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At least 397 records · Page 22Linked to original sources
PubMed2004

Antagonistic interaction between abscisic acid and jasmonate-ethylene signaling pathways modulates defense gene expression and disease resistance in Arabidopsis.

The plant hormones abscisic acid (ABA), jasmonic acid (JA), and ethylene are involved in diverse plant processes, including the regulation of gene expression during adaptive responses to abiotic and biotic stresses. Previously, ABA has been implicated in enhancing disease susceptibility in various plant species, but currently very little is known about the molecular mechanisms underlying this phenomenon. In this study, we obtained evidence that a complex interplay between ABA and JA-ethylene signaling pathways regulate plant defense gene expression and disease resistance. First, we showed that exogenous ABA suppressed both basal and JA-ethylene-activated transcription from defense genes. By contrast, ABA deficiency as conditioned by the mutations in the ABA1 and ABA2 genes, which encode enzymes involved in ABA biosynthesis, resulted in upregulation of basal and induced transcription from JA-ethylene responsive defense genes. Second, we found that disruption of AtMYC2 (allelic to JASMONATE INSENSITIVE1 [JIN1]), encoding a basic helix-loop-helix Leu zipper transcription factor, which is a positive regulator of ABA signaling, results in elevated levels of basal and activated transcription from JA-ethylene responsive defense genes. Furthermore, the jin1/myc2 and aba2-1 mutants showed increased resistance to the necrotrophic fungal pathogen Fusarium oxysporum. Finally, using ethylene and ABA signaling mutants, we showed that interaction between ABA and ethylene signaling is mutually antagonistic in vegetative tissues. Collectively, our results indicate that the antagonistic interactions between multiple components of ABA and the JA-ethylene signaling pathways modulate defense and stress responsive gene expression in response to biotic and abiotic stresses.

Abscisic Acid↗
PubMed2006

The transcription factors WRKY11 and WRKY17 act as negative regulators of basal resistance in Arabidopsis thaliana.

Transcription factors are believed to play a pivotal role in the activation and fine-tuning of plant defense responses, but little is known about the exact function of individual transcription factors in this process. We analyzed the role of the IId subfamily of WRKY transcription factors in the regulation of basal resistance to Pseudomonas syringae pv tomato (Pst). The expression of four members of the subfamily was induced upon challenge with virulent and avirulent strains of Pst. Mutant analyses revealed that loss of WRKY11 function increased resistance toward avirulent and virulent Pst strains and that resistance was further enhanced in wrky11 wrky17 double mutant plants. Thus, WRKY11 and WRKY17 act as negative regulators of basal resistance to Pst. Genome-wide expression analysis and expression studies of selected genes in single and double mutants demonstrated that both transcription factors modulate transcriptional changes in response to pathogen challenge. Depending on the target gene, WRKY11 and WRKY17 act either specifically or in a partially redundant manner. We demonstrate complex cross-regulation within the IId WRKY subfamily and provide evidence that both WRKY transcription factors are involved in the regulation of Pst-induced jasmonic acid-dependent responses. These results provide genetic evidence for the importance of WRKY11 and WRKY17 in plant defense.

Arabidopsis↗
PubMed2004

Purification, characterization and preliminary crystallographic studies of a novel plant defensin from Pachyrrhizus erosus seeds.

Defensins are small cysteine-rich antimicrobial peptides that are widely distributed in plants, insects and mammals. As potent defenders in protecting plants from pathogenic fungal attack, plant defensins are presumed to play an important role in the innate immunity of plants and are expected to find applications in the production of transgenic crops. A novel plant defensin protein SPE10 from Pachyrrhizus erosus seeds was purified and partially sequenced. Crystallization screening using the hanging-drop vapour-diffusion method resulted in two crystal forms, from one of which a diffraction data set was collected to 0.98 A resolution. The crystal belongs to space group P2(1), with unit-cell parameters a = 32.71, b = 28.11, c = 54.85 angstroms, beta = 103.78 degrees. Preliminary crystallographic studies revealed two subunits in the asymmetric unit.

Amino Acid Sequence↗
PubMed2004

Two TIR:NB:LRR genes are required to specify resistance to Peronospora parasitica isolate Cala2 in Arabidopsis.

Resistance responses that plants deploy in defence against pathogens are often triggered following a recognition event mediated by resistance (R) genes. The encoded R proteins usually contain a nucleotide-binding site (NB) and a leucine-rich repeat (LRR) domain. They are further classified into those that contain an N-terminal coiled coil (CC) motif or a Toll interleukin receptor (TIR) domain. Such R genes, when transferred into a susceptible plant of the same or closely related species, usually impart full resistance capability. We have used map-based cloning and mutation analysis to study the recognition of Peronospora parasitica (RPP)2 (At) locus in Arabidopsis accession Columbia (Col-0), which is a determinant of specific recognition of P. parasitica (At) isolate Cala2. Genetic mapping located RPP2 to a 200-kb interval on chromosome 4, which contained four adjacent TIR:NB:LRR genes. Mutational analysis revealed three classes of genes involved in specifying resistance to Cala2. One class, which resulted in pleiotropic effects on resistance to other P. parasitica (At) isolates, was unlinked to the RPP2 locus; this class included AtSGT1b. The other two classes were mapped within the interval and were specific to Cala2 resistance. Representatives of each of these classes were sequenced, and mutations were found in one or the other of two (RPP2A and RPP2B) of the four TIR:NB:LRR genes. RPP2A and RPP2B complemented their specific mutations, but failed to impart resistance when present alone, and it is concluded that both genes are essential determinants for isolate-specific recognition of Cala2. RPP2A has an unusual structure with a short LRR domain at the C-terminus, preceded by two potential but incomplete TIR:NB domains. In addition, the RPP2A LRR domain lacks conserved motifs found in all but three other TIR:NB:LRR class proteins. In contrast, RPP2B has a complete TIR:NB:LRR structure. It is concluded that RPP2A and RPP2B cooperate to specify Cala2 resistance by providing recognition or signalling functions lacked by either partner protein.

Amino Acid Sequence↗
PubMed2005

The conserved Xanthomonas campestris pv. vesicatoria effector protein XopX is a virulence factor and suppresses host defense in Nicotiana benthamiana.

Nicotiana benthamiana leaves display a visible plant cell death response when infiltrated with a high titer inoculum of the non-host pathogen, Xanthomonas campestris pv. vesicatoria (Xcv). This visual phenotype was used to identify overlapping cosmid clones from a genomic cosmid library constructed from the Xcv strain, GM98-38. Individual cosmid clones from the Xcv library were conjugated into X. campestris pv. campestris (Xcc) and exconjugants were scored for an altered visual high titer inoculation response in N. benthamiana. The molecular characterization of the cosmid clones revealed that they contained a novel gene, xopX, that encodes a 74-kDa type III secretion system (TTSS) effector protein. Agrobacterium-mediated transient expression of XopX in N. benthamiana did not elicit the plant cell death response although detectable XopX protein was produced. Interestingly, the plant cell death response occurred when the xopX Agrobacterium-mediated transient expression construct was co-inoculated with strains of either XcvDeltaxopX or Xcc, both lacking xopX. The co-inoculation complementation of the plant cell death response also depends on whether the Xanthomonas strains contain an active TTSS. Transgenic 35S-xopX-expressing N. benthamiana plants also have the visible plant cell death response when inoculated with the non-xopX-expressing strains XcvDeltaxopX and Xcc. Unexpectedly, transgenic 35S-xopX N. benthamiana plants displayed enhanced susceptibility to bacterial growth of Xcc as well as other non-xopX-expressing Xanthomonas and Pseudomonas strains. This result is also consistent with the increase in bacterial growth on wild type N. benthamiana plants observed for Xcc when XopX is expressed in trans. Furthermore, XopX contributes to the virulence of Xcv on host pepper (Capsicum annuum) and tomato (Lycopersicum esculentum) plants. We propose that the XopX bacterial effector protein targets basic innate immunity in plants, resulting in enhanced plant disease susceptibility.

Amino Acid Sequence↗
PubMed2001

Models and data on plant-enemy coevolution.

Although coevolution is complicated, in that the interacting species evolve in response to each other, such evolutionary dynamics are amenable to mathematical modeling. In this article, we briefly review models and data on coevolution between plants and the pathogens and herbivores that attack them. We focus on "arms races," in which trait values in the plant and its enemies escalate to more and more extreme values. Untested key assumptions in many of the models are the relationships between costs and benefits of resistance in the plant and the level of resistance, as well as how costs of virulence or detoxification ability in the enemy change with levels of these traits. A preliminary assessment of these assumptions finds only mixed support for the models. What is needed are models that are more closely tailored to particular plant-enemy interactions, as well as experiments that are expressly designed to test existing models.

Biological Evolution↗
PubMed2001

Organization of genes controlling disease resistance in the potato genome.

Nineteen single dominant genes (R genes) for resistance to viruses, nematodes, and fungi have been positioned on the molecular map of potato using DNA markers. Fourteen of those genes are located in five "hotspots" for resistance in the potato genome. Quantitative trait loci (QTL) for resistance to late blight caused by the oomycete Phytophthora infestans, to tuber rot caused by the bacterium Erwinia carotovora ssp. atroseptica, and to root cyst nematodes have been identified on all 12 potato chromosomes. Some QTL for resistance to different pathogens are linked to each other and/or to resistance hotspots. Based on the genetic clustering with R genes, we propose that some QTL for resistance have a molecular basis similar to single R genes. Mapping potato genes with sequence similarity to cloned R genes of other plants and other defense-related genes reveals linkage between candidate genes, R genes, and resistance QTL. To explain the molecular basis of polygenic resistance in potato we propose (a) genes having structural similarity with cloned R genes and (b) genes involved in the defense response. The "candidate gene approach" enables the identification of markers highly useful for marker-assisted selection in potato breeding.

Animals↗
PubMed2006

Plant NBS-LRR proteins: adaptable guards.

The majority of disease resistance genes in plants encode nucleotide-binding site leucine-rich repeat (NBS-LRR) proteins. This large family is encoded by hundreds of diverse genes per genome and can be subdivided into the functionally distinct TIR-domain-containing (TNL) and CC-domain-containing (CNL) subfamilies. Their precise role in recognition is unknown; however, they are thought to monitor the status of plant proteins that are targeted by pathogen effectors.

Amino Acid Sequence↗
PubMed2006

Fitness benefits of systemic acquired resistance during Hyaloperonospora parasitica infection in Arabidopsis thaliana.

We investigated the fitness benefits of systemic acquired resistance (SAR) in Arabidopsis thaliana using a mutational and transformational genetic approach. Genetic lines were designed to differ in the genes determining resistance signaling in a common genetic background. Two mutant lines (cpr1 and cpr5) constitutively activate SAR at different points in SAR signaling, and one mutant line (npr1) has impaired SAR. The transgenic line (NPR1-H) has enhanced resistance when SAR is activated, but SAR is still inducible similarly to wild type. The fitness benefits were also investigated under two nutrient levels to test theories that preventing pathogen damage and realized resistance benefits may be affected by nutrient availability. Under low-nutrient conditions and treatment with the pathogenic oomycete, Hyaloperonospora parasitica, wild type had a higher fitness than the mutant that could not activate SAR, demonstrating that normal inducible SAR is beneficial in these conditions; this result, however, was not found under high-nutrient conditions. The mutants with constitutive SAR all failed to show a fitness benefit in comparison to wild type under a H. parasitica pathogen treatment, suggesting that SAR is induced to prevent an excessive fitness cost.

Arabidopsis↗
PubMed2002

Identification and molecular tagging of two complementary dominant resistance genes to maize dwarf mosaic virus.

Maize dwarf mosaic is one of the devastating and widespread viral diseases in the world. So far, only a few genes were identified and mapped in the resistant materials. A new resistant elite inbred line Siyi was identified with resistance to maize dwarf mosaic virus strain B at early and adult stage. Two complementary dominant genes conditioned the resistance, with a new genetic model, of the maize inbred line were found at adult stage by the genetic analysis based on parents, F1, F2 and backcrosses in two years. The microsatellite analysis of a F2 population from the cross between Siyi and Mo17 was used to identify the two resistance genes on chromosome 3 and 6 respectively by 87 pairs of microsatellite markers. The linkage distance between phi029 and the one resistance gene on chromosome 3 is 14.5 cM, and phi126 to the other on chromosome 6 is 7.2 cM.

Chromosome Mapping↗
PubMedDate not supplied

Specific immune response to Phleum pratense plant profilin in atopic patients and control subjects.

BACKGROUND: Phleum pratense (Phl p) pollen is a known cause of allergic disease worldwide. Profilins have been identified as functional plant pan-allergens. The role of Phl p profilin in the specific immune response in sensitized Phl p patients is unknown. METHODS: Skin prick test and specific serum IgE levels were performed in 26 patients allergic to Phl p and in 18 nonallergic control donors. Peripheral blood mononuclear cells were isolated from both groups and stimulated with crude extract or highly purified Phl p profilin, and the production of type I and type II cytokines was determined in patients and controls stimulated with specific and polyclonal stimulus. T-cell lines specific to Phl p profilin were established from PBMCs and cross-reactivity with another highly purified profilin from Parietaria judaica (Pj) was evaluated. RESULTS: Patients allergic to Phl p profilin showed increased T-cell-proliferative responses to this profilin compared with control subjects. The production of IL-4 and IFN-gamma in response to the specific stimulus was undetectable. However, the production of IL-4 and IFN-gamma in response to a polyclonal stimulus (PHA) was measurable and different for atopic patients and control subjects: IL-4 was higher (p < 0.001) in allergic patients and IFN-gamma lower (although not significant) in controls. Neither the T-cell responses nor the production of IL-4 in response to a polyclonal stimulus (PHA) correlated with the individual degree of cutaneous response to Phl p profilin or to the levels of specific Phl p IgE. The T-cell lines tested did not show any cross-reactivity with Pj profilin. CONCLUSIONS: Phl p profilin is in part responsible for the T-cell mediated immunological response in patients allergic to Phl p. The response is very specific since Phl p profilin specific T-cell lines did not show cross-reactivity with a highly homologous profilin from Parietaria judaica (Pj). The lack of correlation between the proliferative T-cell response and polyclonal IL-4 production with allergen-specific serum IgE and SPT probably indicates that some of the responding T-cells may be involved in immune reactions other than the support of IgE production.

Adult↗
PubMed2003

Targeting of plant-derived vaccine antigens to immunoresponsive mucosal sites.

Most pathogenic microorganisms enter their host via the mucosal surfaces lining the digestive, respiratory and urino-reproductive tracts of the body. The most efficient means of protecting these surfaces is through mucosal immunization. Transgenic plants are safe and inexpensive vehicles to produce and mucosally deliver protective antigens. However, the application of this technology is limited by the poor response of the immune system to non-particulate, subunit vaccines. Co-delivery of therapeutic proteins with targeting proteins, such as the B subunit of the Escherichia coli heat labile enterotoxin (LTB), could increase the effectiveness of such antigens.

Antigens↗
PubMed2006

The reactive oxygen species network pathways:an essential prerequisite for perception of pathogen attack and the acquired disease resistance in plants.

Availability of complete Arabidopsis (Arabidopsis thaliana) and rice (Oryza sativa) genome sequences, together with molecular recourses of functional genomics and proteomics have revolutionized our understanding of reactive oxygen species (ROS) signalling network mediating disease resistance in plants. So far, ROS have been associated with aging, cellular and molecular alteration in animal and plant cells. Recently,concluding evidences suggest that ROS network is essential to induce disease resistance and even to mediate resistance to multiple stresses in plants. ROS are obligatory by-products emerging as a result of normal metabolic reactions. They have the potential to be both beneficial and harmful to cellular metabolism. Their dual effects on metabolic reactions are dosage specific. In this review we focus our attention on cellular ROS level to trigger beneficial effects on plant cells responding to pathogen attack. By exploring the research related contributions coupled with data of targeted gene disruption, and RNA interference approaches, we show here that ROS are ubiquitous molecules of redox-pathways that play a crucial role in plant defence mechanism. The molecular prerequisites of ROS network to activate plant defence system in response to pathogen infections are here underlined. Bioinformatic tools are now available to scientists for high throughput analysis of cellular metabolisms. These tools are used to illustrate crucial ROS-related genes that are involved in the defence mechanism of plants. The review describes also the emerging findings of ROS network pathways to modulate multiple stress resistance in plants.

Animals↗
PubMed2004

The genetics of non-host disease resistance in wheat to barley yellow rust.

Non-host resistance is investigated as a potential source of durable resistance. However, the genetics of non-host resistance between closely related plant species and their corresponding pathogens would indicate that in these interactions, non-host resistance primarily involves major genes that operate on a gene-for-gene principal similar to that seen in host resistance. Wheat is a non-host of the barley-attacking form of the fungus responsible for yellow rust, i.e. Puccinia striiformis f. sp. hordei. While P. striiformis f. sp. hordei is generally unable to infect wheat, a partial susceptibility was exhibited by the wheat variety Chinese 166. Consequently, in the cross Lemhi x Chinese 166 two major QTLs for resistance to P. striiformis f. sp. hordei were identified: one on chromosome 1D and a second on 2B. These two QTLs accounted for 43.5% and 33.2% of the phenotypic variance for resistance to barley yellow rust, respectively. In addition, two QTLs of smaller effect were also identified: one on chromosome 5A, contributing 5.1% of the variance and a second on chromosome 6A, contributing 10.9% to the phenotype. The QTL on 6A was derived from the susceptible variety, Chinese 166. In all cases the resistance towards P. striiformis f. sp. hordei was associated with a visual chlorosis/necrosis response typical of race-specific host resistance.

Basidiomycota↗
PubMed2004

The anthracnose resistance locus Co-4 of common bean is located on chromosome 3 and contains putative disease resistance-related genes.

The broadest based resistance to anthracnose of common bean ( Phaseolus vulgaris L.) is conferred by the Co-4 locus. We sequenced a bacterial artificial chromosome clone harboring part of the Co-4 locus of the bean genotype Sprite and assembled a single contig of 106.5 kb for functional annotation. This region contained five copies of the COK-4 gene that encodes for a serine threonine kinase protein previously mapped to the Co-4 locus and 19 novel genes with no similarity to any previously identified genes of common bean. Several putative genes of the Co-4 locus seemed to be expressed as they matched perfectly with bean expressed sequence tags. The expression of the COK-4 genes was assessed by reverse transcription (RT)-PCR, and a single 850-bp cDNA fragment was sequenced and compared with the genomic sequences of the COK-4 homologs. Although the COK-4 cDNA was isolated from a different bean cultivar, it showed high similarity (95%) to the exons of genes BA17 and BA21, suggesting that they were expressed. In a phylogenetic tree including all currently available Pto-like sequences from Phaseolus species, the COK-4 homologs formed a single cluster with the Pto gene, whereas two sequences from P. coccineus and all sequences of P. vulgaris formed two closely related clusters. The Co-4 locus was physically mapped to the short arm of bean chromosome 3, which corresponds to linkage group B8. This study represents a first step in gaining an understanding of the genomic organization of an anthracnose resistance locus of common bean and provides molecular data for comparative analysis with other plant species.

Ascomycota↗
PubMed2005

Identification of two novel genes for blackleg resistance in Brassica napus.

Blackleg, caused by Leptosphaeria maculans, is a major disease of Brassica napus. Two populations of B. napus DH lines, DHP95 and DHP96, with resistance introgressed from B. rapa subsp. sylvestris, were genetically mapped for resistance to blackleg disease with restriction fragment length polymorphism markers. Examination of the DHP95 population indicated that a locus on linkage group N2, named LepR1, was associated with blackleg resistance. In the DHP96 population, a second locus on linkage group N10, designated LepR2, was associated with resistance. We developed BC1 and F2 populations, to study the inheritance of resistance controlled by the genes. Genetic analysis indicated that LepR1 was a dominant nuclear allele, while LepR2 was an incompletely dominant nuclear resistance allele. LepR1 and LepR2 cotyledon resistance was further evaluated by testing 30 isolates from Canada, Australia, Europe, and Mexico. The isolates were from B. napus, B. juncea, and B. oleracea and represented different pathogenicity groups of L. maculans. Results indicated that LepR1 generally conferred a higher level of cotyledon resistance than LepR2. Both genes exhibited race-specific interactions with pathogen isolates; virulence on LepR1 was observed with one isolate, pl87-41, and two isolates, Lifolle 5, and Lifolle 6, were virulent on LepR2. LepR1 prevented hyphal penetration, while LepR2 reduced hyphal growth and inhibited sporulation. Callose deposition was associated with resistance for both loci.

Ascomycota↗
PubMed2005

H9, H10, and H11 compose a cluster of Hessian fly-resistance genes in the distal gene-rich region of wheat chromosome 1AS.

H9, H10, and H11 are major dominant resistance genes in wheat, expressing antibiosis against Hessian fly [(Hf) Mayetiola destructor (Say)] larvae. Previously, H9 and H10 were assigned to chromosome 5A and H11 to 1A. The objectives of this study were to identify simple-sequence-repeat (SSR) markers for fine mapping of these genes and for marker-assisted selection in wheat breeding. Contrary to previous results, H9 and H10 did not show linkage with SSR markers on chromosome 5A. Instead, H9, H10, and H11 are linked with SSR markers on the short arm of chromosome 1A. Both H9 and H10 are tightly linked to flanking markers Xbarc263 and Xcfa2153 within a genetic distance of 0.3-0.5 cM. H11 is tightly linked to flanking markers Xcfa2153 and Xbarc263 at genetic distances of 0.3 cM and 1.7 cM. Deletion bin mapping assigned these markers and genes to the distal 14% of chromosome arm 1AS, where another Hf-resistance gene, Hdic (derived from emmer wheat), was also mapped previously. Marker polymorphism results indicated that a small terminal segment of chromosome 1AS containing H9 or H10 was transferred from the donor parent to the wheat lines Iris or Joy, and a small intercalary fragment carrying H11 was transferred from the resistant donor to the wheat line Karen. Our results suggest that H9, H10, H11, Hdic, and the previously identified H9- or H11-linked genes (H3, H5, H6, H12, H14, H15, H16, H17, H19, H28, and H29) may compose a cluster (or family) of Hf-resistance genes in the distal gene-rich region of wheat chromosome 1AS; and H10 most likely is the same gene as H9.

Animals↗