Home About us Contact
|
Home About us Contact | ||
|
|
||
Defence-related Genes (defence-related + gene)
Selected AbstractsCloning, Expression and Characterization of Protein Elicitors from the Soyabean Pathogenic Fungus Phytophthora sojaeJOURNAL OF PHYTOPATHOLOGY, Issue 3 2000J. 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] 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] Studies on the mechanism of resistance to Bipolaris sorokiniana in the barley lesion mimic mutant bst1MOLECULAR PLANT PATHOLOGY, Issue 5 2009MATTIAS PERSSON SUMMARY The Bipolaris sorokiniana tolerant 1 (bst1) barley mutant is derived from fast neutron-irradiated seeds of wild-type Bowman(Rph3). The induced mutation was genetically localized to a position on chromosome 5HL distal to the centromere using amplified fragment length polymorphism markers. In addition, the defence responses and related gene expression in the bst1 mutant after fungal challenge were compared with those occurring in wild-type plants. Hydrogen peroxide generation, determined by 3,3-diaminobenzidine staining, revealed a clearly reduced level of bst1, compared with the wild-type, during the entire experimental time: 8,120 h post-inoculation (hpi). At 48 hpi, the wild-type samples displayed twice as much fungal mass and three times greater H2O2 production than bst1. At the same time, staining of B. sorokiniana showed less fungal growth in the spontaneous lesions of bst1 compared with the wild-type. Monitoring of defence-related genes at 48 hpi demonstrated strong expression of PR-1a, PR-2, PR-5 and PR-10 in bst1. A gene coding for a unique oxidoreductase enzyme, designated as HCP1, was expressed at much higher levels in inoculated leaves of the bst1 mutant than in those of the wild-type plant. Taken together, the results suggest that the defence to B. sorokiniana largely relies on salicylic acid-responsive pathogenesis-related (PR) genes, as well as selected reactive oxygen species and unknown HCP1 -associated factors. [source] Novel elicitin-like proteins isolated from the cell wall of the biocontrol agent Pythium oligandrum induce defence-related genes in sugar beetMOLECULAR PLANT PATHOLOGY, Issue 5 2006SHIGEHITO TAKENAKA SUMMARY We previously reported that cell wall protein fractions (CWPs) of the biocontrol agent Pythium oligandrum have elicitor properties in sugar beet and wheat. Here we have examined the effect of treatment with the D -type of CWP, a fraction that contains two major forms (POD-1 and POD-2), on the induction of defence-related genes in sugar beet. Using PCR-based cDNA library subtraction, we identified five genes that were highly expressed in response to CWP treatment. The five genes are probably of oxalate oxidase-like germin (OxOLG), glutathione S-transferase (GST), 5-enol-pyruvylshikimate-phosphate synthase (EPSPS), phenylalanine ammonia-lyase (PAL) and aspartate aminotransferase (AAT). In addition, we purified and characterized POD-1 and POD-2 and found that POD-1 induced all five genes, whereas POD-2 induced three of the genes, but not OxOLG or GST. A sugar beet bioassay indicated that CWP, POD-1 and POD-2 are each sufficient to induce resistance to sugar beet seedling disease caused by Aphanomyces cochlioides. Although carbohydrate analyses indicated that POD proteins were glycoproteins with similar carbohydrate compositions, containing approximately 15.0% carbohydrate by weight, their peptide portions have elicitor activity. Furthermore, cDNAs of POD-1 and POD-2 proteins were cloned, and the deduced amino acid sequences were found to be 82.9% identical. Characterization of their molecular structures indicated that they have an elicitin domain followed by a C-terminal domain with a high frequency of Ser, Thr, Ala and Pro, which is structurally similar to class III elicitins. However, phylogenetic analysis with 22 representative elicitin and elicitin-like proteins showed that POD-1 and POD-2 are distinct from previously defined elicitin and elicitin-like proteins. Therefore, POD-1 and POD-2 are novel oomycete cell wall elicitin-like glycoproteins. [source] cDNA-AFLP reveals genes differentially expressed during the hypersensitive response of cassavaMOLECULAR PLANT PATHOLOGY, Issue 2 2005BENJAMIN 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 Arabidopsis gene SIGMA FACTOR-BINDING PROTEIN 1 plays a role in the salicylate- and jasmonate-mediated defence responsesPLANT CELL & ENVIRONMENT, Issue 5 2010Y.-D. XIE ABSTRACT The chloroplast-localized SIB1 protein was previously identified by its interaction with SIGMA FACTOR 1 (SIG1), a component of the RNA polymerase machinery responsible for transcription of plastid genes. The physiological function of SIB1 is little known. We found that expression of SIB1 is induced by infection with Pseudomonas syringae, suggesting its possible involvement in the defence response. The sib1 loss-of-function mutation compromises induction of some defence-related genes triggered by pathogen infection and the treatments with salicylic acid (SA) and jasmonic acid (JA), two key signalling molecules in the defence response. Conversely, constitutive over-expression of SIB1 causes the plants to hyper-activate defence-related genes following pathogen infection or the SA and JA treatments, leading to enhanced resistance to infection by P. syringae. SIB1 is a member of the large plant-specific VQ motif-containing protein family, and might act as a link to connect defence signalling with chloroplast function. [source] Molecular analysis of resistance mechanisms to Orobanche cumana in sunflowerPLANT PATHOLOGY, Issue 3 2007P. Letousey Resistance to the dicotyledenous parasite Orobanche cumana in sunflower is characterized by a low number of parasitic attachments and a confinement of the parasite in host tissues leading to its necrosis. To help understand what determines such resistance mechanisms, molecular, biochemical and histological approaches were employed before (early response) and after (late response) attachment of the broomrape parasite to susceptible (2603) and resistant (LR1) sunflower genotypes. The expression patterns of 11 defence-related genes known to be involved in different metabolic pathways (phenylpropanoids, jasmonate, ethylene) and/or in resistance mechanisms against microorganisms were investigated. RT-PCR and cDNA blot experiments revealed that the resistant genotype exhibited a stronger overall defence response against O. cumana than the susceptible one, involving marker genes of the jasmonate (JA) and salicylic acid (SA) pathways. Among them, the SA-responsive gene, def. (defensin), appeared to be characteristic of LR1 sunflower resistance. However, no JA accumulation and similar SA contents (250,300 ng g,1 FW) were measured by GC/MS in both genotypes, parasitized or not. In addition, three cDNAs, isolated by a suppression-subtractive hybridization, were shown to be strongly induced only in the resistant genotype 8 days post-inoculation, when the first O. cumana attachments occurred. These genes, putatively encoding a methionine synthase, a glutathione S-transferase and a quinone oxidoreductase, might be involved in detoxification of reactive oxygen species, suggesting the occurrence of an oxidative burst during the incompatible interaction. Finally, host cell-wall modifications leading to parasite-confinement were correlated with more intense callose depositions in the resistant genotype, concomitant with over-expression of the callose synthase cDNA HaGSL1. [source] The chloroplast protein RPH1 plays a role in the immune response of Arabidopsis to Phytophthora brassicaeTHE PLANT JOURNAL, Issue 2 2009Khaoula Belhaj Summary Plant immune responses to pathogens are often associated with enhanced production of reactive oxygen species (ROS), known as the oxidative burst, and with rapid hypersensitive host cell death (the hypersensitive response, HR) at sites of attempted infection. It is generally accepted that the oxidative burst acts as a promotive signal for HR, and that HR is highly correlated with efficient disease resistance. We have identified the Arabidopsis mutant rph1 (resistance to Phytophthora 1), which is susceptible to the oomycete pathogen Phytophthora brassicae despite rapid induction of HR. The susceptibility of rph1 was specific for P. brassicae and coincided with a reduced oxidative burst, a runaway cell-death response, and failure to properly activate the expression of defence-related genes. From these results, we conclude that, in the immune response to P. brassicae, (i) HR is not sufficient to stop the pathogen, (ii) HR initiation can occur in the absence of a major oxidative burst, (iii) the oxidative burst plays a role in limiting the spread of cell death, and (iv) RPH1 is a positive regulator of the P. brassicae -induced oxidative burst and enhanced expression of defence-related genes. Surprisingly, RPH1 encodes an evolutionary highly conserved chloroplast protein, indicating a function of this organelle in activation of a subset of immune reactions in response to P. brassicae. The disease resistance-related role of RPH1 was not limited to the Arabidopsis model system. Silencing of the potato homolog StRPH1 in a resistant potato cultivar caused susceptibility to the late blight pathogen Phytophthora infestans. [source] Nitric oxide modulates ozone-induced cell death, hormone biosynthesis and gene expression in Arabidopsis thalianaTHE PLANT JOURNAL, Issue 1 2009Reetta Ahlfors Summary Nitric oxide (NO) is involved together with reactive oxygen species (ROS) in the activation of various stress responses in plants. We have used ozone (O3) as a tool to elicit ROS-activated stress responses, and to activate cell death in plant leaves. Here, we have investigated the roles and interactions of ROS and NO in the induction and regulation of O3 -induced cell death. Treatment with O3 induced a rapid accumulation of NO, which started from guard cells, spread to adjacent epidermal cells and eventually moved to mesophyll cells. During the later time points, NO production coincided with the formation of hypersensitive response (HR)-like lesions. The NO donor sodium nitroprusside (SNP) and O3 individually induced a large set of defence-related genes; however, in a combined treatment SNP attenuated the O3 induction of salicylic acid (SA) biosynthesis and other defence-related genes. Consistent with this, SNP treatment also decreased O3 -induced SA accumulation. The O3 -sensitive mutant rcd1 was found to be an NO overproducer; in contrast, Atnoa1/rif1 (Arabidopsis nitric oxide associated 1/resistant to inhibition by FSM1), a mutant with decreased production of NO, was also O3 sensitive. This, together with experiments combining O3 and the NO donor SNP suggested that NO can modify signalling, hormone biosynthesis and gene expression in plants during O3 exposure, and that a functional NO production is needed for a proper O3 response. In summary, NO is an important signalling molecule in the response to O3. [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] Priming by airborne signals boosts direct and indirect resistance in maizeTHE PLANT JOURNAL, Issue 1 2007Jurriaan Ton Summary Plants counteract attack by herbivorous insects using a variety of inducible defence mechanisms. The production of toxic proteins and metabolites that instantly affect the herbivore's development are examples of direct induced defence. In addition, plants may release mixtures of volatile organic compounds (VOCs) that indirectly protect the plant by attracting natural enemies of the herbivore. Recent studies suggest that these VOCs can also prime nearby plants for enhanced induction of defence upon future insect attack. However, evidence that this defence priming causes reduced vulnerability to insects is sparse. Here we present molecular, chemical and behavioural evidence that VOC-induced priming leads to improved direct and indirect resistance in maize. A differential hybridization screen for inducible genes upon attack by Spodoptera littoralis caterpillars identified 10 defence-related genes that are responsive to wounding, jasmonic acid (JA), or caterpillar regurgitant. Exposure to VOCs from caterpillar-infested plants did not activate these genes directly, but primed a subset of them for earlier and/or stronger induction upon subsequent defence elicitation. This priming for defence-related gene expression correlated with reduced caterpillar feeding and development. Furthermore, exposure to caterpillar-induced VOCs primed for enhanced emissions of aromatic and terpenoid compounds. At the peak of this VOC emission, primed plants were significantly more attractive to parasitic Cotesia marginiventris waSPS. This study shows that VOC-induced priming targets a specific subset of JA-inducible genes, and links these responses at the molecular level to enhanced levels of direct and indirect resistance against insect attack. [source] The Arabidopsis MAP kinase kinase MKK1 participates in defence responses to the bacterial elicitor flagellinTHE PLANT JOURNAL, Issue 4 2006Tamás Mészáros Summary Plants sense pathogens through both pathogen-associated molecular patterns and recognition of race-specific virulence factors, which induce basal defence or an accelerated defence (often manifest in the form of local cell death), respectively. A mitogen-activated protein kinase (MAPK) module in Arabidopsis was previously proposed to signal from perception of the bacterial elicitor flagellin to the activation of basal defence-related genes. Here, we present evidence for a parallel MAPK-signalling pathway involved in the response to flg22, a peptide corresponding to the most conserved domain of flagellin. The endogenous Arabidopsis MAP kinase kinase MKK1 is activated in cells treated with flg22, phosphorylates the MAPK MPK4 in vitro, and activates it in vivo in protoplasts. In mkk1 mutant plants, the activation by flg22 of MPK4 and two other flg22-induced MAPKs (MPK3 and MPK6) is impaired. In the mkk1 mutant, a battery of both flg22-induced and flg22-repressed genes show altered expression, indicating that MKK1 negatively regulates the activity of flagellin-responsive genes. Intriguingly, in contrast to the mpk4 mutant, mkk1 shows no morphological anomalies and is compromised in resistance to both virulent and avirulent Pseudomonas syringae strains. Thus, the MKK1 signalling pathway modulates the expression of genes responding to elicitors and plays an important role in pathogen defence. [source] | ||||||||||