beneficial for plants under a range of abiotic and biotic stresses is now beyond doubt. This paper reviews progress in exploring the benefits at two- and three-trophic levels and the underlying mechanism of Si in enhancing the resistance of host plants to herbivorous insects. Numerous studies have shown an enhanced resistance of plants to insect herbivores including folivores, borers, and phloem and xylem feeders. Silicon may act directly on insect herbivores leading to a reduction in insect performance and plant damage. Various indirect effects may also be caused, for example, by delaying herbivore establishment and thus an increased chance of exposure to natural enemies, adverse weather events or control measures that target exposed insects. A further indirect effect of Si may be to increase tolerance of plants to abiotic stresses, notably water stress, which can in turn lead to a reduction in insect numbers and plant damage. There are two mechanisms by which Si is likely to increase resistance to herbivore feeding. Increased physical resistance (constitutive), based on solid amorphous silica, has long been considered the major mechanism of Si-mediated defences of plants, although there is recent evidence for induced physical defence. Physical resistance involves reduced digestibility and/or increased hardness and abrasiveness of plant tissues because of silica deposition, mainly as opaline phytoliths, in various tissues, including epidermal silica cells. Further, there is now evidence that soluble Si is involved in induced chemical defences to insect herbivore attack through the enhanced production of defensive enzymes or possibly the enhanced release of plant volatiles. However, only two studies have tested for the effect of Si on an insect herbivore and third trophic level effects on the herbivore's predators and parasitoids. One study showed no effect of Si on natural enemies, but the methods used were not favourable for the detection of semiochemical-mediated effects. Work recently commenced in Australia is methodologically and conceptually more advanced and an effect of Si on the plants' ability to generate an induced response by acting at the third trophic level was observed. This paper provides the first overview of Si in insect herbivore resistance studies, and highlights novel, recent hypotheses and findings in this area of research. Finally, we make suggestions for future research efforts in the use of Si to enhance plant resistance to insect herbivores. [source] Could a diet enriched with n-3 highly unsaturated fatty acids be considered a promising way to enhance the immune defences and the resistance of Penaeid prawns to environmental stress?AQUACULTURE RESEARCH, Issue 2 2001L Chim Abstract The prawn Penaeus stylirostris (Stimpson), when fed for 28 days with n-3 highly unsaturated fatty acid (HUFA)-enriched feed pellets, demonstrated an enhanced resistance to variations in environmental parameters (a decrease in temperature and salinity over a 4-day period from 28 °C to 17 °C and from 35, to 10, respectively) and an improvement in their immune defence potential, i.e. increased agglutination titre of plasma and increased respiratory burst of haemocytes. [source] Gastric mucosal resistance to acute injury in experimental portal hypertensionBRITISH JOURNAL OF PHARMACOLOGY, Issue 1 2001Sara Calatayud The gastric mucosa of portal hypertensive rats exhibits important microvascular changes and a nitric oxide (NO)-dependent hyperemia. This study analyses whether portal hypertensive mucosa exhibits changes in its ability to withstand aggression. Portal hypertension was induced by partial portal vein ligation (PPVL) or common bile duct ligation (CBDL) and gastric damage was induced by oral administration of ethanol or aspirin. Experiments were performed in conscious or anaesthetized rats and some animals were pre-treated with the NO-synthesis inhibitor L -NAME. Conscious PPVL or CBDL rats showed an increased resistance to the damaging effects of ethanol. Oral administration of aspirin produced less gastric damage in PPVL conscious rats than in the control group. The protective effects of portal hypertension were maintained in animals anaesthetized with ketamine and absent when pentobarbital was employed. Pre-treatment with L -NAME restored the damaging effects of ethanol and aspirin in PPVL rats without modifying the level of damage in control animals. Gastric bleeding induced by oral aspirin, as measured by the luminal release of 51Cr-labelled erythrocytes, was significantly greater in PPVL rats than in control animals. Semi-quantitiative analysis by RT , PCR of the mRNA for endothelial NO-synthase (eNOS), neuronal NOS (nNOS) and inducible NOS (iNOS) levels showed that the expression of iNOS was slightly increased in both the gastric mucosa and smooth muscle of PPVL rats. No changes were observed in eNOS and nNOS expression. Conscious portal hypertensive rats exhibit an enhanced resistance to acute gastric damage which is absent under the influence of some types of anaesthesia and seems related to an increased synthesis of nitric oxide. However, mucosal lesions in these animals show an augmented bleeding per area of injury. British Journal of Pharmacology (2001) 132, 309,317; doi:10.1038/sj.bjp.0703785 [source] | ||||||||||||||||||||||||||||