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Plant Defence Responses (plant + defence_response)
Selected AbstractsGlutamate Fermentation By-product Activates Plant Defence Responses and Confers Resistance Against Pathogen InfectionJOURNAL OF PHYTOPATHOLOGY, Issue 10 2010Daisuke Igarashi Abstract In the food industry, glutamate fermentation by-product (GFB) is generated by purifying glutamate products from microbial fermentation. The potential applications of GFB for upgrading agricultural soil, for foliar fertility, and as plant plankton for shrimp have been studied. We examined the efficacy of GFB foliar application and determined that GFB treatment increased the resistance of Arabidopsis leaves to infection by bacterial pathogens. Microarray gene expression analysis of Arabidopsis leaves after treatment with GFB indicated that the expression of plant defence-related genes increased. In Corynebacterium fermentation, the active substances for induction of the defence response were extracted or solubilized after treatment with heating under acidic conditions. This extract was also effective in strawberry and grape leaves for the induction of hydrogen peroxide production. These findings suggest that foliar application of GFB that contains elicitor molecules derived from fermentation bacteria is useful for plant protection in agricultural fields. [source] Endochitinase activity in the apoplastic fluid of Phellinus weirii -infected Douglas-fir and its association with over wintering and antifreeze activityFOREST PATHOLOGY, Issue 5 2003A. Zamani Summary Extracellular proteins were extracted from Phellinus weirii infected Douglas-fir (Pseudotsuga menziesii var. menziesii) roots and needles to examine endochitinase activity. Chitinases have been associated with the plant's defence response against fungal attack because they hydrolyse chitin, a structural component of fungal cell walls. Protein separation using sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) followed by Western immunoblot analysis using a polyclonal antibody specific to an endochitinase-like protein (ECP) resulted in the detection of up to three polypeptides between 27 and 30 kDa in size. Two-dimensional gel electrophoresis (2-D PAGE) followed by Western immunoblot analysis revealed that the apoplastic fluid contained multiple ECP isoforms with isoelectric points (pIs) ranging from 5.3 to 5.8 and molecular masses of 27,30 kDa. Chitinase activity in needle and root tissues was measured spectrophotometrically using a colorimetric assay. A gel overlay technique using glycol chitin as a substrate for endochitinase was applied to confirm that the ECP antibody detected an enzymatically active protein. The apoplastic fluid collected from P. weirii -infected winter Douglas-fir needles showed anti-freeze activity and seasonal analysis of needle tissue showed some evidence of ECP accumulation in winter months. ECP was distributed systemically throughout the tree. Increased levels of endochitinase activity in the region of P. weirii infection supports a physiological role for ECP in the plant defence response. Résumé Les protéines extra-cellulaires ont été extraites des racines et aiguilles de douglas (Pseudotsuga menziesii var menziesii) infectés par Phellinus weirii (Murr.) Gilbn., pour étudier l'activité endochitinase. Les chitinases ont été associées aux réactions de défense des plantes contre les attaques fongiques parce-qu'elles hydrolysent la chitine, un composant de la paroi des cellules fongiques. La séparation des protéines, réalisée par électrophorèse en gel de polyacrylamide avec sodium dodecyl sulfate (SDS-PAGE), suivie par une analyse par Western immunoblot en utilisant un anticorps polyclonal spécifique d'une protéine de type endochitinase (ECP), a permis la détection de 3 polypeptides de taille comprise entre 27 et 30 kDa. Une électrophorèse sur gel en 2-dimensions (2-D PAGE) suivie par une analyse par Western immunoblot a révélé que le fluide apoplastique contient de multiples isoformes d'ECP avec des pI dans une gamme de 5.3 à 5.8 et des masses moléculaires de 27 à 30 kDa. L'activité chitinase dans les aiguilles et tissus racinaires a été mesurée par spectrophotométrie par une méthode colorimétrique. Une technique d'overlay utilisant de la chitine glycol comme substrat de l'endochitinase a été appliquée pour confirmer que l'anticorps ECP avait détecté une protéine active du point de vue enzymatique. Le fluide apoplastique d'aiguilles récoltées en hiver sur des douglas infectés par P. weirii a montré une activité antigel et l'analyse saisonnière des tissus foliaires a montré une certaine accumulation d'ECP pendant l'hiver. L'ECP est répartie de façon systémique dans l'ensemble de l'arbre. Les niveaux accrus d'activité endochitinase dans la zone infectée par P. weirii suggère un rôle physiologique de l'ECP dans les réactions de défense de la plante. Zusammenfassung Aus Wurzeln und Nadeln von mit Phellinus weirii infizierten Douglasien (Pseudotsuga menziesii var. menziesii) wurden extrazelluläre Proteine extrahiert, um die Endochitinase-Aktivität zu bestimmen. Chitinasen werden mit der pflanzlichen Abwehrreaktion auf Pilzinfektionen in Verbindung gebracht, da sie Chitin, eine Strukturkomponente der pilzlichen Zellwand, hydrolysieren. Die Proteine wurden mit Natrium-Dodecyl-Sulfat-Polyacrylamid-Gelelektrophorese (SDS-PAGE) getrennt, gefolgt von einer Western Immunoblot-Analyse mit einem gegen ein Endochitinase-ähnliches Protein (ECP) spezifischen polyklonalen Antikörper. Hiermit liessen sich bis zu drei Polypeptide zwischen 27-30 kDa nachweisen. Eine zweidimensionale Gelelektrophorese (2-D PAGE) mit anschliessender Western Immunoblot-Analyse ergab, dass die Apoplastenflüssigkeit multiple ECP-Isoformen enthielt (mit pIs von 5,3 bis 5,8 und Molekularmassen von 27 bis 30 kDa). Die Chitinase-Aktivität wurde auch im Nadel- und Wurzelgewebe spektrophotometrisch mit einer Farbreaktion gemessen. Um sicher zu stellen, dass der ECP-Antikörper ein enzymatisch aktives Protein nachwies, wurde eine Gel-Overlay-Methode verwendet, mit Glycolchitin als Substrat für die Endochitinase. Die Apoplastenflüssigkeit der Nadeln von mit P. weirii infizierten Douglasien zeigte in Winterzustand eine Antifrost-Aktivität, ihre Analyse während des gesamten Jahres ergab aber keine Hinweise auf eine ECP-Anreicherung während der Wintermonate. ECP war systemisch im gesamten Baum enthalten. Die erhöhte Endochitinase-Aktivität in Bereichen mit P. weirii -Infektion lässt auf eine physiologische Rolle von ECP in der Pflanzenabwehr schliessen. [source] Early signalling events in the Avr9/Cf-9-dependent plant defence responseMOLECULAR PLANT PATHOLOGY, Issue 1 2000Tina Romeis Resistance of tomato to the leaf mould fungus Cladosporium fulvum is controlled by the interaction between a plant-encoded resistance gene (Cf-9) and pathogen-encoded avirulence (Avr9) gene. Our objective is to understand the underlying molecular mechanisms that transmit the Cf-9/Avr9-dependent pathogen perception event and activate the plant defence response. Our approach toward the understanding of Cf -function is based on the analysis of early Cf-9/Avr9-mediated responses and signalling events. Because Cf-9 transgenically expressed in tobacco retains its specificity and activity to the Avr9 elicitor, signalling experiments were conducted in the heterologous system using these transgenic lines or derived Cf9 tobacco cell cultures. Among the earliest responses to the Avr9/Cf-9 elicitation event were rapid changes in ion-fluxes, the synthesis of active oxygen species (AOS), probably catalysed by a plant NADPH-oxidase, and the transient activation of two MAP kinases. These kinases were identified as WIPK (wounding-induced protein kinase) and SIPK (salicylic-acid induced kinase) from tobacco. Studies with pharmacological inhibitors suggested that the MAP kinases are located in an independent signalling pathway from the Avr9/Cf-9-dependent synthesis of AOS. SIPK and WIPK were involved in pathogen-related elicitation processes as well as in abiotic stress responses. This indicates that the plant defence is triggered via a signalling network that shares components with pathways originating from abiotic environmental stress stimuli. [source] Characterization of Arabidopsis mur3 mutations that result in constitutive activation of defence in petioles, but not leavesTHE PLANT JOURNAL, Issue 5 2008Jennifer D. Tedman-Jones Summary A screen was established for mutants in which the plant defence response is de-repressed. The pathogen-inducible isochorismate synthase (ICS1) promoter was fused to firefly luciferase (luc) and a homozygous transgenic line generated in which the ICS1:luc fusion is co-regulated with ICS1. This line was mutagenized and M2 seedlings screened for constitutive ICS1:luc expression (cie). The cie mutants fall into distinct phenotypic classes based on tissue-specific localization of luciferase activity. One mutant, cie1, that shows constitutive luciferase activity specifically in petioles, was chosen for further analysis. In addition to ICS1, PR and other defence-related genes are constitutively expressed in cie1 plants. The cie1 mutant is also characterized by an increased production of conjugated salicylic acid and reactive oxygen intermediates, as well as spontaneous lesion formation, all confined to petiole tissue. Significantly, defences activated in cie1 are sufficient to prevent infection by a virulent isolate of Hyaloperonospora parasitica, and this enhanced resistance response protects petiole tissue alone. Furthermore, cie1 -mediated resistance, along with PR gene expression, is abolished in a sid2-1 mutant background, consistent with a requirement for salicylic acid. A positional cloning approach was used to identify cie1, which carries two point mutations in a gene required for cell wall biosynthesis and actin organization, MUR3. A mur3 knockout mutant also resists infection by H. parasitica in its petioles and this phenotype is complemented by transformation with wild-type MUR3. We propose that perturbed cell wall biosynthesis may activate plant defence and provide a rationale for the cie1 and the mur3 knockout phenotypes. [source] Proteases in pathogenesis and plant defenceCELLULAR MICROBIOLOGY, Issue 10 2004Yiji Xia Summary Plant pathogens deliver a variety of virulence factors to host cells to suppress basal defence responses and create suitable environments for their propagation. Plants have in turn evolved disease resistance genes whose products detect the virulence factors as a signal of invasion and activate effective defence responses. Understanding how a virulence effector contributes to virulence on susceptible hosts but becomes an avirulence factor that triggers defence responses on resistance hosts has been a major focus in plant research. Recent studies have shown that a growing list of pathogen-encoded effectors functions as proteases that are secreted into plant cells to modify host proteins. In addition, several plant proteases have been found to function in activation of the defence mechanism. These findings reveal that post-translational modification of host proteins through proteolytic processing is a widely used mechanism in regulating the plant defence response. [source] Induction of Systemic Acquired Resistance in Arachis hypogaea L. by Sclerotium rolfsii Derived ElicitorsJOURNAL OF PHYTOPATHOLOGY, Issue 9 2010Durgesh Nandini Abstract Plants evolve a strategy to survive the attacks of potential pathogens by inducing the microbial signal molecules. In this study, plant defence responses were induced in four different varieties of Arachis hypogaea (J-11, GG-20, TG-26 and TPG41) using the fungal components of Sclerotium rolfsii in the form of fungal culture filtrate (FCF) and mycelial cell wall (MCW), and the levels of defence-related signal molecule salicylic acid (SA), marker enzymes such as peroxidase (POX), phenylalanine ammonia lyase (PAL), ,-1,3-glucanase and lignin were determined. There was a substantial fold increase in POX, PAL, SA, ,-1,3-glucanase and lignin content in FCF- and MCW-treated plants of all varieties of groundnut when compared to that of control plants. The enzyme activities were much higher in FCF-treated plants than in MCW-treated plants. The increase in fold activity of enzymes and signal molecule varied between different varieties. These results indicate that the use of fungal components (FCF and MCW) had successfully induced systemic resistance in the four different varieties of groundnut plants against Sclerotium rolfsii. [source] Early season herbivore differentially affects plant defence responses to subsequently colonizing herbivores and their abundance in the fieldMOLECULAR ECOLOGY, Issue 14 2008ERIK H. POELMAN Abstract Induction of plant defences by early season herbivores can mediate interspecific herbivore competition. We have investigated plant-mediated competition between three herbivorous insects through studies at different levels of biological integration. We have addressed (i) gene expression; (ii) insect behaviour and performance under laboratory conditions; and (iii) population dynamics under field conditions. We studied the expression of genes encoding a trypsin inhibitor and genes that are involved in glucosinolate biosynthesis in response to early season herbivory by Pieris rapae caterpillars in Brassica oleracea plants. Furthermore, we studied the interaction of these transcriptional responses with responses to secondary herbivory by the two specialist herbivores, P. rapae and Plutella xylostella, and the generalist Mamestra brassicae. P. rapae -induced responses strongly interacted with plant responses to secondary herbivory. Sequential feeding by specialist herbivores resulted in enhanced or similar expression levels of defence-related genes compared to primary herbivory by specialists. Secondary herbivory by the generalist M. brassicae resulted in lower gene expression levels than in response to primary herbivory by this generalist. Larval performance of both specialist and generalist herbivores was negatively affected by P. rapae- induced plant responses. However, in the field the specialist P. xylostella was more abundant on P. rapae -induced plants and preferred these plants over undamaged plants in oviposition experiments. In contrast, the generalist M. brassicae was more abundant on control plants and preferred undamaged plants for oviposition. P. rapae did not discriminate between plants damaged by conspecifics or undamaged plants. Our study shows that early season herbivory differentially affects transcriptional responses involved in plant defence to secondary herbivores and their population development dependent upon their degree of host plant specialization. [source] The potato StLTPa7 gene displays a complex Ca2+ -associated pattern of expression during the early stage of potato,Ralstonia solanacearum interactionMOLECULAR PLANT PATHOLOGY, Issue 1 2009GANG GAO SUMMARY Although nonspecific lipid transfer proteins (nsLTPs) are widely expressed during plant defence responses to pathogens, their functions and regulation are not fully understood. In this article, we report the isolation of a cDNA for the new nsLTP, StLTPa7, from cultivated potato (Solanum tuberosum) infected with Ralstonia solanacearum. The cDNA was predicted to encode a type 1 nsLTP containing an N-terminal signal sequence and possessing the characteristic features of nsLTPs. A phylogenetic analysis showed that the encoded amino acid sequence of the nsLTP was similar to those of other previously reported plant nsLTPs, which contain a putative calmodulin-binding site consisting of approximately 12 highly conserved amino acid residues. The expression of the StLTPa7 gene was studied during the early stages of potato,R. solanacearum interaction using real-time quantitative polymerase chain reaction (qRT-PCR) and Northern analyses, and a complex calcium (Ca2+)-associated pattern of expression was observed with the following features: (i) transcripts of the StLTPa7 gene were systemically up-regulated by infection with R. solanacearum; (ii) the StLTPa7 gene was stimulated by salicylic acid, methyl jasmonate, abscisic acid and Ca2+; (iii) qRT-PCR showed that, during the early stage of R. solanacearum infection, nsLTP transcripts accumulated over a time course that paralleled that of Ca2+ accumulation, detected using environmental scanning electron microscopy and energy-dispersive X-ray (EDAX) spectrometry; and (iv) the Ca2+ channel blocker, ruthenium red, partially blocked R. solanacearum -induced StLTPa7 expression. This report represents the first use of EDAX analysis to establish a synchrony between Ca2+ accumulation and nsLTP expression in response to potato,R. solanacearum interactions. Collectively, these results suggest that StLTPa7 may be a pathogen- and Ca2+ -responsive plant defence gene. [source] Post-translational modification of host proteins in pathogen-triggered defence signalling in plantsMOLECULAR PLANT PATHOLOGY, Issue 4 2008IRIS J. E. STULEMEIJER SUMMARY Microbial plant pathogens impose a continuous threat to global food production. Similar to animals, an innate immune system allows plants to recognize pathogens and swiftly activate defence. To activate a rapid response, receptor-mediated pathogen perception and subsequent downstream signalling depends on post-translational modification (PTM) of components essential for defence signalling. We discuss different types of PTMs that play a role in mounting plant immunity, which include phosphorylation, glycosylation, ubiquitination, sumoylation, nitrosylation, myristoylation, palmitoylation and glycosylphosphatidylinositol (GPI)-anchoring. PTMs are rapid, reversible, controlled and highly specific, and provide a tool to regulate protein stability, activity and localization. Here, we give an overview of PTMs that modify components essential for defence signalling at the site of signal perception, during secondary messenger production and during signalling in the cytoplasm. In addition, we discuss effectors from pathogens that suppress plant defence responses by interfering with host PTMs. [source] The role of plant defence proteins in fungal pathogenesisMOLECULAR PLANT PATHOLOGY, Issue 5 2007RICARDO B. FERREIRA SUMMARY It is becoming increasingly evident that a plant,pathogen interaction may be compared to an open warfare, whose major weapons are proteins synthesized by both organisms. These weapons were gradually developed in what must have been a multimillion-year evolutionary game of ping-pong. The outcome of each battle results in the establishment of resistance or pathogenesis. The plethora of resistance mechanisms exhibited by plants may be grouped into constitutive and inducible, and range from morphological to structural and chemical defences. Most of these mechanisms are defensive, exhibiting a passive role, but some are highly active against pathogens, using as major targets the fungal cell wall, the plasma membrane or intracellular targets. A considerable overlap exists between pathogenesis-related (PR) proteins and antifungal proteins. However, many of the now considered 17 families of PR proteins do not present any known role as antipathogen activity, whereas among the 13 classes of antifungal proteins, most are not PR proteins. Discovery of novel antifungal proteins and peptides continues at a rapid pace. In their long coevolution with plants, phytopathogens have evolved ways to avoid or circumvent the plant defence weaponry. These include protection of fungal structures from plant defence reactions, inhibition of elicitor-induced plant defence responses and suppression of plant defences. A detailed understanding of the molecular events that take place during a plant,pathogen interaction is an essential goal for disease control in the future. [source] Non-host resistance in plants: new insights into an old phenomenonMOLECULAR PLANT PATHOLOGY, Issue 3 2005THORSTEN NÜRNBERGER SUMMARY Resistance of an entire plant species to all isolates of a microbial species is referred to as non-host or species resistance. An interplay of both constitutive barriers and inducible reactions comprises the basis for this most durable form of plant disease resistance. Activation of inducible plant defence responses is probably brought about by the recognition of invariant pathogen-associated molecular patterns (PAMP) that are characteristic of whole classes of microbial organisms. PAMP perception systems and PAMP-induced signalling cascades partially resemble those known to mediate activation of innate immune responses in animals, suggesting an evolutionarily ancient molecular concept of non-self recognition and immunity in eukaryotes. Genetic dissection has recently provided clues for SNARE-complex-mediated exocytosis and directed vesicle trafficking in executing plant non-host resistance. Recent functional analysis of bacterial effector proteins indicates that establishment of infection in susceptible plants is associated with suppression of plant species resistance. [source] The role of lipopolysaccharides in induction of plant defence responsesMOLECULAR PLANT PATHOLOGY, Issue 5 2003Gitte 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] Bipolaris sorokiniana, a cereal pathogen of global concern: cytological and molecular approaches towards better control,MOLECULAR PLANT PATHOLOGY, Issue 4 2002Jagdish Kumar Summary Bipolaris sorokiniana (teleomorph Cochliobolus sativus ) is the causal agent of common root rot, leaf spot disease, seedling blight, head blight, and black point of wheat and barley. The fungus is one of the most serious foliar disease constraints for both crops in warmer growing areas and causes significant yield losses. High temperature and high relative humidity favour the outbreak of the disease, in particular in South Asia's intensive ,irrigated wheat,rice' production systems. In this article, we review the taxonomy and worldwide distribution, as well as strategies to counteract the disease as an emerging threat to cereal production systems. We also review the current understanding of the cytological and molecular aspects of the interaction of the fungus with its cereal hosts, which makes B. sorokiniana a model organism for studying plant defence responses to hemibiotrophic pathogens. The contrasting roles of cell death and H 2O2 generation in plant defence during biotrophic and necrotrophic fungal growth phases are discussed. [source] Natural genetic resources of Arabidopsis thaliana reveal a high prevalence and unexpected phenotypic plasticity of RPW8- mediated powdery mildew resistanceNEW PHYTOLOGIST, Issue 3 2008Katharina Göllner Summary ,,Here, an approach based on natural genetic variation was adopted to analyse powdery mildew resistance in Arabidopsis thaliana. ,,Accessions resistant to multiple powdery mildew species were crossed with the susceptible Col-0 ecotype and inheritance of resistance was analysed. Histochemical staining was used to visualize archetypal plant defence responses such as callose deposition, hydrogen peroxide accumulation and host cell death in a subset of these ecotypes. ,,In six accessions, resistance was likely of polygenic origin while 10 accessions exhibited evidence for a single recessively or semi-dominantly inherited resistance locus. Resistance in the latter accessions was mainly manifested at the terminal stage of the fungal life cycle by a failure of abundant conidiophore production. The resistance locus of several of these ecotypes was mapped to a genomic region containing the previously analysed atypical RPW8 powdery mildew resistance genes. Gene silencing revealed that members of the RPW8 locus were responsible for resistance to Golovinomyces orontii in seven accessions. ,,These results suggest that broad-spectrum powdery mildew resistance in A. thaliana is predominantly of polygenic origin or based on RPW8 function. The findings shed new light on the natural variation of inheritance, phenotypic expression and pathogen range of RPW8 -conditioned powdery mildew resistance. [source] Disease stress-inducible genes of tobacco: expression profile of elicitor-responsive genes isolated by subtractive hybridizationPHYSIOLOGIA PLANTARUM, Issue 4 2003Daigo Takemoto In order to investigate the change in mRNA profile during tobacco disease response, a subtractive hybridization procedure was used to generate a cDNA library for genes induced in tobacco (Nicotiana tabacum cv. Samsun NN) treated with oomycete elicitor. Database searches with the randomly isolated genes revealed that this cDNA library was enriched for reported disease stress-responsive genes such as pathogenesis-related proteins and cell wall protein genes. The expressions of eight newly isolated genes were induced by inoculation with the non-pathogenic bacteria, Pseudomonas syringae pv. glycinea. The NtEIGs (N.tabacumelicitor- inducible genes) showed similarity to genes for stellacyanin-like protein (NtEIG-A1), glutathione peroxidase (NtEIG-C08), extensin-like protein (NtEIG-C29), WRKY transcription factor (NtEIG-D48), glycine rich protein (NtEIG-E17), , -1, 3-glucanase-like protein (NtEIG-E76), photoassimilate-responsive protein-1 (NtEIG-E80) and wound-induced protein (NtEIG-D10). The expression patterns of NtEIGs in tobacco leaf in response to P. syringae pv. glycinea, salicylic acid (SA), methyl jasmonate (MeJA) and wound stress were analysed. The individual expression patterns of NtEIGs indicate that the transcriptional activation of NtEIGs is regulated by various signals and the products of NtEIGs are involved in different processes at different stages of the plant defence responses. [source] Phylogenetic and transcriptional analysis of a strictosidine synthase-like gene family in Arabidopsis thaliana reveals involvement in plant defence responsesPLANT BIOLOGY, Issue 1 2009M. M. Sohani Abstract Protein domains with similarity to plant strictosidine synthase-like (SSL) sequences have been uncovered in the genomes of all multicellular organisms sequenced so far and are known to play a role in animal immune responses. Among several distinct groups of Arabidopsis thaliana SSL sequences, four genes (AtSSL4,AtSSL7) arranged in tandem on chromosome 3 show more similarity to SSL genes from Drosophila melanogaster and Caenorhabditis elegans than to other Arabidopsis SSL genes. To examine whether any of the four AtSSL genes are immune-inducible, we analysed the expression of each of the four AtSSL genes after exposure to microbial pathogens, wounding and plant defence elicitors using real-time quantitative RT-PCR, Northern blot hybridisation and Western blot analysis with antibodies raised against recombinant AtSSL proteins. While the AtSSL4 gene was constitutively expressed and not significantly induced by any treatment, the other three AtSSL genes were induced to various degrees by plant defence signalling compounds, such as salicylic acid, methyl jasmonate and ethylene, as well as by wounding and exposure to the plant pathogens Alternaria brassicicola and cucumber mosaic virus. Our data demonstrate that the four SSL-coding genes are regulated individually, suggesting specific roles in basal (SSL4) and inducible (SSL5-7) plant defence mechanisms. [source] Complementary action of jasmonic acid on salicylic acid in mediating fungal elicitor-induced flavonol glycoside accumulation of Ginkgo biloba cellsPLANT CELL & ENVIRONMENT, Issue 8 2009MAOJUN XU ABSTRACT The antagonistic action between jasmonic acid (JA) and salicylic acid (SA) in plant defence responses has been well documented. However, their relationship in secondary metabolite production is largely unknown. Here, we report that PB90, a protein elicitor from Phytophthora boehmeriae, triggers JA generation, SA accumulation and flavonol glycoside production of Ginkgo biloba cells. JA inhibitors suppress not only PB90-triggered JA generation, but also the elicitor-induced flavonol glycoside production. However, the elicitor can still enhance flavonol glycoside production even though the JA generation is totally inhibited. Over-expression of SA hydrolase gene NahG not only abolishes SA accumulation, but also suppresses the elicitor-induced flavonol glycoside production when JA signalling is inhibited. Interestingly, expression of NahG does not inhibit the elicitor-induced flavonol glycoside accumulation in the absence of JA inhibitors. Moreover, JA levels are significantly enhanced when SA accumulation is impaired in the transgenic cells. Together, the data suggest that both JA and SA are involved in PB90-induced flavonol glycoside production. Furthermore, we demonstrate that JA signalling might be enhanced to substitute for SA to mediate the elicitor-induced flavonol glycoside accumulation when SA signalling is impaired, which reveals an unusual complementary relationship between JA and SA in mediating plant secondary metabolite production. [source] A new member of the Arabidopsis WRKY transcription factor family, AtWRKY6, is associated with both senescence- and defence-related processesTHE PLANT JOURNAL, Issue 2 2001Silke Robatzek Summary WRKY proteins constitute a large family of plant-specific transcription factors whose precise functions have yet to be elucidated. Here we show that expression of one representative in Arabidopsis, AtWRKY6, is influenced by several external and internal signals often involved in triggering senescence processes and plant defence responses. Progressive 5, deletions of the AtWRKY6 promoter allowed separation of defined regions responsible for the expression in distinct organs or upon pathogen challenge. Nuclear localization of AtWRKY6 was demonstrated; protein truncations and gain-of-function studies enabled delineation of a region harbouring a novel type of functional nuclear localization signal (NLS). [source] Mutualism versus pathogenesis: the give-and-take in plant,bacteria interactionsCELLULAR MICROBIOLOGY, Issue 3 2009María J. Soto Summary Pathogenic bacteria and mutualistic rhizobia are able to invade and establish chronic infections within their host plants. The success of these plant,bacteria interactions requires evasion of the plant innate immunity by either avoiding recognition or by suppressing host defences. The primary plant innate immunity is triggered upon recognition of common microbe-associated molecular patterns. Different studies reveal striking similarities between the molecular bases underlying the perception of rhizobial nodulation factors and microbe-associated molecular patterns from plant pathogens. However, in contrast to general elicitors, nodulation factors can control plant defences when recognized by their cognate legumes. Nevertheless, in response to rhizobial infection, legumes show transient or local defence-like responses suggesting that Rhizobium is perceived as an intruder although the plant immunity is controlled. Whether these responses are involved in limiting the number of infections or whether they are required for the progression of the interaction is not yet clear. Further similarities in both plant,pathogen and Rhizobium,legume associations are factors such as surface polysaccharides, quorum sensing signals and secreted proteins, which play important roles in modulating plant defence responses and determining the outcome of the interactions. [source] Should I stay or should I go?CELLULAR MICROBIOLOGY, Issue 8 2007Nucleocytoplasmic trafficking in plant innate immunity Summary Communication between the cytoplasm and the nucleus is a fundamental feature of eukaryotic cells. Bidirectional transport of macromolecules across the nuclear envelope is typically mediated by receptors and occurs exclusively through nuclear pore complexes (NPCs). The components and molecular mechanisms regulating nucleocytoplasmic trafficking and signalling processes are well studied in animals and yeast but are poorly understood in plants. Current work shows that components of the NPC and the nuclear import and export machinery play essential roles in plant innate immunity. Translocation of defence regulators and Resistance (R) proteins between the cytoplasm and the nucleus are recently uncovered aspects of plant defence responses against pathogens. Future studies will reveal more details on the spatial and temporal dynamics and regulation of this process. [source] Endochitinase activity in the apoplastic fluid of Phellinus weirii -infected Douglas-fir and its association with over wintering and antifreeze activityFOREST PATHOLOGY, Issue 5 2003A. Zamani Summary Extracellular proteins were extracted from Phellinus weirii infected Douglas-fir (Pseudotsuga menziesii var. menziesii) roots and needles to examine endochitinase activity. Chitinases have been associated with the plant's defence response against fungal attack because they hydrolyse chitin, a structural component of fungal cell walls. Protein separation using sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) followed by Western immunoblot analysis using a polyclonal antibody specific to an endochitinase-like protein (ECP) resulted in the detection of up to three polypeptides between 27 and 30 kDa in size. Two-dimensional gel electrophoresis (2-D PAGE) followed by Western immunoblot analysis revealed that the apoplastic fluid contained multiple ECP isoforms with isoelectric points (pIs) ranging from 5.3 to 5.8 and molecular masses of 27,30 kDa. Chitinase activity in needle and root tissues was measured spectrophotometrically using a colorimetric assay. A gel overlay technique using glycol chitin as a substrate for endochitinase was applied to confirm that the ECP antibody detected an enzymatically active protein. The apoplastic fluid collected from P. weirii -infected winter Douglas-fir needles showed anti-freeze activity and seasonal analysis of needle tissue showed some evidence of ECP accumulation in winter months. ECP was distributed systemically throughout the tree. Increased levels of endochitinase activity in the region of P. weirii infection supports a physiological role for ECP in the plant defence response. Résumé Les protéines extra-cellulaires ont été extraites des racines et aiguilles de douglas (Pseudotsuga menziesii var menziesii) infectés par Phellinus weirii (Murr.) Gilbn., pour étudier l'activité endochitinase. Les chitinases ont été associées aux réactions de défense des plantes contre les attaques fongiques parce-qu'elles hydrolysent la chitine, un composant de la paroi des cellules fongiques. La séparation des protéines, réalisée par électrophorèse en gel de polyacrylamide avec sodium dodecyl sulfate (SDS-PAGE), suivie par une analyse par Western immunoblot en utilisant un anticorps polyclonal spécifique d'une protéine de type endochitinase (ECP), a permis la détection de 3 polypeptides de taille comprise entre 27 et 30 kDa. Une électrophorèse sur gel en 2-dimensions (2-D PAGE) suivie par une analyse par Western immunoblot a révélé que le fluide apoplastique contient de multiples isoformes d'ECP avec des pI dans une gamme de 5.3 à 5.8 et des masses moléculaires de 27 à 30 kDa. L'activité chitinase dans les aiguilles et tissus racinaires a été mesurée par spectrophotométrie par une méthode colorimétrique. Une technique d'overlay utilisant de la chitine glycol comme substrat de l'endochitinase a été appliquée pour confirmer que l'anticorps ECP avait détecté une protéine active du point de vue enzymatique. Le fluide apoplastique d'aiguilles récoltées en hiver sur des douglas infectés par P. weirii a montré une activité antigel et l'analyse saisonnière des tissus foliaires a montré une certaine accumulation d'ECP pendant l'hiver. L'ECP est répartie de façon systémique dans l'ensemble de l'arbre. Les niveaux accrus d'activité endochitinase dans la zone infectée par P. weirii suggère un rôle physiologique de l'ECP dans les réactions de défense de la plante. Zusammenfassung Aus Wurzeln und Nadeln von mit Phellinus weirii infizierten Douglasien (Pseudotsuga menziesii var. menziesii) wurden extrazelluläre Proteine extrahiert, um die Endochitinase-Aktivität zu bestimmen. Chitinasen werden mit der pflanzlichen Abwehrreaktion auf Pilzinfektionen in Verbindung gebracht, da sie Chitin, eine Strukturkomponente der pilzlichen Zellwand, hydrolysieren. Die Proteine wurden mit Natrium-Dodecyl-Sulfat-Polyacrylamid-Gelelektrophorese (SDS-PAGE) getrennt, gefolgt von einer Western Immunoblot-Analyse mit einem gegen ein Endochitinase-ähnliches Protein (ECP) spezifischen polyklonalen Antikörper. Hiermit liessen sich bis zu drei Polypeptide zwischen 27-30 kDa nachweisen. Eine zweidimensionale Gelelektrophorese (2-D PAGE) mit anschliessender Western Immunoblot-Analyse ergab, dass die Apoplastenflüssigkeit multiple ECP-Isoformen enthielt (mit pIs von 5,3 bis 5,8 und Molekularmassen von 27 bis 30 kDa). Die Chitinase-Aktivität wurde auch im Nadel- und Wurzelgewebe spektrophotometrisch mit einer Farbreaktion gemessen. Um sicher zu stellen, dass der ECP-Antikörper ein enzymatisch aktives Protein nachwies, wurde eine Gel-Overlay-Methode verwendet, mit Glycolchitin als Substrat für die Endochitinase. Die Apoplastenflüssigkeit der Nadeln von mit P. weirii infizierten Douglasien zeigte in Winterzustand eine Antifrost-Aktivität, ihre Analyse während des gesamten Jahres ergab aber keine Hinweise auf eine ECP-Anreicherung während der Wintermonate. ECP war systemisch im gesamten Baum enthalten. Die erhöhte Endochitinase-Aktivität in Bereichen mit P. weirii -Infektion lässt auf eine physiologische Rolle von ECP in der Pflanzenabwehr schliessen. [source] | ||||||||||||||||||||||